An Overview of
Renewable Natural Gas
from Biogas
January 2021
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Table of Contents
1.0 INTRODUCTION 1
2.0 WHAT IS RNG? 1
2.1 Sources of RNG 1
3.0 OPTIONS FOR RNG DELIVERY AND USE 5
3.1 Pipeline Injection 6
3.2 Local Use 7
4.0 BENEFITS OF RNG 8
4.1 Fuel Diversity and Availability 8
4.2 Local Economic Impacts 8
4.3 Local Air Quality 9
4.4 GHG Emission Reductions 11
4.5 Other Benefits of Natural Gas Vehicles 14
5.0 OPERATIONAL RNG PROJECTS 14
6.0 CONSIDERATIONS FOR PROJECT FEASIBILITY AND POTENTIAL FOR GROWTH 16
7.0 PURIFICATION PROCESSES AND GENERAL TECHNOLOGIES 20
7.1 C02 Removal Technologies 21
7.2 VOC/Siloxane Removal Technologies 24
7.3 N2 Removal Technologies 25
7.4 02 Removal Technologies 26
7.5 The Future of RNG Processing Technologies 26
7.6 Reliable Power Sources for Advanced Treatment 27
7.7 Compressing RNG 27
8.0 BARRIERS, POLICY DRIVERS AND INCENTIVES RELATED TO RNG PROJECT DEVELOPMENT 27
8.1 Economic Barriers 28
8.2 Technical Barriers 29
8.3 Perception of RNG Quality 30
8.4 Policies and Incentives Related to Pipeline Injection 30
8.5 Policies and Incentives Related to Use of RNG as Transportation Fuel 33
8.6 State Regulatory Policies and Incentives Related to Electricity 34
8.7 Policies and Incentives Related to Sustainability and Environmental Goals 35
9.0 EXAMPLES 38
9.1 RNG Projects with Feedstock, Delivery Method and End Use 38
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9.2 Corporate Alternative Fuel Fleets 44
10.0 RESOURCES 45
11.0 ABBREVIATIONS, ACRONYMS AND UNITS OF MEASURE 46
Appendix A: Natural Gas Companies Accepting RNG into Pipelines A-l
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List of Tables
Table 1. AFLEETTool Emission Results for Replacement of Washington, D.C.-Based Older Model Year
Gasoline Pickups or Diesel Refuse Trucks with New (Model Year 2019) Dedicated CNG Pickups or Refuse
Trucks 10
Table 2. CI Ranges of Fossil and Renewable Vehicle Fuels from CARB LCFS-Certified Pathways 12
Table 3. Breakdown of LFG-to-RNG Project Types and Sizes in the United States from the LMOP Landfill
and LFG Energy Project Database 15
Table 4. WRRF Digester Gas-to-RNG Projects Operating in the United States in 2019 15
Table 5. Number of Biogas Utilization Projects for Varying WRRF Capacities 18
Table 6. Typical Flow Rates for Advanced C02 Removal Technologies 24
List of Figures
Figure 1. Organic Waste Types Used to Make RNG 2
Figure 2. LFG Treatment Stages and Biogas End Uses 3
Figure 3. AD Products, Biogas Treatment and End Uses 4
Figure 4. RNG Delivery Options and Typical RNG End Uses 5
Figure 5. Components of a Pipeline Interconnection 6
Figure 6. Example CIs from LFG-RNG-CNG Life Cycle (g C02e/MJ) 13
Figure 7. C02 Removal Technologies for U.S. LFG-to-RNG Projects in 2018 22
Figure 8. C02 Removal Technologies for U.S. Manure-Based Biogas-to-RNG Projects in 2018 22
Figure 9. Breakdown of RNG Processing and Interconnection Costs 31
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1.0 INTRODUCTION
EPA encourages the recovery and beneficial use of biogas as a renewable energy resource, including the
production of renewable natural gas (RNG) when feasible, as a means of reducing emissions and providing
other environmental benefits. RNG is a term used to describe biogas that has been upgraded to use in
place of fossil natural gas, either locally or remotely. EPA's partnership programs for the reduction of
methane (CH4) emissions—the Landfill Methane Outreach Program (LMOP), AgSTAR and Natural Gas
STAR—offer data on potential sources of RNG feedstocks as well as technical and outreach resources and
tools to support RNG project development.
EPA developed this document to provide biogas stakeholders and other interested parties with a resource
to promote and potentially assist in the development of RNG projects. This document summarizes existing
RNG operational projects in the United States and the potential for growth from the main sources of
biogas feedstock. This document provides technical information on how raw biogas is upgraded into RNG
and ultimately delivered and used by consumers. The document also addresses barriers, policies and
incentives related to RNG project development.
2.0 WHAT IS RNG?
RNG is a term used to describe anaerobically-generated biogas that has been upgraded (or refined) for
use in place of fossil natural gas. Raw biogas typically has a CH4 content between 45 and 65 percent,
depending on the source of the biogas, and must go through a series of steps to be converted into RNG.
Treatment includes removing moisture, carbon dioxide (C02) and trace-level contaminants (including
siloxanes, volatile organic compounds [VOCs] and hydrogen sulfide [H2S]), as well as reducing the nitrogen
(N2) and oxygen (02) content. Once purified, the RNG has a CH4 content of 90 percent or greater. RNG
injected into a natural gas pipeline commonly has a CH4 content between 96 and 98 percent.
As a substitute for fossil natural gas, RNG has many potential uses. RNG can be used as vehicle fuel, to
generate electricity, in thermal applications, or as a bio-product feedstock. RNG can be injected into
natural gas transmission or distribution pipelines, or it can be used locally (i.e., at or near the site where
the gas is created). In this document, the term RNG does not encompass synthesis gas (syngas) produced
through gasification of biomass or any other feedstocks.
2.1 Sources of RNG
Currently, there are four main sources of biogas used to produce RNG in the United States: municipal solid
waste (MSW) landfills, anaerobic digestion (AD) at municipal water resource recovery facilities (WRRFs),
AD at livestock farms and AD at stand-alone organic waste management operations. At each of these
types of operations, biogas is produced as the organic materials are broken down by microorganisms in
the absence of 02 (i.e., anaerobic conditions). Figure 1 shows the main organic waste feedstocks that are
placed into an MSW landfill or an AD facility. "Organic" in this context means the wastes come from, or
were made of, plants or animals.
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Figure 1. Organic Waste Types Used to Make RNG
Waste Types Used to Make RNG
Municipal Solid Yard and Crop Food and Food
Waste Sewage Sludge Wastes Processing Wastes Manure
~ nnH ~
MSW Landfills
Landfill gas (LFG) is generated in MSW landfills1 as the organic wastes decompose anaerobically. Instead
of escaping into the air, LFG can be captured, converted and used as an energy resource. Applicable
federal and state regulations require certain landfills to capture and destroy the LFG generated; for these
sites an LFG collection infrastructure is already in place and potentially ready for an energy project. The
diagram in Figure 2 provides an overview of the levels of treatment that LFG can undergo to be used as
an energy resource.
1 More information about MSW landfills is available at U.S. EPA. What Is a Municipal Solid Waste Landfill?
https://www.epa.gOv/landfills/municipal-solid-waste-landfills#whatis. Accessed November 18, 2019.
2
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Figure 2. LFG Treatment Stages and Biogas End Uses
Landfill Gas Treatment Stages End Uses
PRIMARY
TREATMENT
Moisture and
particulate removal
SECONDARY
TREATMENT
Contaminant
removal and
compression
ADVANCED
TREATMENT
Upgrade to
pipeline quality
or vehicle fuel
Knockout Pot
Filter
dpi™1
Blower J
\
Flare
Moisture
Removal
Siloxane/Sulfur Compresso
Removal
I
Flare/Thermal Oxidizer
for Waste/Tail Gas
Removal of CO,,
Compressor
3
Heating
Electricity
Other
Industrial
Uses
Municipal WRRFs
Many municipal WRRFs (also known as wastewater treatment facilities or publicly owned treatment
works) use AD to treat sewage sludge on site, while some facilities send the sludge to other facilities for
AD treatment. Biogas is one of the byproducts of sludge treatment through AD. WRRFs typically generate
biogas with a high CH4 content and extremely low N2 and 02 contents, which make them attractive
candidates for RNG projects.
Approximately 133 to 177 WRRFs with AD were "co-digesting" other waste streams, such as source-
separated food wastes, in 2017.2 Co-digestion of food waste with WRRF sludge allows facilities to use
existing assets and infrastructure to meet the growing interest in food waste management. With co-
digestion, facilities can more efficiently use process equipment when they process multiple waste streams
together. Facilities can also use co-digestion to adjust the proportions of solids being digested to improve
digestion and increase biogas production.
Livestock Farms
Livestock farms can use AD to convert livestock (e.g., dairy, beef, swine, poultry) manure into biogas and
digestate.3 Some manure-based digesters co-digest other waste materials with the manure, including
upstream (pre-consumer) food wastes such as beverage and distillery waste; fats, oils and greases;
2 Goldstein, N. October 2017. The State of Organics Recycling in the U.S. BioCycle 58(9): 22.
https://www,biocvcle,net/2017/10/04/state-organics-recycling-u-s/. Accessed March 4, 2020. See Table 3 and
additional discussion about data from the Water Environment & Reuse Foundation on page 6 of Goldstein's report.
3 Digestate is the nutrient-rich material left over after AD.
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industrial food byproducts; or processing wastes from a dairy or slaughterhouse. Various sources estimate
approximately 100 manure-based AD projects are co-digesting other organic waste materials.4 The
diagram in Figure 3 presents the biogas and typical digestate products from manure-based AD projects
and the levels of treatment that AD biogas can undergo to be used as an energy resource.
Figure 3. AD Products, Biogas Treatment and End Uses
Anaerobic Digestion Products, Biogas Treatment, and End Uses
Siloxane/Sulfur
Removal
DIGESTED
MATERIAL
Moisture
Removal
Compressor
Liquids
Ferti hzer
CO
Removal
Solids
Amendment
,mr^\ Animal
Bedding
Other
Innovative Uses
Compressor
Heating
Electricity
Other
Industrial
Uses
Stand-Alone Organic Waste Management Operations
Stand-alone digesters are the newest source of RNG in the United States. These AD projects break down
source separated organic material—including food waste—to generate biogas, which can be converted
to RNG. Digesters that primarily process food waste can also co-digest other organic materials including
yard waste.5 A 2018 EPA surve\ of U.S. AD facility operators showed that a total of 9.2 million tons of food
waste was processed at 44 stand-alone digesters during 2016. The survey report indicates there were 62
stand-alone digesters operating in 2016, which suggests the actual amount of food waste processed in
Goldstein, N. October 2017. The State of Organics Recycling in the U.S. BioCycle 58(9): 22.
https://www, biocvcle.net/2017/10/04/state-organics-recvcling-u-s/. Accessed March 4, 2020. The article estimates
that 94 manure-based AD projects were co-digesting. April 2017 research conducted using the AgSTAR database,
case studies, articles and profiles showed 111 manure-based projects were co-digesting other materials. In March
2020, the AgSTAR database indicated 104 manure AD projects that co-digest other organic materials.
U.S. EPA. Types of Anaerobic Digesters. Stand-Alone Digesters, https://www.epa.gov/anaerobic-digestion/types-
anaerobic-digesters#StandAloneAD. Accessed March 25, 2019.
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this manner was higher. In addition, 20 of the stand-alone digesters surveyed processed more than 31
million gallons of liquid non-food waste and nearly 83,000 tons of solid non-food waste in 2016.6
3.0 OPTIONS FOR RNG DELIVERY AND USE
As shown in Figure 4, the two main methods for delivering RNG to end users are injection into a pipeline
(fossil natural gas pipeline or dedicated RNG pipeline) or onsite/local applications (e.g., onsite vehicle
fueling station, transport by truck). RNG is so chemically similar to fossil natural gas that it is a "drop-in"
substitute, making it versatile. The methane in RNG is identical to methane in fossil natural gas, but the
two gasses have constituents in very low concentrations that the other does not have. In addition to being
used as vehicle fuel or for generating electricity, RNG can also be used to meet thermal energy demands
(heat, steam, hot water, cooling or other processes) in the industrial, commercial, institutional or
residential sectors.
Figure 4. RNG Delivery Options and Typical RNG End Uses
RNG Delivery Options
RNG End Uses
Local Use
Pipeline Injection
Vehicle Fuel
Electricity
D
Thermal Applications
Over time, market drivers have shaped how RNG is used. In 2011, nearly ali the RNG projects operating in
the United States were providing RNG to generate electricity off site, as an effect of state-level Renewable
Portfolio Standard (RPS) programs.7 As the market for renewable transportation fuels emerged through
federal and state ruies and incentives, the overall number of RNG projects grew rapidly and the end use
6 U.S. EPA. September 2019. Anaerobic Digestion Facilities Processing Food Waste in the United States (2016).
EPA/903/S-19/0Q1. https://www.epa.gov/anaerobic-digestion/anaerobic-digestion-facilities-processing-food-waste-
united-states-survev.
7 Escudero, J. May 2017. Powering Businesses, Homes & Vehicles with Waste: Growing the Economy & Jobs with
Renewable Natural Gas. https://www.eesi.org/files/Johannes Escudero 052317.pdf.
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of the RNG shifted dramatically. In 2017, 76 percent of RNG projects were converting RNG into
transportation fuels, while 24 percent generated electricity off site.8
3.1 Pipeline Injection
Many RNG projects inject the product into a fossil natural gas pipeline. Appendix A lists known natural gas
utilities who have received or plan to receive RNG into their networks. The RNG must meet the
specification requirements of the receiving gas utility. This delivery method can be expensive due to
extensive planning, land purchases, permitting, construction, and interconnection fees and equipment.
However, pipeline injection can convey the RNG across a vast distribution network and provide flexibility
on how and where the RNG is ultimately used.
Interconnection consists of two primary components, a "point of receipt" and a "pipeline extension," as
shown in Figure 5. The point of receipt monitors the quality of the RNG to ensure that it meets
specifications and includes equipment to prevent non-compliant gas from entering the pipeline. The point
of receipt also meters and may odorize the RNG prior to injection. RNG can be delivered to the point of
receipt from the production facility through piping built specifically for this purpose or by truck.
The pipeline extension is a dedicated pipeline to transfer the RNG from the point of receipt to the nearest
fossil natural gas pipeline that has capacity to accept it. All projects have a pipeline extension to allow
space for odorization, gas quality monitoring, and a shut off valve. Some distribution-level pipelines do
not have the capacity to receive RNG injections (which are constant), due either to the cyclical nature of
the pipeline users or to the size and volume of fossil natural gas flow. When the pipeline nearest to an
RNG processing plant cannot accept the RNG, a longer pipeline extension is needed to reach a fossil
natural gas pipeline with adequate capacity.9
Figure 5. Components of a Pipeline Interconnection10
"Pipeline Extension"
Utility Pipeline
"Interconnection" = "Point of Receipt" + "Pipeline Extension"
8 Escudero, J. May 2017. Powering Businesses, Homes & Vehicles with Waste: Growing the Economy & Jobs with
Renewable Natural Gas. https://www.eesi.org/files/Johannes Escudero 052317.pdf.
9 Lucas, J. October 2017. Interconnecting to the SoCalGas Pipeline. Presented at Power of Waste: RNG for California,
Sacramento. https://www.socalgas.com/1443741248177/PowerofWaste SoCalGas Lucas.pdf.
10 Lucas, J. September 2017. Renewable Natural Gas Projects. Presented at EPA Technology Transfer Workshop:
Renewable Natural Gas—Driving Value for Natural Gas and Biogas Sectors.
https://www.epa.gov/sites/production/files/2017-10/documents/lucas rng 2017 panell.pdf. Figure used with
permission from Southern California Gas Company.
Customer Pipeline
(RNG from biogas conditioning/
upgrading plant)
"Point of Receipt" ,/
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Alternatively, RNG can be injected into a dedicated pipeline instead of into a natural gas pipeline network.
Vehicle Fuel
RNG can be used as fuel, as compressed natural gas [CNG] or liquefied natural gas [LNG], in a variety of
vehicle types. According to the U.S. Department of Energy's (DOE's) Alternative Fuels Data Center, in
March 2019 there were 914 public and 678 private CNG stations and 66 public and 55 private LNG stations
in the country.11
As of March 2020, the majority (91 percent) of LFG-sourced RNG pipeline injection projects were providing
at least a portion of the RNG to a vehicle fuel market down the pipeline.12 In these cases, fueling stations
far removed from the biogas source were receiving the RNG at the other end of a pipeline network.
Electricity Production
While many biogas projects generate electricity from partially conditioned biogas, there are a number of
projects (primarily landfill-based) where RNG is injected into a pipeline and used to generate electricity.
Thermal Applications
Numerous biogas energy projects use nearly raw biogas in direct thermal applications such as boilers,
greenhouses and kilns. RNG projects for direct thermal applications are less common, as the bulk of
incentives are for transportation and electricity end uses. However, as discussed in Section 8.7, some state
policies have created a new interest in RNG for direct thermal uses.
3.2 Local Use
The predominant use of RNG on site or locally is for vehicle fuel.
Onsite Vehicle Fuel
Onsite RNG vehicle fuel projects avoid the need to meet natural gas pipeline specifications, and typically
the vehicle fuel specifications are less stringent than the requirements from a pipeline operator. In
addition, these projects avoid the costs to interconnect and transport the gas via pipeline. However, there
must be an adequate and consistent demand for the RNG vehicle fuel. Matching the fleet demand to the
RNG resource can be problematic in some rural areas with a source of biogas, as larger fleets are generally
located in urban centers.
