REDUCTION OF CO2 EMISSIONS FROM MOBILE SOURCES BY
ALTERNATIVE FUELS DERIVED FROM BIOMASS
Robert H. Borgwardt(1), Meyer Steinberg(2), Yuanji Dong(3)
(1) U.S. Environmental Protection Agency, Research Triangle Park, NC 27711
(2) Brookhaven National Laboratory, Upton, NY 11973
(3) Hydrocarb Corporation, New York, NY 10018
ABSTRACT
The Energy Policy Act of 1992 seeks to displace 30 percent of the U.S. petroleum
requirement by the year 2010 with an alternative that, among other things, has greatest impact
on reduction of greenhouse gas emissions. An alternative fuel derived from biomass is probably
the most practicable method of achieving that objective. This paper discusses process options
for utilizing biomass to obtain greatest reduction of carbon dioxide (CO2) emissions from motor
vehicles at least cost. Emphasis is on the Hydrocarb process, currently under evaluation by the
EPA for production of methanol from short-rotation woody crops using natural gas as
cofeedstock. Comparison with other process options is made in terms of feedstock availability,
cost of conversion to liquid fuel, amount of petroleum that can be displaced, and competitiveness
with gasoline price. The analysis indicates that for a given supply of biomass, more displacement
of petroleum can be achieved through methanol production processes than those for ethanol. If
the performance projections can be achieved, the Hydrocarb process should displace 13 percent
more gasoline and obtain 66 percent more CO2 reduction than the best alternative option for
producing alcohol fuel from the same feedstocks. Assumed trends in feedstock costs'are
expected to favor methanol relative to the equivalent price of gasoline.
Prepared for presentation at 1993 AIChE Summer National Meeting, Seattle, Washington
-------
INTRODUCTION
Several recent events have begun to focus attention on alternative transportation fuels in
the U.S. The Clean Air Act, as amended in 1990, provides an initial impetus for the production
of clean fuels such as ethanol, methanol, and reformulated gasoline in order to reduce toxic
emissions in urban areas. The National Energy Strategy (U.S. Department of Energy, 1991)
showed that an alternative fuel of some kind will be needed in large amounts by the year 2000
due to declining petroleum reserves. Specific requirements for identifying the best alternative
fuel for broad use were outlined in the Energy Policy Act of 1992 (U.S. Congress, 1993) which
establishes goals of 10 percent displacement of petroleum by year the 2000 and 30 percent by
the year 2010. According to the Act, the desired alternative should have maximum displacement
of oil imports and greatest benefit to the national economy. Most importantly to the present
discussion, the Act also specifies that greatest reduction of greenhouse gas emissions should be
achieved. Since CO2 is the predominant greenhouse gas emission associated with use of
automotive fuels, the focus of this paper is the reduction of CO2 emissions from the
transportation sector.
The principal criteria that must be taken into account when evaluating potential alternative
fuels are therefore: the extent to which petroleum might be replaced, the degree to which
greenhouse gas emissions might be reduced, and-as always--the cost of production. ~ It would
also be preferable, if possible, that it be liquid, compatible with the existing refueling
infrastructure, and producible from domestic resources, and that it reduce the toxic emissions
associated with petroleum fuels. In the near term, the most practicable approach for reduction
of greenhouse gas emissions from mobile sources is a fuel derived from biomass, produced on
-------
a renewable and sustainable basis. As summarized in Table 1, a number of processes can
produce alcohol fuels from biomass, the most promising of which, from the standpoint of cost,
are the enzymatic hydrolysis process for production of ethanol and the Battelle Columbus
Laboratory (BCL) process for production of methanol by indirect gasification of biomass. Both
of those processes are intended to utilize as feedstocks woody biomass cultivated as short-rotation
woody crops (SRWC) to be harvested every 3-4 years for the specific purpose of conversion to
liquid fuels.