Often, the owner of the biogas source also has a vehicle fleet, for example a public works department that
has a landfill and/or WRRF as well as a CNG-compatible fleet inventory. Some onsite fueling stations also
allow corporate fleets operating in the area to use their stations. In either case, these types of projects,
wherein the vehicles delivering a feedstock (e.g., garbage or food waste) are fueled by RNG from biogas
produced by that feedstock, are considered "closed loop" or circular projects.
Generally, local-use vehicle fuel projects are smaller scale than pipeline injection vehicle fuel projects.
Taking LFG-based RNG as an example, the average flow rate of local-use CNG projects is 145 cubic feet
11 U.S. DOE. Alternative Fueling Station Locator. https://afdc.energy.gov/stations/#/analvze?countrv=US. Accessed
March 27, 2019.
12 U.S. EPA. March 2020. Landfill and Landfill Gas Energy Project Database, https://www.epa.gov/lmop/landfill-gas-
energy-proiect-data.
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per minute (cfm) of biogas inlet, while the average for pipeline injection projects with a vehicle fuel
component is 2,940 cfm of biogas inlet, twenty times larger.13
Virtual Pipeline
If an RNG processing plant is not close to potential end users or an existing pipeline, a "virtual pipeline"
can move compressed RNG from the point of generation to the point of injection or use. In a virtual
pipeline scenario, the RNG is compressed to up to 4,000 pounds per square inch for injection into a natural
gas tube trailer, and then transported off site by truck. Once it reaches the destination, the RNG is
decompressed back down to the pressure required by the receiving facility. The decompression site must
include a "decant" facility that heats the RNG as it decompresses to minimize the freezing of valves and
regulators due to decompression. A virtual pipeline allows remote landfills, farms or other biogas sources
to market their RNG in populated areas. Leasing companies that will contract for loading, transporting
and off-loading the RNG are also available. The costs to transport RNG in a virtual pipeline are in addition
to the costs associated with RNG processing equipment and infrastructure needed to compress and
decompress the gas.
Some projects may employ more than one delivery mechanism to match the RNG supply with demand.
For example, a project may have an onsite vehicle fueling station for a portion of the fuel and transport
the remainder to an offsite fueling station via a virtual pipeline.
4.0 BENEFITS OF RNG
Developing RNG resources is one way to diversify fuel supplies and increase fuel security, provide
economic benefits to communities and end users, improve local air quality and reduce greenhouse gas
(GHG) emissions.
4.1 Fuel Diversity and Availability
Biogas feedstocks for RNG are generated continuously from a variety of sources (offering high availability
rates), and the use of RNG increases and diversifies domestic energy production. For example, Atlantic
City, New Jersey used CNG-fueled buses to provide critical services in 2012 after Hurricane Sandy when
gasoline supplies were limited, showing the value of alternative fuel vehicles during natural disasters.14
4.2 Local Economic Impacts
Developing RNG projects can benefit local economies through the construction of infrastructure and sale
of vehicles that can use this fuel source. Adding a renewable source of vehicle fuel to an area has the
potential to draw outside vehicle fleets to a community, as the CNG produced from biogas can potentially
be sold at a lower cost than fossil fuel-based vehicle fuel (due to incentives such as EPA's Renewable Fuel
Standard [RFS]) or corporations may be looking for ways to green their fleets or increase corporate
sustainability.
A 2017 study conducted for the California Natural Gas Vehicle Coalition analyzed the economic impacts
of converting heavy-duty diesel-fueled trucks in California to RNG fuel, including the benefits of building
13 See details and ranges of project sizes in Table 3 in Section 5.0 of this document. Data source is U.S. EPA. March
2020. Landfill and Landfill Gas Energy Project Database, https://www.epa.gov/lmop/landfill-gas-energy-proiect-
data.
14 Bluestein, L. April 2013. Clean Cities Webinar: Planning Ahead with Alternative Fuels—a lesson from Sandy.
https://cleancities.energy.gOv/files/u/news events/document/document url/49/emergencv preparedness webina
r.pdf.
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RNG processing and fueling station infrastructure and the impact of purchasing CNG vehicles.15 The study
found that California RNG production facilities (based on a mix of landfill, WRRF and dairy feedstocks)
would generate about 8.5 to 11.2 jobs per million diesel gallon equivalent of transportation fuel. By
contrast, the petroleum refinery industry yields about 1.6 jobs per million diesel gallon equivalent of
transportation fuel. Additionally, for every job created through investment in low nitrogen oxide (NOx)-
emitting natural gas trucks, natural gas fueling infrastructure and RNG production facilities, about 2.0 jobs
are created in supporting industries (indirect) and via spending by employees that are directly or indirectly
supported by these industries (induced).
For projects where there is common ownership between the RNG source and the fleet using RNG, vehicle
fuel from RNG can also provide price stability (e.g., compared to diesel fuel purchases) through mid-term
to long-term RNG supply contracts or through creating fuel for internal consumption.
4.3 Local Air Quality
Replacing traditional diesel or gasoline with RNG vehicle fuel can reduce pollutant emissions, resulting in
local air quality benefits.
RNG combusts similarly to fossil natural gas, so pipeline operators make no distinctions between the two
once the RNG meets the required specification and is injected into the pipeline network. Fossil natural gas
typically contains several non-methane hydrocarbons, including ethane, propane, butane and pentane,
as well as some trace organics, all in small concentrations. RNG does not generally contain non-methane
hydrocarbons but does share some other low-concentration constituents with fossil natural gas, such as
C02, N2, 02, H2S and total sulfur. Fossil natural gas and RNG both contain trace organics (e.g., aromatic
hydrocarbons, aldehydes and ketones), but samples of RNG show these in much lower concentrations
than in fossil natural gas.1617
Since 2017, most newly built vehicles are required to meet the same emission standards (including NOx,
particulate matter [PM] and carbon monoxide [CO]) regardless of fuel type,18 so new natural gas vehicle
emissions are comparable to those of new gasoline and diesel vehicles. However, when older model
gasoline or diesel vehicle fleets are replaced with new natural gas vehicles, certain local air pollutant
emissions are often reduced on an as-driven basis.
For example, replacement or aftermarket conversion of older gasoline vehicles with natural gas models
can provide reductions across pollutants. The Argonne National Laboratory's Alternative Fuel Life-Cycle
Environmental and Economic Transportation (AFLEET) tool19 can be used to estimate emission reductions
15 ICF. May 2017. Economic Impacts of Deploying Low NOx Trucks Fueled by Renewable Natural Gas.
https://www.masstransitmag.com/home/document/12330911/economic-impacts-of-deploving-low-nox-trucks-
fueled-bv-renewable-natural-gas.
16 Gas Technology Institute. May 2012. Guidance Document for the Introduction of Landfill-Derived Renewable Gas
into Natural Gas Pipelines. https://www.gti.energy/wp-
content/uploads/2018/09/120007 Landfill Guidance Document FINALREPQRT-05-9-2012.pdf.
17 Wiley, Kristine. October 2018. Renewable Natural Gas (RNG): Gas Quality Considerations. Presented at 2018 Natural
Gas STAR and Methane Challenge Renewable Natural Gas Workshop, https://www.epa.gov/natural-gas-star-
program/2018-natural-gas-star-and-methane-challenge-renewable-natural-gas-workshop.
18 U.S. EPA. Final Rule for Control of Air Pollution from Motor Vehicles: Tier 3 Motor Vehicle Emission and Fuel
Standards, https://www.epa.gov/regulations-emissions-vehicles-and-engines/final-rule-control-air-pollution-motor-
vehicles-tier-3.
19 Argonne National Laboratory. November 2018. AFLEET Tool, https://afleet-web.es.anl.gov/home/. Emission
estimates based on a fleet replacement location in Washington, D.C.
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for fleet replacement on an as-driven basis. A fleet location of Washington, D.C., was used for illustrative
purposes along with the AFLEET tool's default input parameters, including annual mileage and fuel
economy. Similar patterns in emission reduction percentages were derived for other fleet locations.
The AFLEET tool was used to analyze the emissions from gasoline pickups and refuse trucks in three older
model years, with model year 2010 representing a median life age for the national pickup population and
model year 2012 representing a median life age for the national refuse truck population.
The results in Table 1 indicate substantial percentage reductions in NOx, VOC, PMi0, PM2.s, CO and sulfur
dioxide (SOx) emissions for each of the older gasoline pickup models, as compared with a new (model
year 2019) CNG pickup, with the most significant reductions achieved for the oldest model year. For refuse
trucks, substantial emission reductions were shown for NOx, exhaust VOC, PMio, PM2.5 and SOx, again
with the largest reductions from the oldest vehicle replacements.
Table 1. AFLEET Tool Emission Results for Replacement of Washington, D.C.-Based Older Model Year
Gasoline Pickups or Diesel Refuse Trucks with New (Model Year 2019) Dedicated CNG Pickups or
Refuse Trucks
Fuel/Vehicle
Type
Model
Year
Percentage Emission Reductions if Replaced by 2019 Model Year CNG
Vehicle
NOx
VOC
(Exhaust)
VOC
(Evaporative)
O
rH
Q-
PM,S
CO
SOx
Gasoline
Pickup
2005
87.4%
86.0%
87.5%
73.0%
68.9%
84.3%
38.1%
2007
80.2%
78.8%
85.4%
73.0%
65.0%
81.9%
38.1%
2010
66.7%
69.1%
75.6%
66.3%
60.0%
74.6%
38.1%
Diesel Refuse
Truck
2006
99.4%
93.9%
7.14%
97.0%
96.9%
-571%
43.0%
2009
99.2%
43.8%
7.14%
42.2%
41.5%
-2,180%
43.0%
2012
96.8%
16.9%
7.14%
38.1%
38.5%
-3,025%
43.0%
However, CO emissions increased significantly for the CNG refuse trucks relative to the diesel baseline.
This increase is due to the newest CNG refuse trucks being powered by spark-ignited cycle engines with
three-way catalysts. Compared to the diesel refuse trucks, which are powered by compression ignition
cycle engines, the CNG spark-ignited engines operate at tightly controlled stoichiometric fuel-air ratios
that allow for three-way catalyst control20 of NOx, VOC and CO emissions but produce inherently higher
CO emissions. However, new CNG refuse trucks do still comply with existing heavy-duty engine emission
standards even with the higher CO emissions. When replacing older heavy-duty diesel vehicles with new
dedicated CNG vehicles, local communities should consider this trade-off of lower NOx and PM emissions
20 Three-way catalysts are exhaust emission control devices for achieving simultaneous control of tailpipe NOx, VOC
and CO emissions. Three-way catalysts typically are deployed in conjunction with closed loop, stoichiometric fuel-air
ratio fuel delivery to the engine for achieving the highest efficiency in catalytic reduction of NOx, and oxidation of
VOCs and CO in the engine exhaust emissions stream.
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but higher CO emissions with respect to existing local air quality conditions and compliance with national
standards.
Apart from combustion emissions, gasoline and diesel vehicles produce hydrocarbon emissions from the
evaporation of fuel in onboard fuel tanks, but natural gas vehicle fuel systems emit minimal evaporative
hydrocarbon emissions because they are sealed to the atmosphere.
4.4 GHG Emission Reductions
When fossil natural gas is replaced by RNG, the resulting GHG emission reductions provide a climate
benefit. One way to characterize the climate benefit of a fuel is to determine its "carbon intensity" (CI) or
"carbon footprint" based on a complete life cycle assessment that estimates the GHG emissions
associated with producing and consuming the fuel. Argonne National Laboratory's AFLEET tool estimates
that natural gas vehicles operating on fuel derived from RNG can yield GHG emission reductions of up to
75 percent, compared to gasoline or diesel vehicles.21 The California Air Resources Board (CARB) uses
similar life cycle assessment tools to estimate the GHG emissions associated with vehicle fuels for
implementation of the state's Low Carbon Fuel Standard (LCFS).
Natural gas in any form (fossil or RNG) is less carbon-intensive than the other fossil fuels it typically
replaces, including conventional transportation fuels (e.g., gasoline, diesel) in most cases and coal or
petroleum for generating electricity.22,23 RNG provides an additional benefit over fossil natural gas
because it generally has a lower total carbon footprint, after accounting for emissions from fuel
production, transport and use.24,25,26 RNG's carbon footprint is even lower if a project can also take into
account directly reducing CH4 emissions from the organic waste used to produce the fuel.
Fuels from some RNG feedstocks can achieve negative carbon footprints by reducing CH4 emissions
through avoiding "business-as-usual" disposal pathways, such as projects that involve AD of manure and
organic wastes.27,28 In contrast, projects in which RNG is sourced from a landfill or WRRF where business-
as-usual practices collect and destroy CH4 cannot account for any climate benefit from that CH4
destruction. These projects can account for the emissions avoided through recovering energy that would
21 Argonne National Laboratory. AFLEET Tool, https://afleet-web.es.anl.gov/home/. Accessed March 4, 2020.
22 U.S. EIA. Frequently Asked Questions. How Much Carbon Dioxide Is Produced When Different Fuels Are Burned?
https://www.eia.gov/tools/faas/faq.php?id=73&t=ll. Accessed March 4, 2020.
23 U.S. EPA. February 2018. Emissions & Generation Resource Integrated Database (eGRID). eGRID2016.
24 Kampman, B., C. Leguijt, T. Scholten, J. Tallat-Kelpsaite, R. Bruckmann, G. Maroulis, J.P. Lesschen, K. Meesters, et al.
December 2016. Optimal Use of Biogas from Waste Streams: An Assessment of the Potential of Biogas from
Digestion in the EU Beyond 2020. European Commission.
https://ec.europa.eu/energy/sites/ener/files/documents/ce delft 3g84 biogas beyond 2020 final report.pdf.
25 Hass, H., H. Maas, R. Edwards, L. Lonza, J.F. Larive, and D. Rickeard. January 2014. Well-to-wheels report version 4.a:
JEC well-to-wheels analysis of future automotive fuels and powertrains in the European context. Report EUR 26236
EN. European Commission, https://ec.europa.eu/irc/en/publication/eur-scientific-and-technical-research-
reports/well-wheels-report-version-4a-iec-well-wheels-analvsis.
26 Clark, C.E., J. Han, A. Burnham, J.B. Dunn, and M. Wang. December 2011. Life-Cycle Analysis of Shale Gas and
Natural Gas. ANL/ESD/11-11. Argonne National Laboratory, https://greet.es.anl.gov/publication-shale gas.
27 CARB and California Environmental Protection Agency. November 2014. Compliance Offset Protocol Livestock
Projects: Capturing and Destroying Methane from Manure Management Systems.
https://ww3.arb.ca.gov/cc/capandtrade/protocols/livestock/livestock.htm.
28 CARB and California Environmental Protection Agency. August 2018. Tier 1 Simplified CI Calculator Instruction
Manual: Biomethane from Anaerobic Digestion of Organic Waste, https://ww3.arb.ca.gov/fuels/lcfs/ca-greet/ca-
greet.htm.
11
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otherwise be flared and wasted (as energy recovery is not required), however they have a positive carbon
footprint overall.
Average CI Comparison for Vehicle Fuels
Using data from pathways that CARB has certified under the LCFS for 2021, Table 2 provides a comparison
of average CIs for several renewable vehicle fuels to fossil-based fuels.
Table 2. CI Ranges of Fossil and Renewable Vehicle Fuels from CARB LCFS-Certified Pathways29
Fuel Categorya
Feedstock
Average CI
(g COze/MJ)b
Range
(g COze/MJ)
Number
of
Pathways
Diesel
Fossil Crude
100
100
1
CNG, Fossil
Fossil Natural Gas
79
79
1
LNG, Fossil
Fossil Natural Gas
No data
-
-
CNG, Renewable
LFG
53
30 to 83
30
Manure
-313
-533 to -151
24
Wastewater
47
37 to 58
3
Food and Green Waste
No data
-
-
LNG, Renewable
LFG
61
43 to 80
14
Manure
-336
-360 to -312
3
Wastewater
48
42 to 55
2
Food and Green Waste
No data
-
-
a CARB accounts for relative energy efficiencies of different drive technologies relative to the baseline gasoline or
diesel technologies by using energy economy ratios (EERs). EERs account for differences in fuel efficiency for a given
vehicle type and alternative transportation fuel and compares it to a benchmark, conventional vehicle. Vehicle type-
and fuel-specific EERs should be applied to average fuel CIs to facilitate comparison across fuel types. The average CI
values provided in this table do not yet have EERs applied to them.30
b The exact CI of diesel is 100.45 grams of C02 equivalent per megajoule (g C02e/MJ), per CARB documentation.
The CIs of fuels from different RNG feedstocks and fossil natural gas are characterized by impacts
occurring at distinct phases of the fuel life cycle. For example, tailpipe emissions of C02 from RNG fuels
are considered carbon neutral because the carbon is biogenic, while tailpipe emissions of C02 from fossil
natural gas fuels are not. As a result, CIs of fossil natural gas-based vehicle fuels are most impacted by
tailpipe emissions, with lesser contributions from refining and resource extraction. As another example,
RNG fuels derived from LFG receive no credits for CH4 reduction under the LCFS because the baseline set
by CARB for this pathway is flaring of the LFG. As a result, LFG-derived vehicle fuels have CIs that are most
heavily influenced by the biogas upgrading plant and emissions during pipeline transport.31 The exact CI
29 CARB. LCFS Pathway Certified Carbon Intensities.
https://www.arb.ca.gov/fuels/lcfs/fuelpathwavs/pathwavtable.htm. File provided by CARB on December 3, 2020.
CARB updates the pathway file regularly.
30 California Code of Regulations. 2020. Title 17. Public Health. Division 3. Air Resources. Chapter 1. Air Resources
Board. Subchapter 10. Climate Change. Article 4. Regulations to Achieve Greenhouse Gas Emission Reductions.
Subarticle 7. Low Carbon Fuel Standard. Section 95486. Generating and Calculating Credits and Deficits. May 27,
2020. https://govt.westlaw.com/calregs/lndex?transitionType=Default&contextData=%28sc.Default%29. Accessed
September 3, 2020.
31 CARB and California Environmental Protection Agency. 2018. Tier 1 Simplified CI Calculator for Biomethane from
North American Landfills, https://ww3.arb.ca.gov/fuels/lcfs/ca-greet/ca-greet.htm. Accessed March 4, 2020.
12
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used to power the gas upgrading equipment and compression in the pipeline, as well as the length of the
transmission pipeline.
CIs for a Hypothetical LFG-to-CNG Project
Figure 6 illustrates example CIs associated with each major step in a hypothetical LFG-to-CNG project: LFG
recovery at the landfill, treatment/processing of the raw LFG into RNG, transporting the RNG via pipeline
networks to the CNG fueling stations, compression of the RNG at CNG fueling stations and emissions from
the CNG vehicles. These example CIs were determined using CARB's Tier 1 Simplified CI Calculator for
Biomethane from North American Landfills with the following inputs and assumptions:
• Input of 3,100 cfm raw LFG at 50 percent CH4.
• RNG processing plant that:
o Is powered by grid-purchased electricity.
o Does not require any supplemental propane or fossil natural gas to achieve the target
specifications for pipeline injection of the RNG.
o Has an energy consumption of 0.009 kilowatt-hours per standard cubic foot (scf) of LFG
and a 90 percent capture efficiency of CH4, yielding 455 British thermal units (Btu) of
RNG per scf (Btu/scf) of LFG.
• Three thousand miles of gas pipeline to transport the RNG from the landfill to the CNG fueling
stations.
• U.S. average mix for the energy used to power the LFG recovery equipment, RNG
upgrading/processing plant and transport of the LFG via pipeline.
• California grid mix for the energy used to compress RNG at the CNG fueling station.
Figure 6. Example CIs from LFG-RNG-CNG Life Cycle (g C02e/MJ)
RNG
Processing
Facility
Pipeline
Transmission
17.9
13
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4.5
Other Benefits of Natural Gas Vehicles
Natural gas vehicles, including those using RNG-derived fuel, offer other benefits to the community.
Members of the public often view local green programs positively, which can present great marketing and
publicity opportunities for a community. According to Clean Energy Fuels, dedicated natural gas-fueled
refuse trucks produce less noise than comparable diesel-fueled refuse trucks, with a difference greater
than 10 decibels at idle.32 Reducing noise from trucks has positive and measurable health and economic
benefits.33
5.0 OPERATIONAL RNG PROJECTS
Across all feedstocks, 34 states have more than 100 RNG projects operating and approximately 40 under
construction as of February 2020.34 EPA provides a national map showing the locations of projects
producing RNG from either LFG or manure-based AD biogas.35
MSW Landfills
According to the EPA LMOP Landfill and LFG Energy Project Database, as of March 2020 there were 564
operational LFG energy projects, 65 of which produced RNG.36 Table 3 provides a summary of the 65 LFG-
to-RNG projects in the United States, including the number of projects and their sizes in terms of the
amount of LFG used to create the RNG. The majority of these projects are producing RNG for use as
transportation fuel, whether used locally (on site or near the landfill) or transported via pipeline to a
location further away. The other projects use the RNG to generate electricity in thermal applications or to
offset fossil natural gas usage in another manner.37
The first LFG-to-RNG project in the United States operated from 1975 to 1985 at the Palos Verdes Landfill
in Los Angeles County, California.38,39 The plant was designed to process 2 million standard cubic feet per
day (mmscfd) of raw LFG into approximately 1 mmscfd of RNG for injection into a nearby pipeline.40
32 Clean Energy Compression. July 2015. What Refuse Truck Fleets Are Doing to Make Our Air Cleaner.
https://www.cleanenergvfuels.com/compression/blog/refuse-truck-fleets-switch-natural-gas-power-who-when-
where-whv/.
33 Pignier, N. May 2015. The Impact of Traffic Noise on Economy and Environment: A Short Literature Study. KTH Royal
Institute of Technology. https://www.diva-portal.Org/smash/get/diva2:812062/FULLTEXT01.pdf.
34 Coalition for Renewable Natural Gas. RNG Production Facilities Database, http://www.rngcoalition.com/rng-
production-facilities. Accessed February 11, 2020.
35 U.S. EPA. RNG Project Map. https://www.epa.gOv/lmop/renewable-natural-gas#rngmap. Accessed July 22, 2019.
36 U.S. EPA. March 2020. Landfill and Landfill Gas Energy Project Database, https://www.epa.gov/lmop/landfill-gas-
energy-proiect-data.
37 U.S. EPA. March 2020. Landfill and Landfill Gas Energy Project Database, https://www.epa.gov/lmop/landfill-gas-
energy-proiect-data.
38 Cosulich, J., S.-L. Ahmed, and J.F. Stahl. 1992. Palos Verdes Landfill Gas to Energy Facility.
http://gwcouncil.org/publications/nawtec/proceedings-of-15th-biennial-conference/.
39 Bowerman, F., N. Rohatgi, K. Chen, and R. Lockwood. July 1977. A Case Study of the Los Angeles County Palos
Verdes Landfill Gas Development Project. EPA/600/3-77/047.
https://cfpub.epa.gov/si/si public record Report.cfm?Lab=ORD&dirEntrvlD=49543.
40 U.S. DOE. March 1978. Proceedings of a Symposium on the Utilization of Methane Generated in Landfills.
https://www.osti.gov/biblio/6652887.
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Table 3. Breakdown of LFG-to-RNG Project Types and Sizes in the United States from the LMOP
Landfill and LFG Energy Project Database
RNG Delivery Method /
Project Type
Number of
Projects
Project Size LFG Flow (cfm)
Local / CNG
6
49 to 201 (average 145)
Local / LNG
1
2,410
Pipeline Injection / Vehicle
Fuel
53
413 to 10,417 (average 2,753)
Pipeline Injection / Industrial,
Electricity or Other
5
757 to 5,833 (average 2,940)
Municipal WRRFs
In 2013, about 48 percent of the total wastewater flow in the United States was treated through AD.41
According to the U.S. GHG Inventory, in 2017 approximately 18,260 million gallons per day (MGD) of
wastewater effluent were sent to WRRFs with AD.42 In 2019, 13 WRRF biogas projects (listed in Table 4)
were creating RNG.43,44
Table 4. WRRF Digester Gas-to-RNG Projects Operating in the United States in 2019
WRRF Project Location
Start Year
WRRF Average Flow Rate in
MGD
91st Avenue, Phoenix, AZ
2019
138
City of San Mateo, CA
2016
15.7
Las Gallinas Valley Sanitary District, CA
2017
2.67
Point Loma, CA
2012
175
Persigo (Grand Junction), CO
2015
8.5
South Platte Water Renewal Partners, CO
2019
~24
Honouliuli, HI
2016
26.1
Dubuque, IA
2017
7
Warrior Biogas Reuse Project, KS
2018
5.5
Newark, OH
2011
8
San Antonio Water Systems, TX
2010
94.7
South Treatment Plant, WA
1987
70
Janesville, Wl
2012
13
Livestock Farms
According to the EPA AgSTAR project database, as of March 2020 there are 255 operational digester
projects that accept livestock manure. The majority (79 percent) of the manure-based digester projects
41 U.S. DOE. July 2016. 2016 Billion-Ton Report: Advancing Domestic Resources for a Thriving Bioeconomy.
https://www.energy.gov/sites/prod/files/2016/12/f34/2016 billion ton report 12.2.16 O.pdf.
42 Working spreadsheet for 2017 U.S. GHG Inventory for Wastewater Treatment.
43 Mintz, M., P. Vos, M. Tomich, and A. Blumenthal. October 2019. Database of Renewable Natural Gas (RNG) Projects:
2019 Update. Argonne National Laboratory, https://www.anl.gov/es/reference/renewable-natural-gas-database.
44 Gilbert, D. November 2019. "Biogas" Project Up and Running at Wastewater Plant.
https://littletonindependent.net/stories/biogas-proiect-up-and-running-at-wastewater-plant.288922.
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are at dairy farms, and 14 percent are at swine farms. The remainder process a mix of animal manure
effluents, including those from poultry and beef cattle.45
The earliest U.S. manure-based digester project to create RNG began in 2004 at Whitesides Dairy in Idaho.
The Whitesides project was the first biogas production facility at a large commercial dairy in the state and
provided approximately 10 million cubic feet of RNG annually to Intermountain Gas until 2009, when the
project ended.46
The majority (84 percent) of manure-based digester projects are generating electricity, and many of them
are also recovering waste heat in combined heat and power47 (or cogeneration) projects. More than 20
manure-based digester projects are currently producing RNG from their biogas with a variety of RNG end
uses including electricity, vehicle fuel and pipeline gas.48
Organic Waste Management Operations
EPA's 2018 AD survey results show that of the 43 stand-alone facilities that reported on their biogas end
use, five produce CNG for either company vehicles or for sale to other customers, while none provide RNG
for pipeline injection.49
6.0 CONSIDERATIONS FOR PROJECT FEASIBILITY AND POTENTIAL FOR
GROWTH
In addition to the sites discussed in Section 5.0 that are recovering biogas as a renewable energy resource,
there are many other biogas-producing sites in the United States that could potentially capture their
biogas for energy. Based on market conditions and incentives, several of the sites already recovering
biogas for electricity generation or other applications could switch to producing RNG instead; several LFG
energy projects have already made this change. In addition, more organic waste in this country could be
digested for energy recovery instead of being landfilled. A subset of the sources in these categories could
produce RNG.
Considerations for the feasibility of an RNG project include:
• The quantity and quality of biogas available for conversion (e.g., LFG and WRRF biogas tend to
require more constituent removal than manure-based or organic waste AD projects);
• Economic considerations (e.g., financing options, available incentives);
• End user availability for the RNG (e.g., proximity to a fossil natural gas pipeline without physical
connection barriers, a local distribution company's interest in taking RNG, a local vehicle fuel
demand, a natural gas-consuming business with sustainability goals); and
• A reliable power source for the compression and cleanup processes.
45 U.S. EPA. March 2020. Livestock Anaerobic Digester Database, https://www.epa.gov/agstar/livestock-anaerobic-
digester-database.
46 U.S. EPA. March 2020. Livestock Anaerobic Digester Database, https://www.epa.gov/agstar/livestock-anaerobic-
digester-database.
47 Combined heat and power or cogeneration projects recover and beneficially use the waste heat from the
combustion unit that is generating electricity, thus providing a greater overall efficiency.
48 U.S. EPA. March 2020. Livestock Anaerobic Digester Database, https://www.epa.gov/agstar/livestock-anaerobic-
digester-database.
49 U.S. EPA. September 2019. Anaerobic Digestion Facilities Processing Food Waste in the United States (2016).
EPA/903/S-19/001. https://www.epa.gov/anaerobic-digestion/anaerobic-digestion-facilities-processing-food-waste-
united-states-survev.
16
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Higher flows of biogas (e.g., greater than 1,000 cfm for LFG-sourced projects) are needed for pipeline
injection projects to be financially feasible, but local-use RNG-to-vehicle fuel projects are feasible at lower
flows (e.g., as low as 50 cfm for LFG-sourced projects). Gas conditioning technology improvements have
allowed smaller biogas volumes to be economically treated when used directly in onsite vehicle fueling
stations or aggregated with output from other sites to make use of one fossil natural gas pipeline
interconnect.
Prior to implementing any type of biogas energy project, an end user (or buyer of environmental
attributes) must be identified and appropriate agreements must be in place. For RNG projects, if onsite
vehicle fueling, direct pipeline injection or virtual pipeline transport is not feasible, an otherwise attractive
project may not be viable.
MSW Landfills
There is a significant opportunity for growth in RNG from LFG. LMOP defines a "candidate" landfill as a
landfill that is currently accepting waste or has been closed five years or less, has at least one million tons
of waste, and does not have an operational, under-construction or planned LFG energy project. A landfill
can also be designated as a candidate landfill based on actual interest for a project at the site. As of March
2020, there were approximately 480 candidate landfills with the potential to collect a combined 500
mmscfd of LFG. Out of these 480 landfills, approximately 375 have between 100 and 1,000 cfm of LFG
available, and approximately 90 have greater than 1,000 cfm of LFG. There are also landfills with
operational energy projects that are flaring excess LFG—approximately 85 of these landfills have 100 to
1,000 cfm of excess gas, and approximately 30 have more than 1,000 cfm of excess gas.50
Municipal WRRFs
A 2014 National Renewable Energy Laboratory report analyzed flow rate data from approximately 18,000
WRRFs to estimate their CH4 potential. After subtracting out the biogas used for combined heat and
power projects at WRRFs, the National Renewable Energy Laboratory estimated 1.9 million metric tons of
CH4 available for recovery from these facilities.51
The Water Environment Federation (WEF) maintains a "phase 1" database that lists information for
approximately 1,250 WRRFs that have AD on site or send sludge to another facility to be treated by AD.52
The economic viability of a WRRF biogas project primarily depends on the amount of organic feedstock
(e.g., wastewater sludge, commercial or industrial waste) that is available for AD. Typically, a larger WRRF
(in terms of influent flow) has a greater opportunity for biogas capture and use. In March 2015, Argonne
National Laboratory analyzed data in the WEF database, which included a summary of the counts of biogas
utilization projects for varying WRRF capacities, as shown in Table 5.
50 U.S. EPA. March 2020. Landfill and Landfill Gas Energy Project Database, https://www.epa.gov/lmop/landfill-gas-
energy-proiect-data.
51 Saur, G., and A. Milbrandt. July 2014. Renewable Hydrogen Potential from Biogas in the United States. NREL/TP-
5400-60283. https://www.nrel.gov/docs/fvl4osti/60283.pdf.
52 WEF. 2015. Biogas Data, http://www.resourcerecovervdata.org/biogasdata.php. Accessed March 27, 2019.
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Table 5. Number of Biogas Utilization Projects for Varying WRRF Capacities53
WRRF Average
Flow Rate in MGD
Number of WRRFs
with AD
Number Using Biogas /
Number Not Using Biogas
<1
96
55/41
1 to 10
690
505/185
10 to 100
276
238/38
100 to 1,000
29
26/3
The WEF database contains approximately 5,100 WRRFs in total, so it does not represent the entire list of
operating WRRFs nationwide, which is between 15,000 and 18,000 WRRFs.54 Of the WRRFs in the WEF
database, 3,200 have an average flow rate greater than 1 MGD; more than 60 percent of these facilities
do not send solids to AD, and therefore do not produce biogas. There are 12,000 facilities with average
flow rates less than 1 MGD, and only a small number of these facilities have AD;55 WRRFs of this size are
not expected to support an RNG project.
The project information in Table 4 of this document shows that of the 13 WRRF biogas-to-RNG projects
operating in 2019, about half are at WRRFs greater than 15 MGD in average flow rate. Table 5 notes 185
WRRFs with average flow rates between 1 and 10 MGD that have AD but are not beneficially using the
biogas; these WRRFs could potentially use their biogas for a local-use RNG project if demand is present.
For the 41 WRRFs with average flow rates greater than 10 MGD that have AD but are not using the biogas
for energy, they likely could produce RNG from their biogas for either local or pipeline delivery if other
project considerations are favorable. There is likely additional RNG generation potential at WRRFs not
represented in the WEF database.
Livestock Farms
Candidate sites are generally considered to be dairies with at least 500 cows or swine facilities with at
least 2,000 sows or feeder pigs. This is a rough estimate that accounts for the general manure production
rates and composition of these animals and should only be used for general screening, since smaller
operations have been successfully developed into beneficial use applications. According to estimates from
53 U.S. DOE. July 2016. 2016 Billion-Ton Report: Advancing Domestic Resources for a Thriving Bioeconomy.
https://www.energy.gov/sites/prod/files/2016/12/f34/2016 billion ton report 12.2.16 O.pdf. Citing Shen, Y., J.L.
Linville, M. Urgun-Demirtas, M.M. Mintz, and S.W. Snyder. 2015. An Overview of Biogas Production and Utilization
at Full-Scale Wastewater Treatment Plants (WWTPs) in the United States: Challenges and Opportunities Towards
Energy-Neutral WWTPs. Renewable & Sustainable Energy Reviews 50: 346-62. The WRRF counts in Table 5 sum to
fewer than the count of 1,250 WRRFs noted in the text; the remaining ~150 WRRFs in the WEF database that were
not noted in the 2015 Argonne study are presumed to have not had sufficient average flow rate data to be
categorized by size.
54 Lono-Batura, M., Y. Qi, and N. Beecher. December 2012. Biogas Production and Potential from U.S. Wastewater
Treatment. BioCycle 53(12): 46. https://www.biocvcle.net/2012/12/18/biogas-production-and-potential-from-u-s-
wastewater-treatment/. Citing U.S. EPA 2008 Clean Watershed Needs Survey.
55 Lono-Batura, M., Y. Qi, and N. Beecher. December 2012. Biogas Production and Potential from U.S. Wastewater
Treatment. BioCycle 53(12): 46. https://www.biocvcle.net/2012/12/18/biogas-production-and-potential-from-u-s-
wastewater-treatment/.