TABLE 1. CURRENT OPTIONS FOR PRODUCING ALCOHOL FUELS FROM BIOMASS
Process Alcohol production Reference
cost, $/GJ (LHV)a
Ethanol by acid hydrolysis
Ethanol by enzymatic hydrolysis (cellulose)
Methanol by steam-oxygen gasification
Ethanol by fermentatiion of corn
Ethanol by enzymatic hydrolysis (cellulose + xylose)
Methanol by indirect gasification (BCL process)
24.4
22.3
13.4
13.3
11.1
9.6
Wright etal., 1985
Wright, 1988
Reed, 1981
Jones, 1989
Wyman et ai, 1992
Larson and Katofsky, 1992
'Lower heating value
In 1990, the Brookhaven National Laboratory proposed another route to the Environmental
Protection Agency for production of methanol from woody biomass using natural gas as
cofeedstock. The potential advantages of the process, in addition to cost, are higher yield of
alcohol fuel from a given biomass supply and therefore a greater displacement of petroleum. To
the present time, the EPA has been supporting theoretical and experimental studies of the process,
-------
called Hydrocarb, that are summarized in this paper and compared with the best alternatives of
Table 1 in terms of the principal criteria for evaluating those alternatives, beginning with
production cost.
BIOMASS COST
For most biomass conversion processes, the cost of feedstock is the dominant factor
affecting the production cost of alcohol fuels. The cost of biomass is the sum of its production
and transport costs. Data published by Strauss et al. (1989) for least-cost SRWC production in
the Pennsylvania area are given as $65.71/(dry)Mg*. The cost of cultivating the biomass was
given by Strauss in 1989 as $35.41/(dry)Mg; more recent data (Strauss et al., 1990) show a
reduction in cultivation cost to $32.40/(dry)Mg for an optimized, 3-year rotation period with
fertilization. Assuming a chipping cost of $6.80/(dry)Mg as reviewed by Kenney (1991), the
breakdown of current production costs is shown in Table 2.
TABLE 2. BREAKDOWN OF PRODUCTION COSTS FOR WOODY BIOMASS
$/(dry)Mg
Cultivation 32.40
Harvest/baling 8.00
Loading/unloading 4.20
Chipping 6.80
Other 3.00
Wet storage 10.20
Total production cost $64.60
*(dry)Mg = dry metric tonne
-------
The Table 2 estimate can be compared with other published values obtained from different test
sites such as those of Perlack and Ranney (1987) which averaged $62.87/(dry)Mg for six regions
of the U.S. and Ismail and Quick (1991) for poplar tree plantations in Canada. A value of
$63.70/(dry)Mg is therefore assumed here as representative of the current SRWC production cost.
An examination of biomass transport costs in the U.S. was recently published by Bhat el
al. (1992) which are given as:
U.S. dollars/(wet)Mg = (3.65 + 0.62^/18.14 (1)
for woody crops, and
U.S. dollars/(wet)Mg = (34.08 + 0.62rf)/15.42 (2)
for herbaceous crops, where
d = the round-trip distance (km) between farm and processing plant
(or twice the mean farm-to-plant radial distance).
The moisture content of fresh cut biomass is generally about 50 percent. If, as is true in many
cases, the biomass yield per hectare and the production cost of herbaceous crops are similar to
those of woody crops, it is clear from the above equations that woody crops will provide
feedstock at the least cost for biomass delivered to large energy conversion plants.
Delivered Cost of Biomass
The delivered cost increases with transport distance which is a function of the size of the
biomass supply region from which the feedstock is obtained. Since the size of that supply region
is a function of the plant size, one must begin with a choice of plant size in order to calculate
a methanol production cost. The delivered costs of biomass for plant sizes corresponding to 9090
and 5300 (dry)Mg/day at a 90 percent operating factor are presented in Table 3. Selection of
-------
these plant sizes is based on available data to be used for estimating Hydrocarb costs and
comparing those costs with other published data, to be discussed later.
Given a biomass production cost of $63.70/(dry)Mg, we assume that the biomass supply
region consists of three concentric sectors surrounding the plant site (Figure 1): the nearest
sector contains 18 percent of its total area dedicated to plantations producing SRWC; that sector
is surrounded by a second sector containing 9 percent of its area dedicated to SRWC, and the
third, outermost, sector of the supply region has 3 percent of its area planted in SRWC. In
accordance with the current range of SRWC yields obtained in research field trials (Wright ct a!,,
1992), the productivity is assumed to be II (dry)Mg/ha-yr in each sector with 90 percent
recovery of the biomass produced. These assumptions yield the results shown in Table 3 which
indicate that transport cost will add 10-13 percent to the cost of biomass production. These
delivered costs of feedstock will be used to compare alcohol production costs for the process
options.
Biomass % of total area
supply dedicated lo biomass
region production
A
B
C
18
9
3
Figure 1. Assumed layout of biomass supply region for 9090 (dry)Mg/day
energy conversion plant.
-------
TABLE 3. DELIVERED COST OF WOODY BIOMASS,
INCLUDING PRODUCTION AND TRANSPORT
Size of energy conversion plant,
(dry)Mg/day
5300 9090
Maximum radius of biomass supply region, km 91.7 120
Production cost, $/(dry)Mg 63.70 63.70
Average transport cost (eq. 1), $/(dry)Mg 7.39 9.56
Total delivered cost, $/(dry)Mg 71.26 73.43
THE HYDROCARB PROCESS
The Hydrocarb process, conceived at the Brookhaven National Laboratory, has been
under evaluation by the EPA (Steinberg et al., 1991; 1993) as a new source of transportation fuel
that could reduce CO2 emissions from mobile sources and meet future needs for a clean
alternative fuel on a large scale. The optimum flow sheet, developed by computer simulations
to maximize methanol yield and minimize cost, is illustrated in Figure 2. Biomass and natural
gas are fed to a gasifier operating at 800°C to produce methane in an exothermic reaction with
recycled hydrogen. The gasifier effluent is pyrolyzed to hydrogen and carbon monoxide in a
second reactor at 1100°C, and methanol, the desired product, is synthesized in a third reactor by
conventional catalytic technology. The entire system operates at 50 atm pressure. The principal
differences between this and other biomass/methanol processes, from the equipment standpoint,
is the recycle of excess hydrogen to the gasifier, the recovery of thermal energy from the high-
temperature step, elimination of a shift converter, and elimination of cold gas cleanup to remove
CO2, sulfur, and volatile alkalies. From the process standpoint, the main difference is
-------
oo
Steam 50
268°C
CH,
40kg
DRYER
'
kg ,
i
Wo
11
r
HYDRO-
GASIF1CATK
CO 5.46
C02 3.3
Od100k9 SH6 ^ot
8% H20 r?° °-°3
2 Hj 64.72
N2 8.02
CH,OH 1.0
DN
REACTOR
800°C
Char & Ash
6.3kg
>
Carbon
8.54 ka
Flue gas
958°C 21 .8 kg mol
CO 6.78
C02 3.28 /C J
X
Purge gas HjO
0.19 kg mol 9.0 ka
i
-3
' A
1 __
s^^^
50"C
CH, 30.92 / ^ \
H2O 16.24 f HEAT \
H2
N2
36.54 I EXCHANGER
v^y
\S "*•
28.95 kg mol s- ^
t
METHANE
PYROLYS
REACTOF
1100°C
S
V
1100°C
s
5B2°C
co 18.64 )c ~y
CO. 0.4 /
i
"V
CONDENSER
50°C
^ c
c
c
^
38.44 ^
kg mol |
(
f
519°C 260°C
All r.n' Q Q7 f • BOILER I
II U
4
1— " 1^ W -•/ / 1
Alumina H 0 2 8 \ /• — x.
H2 63.58 ]
/"*^11DI IOTI"*vQ
COMBUSTOR
1400°C
t ''
Purge gas 0.19 kg mol — I
CH. 23.6 ka
J
N2 4.59
38.44 kg mol
f \
1
t
J
s
METHANOL
CONVERTER
260°C
Steam 50.9 kg
'ItO0/"1
CH,OH
165.8 kg
CO 4.99
CO2 3.03
CH4 15.95
HjO 0.78
59.17
7.34
CH.,OH 8.74
66.09 kg mol
Figure 2. Flow sheet for production of methanol from biomass and natural gas by the Hydrocarb process*
-------
incorporation of natural gas as cofeedstock to enhance the production of methanol synthesis gas.