18
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DOE, nearly 1.5 billion cubic feet of digester gas from farms that could be recovered for energy are flared
each year.56
AgSTAR estimates that more than 8,000 large swine or dairy farms could create RNG from manure-based
digesters, including nearly 800 dairies in California alone (the largest dairy-producing state).57 As of March
2020, there were approximately 10 dairy digester projects under construction in California and another
31 under development.58 If all 8,000 of the candidate farms produced and captured biogas to produce
RNG, AgSTAR estimates they could create the equivalent of 1.3 billion diesel gallons, enough to fuel nearly
150,000 refuse trucks.59
Organic Waste Management Operations
EPA reports that about 94 percent of the food that is thrown away in this country is either landfilled or
combusted for energy. Of the 40.7 million tons of food waste generated in 2017, 30.6 million tons were
landfilled and 7.5 million tons were combusted with energy recovery. The remaining approximately 2.6
million tons were composted.60 In 2015, EPA and the U.S. Department of Agriculture created the U.S. 2030
Food Loss and Waste Reduction Goal, which includes a goal to reduce food waste going to landfills or
combustion with energy recovery by 50 percent over a 2010 baseline.61
AD facilities can process food waste that would otherwise be landfilled or combusted. In 2015, it was
estimated that the number of stand-alone AD facilities could double in the next five to ten years, while
processing capacity could quadruple in the next five years.62 It is also estimated that AD of 100 tons of
organic waste per day can generate enough biogas to create between 900 and 1,400 gasoline gallon
equivalents (GGE) of CNG per day, depending on the type of organic waste, AD technology used and CH4
capture efficiency of the RNG technology used.63,64,65
56 U.S. DOE. July 2016. 2016 Billion-Ton Report: Advancing Domestic Resources for a Thriving Bioeconomy.
https://www.energy.gov/sites/prod/files/2016/12/f34/2016 billion ton report 12.2.16 O.pdf.
57 U.S. EPA. June 2018. Market Opportunities for Biogas Recovery Systems at U.S. Livestock Facilities.
https://www.epa.gov/sites/production/files/2018-06/documents/epa430rl8006agstarmarketreport2Q18.pdf.
58 U.S. EPA. March 2020. Livestock Anaerobic Digester Database, https://www.epa.gov/agstar/livestock-anaerobic-
digester-database.
59 U.S. EPA. June 2018. Market Opportunities for Biogas Recovery Systems at U.S. Livestock Facilities.
https://www.epa.gov/sites/production/files/2018-06/documents/epa430rl8006agstarmarketreport2Q18.pdf.
60 U.S. EPA. November 2019. Advancing Sustainable Materials Management: 2017 Fact Sheet. EPA/530/F-19/007.
https://www.epa.gov/facts-and-figures-about-materials-waste-and-recvcling/advancing-sustainable-materials-
management.
61 U.S. EPA. United States 2030 Food Loss and Waste Reduction Goal, https://www.epa.gov/sustainable-management-
food/united-states-2030-food-loss-and-waste-reduction-goal. Accessed March 5, 2020.
62 EREF. August 2015. Anaerobic Digestion of Municipal Solid Waste: Report on the State of Practice.
63 U.S. EPA. March 2008. Anaerobic Digestion of Food Waste. Final Report. Table ES-1.
https://nerc.org/documents/anaerobic digestion report march 2008.pdf.
64 U.S. EPA. May 2017. LFGcost-Web. Version 3.2. https://www.epa.gov/lmop/lfgcost-web-landfill-gas-energy-cost-
model.
65 U.S. EPA. May 2019. Documentation for Greenhouse Gas Emission and Energy Factors Used in the Waste Reduction
Model (WARM). Organic Materials Chapters, https://www.epa.gov/sites/production/files/2019-
06/documents/warm v!5 organics.pdf.
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7.0 PURIFICATION PROCESSES AND GENERAL TECHNOLOGIES
Raw biogas, which is typically between 45 and 65 percent CH4 depending on the feedstock, must go
through a series of steps to be converted into RNG (at 90 percent CH4 or greater, depending on the
specification for the pipeline or other end use). Constituents of RNG that most often have specifications
or limits to meet are C02, 02, inert gases (including N2), total sulfur, H2S, siloxanes and VOCs. Other
properties that are prescribed by pipelines or end users include heating value, temperature, pressure and
moisture content.
Typical steps to convert raw biogas to RNG are reviewed below. As shown in Figure 2 and Figure 3, the
treatment can be divided into:
• Primary: basic moisture and particulate removal.
• Secondary: additional moisture removal, contaminant removal and compression.
• Advanced: C02, 02, N2 and VOC removal and further compression.
The primary and secondary treatment stages produce a medium-Btu gas, which means the heating value
of the gas is less than that of fossil natural gas (typically about half). The advanced treatment stage
produces RNG, with a heating value similar to fossil natural gas.
As part of advanced treatment, some CH4 is stripped out along with the C02 and other residual
constituents—especially H2S—and routed to a flare or thermal oxidizer for destruction. The amount of
CH4 stripped out as "tail gas" depends on the technology used to upgrade the gas, the ultimate CH4
specification for the RNG and the cost-benefit ratio of additional CH4 capture versus the additional capital
expense to achieve it.
Primary Treatment
Primary treatment consists of basic moisture and particulate removal from the raw biogas. The gas passes
through a knockout pot, filter and blower to remove moisture. This treatment is all that is required for
destroying the LFG in a combustion flare; in addition, some LFG energy projects have used only primary
treatment when combusting LFG in medium-Btu applications such as leachate evaporators, boilers and
kilns.
Secondary Treatment
Secondary treatment consists of additional moisture removal, contaminant removal and compression.
The process first uses an after cooler to condense and remove additional moisture, then removes
contaminants such as siloxanes and sulfur. The type of contaminants removed depends on the end use
and which constituents are present in the biogas and at what levels. The gas can also be compressed
further as needed. These secondary treatments are used to produce medium-Btu gas for direct thermal
applications such as boilers or for electricity generation applications such as engines and turbines.
Advanced Treatment
Advanced treatment is critical to transform biogas into RNG. Advanced treatment must remove C02, 02,
N2, VOCs and siloxanes (as needed), although some projects may remove these types of contaminants in
an earlier stage. The selection of the advanced treatment technology type is site-specific and project-
specific, and there are advantages and disadvantages to each type. Sections 7.1 through 7.4 describe
advanced treatment technologies in detail, along with their benefits and drawbacks.
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Fuel Specifications
For pipeline injection projects, regardless of the eventual end use at the other end of a pipeline network,
there is typically a higher CH4 content specification to meet than for onsite vehicle fuel projects. As a
result, these projects usually recover a higher fraction of the CH4, typically in the 96 to 98 percent range.
Pipeline specifications also put low limits on the levels of 02 and inert gases that are allowed in the RNG.66
Tail gas from these projects must be destroyed in a flare or thermal oxidizer, using supplemental fuel since
tail gas does not have a sufficient heating value to sustain combustion.
In the United States, CNG vehicle fuel project developers generally design projects to meet the technical
requirements set by the Society of Automotive Engineers Surface Vehicle Recommended Practice J1616™
for Compressed Natural Gas Vehicle Fuel (SAE J1616). SAE J1616 sets minimum requirements for CNG fuel
composition and properties to ensure vehicle, engine and component durability, safety and performance.
It provides technical requirements for several fuel properties and potential constituents including CH4,
sulfur compounds, 02 and particulate material. SAE J1616 references CARB's CNG commercial fuel
composition for several specifications, including 88 percent CH4 (minimum) and 1 percent 02
(maximum).67
7.1 CO2 Removal Technologies
There are four common ways to remove C02 during the advanced treatment stage: membranes, pressure
swing adsorption (PSA), solvent scrubbing and water scrubbing. Each technology has strengths and
weaknesses that are evaluated and balanced on a case-by-case basis for each potential RNG facility to
select the technology best suited for that particular site. Each technology can achieve RNG quality
standards necessary for pipeline injection or onsite vehicle use, but it is often a matter of upfront capital
expense versus ongoing operating expense.
Based on 2018 data in Argonne National Laboratory's database of RNG projects, the C02 removal
technology distribution for RNG projects at landfills in the United States was 27 percent using solvent
scrubbing, 24 percent using membrane systems, 10 percent using PSA and 8 percent using both
membranes and PSA, with the balance using water scrubbing or an unknown technology. For manure-
based AD biogas-to-RNG projects in the United States in 2018, 64 percent were using membrane systems,
12 percent were using PSA and 6 percent were using water scrubbing, with the balance using another
technology.68 Figure 7 and Figure 8 show these breakdowns in chart form.
66 Smyth, P., and J. Pierce. January 2011. Quantification of the Incremental Cost of Nitrogen and Oxygen Removal at
High-Btu Plants. Presented at 14th Annual EPA LMOP Conference and Project Expo. p. 33.
https://www.epa.gov/sites/production/files/2016-06/documents/smvth.pdf.
67 Society of Automotive Engineers International. March 2017. Recommended Practice for Compressed Natural Gas
Vehicle Fuel. Surface Vehicle Recommended Practice J1616™. Section 4, Technical Requirements, and Appendix D,
Table D.2, CARB Commercial Fuel Composition, https://www.sae.org/standards/content/il616 201703/.
68 Mintz, M., P. Vos, M. Tomich, and A. Blumenthal. October 2019. Database of Renewable Natural Gas (RNG) Projects:
2019 Update. Argonne National Laboratory, https://www.anl.gov/es/reference/renewable-natural-gas-database.
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Figure 7. C02 Removal Technologies for U.S. LFG-to-RNG Projects in 2018
Membrane
24%
Other or
Unknown
33%
PSA
10%
Solvent
Scrubbing
24%
Water
Scrubbing
2%
Membrane &
PSA
7%
Figure 8. C02 Removal Technologies for U.S. Manure-Based Biogas-to-RNG Projects in 2018
Other or
Unknown
18%
Water
Scrubbing
6%
PSA
12%
Membrane
64%
By comparison, Europe had more than 80 RNG projects in 2014, with approximately 65 percent of the
projects using water or solvent scrubbing, 23 percent using PSA and 11 percent using membranes,69
69 U.S. EPA. September 2016. Evaluating the Air Quality, Climate & Economic Impacts of Biogas Management
Technologies. EPA/600/R-16/099. https://nepis.epa.gov/Exe/ZvPDF.cgi/P100QCXZ.PDF?Dockev=P100QCXZ.PDF.
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Membrane Systems
A membrane is a type of filter that has a specific pore size rating and operates similarly to a screen or
sieve, retaining particles larger than the membrane's pore size. The material that the membrane is
constructed from and the method by which the large particles are captured is technology specific.
Membranes are often used to remove C02 and other unwanted constituents when upgrading raw biogas
to RNG.
Single-Pass Membrane System
Onsite CNG vehicle fuel use typically does not require a heating value as high as that required by pipeline
injection projects, and it also allows some minor levels of 02 and inert gases. Therefore, onsite vehicle
fuel applications with smaller biogas volumes often use a single-pass membrane system that captures
approximately 65 to 80 percent of the CH4. These systems either send the remaining 20 to 35 percent of
the CH4 out as tail gas for economical destruction in an onsite flare or blend it with the remaining biogas
for use in turbine or reciprocating engine electrical generating equipment. More efficient gas conditioning
technology that would produce a gas with a higher heating value is available for small biogas flows, but
historically it has not been economically feasible due to the added capital expense.
Multiple-Pass Membrane System
Larger-scale onsite vehicle fuel applications can use membrane technology similar to that of smaller-scale
applications, but with more efficient processes that capture additional CH4 via multiple passes through
the membranes. Many of these sites use gas conditioning technology that captures approximately 96 to
99 percent of the CH4. Tail gas from these projects must be destroyed in a flare or thermal oxidizer using
supplemental fuel, since the tail gas does not have a sufficient heating value to sustain combustion.70 The
increased volume of RNG produced from conditioning larger biogas volumes can typically justify the added
capital and operational expenses and the addition of a thermal oxidizer.
PSA
In PSA systems, adsorbent media are pressurized with the incoming biogas. A difference in molecular size
allows CH4 to pass through into the product gas, while the media capture C02 and, to a lesser extent, N2.
Once the media have been saturated, they are depressurized, and the C02 and N2 are released into the
tail gas stream. A typical PSA system employs multiple vessels operating in different stages of
pressurization, depressurization and regeneration. PSA can capture between 95 and 98 percent of the
CH4; the exact percentage will vary depending on the design of the PSA, which is optimized to balance
system performance and system economics.
Solvent Scrubbing
Solvent scrubbing processes use a chemical solvent such as amine or a physical solvent like Selexol to strip
C02 and H2S from the biogas stream. C02 is adsorbed into the solvent, allowing CH4 to pass through into
the RNG product stream. In an amine system, the solution is heated in a separate vessel to release the
C02 into the tail gas stream; in a Selexol process, the solvent is depressurized, which releases the C02.
CH4 capture efficiency varies between 97 and 99 percent for physical solvents but is often greater than
99 percent for amine solvents given that amine solutions are particularly selective for C02.
70 U.S. EPA. September 2016. Evaluating the Air Quality, Climate & Economic Impacts of Biogas Management
Technologies. EPA/600/R-16/099. p. 29.
https://nepis.epa.gov/Exe/ZvPDF.cgi/P100QCXZ.PDF?Dockev=P100QCXZ.PDF.
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Water Scrubbing
Water scrubbing (sometimes called water wash) is a simple process in which the biogas is pressurized into
water. C02 is adsorbed into the water while the CH4 passes through into the RNG product gas stream. The
water is then depressurized, and the C02 is allowed to pass through in the tail gas. CH4 capture efficiency
of water scrubbing systems is typically greater than 99 percent.
Biogas Flow Rates for C02 Removal Technologies
Each C02 removal technology allows for a different range of biogas flow rates. Typical flow rates for the
four main technologies are summarized in Table 6. Process flow diagrams of the four main types of
advanced C02 removal technologies (membrane, solvent, PSA, water scrubbing) were presented in a
webinar by LMOP Industry Partner DTE Biomass Energy.71
Table 6. Typical Flow Rates for Advanced C02 Removal Technologies
Technology
Inlet Biogas Flow Range (standard cfm [scfm])
Single-Pass Membrane
50 to 400
Multiple-Pass Membrane
200 to 5,000+
PSA
800 to 5,000+
Solvent Scrubbing
1,000 to 5,000+
Water Scrubbing
50 to 3,000
Additional discussion of primary, secondary and advanced treatment is available in Chapter 3 of the LMOP
LFG Energy Project Development Handbook.72
7.2 VOC/Siloxane Removal Technologies
For any vehicle fuel or pipeline injection project, a critical part of the LFG conditioning process is the
removal of VOCs and siloxanes. Even trace amounts of siloxanes can damage engines, turbines and
compressors and so must be removed. VOCs are an environmental pollutant that would be sufficiently
destroyed in an engine or turbine, but they are similar in molecular structure to siloxanes. This means any
medium that is designed to remove siloxanes will also capture VOCs—usually one cannot be removed
without capturing the other.
The concentration of siloxanes within biogas can vary widely by source type and the specific site. A 2017
report prepared by the California Biogas Collaborative noted the following ranges by source type for
siloxane concentrations in raw biogas: 0 to 400 milligrams per cubic meter (mg/m3) for WRRFs, 0 to 50
mg/m3 for landfills and 0 to 0.2 mg/m3 for livestock farms (no results available for stand-alone MSW
digesters).73 These results indicate that siloxane contamination is a potential issue mainly with WRRF
biogas and LFG, primarily because siloxanes are found in many cosmetic, health and beauty products.
71 Hill, M.R. November 2017. Upgrading Landfill Gas to Pipeline Quality Natural Gas.
https://www.epa.gov/sites/production/files/2017-ll/documents/lmop webinar november 16 2017.pdf.
72 U.S. EPA. June 2017. LFG Energy Project Development Handbook, https://www.epa.gov/lmop/landfill-gas-energy-
proiect-development-handbook.
73 California Biomass Collaborative. January 2017. Renewable Energy Resource, Technology, and Economic
Assessments. Appendix H—Task 8: Comparative Assessment of Technology Options for Biogas Clean-Up. CEC-500-
2017-007-APH. https://cwec.ucdavis.edu/wp-content/uploads/03-16-2017-CEC-500-2017-007.pdf.
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For projects with smaller gas flows or projects with higher gas flows but relatively low concentrations of
VOCs and siloxanes, a non-regenerative carbon medium is typically used to remove the contaminants.
Companies that specialize in the removal of these compounds will analyze gas samples and prepare a site-
specific carbon medium 'recipe' best suited for removing them. Under normal operation, gas quality is
periodically monitored to determine when the medium is saturated and replacement is necessary. These
types of media can be disposed of in a landfill, and no other special handling is required.
For higher gas flows or projects with high concentrations of VOCs or siloxanes, a regenerative process is
required. As with the non-regenerative systems, a medium is used to capture the contaminants, but
instead of disposing of media once saturated, the media are regenerated through a temperature or PSA
process. VOCs and siloxanes de-adsorb with a change in pressure or temperature and are directed to a
flare for combustion. These flares require pilot gas to fuel the flare, which can be either biogas, propane
or fossil natural gas.
7.3 N2 Removal Technologies
N2 removal (or rejection) may be required as a part of the biogas conditioning system, depending on the
biogas inlet N2 levels and the required RNG specifications. Because of the potential intrusion of ambient
air (which contains N2) when biogas is collected from landfills, N2 is typically more of an issue in LFG as
compared to biogas from anaerobic digesters. An exception to this can be biogas collected from
agricultural waste lagoons with membrane covers, as these systems can also allow air leaks into the gas
stream.
N2 is difficult and expensive to remove from biogas given the similar diameters of N2 and CH4 molecules,
which are approximately 3.6 angstroms and 3.8 angstroms, respectively.
Nitrogen rejection systems remove N2 gas from biogas streams via PSA or membranes. The typical RNG
conditioning process initially removes trace-level contaminants and most C02, while allowing N2 to pass
through the system with the CH4. A secondary N2-specific rejection system may be required at the end of
the gas conditioning system to remove N2 to acceptable end use levels. Some biogas conditioning systems
remove N2 concurrently with C02 using adsorbents that have a high kinetic selectivity toward N2 and 02.