Table 4 summarizes performance estimates resulting from the process simulations.
TABLE 4. PERFORMANCE ESTIMATES FOR THE HYDROCARB PROCESS
Mols methanol/mol biomass fed 1.36
Mols methanol/mol CH4 fed 1.30
Gasifier throughput, kg-mol/liter of methanol product 0.139
Net CO2 emission, mol/mol methanol produced and utilized 0.631
Thermal efficiency (HHV), % 67
Development Status
The performance estimates of Table 4 assume chemical equilibrium in each process
stream, as given in Figure 2. The degree to which the performance estimates can be attained will
be determined in bench scale tests of the reactor hardware soon to be undertaken by the EPA
with funds from the Strategic Environmental R&D Program of the Department of Defense, and
cosponsorship with the California South Coast Air Quality Management District. The 50-atm
methanol synthesis step and the biomass gasification step, including control of alkali vqlatiles and
entrained particulates, are within current state of the art. The other principal step, methane
pyrolysis, is not. The pyrolysis reactor requires indirect heat transfer with inert solids
recirculated at high volume between the fluidized bed reactor and an external combustor/riser.
Although many aspects of the required pyrolysis system have been operated successfully in the
Cogas process (Hebden and Stroud, 1981) and the Universal Oil Products catalytic hydrocarbon
cracking process (Pohlenz and Scott, 1966), none has been operated at the pressure and
temperatures required by Hydrocarb. Substantial engineering challenges must therefore be met,
-------
beginning with choice of materials and extending to control of heat carrier attrition, refractory
erosion, high temperature gas/solid separation, high pressure combustion of carbon black, and
isolation of combustion gases from the process stream.
Economic Assessment
Our estimate of the capital cost of a Hydrocarb plant is obtained from a comparative
analysis based on the detailed evaluation of the Texaco coal gasification, dedicated methanol
plant that was prepared by Fluor Engineers and Constructors (Buckingham et al., 1981). That
plant, operating at a gasifier pressure of 59 atm, produces 1.25xl07 liters/day of methanol with
a gasifier throughput of 0.158 kg-mol per liter of methanol product. We take credit for the
absence of an air separation unit in Hydrocarb and take partial credit for the shift converter and
Selexol gas scrubbing units. The Texaco system, which is equivalent to a Hydrocarb plant
processing 5300 (dry)Mg/day of biomass, was estimated by Fluor to require a plant facilities
investment (PFI) of $1.076xl09 in 1979 dollars. With the appropriate credits, adjusting for
differences in throughput, and accounting for inflation (by a factor of 1.55), we estimate the PFI
for Hydrocarb at $1.057xl09 in current dollars.
Our economic evaluation assumes operating and maintenance (O&M) costs to be slightly
lower than Texaco's 6 percent of PFI which included a significant cost for disposal of coal ash.
I
With the reduced ash disposal cost for Hydrocarb, O&M is calculated to be 5 percent of PFI, or
$1.609 x lOVday for a 5300 (dry)Mg/day plant.
Total capital investment (TCI) is normally about 125 percent of PFI (and is the case for
Fluor's Texaco evaluation). Therefore, it is assumed here that the TCI (which includes allowance
for funds during construction, working capital, land, royalties, etc.) for a 5300 (dry)Mg/day
10
-------
Hydrocarb plant will be $10.57 x 108 x 1.25 = $13.21 x 108 in current dollars.
Alcohol Production Cost Estimate
The cost of producing methanol in a 5300 (dry)Mg/day Hydrocarb plant with a delivered
cost of biomass assumed to be $71.26/(dry)Mg is calculated as follows, assuming a 6 percent
capital charge rate and 15 percent return on investment:
From the material and energy balances of the process simulation, 63.6 Mg of CH4 feed
is required per 88.3 (dry)Mg of biomass feed. At a cost of $2.50 per 1000 ft3 (28.3 m3), the
daily cost of natural gas feed for this Hydrocarb plant will be
63.6 x 22400 x 2.5 x 5300
= $470,500/day
88.3 x 16.043 x 28.32
The daily operating costs are then:
Biomass 5300x71.26 = $377,680
Natural gas = $470,500
O&M 0.05(10.57 x 108)/365(0.9) = $160,880
Capital charge 0.06(13.21 x 108)/365(0.9) = $241,300
Total daily operating cost $1,250,400
From the material and energy balances, 165.8 kg of methanol is obtained from 88.3 kg of
biomass and 63.6 kg of CH4; therefore, the cost of production (Cp) for 15 percent return on
investment (ROI) is:
165.8 x 5300 x 1000 x 2.205 0.15 x 13.21 x 108
Cpx - 1,250,400 =
88.3 x 8.34 x 0.796 365 x 0.9
Giving Cp = $0.561/gallon or $9.36/GJ (LHV).
11
-------
Comparison with other alcohol processes Cost estimates for the production of ethanol and
methanol from biomass by other routes have recently been published. In the case of ethanol, the
estimates are given for the enzymatic hydrolysis process for two plant sizes, 1745 (dry)Mg/day
and 9090 (dry)Mg/day (Wyman et al., 1992). Methanol costs were recently reviewed by Larson
and Katofsky (1992) for four biomass gasification processes rated at 1650 (dry)Mg/day plant size;
of those methanol processes, the BCL indirectly heated gasifier was shown to yield significantly
lower production cost than the others. The result of Larson and Katofsky's evaluation of the
BCL process is summarized in Table 5 together with the above data for Hydrocarb and the data
for the two enzymatic ethanol systems evaluated by Wyman et al.
TABLE 5. COST ESTIMATES FOR PRODUCTION OF ALCOHOL FUELS FROM BIOMASS
Hydrocarb
methanol
Plant size, (dry)Mg/day
Plant facilities investment (PFI), millions of US$
Total capital investment (TCI), % of PFI
O&M, % of PFT
Total operating costb, millions of US$/yr
Capital charge rate, %
Return on investment, %
Alcohol production, millions of liters/yr
Biomass cost, US$/(dry)Mg
Plant operating factor, %
Alcohol production cost, $/GJ (LHV)
5300
1057
125
5.0
53
6
15
4100d
71.26
90
9.36
Enz. Hydrol.
ethanol
1745
128
123
4.5
17. 8C
6
7
219e
46
90
13.12
9090
432.75
124
4.5
66°
6
7
1096£
46
90
11.06
BCL
methanol
1650
152
146
7.0
13.5
6
16
333d
37.6
90
9.62
"Excluding catalysts (enzymes)
Excluding feedstock
Including credit for exported electricity
"99+% CH3OH; less than 0.75% H2O
•90.3% QH5OH; 4.7% H2O; denatured with 5% gasoline
12
-------
It is clear from Table 5 that a comparison of alcohol production costs requires
normalization of their implicit assumptions regarding plant size, return on investment, and
biomass cost. The data were therefore recalculated for a common plant size of 9090 (dry)Mg/day
and 7 percent ROI using scaling factors that duplicate the results of the ethanol scaleup from
1745 to 9090 (dry)Mg/day according to the following procedure:
(
Total capital investment for 9090 (dry)Mg/day plant = TCI x (9090/plant size)0744
and: O&M cost for 9090 (dry)Mg/day plant = O&M x (9090/plant size)08
Figure 3 shows the resulting relationship between alcohol production cost at the plant gate
and the delivered cost of biomass when the data of Table 5 are normalized to the same
assumptions. At the expected cost of biomass delivered to a plant of this size, $73.4/(dry)Mg
(Table 3), the comparison suggests that Hydrocarb may produce alcohol fuel at a cost about half
that of the best ethanol process and about 25 percent less than the best alternative methanol
process. It is also significant that Hydrocarb is less sensitive to the cost of biomass than the
other processes, due mainly to the fact that natural gas is a lower cost feedstock than biomass,
and also because a higher yield of alcohol is obtained per unit of biomass fed.