N2 removal processing can reduce the CH4 recovery rates—the impact on CH4 recovery varies depending
on the inlet N2, outlet N2 specifications and the technology used to remove the N2. In one example, the
CH4 recovery drops from 90 to 81.5 percent when an N2 and 02 removal unit is added to the process.74
74 Smyth, P., and J. Pierce. January 2011. Quantification of the Incremental Cost of Nitrogen and Oxygen Removal at
High-Btu Plants. Presented at 14th Annual EPA LMOP Conference and Project Expo.
https://www.epa.gov/sites/production/files/2016-06/documents/smvth.pdf.
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Many system designers and project developers advocate for
reducing the N2 content at the source, prior to biogas
conditioning, as a more cost-effective method of achieving
the outlet N2 specification. There are hardware and
software options available to help LFG system operators
improve wellfield efficiencies and mitigate cleanup costs. An
LMOP 2017 webinar provides information on landfill
wellfield design, construction and operational
considerations for RNG projects.75
LMOP's RNG Flow Rate Estimation Tool76 can serve as a
screening guide to help stakeholders quickly estimate
normalized gas flows for LFG-to-RNG projects.
7.4 O2 Removal Technologies
Many natural gas utilities have strict limits on 02 for RNG that is injected into a pipeline network. Excessive
amounts of 02 can accelerate pipeline infrastructure corrosion, resulting in many utilities setting the
upper limit of allowable 02 from 0.2 percent to as low as 2 parts per million. For RNG used directly in
vehicles, SAE J1616 has no limit for 02 due to the low water vapor content requirements. CARB's
specifications for commercial CNG chemical composition set a 1 percent 02 upper limit. While it is usually
feasible to reduce 02 in LFG to less than 1 percent through wellfield tuning and improvements, 02 removal
systems are often required for pipeline injection projects on landfills.
Stand-alone 02 removal systems remove 02 through a catalytic reactor and typically are the last step in
the LFG conditioning process. Biogas is heated and passed over a catalyst bed, where the 02 reacts with
some of the CH4 to create C02 and water. The biogas exiting the reactor is saturated with moisture and
must be dehydrated, typically by using a desiccant dryer or temperature swing adsorption process. Other
processes involved in the conditioning of LFG, such as membrane separators and PSA, do remove some
02, which must be considered when designing and sizing a project. Some PSA systems are also effective
in removing nearly all 02.
Due to the added capital and operating costs of incorporating an 02 removal system, these systems are
often found to be cost-prohibitive for projects with an LFG flow rate less than 1,000 scfm. Costs to heat
the biogas and remove moisture must also be considered when developing project financials. These
systems may negatively impact CH4 capture efficiency and add C02 to the product gas stream as well. The
CH4 loss and C02 addition are small, but not negligible.
7.5 The Future of RNG Processing Technologies
There are continuing advancements in RNG processing technologies to improve CH4 recovery rates,
reduce the impacts of elevated N2 and reduce the energy intensity of each process. Increased selectivity
in membrane and PSA systems, along with solvent technology, continue to be developed. These
improvements will likely continue as long as there is a strong market for RNG.
LMOP's RNG Flow Rate Tool calculates
the adjusted flow rate and
corresponding heat content (Btu) value
of LFG after adjusting a wellfield to
meet the inlet specifications for RNG
treatment/processing technology.
Treatment technologies often specify
that the inlet gas must contain N2
levels lower than what may be typically
measured in LFG; adjusting the
collection system to achieve N2 levels
may impact the LFG flow rate.
75 U.S. EPA. November 2017. Wellfield Operations and Technologies for Upgrading Landfill Gas.
https://www.epa.gov/lmop/wellfield-operations-and-technologies-upgrading-landfill-gas. Accessed April 3, 2019.
76 U.S. EPA. January 2020. Renewable Natural Gas Flow Rate Estimation Tool, https://www.epa.gov/lmop/renewable-
natural-gas-flow-rate-estimation-tool.
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7.6
Reliable Power Sources for Advanced Treatment
Advanced treatment to upgrade biogas into RNG requires a reliable power source. The power can be
purchased from the grid or generated on site.
If the electricity market pricing is favorable and enough power service is available at the location of the
project, the local electric utility can power the processing plant. Even with reliable power purchased from
the grid, some RNG projects have backup emergency generators to power the processing in the case of a
power outage.
Some RNG projects also generate power for the production facility on site. If the process is powered with
renewable energy such as solar, wind, excess biogas not sent to the RNG processing plant or even residual
tail gas from the RNG processing plant, the overall CI of the LFG-to-fuel pathway can be reduced, which
could result in additional credits from RNG used for transportation fuel.
The tail gas left over from the upgrading process has a diluted CH4 content that can typically vary from
less than 1 percent to as much as 30 percent. For example, at the Cedar Hills Regional Landfill in
Washington, the tail gas from the RNG processing plant is mixed with unconditioned LFG and routed to a
series of 300-kilowatt Detroit Diesel engines modified for biogas operation, which generate 4 to 5
megawatts of electricity or approximately 80 percent of the electricity needed to run the plant.77
7.7 Compressing RNG
Final compression of the RNG depends on how the gas will be used. For vehicles, final CNG storage
compression is around 3,500 pound-force per square inch gauge (psig). If the gas is transported via
tube/tank trailer, the compression can be as high as 4,000 psig, while for pipeline injection, the
compression varies between 50 to 1,000 psig depending on the interconnect location and the pipeline.78
8.0 BARRIERS, POLICY DRIVERS AND INCENTIVES RELATED TO RNG PROJECT
DEVELOPMENT
RNG project development faces two main types of barriers: economic and technical. The economics of
project development can be challenging to overcome, primarily due to the abundance and prolonged low
cost of fossil natural gas. Under current market conditions, it is more expensive to produce RNG from any
feedstock than it is to purchase fossil natural gas. This price disparity is often amplified by the challenges
and costs associated with pipeline interconnection to move the RNG to end use customers.
On the technical side, upgrading raw biogas to RNG requires meeting numerous gas quality specifications,
which can vary by state or pipeline system and can be difficult to achieve cost-effectively depending on
the biogas source. Additionally, utilities may have the misconception that RNG is not as clean as, or is
somehow lower in quality than, fossil natural gas. The following sections describe the nature of each
barrier in detail, with solutions to overcome them.
77 U.S. EPA. March 2020. Landfill and LFG Energy Project Database (LMOP Project IDs 1685-0 and 1685-1).
https://www.epa.gov/lmop/landfill-gas-energy-proiect-data. See also http://www.bioenergv-wa.com/faq/.
78 American Biogas Council. How to Make RNG/Biomethane. https://americanbiogascouncil.org/resources/how-to-
make-rng-biomethane/. Accessed March 28, 2019.
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8.1
Economic Barriers
The two main economic barriers to producing RNG are the capital and operating costs associated with
capturing and cleaning biogas into RNG, relative to the current low price of fossil natural gas, and the cost
of delivering RNG to customers, often by building a pipeline interconnection or investing in equipment to
deliver the RNG another way. Because fossil natural gas has been less expensive to produce in recent
years, it is difficult for RNG to be cost-effective on a straight economic basis. The cost disparity between
RNG and conventional fossil natural gas production can be mitigated by policy or legislation that creates
demand for and premium pricing for RNG. In addition, in some cases the cost to capture the biogas can
be considered a "sunk" cost because the facility has already put in biogas collection infrastructure apart
from the RNG (biogas upgrading) project.
Without a pipeline interconnection, it is often difficult to link an RNG supply to customer demand, which
could be local or remote. However, the costs associated with gas cleanup and/or interconnection can be
reduced through scale economies from partnerships and shared infrastructure, such as digester clusters
that share a single upgrading skid and injection point.
Cost of Processing to RNG Quality
The 2019 average Henry Hub spot price of fossil natural gas was $2.57 per million Btu ($3.17 in 2018 and
$2.99 in 2017).79 At this price, it is impossible for RNG to directly compete with the market price of fossil
natural gas (i.e., without environmental attribute value), given the costs associated with capturing biogas
and processing it into RNG. A collaborative study published in 2016 determined a cost range of $7 per
million Btu (very large-scale) to $25 per million Btu (small-scale) for projects upgrading biogas to RNG for
pipeline injection.80 While state and federal environmental attribute market incentives (i.e., credits) exist,
particularly for use as an on-road transportation fuel, the pricing and stability of environmental attributes
created under these programs can be volatile. For example, between March 2015 and March 2020, the
price of D3 Renewable Identification Numbers (RINs) under the EPA RFS was as low as $0.48 and as high
as $2.95.81 Given this volatility, some financial institutions may be hesitant to accept these credits, or
apply a steep discount to the credit value when calculating the potential revenue these environmental
attributes may provide to a project.82 It takes a certain type of investor with a particular risk profile to be
comfortable with financing an RNG project. Additional policy mechanisms and voluntary or mandatory
markets to create longer-term stability and additional value for RNG's environmental attributes,
regardless of how the RNG is ultimately used, would help encourage investment or allow for longer-term
purchase agreements, similar to how RPS programs for electricity helped generate longer-term power
purchase agreements (PPAs) with premium pricing for electricity projects.
Cost of Pipeline Interconnection
Pipeline interconnection can be a significant barrier to RNG project implementation, particularly when
working with local distribution companies. The interconnection equipment, pipeline extensions and an
often-lengthy planning process can add costs to the point of making a project uneconomical. In California,
79 U.S. EIA. Natural Gas. April 2020. Henry Hub Natural Gas Spot Price.
https://www.eia.gov/dnav/ng/hist/rngwhhdm.htm. Accessed April 30, 2020.
80 U.S. EPA. September 2016. Evaluating the Air Quality, Climate & Economic Impacts of Biogas Management
Technologies. EPA/600/R-16/099. https://nepis.epa.gov/Exe/ZvPDF.cgi/P100QCXZ.PDF?Dockev=P100QCXZ.PDF.
81 U.S. EPA. RIN Trades and Price Information, https://www.epa.gov/fuels-registration-reporting-and-compliance-
help/rin-trades-and-price-information. Accessed April 29, 2020.
82 M.J. Bradley & Associates. July 2019. Renewable Natural Gas Project Economics.
https://www.mibradlev.com/sites/default/files/RNGEconomics07152019.pdf.
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for example, interconnection costs average between $1.5 and $3 million per site, depending on facility
size and location (see Figure 9).83 These high costs and long lead times can be challenging for RNG project
developers and make projects difficult to finance. In addition, utilities that are required to provide least-
cost services to their customers are restricted from taking on these added costs without regulatory
approval(s), adding to the complexity.
An impediment to many manure-based and small stand-alone and wastewater digester projects pursuing
RNG pipeline injection is the high cost of natural gas utility interconnects as compared to the relatively
small quantity of RNG produced per project. However, in recent years, the cost and scale at which biogas
cleanup technology can work has been reduced considerably.
Moreover, multiple projects have successfully enabled development and use of a single interconnect
(injection point) for aggregating biogas from more than one manure-based digester project. Under this
"hub and spoke" model, partially conditioned biogas can be transported to one RNG conditioning and
utility interconnect location or multiple RNG gas conditioning facilities can transport RNG fuel via a virtual
pipeline with compressed gas tube trailers to a common interconnect location. Each method has been
demonstrated in the past few years.
8.2 Technical Barriers
Varying Specifications for RNG Injection
In the United States, hundreds of independent gas systems make up the natural gas pipeline network, and
each system has its own requirements. Some of these requirements, such as elevated heating (Btu) values,
may effectively prohibit RNG interconnection. For example, a project may not be able to get financing out
of concern that the RNG will not consistently meet strict specifications, leading to lost revenue. If pipeline
specifications were more standardized, there would be more clarity and certainty for RNG project
developers as well as equipment and technology providers.
In California, Southern California Gas Company (SoCalGas) Rule 30 included a minimum heating value of
990 Btu/scf as one of its pipeline requirements. Given the technical and economic challenges of
consistently meeting that specification (equivalent to 98 percent CH4), very few RNG projects were built
in California. In fact, more than 95 percent of the RNG earning LCFS credits in 2017 was sourced from out-
of-state facilities.84 SoCalGas undertook extensive testing to evaluate whether any RNG with a lower
heating value could be accepted into the pipeline without introducing risk to the pipeline network.
Because of the tests, Rule 30 was amended in 2017 to allow the interconnection parties to request a gas
quality deviation for lower heating values. However, the California Public Utilities Commission (CPUC)
must approve any waiver before the RNG is injected into the pipeline, which adds time and cost to a
project.85
Treatment Processes
Another potential challenge in developing an RNG project is the quality of the source biogas. While it is
technically possible to condition biogas of almost any quality into RNG, systems that can process large
flows of biogas at extremely low CH4 concentrations or with high levels of undesirable constituents (such
83 CPUC. June 2015. Decision Regarding the Costs of Compliance with Decision 14-01-034 and Adoption of Biomethane
Promotion Policies and Program. Decision 15-06-029.
http://docs.cpuc.ca.gov/PublishedDocs/Published/G000/M152/K572/152572Q23.PDF.
84 Notes from attending US Biogas 2017 conference.
85 Lucas, J. October 2017. SoCalGas' Interconnection Process, Tools and Improvements. Presented at US Biogas 2017.
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as H2S, VOCs, siloxanes, N2, or 02) are difficult to scale down to smaller flow ranges. This can eliminate
projects from consideration until the inlet biogas quality can be increased. Non-landfill sources of biogas
typically generate lower biogas flows than landfills do, but the biogas is cleaner than LFG (e.g., greater
than 60 percent CH4 and less costly to purify).
For landfills, one of the largest impediments to additional RNG project development is the presence of N2
in the LFG. N2 is an inert gas that reduces the heating value of the RNG, and with most gas conditioning
technologies it is difficult to remove. Gas conditioning technology or LFG wellfield operational changes
that can address these elevated N2 levels are discussed in Section 7.0.
8.3 Perception of RNG Quality
One common misconception about RNG is that it is of sub-par quality (e.g., has higher contaminant levels)
compared to fossil natural gas. Comparisons of constituent concentrations for fossil natural gas and RNG
from three types of feedstocks by the Gas Technology Institute show that RNG typically has lower or
similar concentrations for pollutants such as C02, 02, H2S, total sulfur, aromatic hydrocarbons and other
VOCs, while RNG typically has higher concentrations of pollutants such as metals, siloxanes and
halocarbons.86 Education can help to inform project stakeholders and the public about RNG and its
development while emphasizing the benefits that can be realized from these projects. Several groups have
created outreach materials to educate different audiences and to provide technical assistance to
stakeholders evaluating RNG projects. For example:
• SoCalGas developed an RNG tool kit that includes the basics of RNG, information on
upgrading technologies, gas specifications, interconnection questions, incentives, and other
tools and resources. Other than the broad overview materials, most of these resources are
specific to California.
• The Coalition for Renewable Natural Gas provides state and federal policy tracking, data for
RNG projects, a model pipeline specification and reports.
• The U.S. DOE Alternative Fuels Data Center provides data and tools related to RNG, with an
emphasis on vehicle fuel applications.
• Energy Vision has profiled many RNG projects and compiled several reports and fact sheets
detailing the environmental, economic and air quality benefits this strategy achieves.
8.4 Policies and Incentives Related to Pipeline Injection
A policy change that can help overcome RNG project development barriers is the establishment of
interconnection incentives and flexible, transparent biogas quality guidelines for pipeline injection.
Interconnection incentive programs help developers offset the upfront costs of establishing a project.
Established yet flexible quality guidelines or standards make it easier for developers to design the proper
biogas treatment system for the appropriate amount of upgrading to meet the specifications. Examples
of incentive programs and biogas quality standards for pipeline injection are discussed below.
Example: Policies and Incentives in California
California Senate Bill (SB) 1383 directed CARB to implement regulations to reduce CH4 emissions by
40 percent by 2030 as compared to 2013 levels. Further, given dairy farming's prominent contribution to
Wiley, Kristine. October 2018. Renewable Natural Gas (RNG): Gas Quality Considerations. Presented at 2018 Natural
Gas STAR and Methane Challenge Renewable Natural Gas Workshop, https://www.epa.gov/natural-gas-star-
program/2018-natural-gas-star-and-methane-challenge-renewable-natural-gas-workshop.
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CH4 emissions in the state, SB 1383 included provisions directing gas corporations to implement at least
five (combined total in the state, not per corporation) dairy-based RNG pipeline injection projects. The bill
allows for "reasonable pipeline infrastructure costs" to be recoverable in the rates.87
The California biomethane interconnection incentive program has $40 million available to offset
interconnection costs through December 31, 2021. The program provides 50 percent of eligible biogas
collection and interconnection costs (up to $5 million per project) for cluster (three or more) dairy projects
and 50 percent of eligible interconnection costs (up to $3 million per project) for other RNG sources
including landfills, WRRFs, stand-alone organic waste digesters and non-cluster (one or two) dairy
projects.88-89
SoCalGas has estimated the life cycle costs to upgrade biogas into RNG and inject it into the pipeline and
analyzed the relative cost of each component to help prospective projects evaluate the major cost drivers
in their projects. The cost breakdown in Figure 9 incorporates a $3 million subsidy from the biomethane
interconnection incentive program for eligible interconnection costs.90
Figure 9. Breakdown of RNG Processing and Interconnection Costs91
Pipeline
Location
is Key!!
Breakdown
includes
interconnection
subsidy of 50%,
maximum of
$3.0 million per
project
87 Lucas, J. September 2017. Renewable Natural Gas Projects. Presented at EPA Technology Transfer Workshop:
Renewable Natural Gas—Driving Value for Natural Gas and Biogas Sectors.
https://www.epa.gov/sites/production/files/2017-10/documents/lucas rng 2017 panell.pdf.
88 Lucas, J. September 2017. Renewable Natural Gas Projects. Presented at EPA Technology Transfer Workshop:
Renewable Natural Gas—Driving Value for Natural Gas and Biogas Sectors.
https://www.epa.gov/sites/production/files/2017-10/documents/lucas rng 2017 panell.pdf.
89 California State Assembly. September 2016. AB 2313: Renewable Natural Gas: Monetary Incentive Program for
Biomethane Projects: Pipeline Infrastructure.
https://leginfo.legislature.ca.gov/faces/billTextClient.xhtmlPbill id=201520160AB2313. Accessed April 3, 2019.
90 Lucas, J. September 2017. Renewable Natural Gas Projects. Presented at EPA Technology Transfer Workshop:
Renewable Natural Gas—Driving Value for Natural Gas and Biogas Sectors.
https://www.epa.gov/sites/production/files/2017-10/documents/lucas rng 2017 panell.pdf.
91 Lucas, J. September 2017. Renewable Natural Gas Projects. Presented at EPA Technology Transfer Workshop:
Renewable Natural Gas—Driving Value for Natural Gas and Biogas Sectors.
https://www.epa.gov/sites/production/files/2017-10/documents/lucas rng 2017 panell.pdf. Figure used with
permission from Southern California Gas Company.
Estimated Breakdown of Lifecycle Costs to Produce and Inject RNG into the
{based on 1.5 million scfd of biogas for 15 years}
1.5 million scfd
<2
Pipeline Extension Cost
Incremental Testing a
Monitoring
I?
/
¦ Utility Point of Receipt O&M
¦ Utility Point of Receipt - Upfront
¦ Capital - Biogas Upgrading
¦ O&M - Biogas Upgrading
Labor/Materials
¦ O&M - Biogas Upgrading
Parasitic Load
n
1,000 10,560
Length of Pipeline Extension (Feet)
1) Pipeline Extension costs are based on installing pipeline in roads with curb/gutters.
2) Estimated costs assume testing for all 17 biogas constituents and includes the cost
q p ip \ of the tests and associated labor.
OOUcllUaS a yy Sempra Energy utility
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Example: Policies and Incentives in Washington
On March 22, 2018, the Governor of Washington signed House Bill 2580, "Promoting Renewable Natural
Gas."92 This established a voluntary program that encourages increased production of RNG through tax
incentives and tools, including an inventory of potential RNG supply and associated costs. The legislation
also directed relevant state agencies and regulatory bodies to establish voluntary gas quality standards
for injection of RNG into the natural gas system, and policy recommendations to promote RNG
development. The Washington State Department of Commerce and Washington State University's Energy
Program, an LMOP State Partner, jointly provided a study to the legislature in December 2018, with an
inventory of RNG opportunities and information on economics and policies related to RNG project
development within the state.93
Example: Gas Quality Standards at a State Level
Illinois set standards in the mid-1980s for transportation of natural gas, including CH4 from landfills. The
gas must meet the standards implemented by the Illinois Commerce Commission before it may be placed
into the public utility gas system.94
Missouri has historical quality standards for natural gas that are applicable to all gases being furnished by
a utility that falls under the jurisdiction of the Missouri Public Service Commission.95 This standard was
established before "RNG" was a common term, but RNG is included because the standard is applicable to
all gas distributed in the state.
Example: Gas Quality Standards at the Utility Level
The Coalition for Renewable Natural Gas tracks gas quality specifications for more than 40 major
transmission gas pipeline operators in the United States, with links to their tariffs.96
Example: Interconnect Guide for RNG in Northeastern States
In September 2019, the Northeast Gas Association and the Gas Technology Institute published a guide to
provide a technical framework for introducing RNG into the natural gas distribution pipeline network in
parts of the northeastern United States. Although basic criteria had been established for alternative gases
including RNG, inconsistent approaches to evaluating acceptance criteria and trace constituent
composition had proven to be a barrier to wide-scale acceptance of RNG directly into distribution
networks. The guide was written to maximize acceptance of this valuable energy resource, by minimizing
technical uncertainty and better quantifying potential risks, without compromising public safety and
92 Washington State Legislature. Bill Information: HB 2580-2017-18.
https://app.leg.wa.gov/billsummarvPBilINumber=2580&Year=2017. Accessed March 27, 2019.
93 Washington State Department of Commerce and Washington State University Energy Program. December 2018.
Promoting Renewable Natural Gas in Washington State, http://www.commerce.wa.gov/wp-
content/uploads/2019/01/Energv-Promoting-RNG-in-Washington-State.pdf.
94 Illinois Public Utility Commission. 1987. Safety and Quality Standards for Gas Transportation for a Private Energy
Entity by Gas Utilities. Section 530.10: Standards.
http://www.ilga.gov/commission/icar/admincode/083/0830Q530sections.html. Accessed March 27, 2019.
95 Missouri Public Service Commission. 2019. Rules of Department of Economic Development: Division 240—Public
Service Commission. Chapter 10—Utilities. Standards of Quality. 4 CSR 240-10.30.
https://www.sos.mo.gov/cmsimages/adrules/csr/current/4csr/4c240-10.pdf.
96 Coalition for Renewable Natural Gas. Major Transmission Pipeline Tariffs, http://www.rngcoalition.com/pipeline-
database. Accessed April 3, 2019.
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facility integrity. The guideline also addresses current challenges to RNG injection through the following
objectives:97
• Provide a consistent approach for assessing project viability.
• Define requirements to avoid interruption of service.
• Provide a standardized framework to reduce uncertainty and optimize design.
• Outline structure for the RNG development process.
• List roles and responsibilities for each party.
The guideline includes helpful elements such as a process flow diagram, checklists, proposed biogas
constituent sampling plans, a list of technical references and a sample interconnect agreement.
8.5 Policies and Incentives Related to Use of RNG as Transportation Fuel
Federal
The federal RFS requires obligated parties to meet a Renewable Volume Obligation based on the amount
of petroleum-based fuels they produce or import annually; one way to meet the Renewable Volume
Obligation is by obtaining tradeable credits known as RINs. which are issued to producers of renewable
fuels. To generate RINs, a fuel must meet one of the EPA-approved pathways. RNG can fall under two
different RIN categories based on the biogas source:
• D3, the category for biogas from landfills, municipal wastewater treatment facility digesters,
agricultural digesters, and separated MSW digesters; and biogas from the cellulosic
components of biomass processed in other waste digesters.
• D5, the category for biogas from waste digesters (e.g., organic fraction of municipal solid
waste or food waste).
State-Specific LCFSs
California's LCFS was designed to encourage the use and production of cleaner low-carbon fuels in the
state. The LCFS sets CI targets that transportation fuel providers in the state must meet each year. The CI
targets decrease over time, which results in a higher percentage of lower CI fuels (e.g., natural gas, RNG,
hydrogen, electricity) in the fuel mix. The LCFS parameters are expressed in terms of the CI of gasoline
and diesel and the fuels that replace them. A fuel's CI is the measure of GHG emissions associated with
producing and consuming it and is based on a complete life cycle analysis. Fuels with CIs lower than the
annual standard set by the LCFS generate credits, while fuels with higher CIs generate deficits. The LCFS
includes various fuel pathways, including for RNG made from the various feedstocks of anaerobic digester
biogas or LFG.98
Oregon's Clean Fuels Program seeks to reduce the CI of transportation fuels in Oregon. It functions very
similarly to California's LCFS and also includes approved pathways for RNG made from AD biogas or LFG
97 Northeast Gas Association and Gas Technology Institute. August 2019. Interconnect Guide for Renewable Natural
Gas (RNG) in New York State, https://www.northeastgas.org/pdf/nga gti interconnect 0919.pdf.
98 California Low Carbon Fuel Standard, California Code of Regulations, Title 17, Sections 95480-95489; 95491-95497.
https://www.arb.ca.gov/regact/2015/lcfs2015/lcfsfinalregorder.pdf.
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as the feedstock." The CFP includes standards for gasoline and its fuel substitutes and diesel and its fuel
substitutes.
National Ambient Air Quality Standards
Local jurisdictions that are unable to meet EPA-established National Ambient Air Quality Standards must
develop strategies to attain the standards, including a timeline to achieve compliance. In urban areas of
non-attainment for ozone and PM, transportation-related emission reduction strategies must be part of
the solution. Replacing heavy-duty diesel vehicles with natural gas vehicles running on RNG provides near-
zero emissions of NOx and serves as a low-carbon alternative. This can be an important part of the
implementation plan for these urban centers to achieve attainment.
Municipal Natural Gas Fleet Conversion
Municipal vehicle fleets—especially transit buses and refuse trucks—are often among the largest fuel
consumers in a city. Many U.S. cities have committed to reducing the petroleum dependency of their
fleets by replacing their existing fleets with vehicles that run on alternative fuel, including RNG. In 2016,
eight major cities (Atlanta, Charlotte, Indianapolis, Orlando, Rochester, Sacramento, San Diego and West
Palm Beach) formed the Energy Secure Cities Coalition, with a combined goal of replacing 50,000
petroleum-fueled vehicles with alternative-fueled vehicles by 2025.100
In addition to city-owned fleet upgrades, other municipalities have built CNG fleet requirements into their
franchise agreements with third-party waste haulers that operate within their jurisdiction to achieve
greener fleets. For example, in Seminole County, Florida, two waste haulers that cover approximately
65,000 homes are required to replace their diesel trucks with CNG vehicles by the end of 2020.101 The EPA
Managing and Transforming Waste Streams Tool has sample franchise agreement language for requiring
CNG or other alternative fuel vehicles.102
8.6 State Regulatory Policies and Incentives Related to Electricity
While power prices have been relatively low and are forecasted to remain low for the foreseeable future,
some state RPS programs have renewable energy certificates (RECs) that are favorable to RNG derived
from biogas.
In 2018 legislation, California adopted an updated and aggressive RPS under SB 100. The RPS now requires
60 percent renewables-sourced electricity by 2030 and 100 percent carbon-free electricity by 2045. RNG
is eligible to generate RECs if certified by the California Energy Commission (CEC) but Assembly Bill 2196
99 Oregon Department of Environmental Quality. Fuel Pathways—Carbon Intensity Values.
https://www.oregon.gov/deq/ghgp/cfp/Pages/Clean-Fuel-Pathways.aspx. Accessed December 23, 2020.
100 Securing America's Future Energy. March 2016. Eight Major Cities Unite to Form Energy Secure Cities
Coalition—Fleets Embracing Alternative Fuels to Improve America's National and Economic Security.
https://archive.secureenergv.org/press/eight-maior-cities-unite-to-form-energy-secure-cities-coalition-fleets-
embracing-alternative-fuels-to-improve-americas-national-and-economic-securitv/.
101 Comas, M.E. July 2017. Seminole Switching to Natural-Gas Garbage Trucks. Orlando Sentinel.
http://www.orlandosentinel.com/news/seminole/os-seminole-countv-waste-natural-gas-20170727-storv.html.
102 U.S. EPA. Managing and Transforming Waste Streams—A Tool for Communities.
https://www.epa.gov/transforming-waste-tool/local-government-clauses-transforming-waste-streams-
communitiesffpurchasing. Accessed July 22, 2019.
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in 2012 reduced reliance on non-California RNG for the purposes of RPS compliance; this provides
additional incentive for potential RNG producers located in California.103
California's SB 1122 created the Bioenergy Market Adjusting Tariff, which offers eligible small bioenergy
renewable generators the opportunity to export electricity to the state's three large investor-owned
utilities through a fixed-price standard contract. Category 1 covers biogas from WRRFs, municipal organic
waste diversion, food processing and co-digestion, while category 2 covers dairy and other agricultural
bioenergy. This has created an opportunity for smaller biogas projects (less than 3 megawatts) to receive
long-term PPAs.104
The North Carolina RPS, whose targets are not as aggressive as California's, has an animal waste carve-
out that is driving investment in manure-based RNG-to-electricity projects. As a result, these RNG projects
can negotiate for long-term PPAs to help utilities achieve the mandated RPS targets. Swine waste carve-
outs constituted 0.07 percent of prior year retail sales in 2017, constituted 0.14 percent of prior year retail
sales in 2019 and will constitute 0.20 percent of prior year retail sales by 2022.105 See Section 9.0 for a
cluster project example in Missouri that is being used to satisfy North Carolina RPS requirements.
As of April 2020, 30 states, Washington, D.C., and three territories had an RPS for electricity; seven states
and one territory had a Renewable Portfolio Goal for electricity; three states had a Clean Energy Standard;
and two states had a Clean Energy Goal.106107
8.7 Policies and Incentives Related to Sustainability and Environmental Goals
Limited incentives and policy drivers are currently available to direct thermal end uses of RNG, but some
state and local voluntary programs are emerging. Additionally, corporate sustainability goals create
demand for RNG, including goals that involve carbon footprint reductions or other types of emission
reductions.
More than 20 states are initiating economy-wide GHG targets, setting long-term goals and implementing
policies to achieve GHG reductions.108 As these policies are implemented, they can affect all industries
operating in the state, including local distribution companies. As a result, these companies are searching
for lower-carbon feedstocks to reduce their carbon footprint.
Much like a consumer would pay to participate in a voluntary green power program at their local electric
utility, consumers in Pennsylvania now have an option to purchase a credit for RNG sourced from LFG.
The Energy Co-op in Pennsylvania has offered voluntary Renewable Natural Gas Credits in partnership
103 Ingram, W. October 2017. Reducing Methane Emissions from California's Wastes. Presented at US Biogas 2017.
104 CPUC. Bioenergy Feed-in Tariff Program (SB 1122). http://www.cpuc.ca.gov/SB 1122/. Accessed March 25, 2019.
105 Payne, T., and B. Gale. September 2017. Roeslein Alternative Energy & Duke Energy—Missouri Swine Waste Green
Gas Project, https://www.epa.gov/natural-gas-star-program/duke-energy-rng-green-electricitv-livestock-waste-
missouri-and-north. Accessed April 3, 2019.
106 NC Clean Energy Technology Center. Database of State Incentives for Renewables & Efficiency. Renewable & Clean
Energy Standards (map), http://www.dsireusa.org/resources/detailed-summarv-maps/. Accessed March 9, 2020.
107 National Conference of State Legislatures. April 2020. State Renewable Portfolio Standards and Goals.
https://www.ncsl.org/research/energy/renewable-portfolio-standards.aspx. Accessed June 25, 2020.
108 M.J. Bradley & Associates. April 2017. Renewable Natural Gas. The RNG Opportunity for Natural Gas Utilities.
https://mibradlev.com/reports/renewable-natural-gas-rng-opportunitv-natural-gas-utilities.
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with PECO, the local gas utility, since 2016.109 Vermont Gas launched a similar program in 2017,110 and as
of 2019, efforts were underway in California, New York and Minnesota. Similarly, FortisBC in Canada has
offered a voluntary RNG program since 2011 that allows customers to pay a premium to increase the
blend of RNG into their natural gas supply.111 There are a variety of brokers to help certify that the RNG
volume sold through a voluntary utility program matches the quantity of RNG injected into its system.
Customers pay a higher gas supply rate depending on their selected RNG percentage.
In March 2019, SoCalGas in California announced a plan to replace 5 percent of its fossil natural gas supply
with RNG by 2022 and 20 percent by 2030, as part of the company's vision to be the "cleanest natural gas
utility in North America." Toward this goal, SoCalGas filed a request with the CPUC to allow its residential
and small commercial/industrial customers the option to purchase RNG. Customers who choose to
participate would select from a range of dollar amounts or a percentage of total gas usage (for commercial
customers), and their monthly gas bill would have a line item showing the extra cost. A settlement
agreement was filed with CPUC in April 2020 which provided some updated functions of this RNG tariff
program, and CPUC was expected to make a decision on the program later in 2020.112,113,114,115
The Midwest Renewable Energy Tracking System (M-RETS) is a web-based system used by power
generators, utilities, marketers and qualified reporting entities to track and retire RECs generated under
RPSs and other environmental credit systems. In 2019, M-RETS began adapting its software to meet the
needs of emerging voluntary programs for thermal energy credits, which were anticipated based on
corporate sustainability goals and commitments. M-RETS launched its platform to track renewable
thermal certificates in January 2020.116
Many corporations and local governments are developing their own GHG emission inventories and
incorporating the results into sustainability plans for reducing their carbon footprints and potentially even
becoming carbon neutral. Carbon neutrality is when an emitter reduces its carbon footprint to zero
through various measures, including emission reduction projects.117 One standard that corporations use
109 The Energy Co-op. Renewable Natural Gas. https://www.theenergy.coop/services-we-offer/natural-gas/. Accessed
March 25, 2019.
110 Vermont Gas. VGS Renewable Natural Gas. https://www.vermontgas.com/renewablenaturalgas/. Accessed July 23,
2019.
111 FortisBC. Renewable Natural Gas. https://www.fortisbc.com/services/sustainable-energy-options/renewable-
natural-gas. Accessed March 25, 2019.
112 Sempra Energy. February 2019. SoCalGas Seeks to Offer Renewable Natural Gas to Customers.
https://www.sempra.com/socalgas-seeks-offer-renewable-natural-gas-customers. Accessed October 4, 2019.
113 Sempra Energy. March 2019. SoCalGas Announces Vision to Be Cleanest Natural Gas Utility.
https://www.sempra.com/newsroom/spotlight-articles/socalgas-announces-vision-be-cleanest-natural-gas-utilitv.
Accessed October 4, 2019.
114 Paulson, L. California Energy Markets. April 2020. SoCal Gas RNG Tariff Filed With CPUC.
https://www.newsdata.com/california energy markets/regulation status/socal-gas-rng-tariff-filed-with-
cpuc/article bl30e2dc-8664-llea-8c42-33938bdf0f9b.html. Accessed June 24, 2020.
115 SoCalGas. June 12, 2020. RNG Tariff Overview.
https://docs.cpuc.ca.gov/PublishedDocs/Efile/G000/M340/K738/34Q738713.PDF.