Ethanol forms an azeotrope containing 10.7 mol percent water which is difficult to
separate, and further refinement is not attempted for the enzymatic process. Fuel grade ethanol
consequently contains 4.7 wt percent water after gasoline is added as a necessary denaturant.
Methanol does not form an azeotrope with water and does not require a denaturant. Fuel grade
methanol will therefore be essentially pure CH3OH.
13
-------
2 12
O
10
_L
J_
50 60 '0 BO
DELIVERED BIOMASS COST, $/(dry)Mg
Figure 3. Comparison of alcohol production costs for a 9090 (dry)Mg/day energy conversion
plant with 7 percent return on investment.
Eguivalent Gasoline Price
Following the calculation procedure outlined above, but assuming a 9090 (dry)Mg/day
plant size and 15 percent ROI, the cost of methanol production by Hydrocarb is calculated to be
$0,526/gal (3.79 liter). The equivalent gasoline price can be obtained by adding the marketing
costs as specified by the Office of Technology Assessment (U.S. Congress, 1990): $0.08 for
markup, $0.06 for distribution, and $0.12 for taxes per gallon (3.79 liter) of methanol and
14
-------
multiplying by the volumetric equivalence ratio of methanol/gasoline. Assuming an equivalence
ratio of 1.57 for vehicles optimized for neat methanol, the equivalent gasoline price is:
($0.526 + 0.08 + 0.06 + 0.12)1.57 = $1.23/gal (3)
In 1992, the average price of gasoline in the U.S., weighted according to the amount of each
grade sold, was $1.19/gal. One can therefore conclude that Hydrocarb methanol would cost
about $0.04/gal more than the current gasoline price. With or without the energy tax considered
by the Congress, if methanol can be produced at the projected costs, it should be competitive
with current gasoline prices.
The volumetric ratio of 1.57 used in eq. 3 assumes a 27 percent improvement in fuel
economy for methanol vehicles, due to its higher thermal efficiency in internal combustion
engines. This ratio is obtained from tests performed by the EPA Office of Mobile Sources (U.S.
EPA, 1989) on conventional vehicles powered with neat methanol. Those vehicles employed
some, but not all, of the characteristics that take advantage of methanol's chemical and
combustion properties which make it an inherently more efficient fuel than gasoline. The most
important of those properties are its higher octane rating, which allows a higher compression
ratio, its wide flammability limits, which permit good combustion at high air-to-fuel ratios, and
its higher power output, which allows the use of a smaller, more efficient engine. Two converted
gasoline engines (U.S. EPA, 1989) and two modified diesel engines (Bruetsch and Hellman,
1992) have been tested with an overall average improvement of 27 percent in thermal efficiency.
Most other performance comparisons reported in the literature were obtained with vehicles
designed for gasoline or M85, which give poorer performance than can be expected when both
the engine and vehicle are designed specifically for use with neat methanol. Although no vehicle
15
-------
has yet been designed to take advantage of all properties of neat methanol as its intended fuel,
the best data available to date indicate that such vehicles can achieve 30 percent improvement
in thermal efficiency relative to gasoline.
Effect of Future Cost Escalations
We have assumed the current price of natural gas to be $2.50/106 Btu (1.06 GJ) in the
above cost comparisons. This is representative of the current price, but it has recently been as
low as $1.10/106 Btu (1.06 GJ) in some areas of the U.S.. The sensitivity of the Hydrocarb
methanol production cost to the price of natural gas is shown in Figure 4 for a 9090 (dry)Mg/day
plant and 15 percent ROI. The price of natural gas is expected to increase in the future with the
price of other energy sources, particularly crude oil. The Gas Research Institute (GRI)(Dreyfus
and Koklauner, 1992) project a 38 percent escalation of the crude oil price in constant 1992
dollars by the year 2010. It may be assumed that the price of natural gas will escalate by the
same amount, from $2.50 to $3.45/106 Btu (1.06 GJ) by the year 2010. If we use this value for
the price of natural gas and assume that the real cost of biomass does not escalate (it may in fact
decrease in constant dollars if projected improvements of yield, genetics, and cultivation practices
are realized), then the cost of Hydrocarb methanol in the year 2010 would increase from the
current value of $0.526 to $0.580/gal (3.79 liter) which is equivalent to a gasoline price of
$1.32/gal (3.79 liter). '
The GRI projection of the average retail gasoline price for the year 2010 is $1.58/gal
(3.79 liter). Assuming no energy tax on gasoline in the year 2010, the cost of methanol would
be $0.26/gal (3.79 liter) less than the equivalent price of gasoline. The projected trends therefore
favor methanol as a cheaper fuel than gasoline.