116 U.S. Gain. January 2020. US Gain to provide RNG through new M-RETS RTC platform. Biomass Magazine.
http://biomassmagazine.com/articles/16783/us-gain-to-provide-rng-through-new-m-rets-rtc-platform. Accessed
February 20, 2020.
117 Natural Capital Partners. CarbonNeutral Protocol, https://www.carbonneutral.com/the-carbonneutral-protocol.
Accessed April 15, 2019.
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to help determine their carbon footprint is The Greenhouse Gas Protocol: A Corporate Accounting and
Reporting Standard118 which categorizes emissions into three areas:
• Scope 1 emissions are direct GHG emissions from sources that are owned or controlled by
the company.
• Scope 2 emissions are GHG emissions from the generation of purchased electricity that the
company consumes.
• Scope 3 emissions are all other indirect GHG emissions that are a result of the company's
activities where the company neither owns nor controls the source (reduction of Scope 3
emissions is considered optional for reaching carbon neutrality).
In 2013, L'Oreal USA, an LMOP Energy Partner, launched a sustainability program which included a goal
to reduce carbon emissions from its manufacturing and distribution facilities by 60 percent by 2020 (as
compared to a 2005 baseline). By 2017, L'Oreal had already achieved an 84 percent reduction of its C02
emissions (completely mitigating its Scope 2 emissions) but wanted to do more to address its Scope 1
emissions and become carbon neutral. After considering different ways to meet this goal, L'Oreal
determined that buying RNG from a local landfill in place of fossil natural gas to fulfill the thermal energy
needs of its 19 U.S. facilities would meet this goal and also be in keeping with L'Oreal's goal of having a
tangible impact on the local community. See Section 9.0 for details on L'Oreal's "directed biogas" project
with Big Run Landfill in Kentucky.119120121
118 World Resources Institute and World Business Council for Sustainable Development. The Greenhouse Gas Protocol:
A Corporate Accounting and Reporting Standard, https://ghgprotocol.org/corporate-standard. Accessed April 15,
2019.
119 In a directed biogas project, the end user extracts an amount of natural gas from the pipeline that is equivalent to
the amount of RNG that was injected into the pipeline from the project. The exact RNG molecules are not
necessarily delivered to the end user, but the same amount of fuel is used.
120 Harf, J. June 2018. L'Oreal USA on Why Thermal Energy Is Key to Their Sustainability Goals.
https://www.renewablethermal.org/loreal-usa-on-whv-thermal-energy-is-kev-to-their-sustainabilitv-goals/.
Accessed April 15, 2019.
121 Harf, J. December 2018. Webinar: Renewable Natural Gas from Landfill Gas and Sustainability at L'Oreal.
https://www.epa.gov/lmop/webinar-renewable-natural-gas-landfill-gas-and-sustainabilitv-loreal. Accessed April 15,
2019.
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9.0 EXAMPLES
9.1 RNG Projects with Feedstock, Delivery Method and End Use
MSW Landfills
Altamont Landfill MSW to Vehicle Fuel (LNG)
Location: Alameda County, California
RNG Start Year: 2009
Description: There is only one known currently operating onsite LFG-to-LNG project in the United
States, which is at the Altamont Landfill.122 Since the LNG plant started up in 2009, Waste
Management and Linde have displaced 2.5 million gallons of diesel fuel per year by
producing up to 13,000 gallons of LNG per day, enough to fuel 300 garbage trucks. The
landfill also produces enough electricity from LFG to power the LNG plant and about
8,000 homes per year.123
Big Run Landfill MSW to Pipeline Injected RNG for Vehicle Fuel and Directed Biogas
Location: Ashland, Kentucky
RNG Start Year: 2020
Description: Big Run Power Producers cleans LFG using membrane and PSA technologies and injects
the RNG into a natural gas pipeline about two miles away from the landfill. For the first
five years, RNG buyer L'Oreal USA will sell RINs in the vehicle fuel marketplace to recoup
their investment. To avoid double counting of the environmental attributes, L'Oreal will
also buy carbon offsets for their facilities from a different RNG project. Starting in the
sixth year, L'Oreal will stop selling RINs and 40 percent of the RNG from this directed
biogas project (located 135 miles away from L'Oreal's largest manufacturing plant) will
supply L'Oreal's 19 U.S. facilities with 280,000 million Btu per year for thermal energy
use, mainly for heating buildings and process water.124,125
122 U.S. EPA. 2010. Altamont Landfill Gas to Liquefied Natural Gas Project, https://www.epa.gov/lmop/landfill-gas-
energy-proiect-dataffaltamont. Accessed April 1, 2019.
123 Waste Management, "Case Study: Altamont Landfill and Resource Recovery Facility".
https://www.wm.com/documents/pdfs-for-services-section/Case-studies-
municipal/PSS CsStdvAltamLndfllREVISE rFiig.pdf.
124 Renewable Thermal Collaborative. L'Oreal USA On Why Thermal Energy is Key to Their Sustainability Goals. June
2018. https://www.renewablethermal.org/loreal-usa-on-whv-thermal-energy-is-kev-to-their-sustainabilitv-goals/.
Accessed April 15, 2019.
125 Harf, J. December 2018. Webinar: Renewable Natural Gas from Landfill Gas and Sustainability at L'Oreal.
https://www.epa.gov/lmop/webinar-renewable-natural-gas-landfill-gas-and-sustainabilitv-loreal. Accessed April 15,
2019.
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Greentree Landfill MSW to Pipeline Injected RNG for Electricity
Location: Kersey, Pennsylvania
RNG Start Year: 2007
Description: The project developed at Greentree Landfill employs membrane, PSA and activated
carbon technologies to upgrade approximately 8.4 mmscfd of LFG into RNG (plant
capacity is about 15 mmscfd of raw LFG). A dedicated 7-mile pipeline delivers the RNG
to the National Fuel Gas interstate pipeline network; the project is expected to produce
more than 2 billion cubic feet of RNG per year. Ultimately, through a series of gas sales
contracts, the RNG is being used in combined cycle equipment to generate renewable
electricity and RECs.126
Rodefeld Landfill MSW and Manure to Pipeline Injected RNG to Vehicle Fuel
Location: Madison, Wisconsin
RNG Start Year: 2011/2019
Description: Dane County, Wisconsin, has been creating vehicle fuel from LFG on site since 2011 (and
generating electricity before that), but completed a new project in 2019 to inject RNG
into ANR-TransCanada's natural gas interstate transmission pipeline for use at regional
CNG fueling stations. As part of this effort, the County built an off-loading station to allow
other biogas plants (including manure-based AD facilities) in the area that convert their
gas into RNG to truck their RNG to this station (for a small fee) to tap into the pipeline
connection. The project is expected to displace at least 3 million gallons of fossil fuels
during the first 12 months of operation.127
St. Landry Parish Landfill MSW to Vehicle Fuel (CNG)
Location: St. Landry Parish, Louisiana
RNG Start Year: 2012
Description: St. Landry Parish, in conjunction with BioCNG, developed a multiphase onsite LFG
conditioning and CNG fueling system and an offsite virtual pipeline RNG station. The
initial project phase started in 2012, processing 50 scfm of LFG to produce up to 210 GGE
of CNG per day for the Parish's use. About three years later, the Parish entered into an
agreement with a private waste hauler to fuel its fleet of refuse hauling trucks and
constructed a 100-cfm gas conditioning system that produced an additional 420 GGE of
vehicle fuel. The Parish added a tube trailer filling system at the landfill, and constructed
an offsite RNG trailer off-loading decant panel and a CNG fueling station with natural gas
back-up.128-129
126 2007 EPA LMOP Project of the Year Award Application. Greentree High Btu Landfill Gas Project. November 2007.
127 Voegele, E. May 2019. Dane County, Wisconsin, celebrates the opening of RNG project.
http://biomassmagazine.com/articles/16126/dane-countv-wisconsin-celebrates-the-opening-of-rng-proiect.
Accessed July 22, 2019.
128 Tetra Tech. St. Landry Parish Landfill Biogas Expansion Project, Louisiana, http://www.tetratech.com/en/proiects/st-
landrv-parish-landfill-biogas-expansion-proiect-louisiana. Accessed March 28, 2019.
129 Wittmann, S. May 2016. Not Stopping at First. Renewable Energy From Waste (May/June).
http://www.unisonsolutions.com/wp-content/uploads/2016/07/St-Landrv REWmag-Mav-June-2016.pdf.
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Municipal WRRFs
Janesville WRRF Sewage Sludge to Vehicle Fuel (CNG)
Location: Janesville, Wisconsin
RNG Start Year: 2012
Description: Janesville has the first community-scale WRRF in the country to fuel public fleet vehicles
with CNG produced from biogas on site.130 The city has digested biosolids since 1970 and
generated electricity from biogas since 1985.131 In 2010, the WRRF began implementing
upgrades to further treat a portion of the biogas and also start co-digesting industrial
organic wastes. In June 2012, the city began fueling about 10 CNG municipal vehicles with
plans to increase that number to 40 vehicles in the future.132 The WRRF processes about
18 MGD of wastewater, generates 140 cfm of biogas (of which 50 cfm is used to create
CNG) at 62 percent CH4, and has a maximum fuel production capacity of 275 GGE per
day.133
Newtown Creek WRRF Sewage Sludge to Pipeline Injected RNG
Location: New York City, New York
RNG Start Year: 2020 (expected)
Description: The Newtown Creek WRRF is the largest WRRF in New York City, treating up to 310 million
gallons of wastewater on an average day and producing more than 500 million cubic feet
of biogas per year from eight digesters that together can hold a total of 24 million gallons
of sludge.134 About 40 percent of the biogas is used in boilers to provide heat for the
digesters and other buildings, with the remaining 60 percent being flared. Since at least
2014, the city has been exploring the use of excess biogas to create RNG,135 and as of
March 2019, plans were underway to inject RNG into the National Grid pipeline
distribution system for residential and commercial consumption.136 The facility is
anticipated to provide enough RNG to heat 2,500 homes and may co-digest an organic
slurry from food waste to boost biogas production.137
130 Energy Vision. 2013. Turning Waste into Vehicle Fuel: Renewable Natural Gas (RNG). A Step-by-Step Guide for
Communities. https://energv-vision.org/ev-publications/EV-RNG-Communitv-Guide.pdf.
131 U.S. DOE Midwest CHP Technical Assistance Partnership. Janesville Wastewater Treatment Plant.
https://chptap.lbl.gov/profile/109/JanesvilleWWT-Proiect Profile.pdf.
132 Energy Vision. 2013. Turning Waste into Vehicle Fuel: Renewable Natural Gas (RNG). A Step-by-Step Guide for
Communities. https://energv-vision.org/ev-publications/EV-RNG-Communitv-Guide.pdf.
133 BioCNG. Fact Sheet: City of Janesville Wastewater Treatment Plant, http://biocng.us/wp-
content/uploads/2015/06/Janesville-Fact-Sheet-2015.pdf.
134 Siegel, N. January 2018. October Tour Recap: Newtown Creek Wastewater Treatment Plant. GreenHomeNYC.
https://greenhomenvc.org/blog/october-tour-recap-newtown-creek-wastewater-treatment-plant/. Accessed April
1, 2019.
135 NYC Environmental Protection. December 2013. City Announces Innovative New Partnerships That Will Reduce the
Amount of Organic Waste Sent to Landfills, Produce a Reliable Source of Clean Energy and Improve Air Quality.
https://wwwl.nvc.gov/html/dep/html/press releases/13-121pr.shtml#.XKJaTqR7IEZ. Accessed April 1, 2019.
136 Neighbour, D., and G. Zwicker. March 2019. What China Can Learn from New York City about Wastewater
Management. Scientific American, https://blogs.scientificamerican.com/observations/what-china-can-learn-from-
new-vork-citv-about-wastewater-management/. Accessed April 1, 2019.
137 Chahbazpour, D. September 2017. National Grid—Newtown Creek Renewable Gas Demonstration. Presented at EPA
Technology Transfer Workshop: Renewable Natural Gas—Driving Value for Natural Gas and Biogas Sectors.
https://www.epa.gov/natural-gas-star-program/renewable-natural-gas-driving-value-natural-gas-and-biogas-
sectors-workshop.
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Point Loma WRRF Sewage Sludge to Pipeline Injected RNG for Electricity
Location: San Diego, California
RNG Start Year: 2012
Description: BioFuels Energy, LLC, financed, built and operates the RNG production facility at the Point
Loma Wastewater Treatment Facility. The facility can process up to 1.6 mmscfd of biogas
generated from eight digesters.138 BioFuels Energy cleans the biogas to San Diego Gas &
Electric's pipeline gas specifications, and after injection into the pipeline system, the RNG
is "directed" to fuel cells at two customers: University of California-San Diego (2.8
megawatts) and City of San Diego South Bay Water Reclamation Plant (1.4 megawatts).139
This process uses existing pipelines and increases the options for biogas usage. This
project was the first in California to inject RNG into a natural gas pipeline.140
San Antonio Water System (SAWS) Sewage Sludge to Pipeline Injected RNG
Location: Bexar County, Texas
RNG Start Year: 2010
Description: SAWS partnered with Ameresco to produce biogas by adding a new biosolids AD process
to its facility. In 2010, Ameresco began processing more than 1.5 mmscfd of biogas at 60
percent CH4 to deliver at least 900,000 cubic feet of RNG per day to a nearby fossil natural
gas pipeline for sale on the open market. In addition to offsetting the use of fossil natural
gas, SAWS receives approximately $200,000 in royalties annually from the sale of the
biogas, which helps keep its rates reasonable.141142
138 BioFuels Energy, LLC. Projects. Biogas Projects, https://biofuelsenergyllc.com/proiects. Accessed March 13, 2020.
139 Mazanec, F.. BioFuels Energy, LLC. October 2016. Turning Waste Into Renewable Natural Gas: Point Loma
Wastewater Treatment Plant Case Study—Five Years After Commercial Operation.
https://www.socalgas.com/1443740098116/Biogas-to-RNG-at-Point-Loma-Wastewater-Treatment-Facilitv.pdf.
140 Argonne National Laboratory. August 2017. Waste-to-Fuel: A Case Study of Converting Food Waste to Renewable
Natural Gas as a Transportation Fuel. ANL/ESD-17/9. https://afdc.energy.gOv/files/u/publication/waste to fuel.pdf.
141 San Antonio Water System. Biogas. https://www.saws.org/vour-water/water-recvcling/biogas/. Accessed March 13,
2020.
142 Ameresco. 2017. Case Study: San Antonio Water System, TX. http://www.ameresco.com/wp-
content/uploads/2017/ll/san-antonio-water-svstem-tx.pdf.
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Livestock Farms
Hilarides Dairy Manure to Vehicle Fuel (CNG)
Location: Tulare County, California
RNG Start Year: 2009
Description: Hilarides Dairy is a family-run dairy that has been digesting manure from more than 9,000
cows in a covered lagoon digester since December 2004.143 Part of the 226,000 cubic feet
of biogas produced per day in 2017 produced CNG to fuel two heavy-duty milk trucks and
six on-farm pickup trucks, displacing 230,000 gallons of diesel annually.144 When Hilarides
began cleaning and compressing its biogas for vehicle fuel in early 2009, it became the
first dairy in the United States to do so. The dairy also continues to generate electricity
from about two-thirds of the generated biogas.145146
Roeslein Cluster Project Manure to Pipeline Injected RNG to Electricity and Vehicle Fuel
Location: Missouri
RNG Start Year: 2016
Description: The North Carolina RPS includes a carve-out for renewable energy from animal waste
(poultry and swine), and a utility can meet a portion of the targets through out-of-state
purchases. Duke Energy opted to incorporate RNG from manure-based digesters in
Missouri to meet its North Carolina RPS obligations, agreeing to purchase one-third of
the RNG from a cluster project of nine farms through a 10-year PPA. Roeslein Alternative
Energy's RNG production will be built out in phases through 2020; three of the farms
were producing RNG as of 2018. The Ruckman Farm began processing 1,350 cfm of biogas
using a PSA system in June 2016, injecting the RNG into the American Natural Resources
gas pipeline. Locust Ridge Farm and Valley View Farm use membrane systems to process
about 400 scfm of biogas each and truck their RNG via a virtual pipeline to the
interconnection point at Ruckman Farm. One of Duke's combined cycle power plants in
the Southeast pulls the appropriate amount of gas from the local pipeline to generate
electricity. Beyond its obligations to Duke, this project also sells excess RNG into the
vehicle fuel market.147 148 149
143 Western United Resource Development, Inc. December 2006. Prepared for CEC. PIER Final Project Report. Dairy
Power Production Program: Dairy Methane Digester System, 90-Day Evaluation Report—Hilarides Dairy. Formerly
available at https://www.energv.ca.gov/2006publications/CEC-500-2006-086/CEC-500-2006-Q86.PDF.
144 Elger, N. April 2017. Innovative Business Models for On-farm Anaerobic Digestion. Presented at Waste to Worth
2017. https://www.epa.gov/sites/production/files/2017-05/documents/innovative-business-models-w2w-2017.pdf.
145 Elmore, C. March 2009. Alternative Fuels: Got Methane? OEM Off-Highway.
https://www.oemoffhighwav.com/trends/hvbrids/article/10166466/alternative-fuels-got-methane. Accessed
March 28, 2019.
146 Richardson, L. April 2009. 'Cow-Powered' Milk Truck Debuts. www.CaliforniaFarmer.com (April).
http://www.suscon.org/pdfs/news/pdfs/200904 CaliforniaFarmer Cow-PoweredMilkTruckDebuts.pdf.
147 Payne, T., and B. Gale. September 2017. Roeslein Alternative Energy & Duke Energy—Missouri Swine Waste Green
Gas Project, https://www.epa.gov/natural-gas-star-program/duke-energy-rng-green-electricitv-livestock-waste-
missouri-and-north. Accessed April 3, 2019.
148 Fletcher, K. August 2016. Roeslein Alternative Energy's WTE Project Begins RNG Production. Biomass Magazine.
http://biomassmagazine.com/articles/13624/roeslein-alternative-energvs-wte-proiect-begins-rng-production.
Accessed April 3, 2019.
149 Scherer, R. August 2017. Regional Biogas Project Advancing. News-Press Now.
http://www.newspressnow.com/news/business/regional-biogas-proiect-advancing/article Id8b3ab2-c99b-52ba-
8445-4aca371639ef.html. Accessed April 3, 2019.
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Stand-Alone Organic Waste Management Operations
Blue Line Biogenic CNG Facility Organic Waste to Vehicle Fuel (CNG)
Location: South San Francisco, California
RNG Start Year: 2014
Description: South San Francisco Scavenger Company (SSFSC) and Blue Line Transfer developed this
dry AD system with eight modular AD tunnels and a total processing capacity of 11,200
tons per year. The green waste and food waste feedstocks are collected from commercial
and residential (approximately 20,000 households) customers. The project is producing
between 380 and 500 diesel gallon equivalents of RNG per day, which fuel 34 CNG
vehicles owned by SSFSC. The trucks are filled every weeknight using a slow fill system
that provides a mix of CNG from RNG and fossil natural gas, but on weekends the trucks
receive renewable CNG only. SSFSC is selling D5 RINs and carbon credits under
California's LCFS.150151
CR&R AD Facility Organic Waste to Pipeline Injected RNG for Vehicle Fuel (CNG)
Location: Perris, California
RNG Start Year: 2016
Description: CR&R Environmental Services' AD project uses residential and commercial green (yard)
and food waste feedstocks, with an initial maximum capacity of 83,600 tons per year
(three more phases will follow at a capacity of 83,600 tons each). The system was
designed to also accept other types of organic waste including solid and liquid food
waste.152 At full build-out, the facility will be able to convert about 334,000 tons of waste
per year into 4 million diesel gallon equivalents of RNG and 250,000 tons of fertilizer.153
In 2017, the biogas produced was cleaned and compressed into CNG for use by 75 CR&R
refuse trucks, but in 2018 CR&R began injecting all the RNG into the SoCalGas fossil
natural gas system via a newly built 1.4-mile pipeline, becoming the first RNG project in
California to do so. CR&R now pulls the RNG back out of the pipeline to compress it for
its vehicles. 154 155 in late 2018, the facility's LCFS application was approved with its
requested CI.156
150 Goldstein, N. May 2018. Facilitating Food Waste Digestion. BioCycle 59(4): 32.
https://www.biocvcle.net/2018/05/01/facilitating-food-waste-digestion/. Accessed October 2, 2019.
151 Goldstein, N. July 2016. Biogas to Fleet Fuel in South San Francisco. BioCycle 57(6): 35.
https://www.biocvcle.net/2016/07/14/biogas-fleet-fuel-south-san-francisco/. Accessed October 2, 2019.
152 Goldstein, N. May 2017. High Solids Digester Services California Municipalities. BioCycle 58(4): 44.
https://www.biocvcle.net/2017/05/01/high-solids-digester-services-california-municipalities/. Accessed April 3,
2019.
153 Pauley, C. November 2018. CR&R Anaerobic Digestion Facility: Renewable Fuel from Organic Waste Recycling.
Presented at CBA Symposium—Sacramento, https://www.epa.gov/sites/production/files/2017-
ll/documents/cba2017-crr anaerobic digestion facitiltv.pdf.
154 Goldstein, N. May 2017. High Solids Digester Services California Municipalities. BioCycle 58(4): 44.
https://www.biocvcle.net/2017/05/01/high-solids-digester-services-california-municipalities/. Accessed April 3,
2019.
155 Waste360 Staff. July 2018. RNG Produced in California by CR&R Flows into SoCalGas Pipelines for the First Time.
Waste360. https://www.waste360.com/gas-energy/rng-produced-california-crr-flows-socalgas-pipelines-first-time.
Accessed April 3, 2019.
156 BioCycle. February 2019. Anaerobic Digest. BioCycle 60(2): 14. https://www.biocvcle.net/2019/02/01/anaerobic-
digest-91/. Accessed April 3, 2019.
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9.2 Corporate Alternative Fuel Fleets
Corporate sustainability goals are also driving a shift from diesel-based fleets to natural gas-based fleets.
Waste Management, Inc. CNG and LNG
Waste Management has set a goal to reduce fleet emissions by 45 percent by 2038, as compared to a 2010
baseline, by transitioning 90 percent of its fleet from diesel to alternative fuel vehicles. At the end of 2017,
Waste Management had more than 32,000 fleet vehicles overall, including more than 6,500 running on some
form of natural gas and 33 percent of those natural gas vehicles fueled by an RNG source. All of the
company's fleet operating in California, Oregon and Washington runs on RNG-sourced fuel.157 Two examples
of Waste Management-owned landfills that produce RNG vehicle fuel are the Altamont Landfill (California),
with a renewable LNG facility that fueled 170 of the company's waste trucks in 2017, and the Outer Loop
Landfill (Kentucky), which produces enough CNG to fuel approximately 800 vehicles.158
United Parcel Service (UPS) CNG and LNG
UPS has 51 natural gas fueling stations across the country (including six new CNG stations in 2017) and a
fleet of more than 5,200 natural gas vehicles (including 450 purchased during 2017). During 2017, UPS used
more than 15 million gallons of vehicle fuel from RNG in its fleet, an increase from 4.6 million gallons in 2016.
In the same year, UPS signed two new agreements to purchase 1.5 million gallons of RNG per year from Fair
Oaks Dairy in Indiana and 10 million gallons of RNG per year from Big Ox Energy, based in Wisconsin.159,160
In 2019, UPS announced the company will purchase a total of 170 million gallon equivalents of RNG from
Clean Energy Fuels Corp. through 2026 for use at 18 of its stations in 12 states. This decision is part of UPS'
goal to have alternative fuel make up 40 percent of its total ground fuel purchases by 2025 and reduce its
ground fleet's GHG emissions by 12 percent by 2025.161
157 Waste Management. 2018. Driving Change. 2018 Sustainability Report.
http://www.wm.com/sustainabilitv/pdfs/WasteManagement SustainabilitvReport 2018.pdf.
158 U.S. EPA. March 2020. Landfill and LFG Energy Project Database, https://www.epa.gov/lmop/landfill-gas-energy-
proiect-data.
159 UPS. Environmental Responsibility: Fuels & Fleets, https://sustainabilitv.ups.com/fuels-and-fleets/. Accessed April 3,
2019.
160 UPS. November 2017. UPS Increases Use of RNG Through Agreement with Big Ox Energy. Biomass Magazine.
http://biomassmagazine.com/articles/14862/ups-increases-use-of-rng-through-agreement-with-big-ox-energy.
Accessed April 3, 2019.
161 UPS. May 2019. UPS Makes Largest Purchase of Renewable Natural Gas Ever in the U.S. GlobeNewswire.
https://www.globenewswire.eom/news-release/2019/05/22/1840772/0/en/U PS-Makes-La rgest-Purchase-Of-
Renewable-Natural-Gas-Ever-ln-The-U-S.html. Accessed July 23, 2019.
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10.0 RESOURCES
Hyperlinked Resource
Organization
Alternative Fuels Data Center
U.S. DOE
AD webpage
U.S. EPA
AD Facilities Processing Food Waste in the United
1 1 Q FDA
States: Survey Results
Biogas Toolkit
U.S. EPA
Gas Quality Database (information from maior
The Coalition for Renewable Natural Gas
transmission pipeline tariffs)
Interconnect Guide for RNG in New York State
Northeast Gas Association; Gas Technology
Institute
Landfill and LFG Energy Project Database
U.S. EPA LMOP
LFG Energy Project Development Handbook
U.S. EPA LMOP
Livestock Anaerobic Digester Database
U.S. EPAAgSTAR
Managing and Transforming Waste Streams: A Tool
II S FPA
for Communities
U ¦ *-} • 1 P rt
Renewable thermal credit tracking system
M-RETS
RIN Calculator
American Biogas Council
RNG Database
Argonne National Laboratory
RNG Flow Rate Estimation Tool
U.S. EPA LMOP
RNG Project Map
U.S. EPA LMOP/AgSTAR
RNG Tool Kit
SoCalGas
RNG webpage
U.S. EPA LMOP
WRRF "phase 1" database
Water Environment Federation
45
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11.0 ABBREVIATIONS, ACRONYMS AND UNITS OF MEASURE
AD anaerobic digestion
AFLEET Alternative Fuel Life-Cycle Environmental and Economic Transportation
Btu British thermal unit
CARB California Air Resources Board
CEC California Energy Commission
cfm cubic feet per minute
CH4 methane
CI carbon intensity
CNG compressed natural gas
CO carbon monoxide
C02 carbon dioxide
CPUC California Public Utilities Commission
DOE U.S. Department of Energy
g C02e/MJ grams of C02 equivalent per megajoule
GGE gasoline gallon equivalents
GHG greenhouse gas
H2S hydrogen sulfide
LCFS Low Carbon Fuel Standard
LFG landfill gas
LMOP U.S. EPA Landfill Methane Outreach Program
LNG liquefied natural gas
M-RETS Midwest Renewable Energy Tracking System
mg/m3 milligrams per cubic meter
MGD million gallons per day
mmscfd million standard cubic feet per day
MSW municipal solid waste
N2 nitrogen
NOx nitrogen oxide
46
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02 oxygen
PM particulate matter
PPA power purchase agreement
PSA pressure swing adsorption
psig pound-force per square inch gauge
REC renewable energy certificate
RIN Renewable Identification Number
RFS Renewable Fuel Standard
RNG renewable natural gas
RPS Renewable Portfolio Standard
SAE J1616 Society of Automotive Engineers Surface Vehicle Recommended Practice J1616™ for
Compressed Natural Gas Vehicle Fuel
SAWS San Antonio Water System
SB Senate bill
scf standard cubic foot
scfm standard cubic feet per minute
SoCalGas Southern California Gas Company
SOx sulfur dioxide
SSFSC South San Francisco Scavenger Company
UPS United Parcel Service
VOC volatile organic compound
WEF Water Environment Federation
WRRF water resource recovery facility
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Appendix A: Natural Gas Companies Accepting RNG into Pipelines
Company Name and Website
State(s) where
RNG is Injected
Feedstock(s)1
Company Information about RNG
Company's Pipeline Interconnection Standard /
Tariff / Similar
Ameren Illinois
Illinois
LF, OW
ANR Pipeline Company
Missouri, Wisconsin
Ag, LF
TransCanada Biogas Interconnect Facility Requirements
Arkansas Oklahoma Gas Corporation
Arkansas
LF
Atmos Energy Corporation
Louisiana, Texas
LF
Atmos Energy Environment page
Atmos Energv Utility Operations page
Black Hills Corporation
Iowa, Nebraska
LF, WW
CenterPoint Energy
Texas
LF
CenterPoint Energy Natural Gas Innovation Act
CenterPoint Energv Rates & Tariffs
Columbia Gas of Ohio, Inc.
Ohio
LF, OW
Columbia Gas of Ohio Regulatorv Information
Consumers Energy
Michigan
LF
Consumers Energv Gas Standard Customer Forms
Dominion Energy Ohio
Ohio
LF
Dominion Energy Renewable Natural Gas page
Dominion Energv Ohio Tariff Information
Dominion Energy Questar Pipeline
Utah
WW
Dominion Energv Questar Pipeline FERC Gas Tariff
Dominion Energy Transmission, Inc.
Ohio
LF
Dominion Energv Transmission FERC Gas Tariff
DTE Energy
Michigan
LF
DTE BioGreenGas
Michigan Public Service Commission - Natural Gas Rate Books
Duke Energy
Ohio
LF
Duke Energv Ohio Gas Tariff
East Tennessee Natural Gas
Tennessee
LF
Enbridge Gas RNG page
East Tennessee Natural Gas Tariff
Enable Midstream Partners
Louisiana
LF
Enable Gas Transmission, LLC (EGT) website
-------
Appendix A: Natural Gas Companies Accepting RNG into Pipelines
, . State(s) where , , Company s Pipeline Interconnection Standard /
Company Name and Website . . . Feedstock(s) Company Information about RNG „ ..
RNG is Injected Tariff / Similar
Enterprise Pipeline
Texas
LF
Eauitrans Midstream
Pennsylvania
LF
Eauitrans, L.P. FERC Gas Tariff
Four-S Oil Company
Texas
LF
Fremont Department of Utilities Gas Distribution
Nebraska
WW
General Gas Pipeline, LLC
Tennessee
LF
Great Lakes Gas Transmission Company
Michigan
LF
Great Lakes Gas Transmission Tariff
Gulf South Pipeline
Louisiana, Texas
LF
Gulf South Pipeline Companv Tariff
Hawaii Gas Transmission and Distribution
Hawaii
WW
Hawaii Gas RNG page
Houston Pipe Line Company
Texas
LF
Houston Pipe Line Companv Gas Quality Specifications
Kinder Morgan
Arizona, Mississippi,
Oklahoma, Texas
LF, WW
Kinder Morgan Tariffs page
Memphis Light, Gas and Water (MLGW)
Tennessee
LF
Metropolitan Utilities District of Omaha
Nebraska
LF
Montana-Dakota Utilities Co.
Montana
LF
Montana-Dakota Utilities - Rates and Tariffs
Mountaineer Gas Company
West Virginia
LF
Mountaineer Gas Companv - Rates and Tariffs
National Fuel Gas
Pennsylvania
LF
National Fuel Gas Distribution Corporation Gas
Transportation Operating Procedures Manual
National Fuel PA Regulatory, Tariff and GTOP
-------
Appendix A: Natural Gas Companies Accepting RNG into Pipelines
Company Name and Website
State(s) where
RNG is Injected
Feedstock(s)1
Company Information about RNG
Company's Pipeline Interconnection Standard /
Tariff / Similar
National Gas & Oil Cooperative
Ohio
WW
National Grid
New York
LF, WW
Renewable Gas - Vision for a Sustainable Gas Network
National Grid - Service Rates
Northern Indiana Public Service Company
(NIPSCO)
Indiana
Ag
NIPSCO Rate for Gas Service Renewable Gas Balancing Service
Northern Natural Gas
Kansas, Nebraska,
Wisconsin
Ag, WW
Northern Natural Gas Tariff page
NW Natural
Oregon
WW
NW Natural RNG page
NW Natural Oregon Tariff Book
Pacific Gas and Electric Company (PG&E)
California
Ag
PG&E Interconnecting biomethane suppplv page
PG&E Tariffs page
Panhandle Eastern Pipe Line Company
Kansas
LF
Panhandle Eastern Pipe Line Company FERC NGA Gas Tariff page
Peoples Natural Gas
Pennsylvania
LF
Peoples Producers, Suppliers & Gas Supply page
Peoples Gas Qualitv Quick Reference Guide
Philadelphia Gas Works
National
LF
Piedmont Natural Gas Company, Inc.
North Carolina
Ag
Piedmont Natural Gas Index of Tariff & Service Regulations
Puget Sound Energv
Washington
LF, WW
Puget Sound Energv Natural gas tariffs & rules page
Southern California Gas Company (SoCalGas)
California
Ag, OW, WW
SoCalGas Renewable Gas page
SoCalGas Rule No. 30 Transportation of Customer-Owned Gas
Southern Company Gas
Georgia
LF
Southern Company Gas (Atlanta Gas Light
Company)
Georgia
LF
Atlanta Gas Light Company Tariff
Southern Star Central Gas Pipeline
Kansas, Oklahoma
LF
FERC Gas Tariff of Southern Star Central Gas Pipeline, Inc.
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Appendix A: Natural Gas Companies Accepting RNG into Pipelines
Company Name and Website
State(s) where
RNG is Injected
Feedstock(s)1 Company Information about RNG
Company's Pipeline Interconnection Standard /
Tariff / Similar
Summit Utilities, Inc.
Maine
Ag Summit Announces RNG Initiative - Mav 2019
Texas Gas Transmission LLC
Kentucky
LF
Texas Gas Transmission, LLC Tariff
UGI Utilities
Pennsylvania
LF
UGI Tariffs
Utica Gas Services (subsidiary of Williams Gas
Pipeline)
Ohio
LF
Vectren Energy Delivery
Ohio
LF
Vectren Rates & tariffs page
Vermont Gas
Iowa, Quebec,
Vermont
Ag, LF, WW VGS Renewable Natural Gas page
Williams Gas Pipeline
Washington
LF
Transcontinental Gas Pipe Line Company, LLC FERC Gas Tariff
Wisconsin Public Service Corporation
Wisconsin
OW
Xcel Energy
Colorado
WW
XTO Energy
Oklahoma
LF
Main Sources of Data for Inclusion of Utilities in this List
• U.S. EPA. March 2020. Landfill and LFG Energy Project Database.
https://www.epa.gov/lmop/landfill-gas-energy-proiect-data.
• U.S. EPA. March 2020. Livestock Anaerobic Digester Database.
https://www.epa.gov/agstar/livestock-anaerobic-digester-database.
• Mintz, M., P. Vos, M. Tomich, and A. Blumenthal. October 2019. Database of Renewable
Natural Gas (RNG) Projects: 2019 Update. Argonne National Laboratory.
https://www.anl.gov/es/reference/renewable-natural-gas-database.
Feedstock(s) of the RNG Injected
Ag
LF
WW
OW
biogas from agricultural digester (may co-digest organic waste)
landfill gas
biogas from wastewater digester (may co-digest organic waste)
biogas from organic waste digester (food waste and/or other
organic waste types)
A-4
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