16
-------
0.7
ro
CO
O
o
z
o
Q
O
cc
Q.
d
<
°6
0.5
04
0.3
Current equivalent gasoline price
With energy lax - - - -
Without tax ....
j_
012345
NATURAL GAS PRICE, $/mi!lion Btu
Figure 4. Estimated methanol production cost as a function of the price of natural gas;
plant size = 9090 (dry)Mg/day, biomass = $73/(dry)Mg, return on investment = 15%.
IMPACT ON PETROLEUM DISPLACEMENT AND GREENHOUSE GAS EMISSIONS
The Energy Policy Act of 1992 (U.S. Congress, 1993) is intended to promote the
replacement of petroleum motor fuels with alternative fuels to the maximum extent practicable
and to ensure the availability of the alternative that will have greatest impact on reducing oil
imports, improving the national economy, and reducing greenhouse gas emissions. It establishes
numerical replacement goals of 10 percent by the year 2000 and 30 percent by the year 2010.
17
-------
Alcohol fuels derived from domestically produced biomass and competitive with
petroleum fuels would significantly benefit the national economy if 30 percent of the petroleum
requirement could be displaced. Not only would oil imports be reduced, but many jobs would
be created within the U.S. industrial and farming sectors. As indicated by Figure 3, methanol
is likely to be the least costly alcohol option and, if produced by Hydrocarb, the most competitive
with gasoline. If successfully developed, Hydrocarb methanol should be less costly than
petroleum fuels by the year 2010.
Lowest cost is of little importance, however, if the available biomass cannot be converted
into sufficient amounts of fuel to substantially offset the needs of the transportation sector. Table
6 compares the amount of alternative fuel that could be produced from 1 tonne of biomass, the
corresponding gasoline displacement, and the CO2 reduction from a vehicle fleet, if that biomass
were converted to alcohol by one of three process options. On this basis of comparison,
Hydrocarb would more than triple the amount of gasoline displaced by conversion of the biomass
to liquid fuel. The last column of Table 6 indicates the amount of methanol that could be
produced from the natural gas (720 kg/tonne of biomass) that is required for Hydrocarb if that
gas were used in a separate plant to produce methanol by the conventional steam reforming
process. Thus, if one considers the BCL process supplemented by a conventional methanol plant,
the comparison indicates that the two processes would displace 12 percent less gasoline than a
single Hydrocarb plant and obtain 49 percent less CO2 reduction. The improved technology
option for ethanol production assumes that a large increase in biomass conversion efficiency can
be achieved, together with a major reduction of capital cost for the enzymatic process.
Comparison with that option in Table 6 indicates a Hydrocarb advantage of 20 percent more
18
-------
gasoline displacement and 135 percent greater CO2 reduction.
TABLE 6. CO2 REDUCTION POTENTIALS FROM 1 TONNE OF BIOMASS
Alcohol production technology
Ethanol Methanol Methanol Methanol from
by enzymatic hydrolysis by BCL by natural gas" by
(current) (improved) gasification Hydrocarb steam reforming
Alcohol produced, kg-mol 5.7 8.8 18 59 34
Gasoline displaced, gal 70 108 125 405 230
Net CO2 eliminated, kg 630 970 1130 2490 87
"Assuming that the natural gas used for Hydrocarb were convened to methanol in a
separate plant
As suggested by Table 5, earlier estimates of alcohol production costs from biomass
generally assumed plant sizes ranging from 1500 to 2000 (dry)Mg/day. In order to displace 30
percent of the petroleum requirement in the year 2010 (about 7.9 EJ) with biomass conversion
plants of that size, the number of plants necessary would be unrealistically large as indicated by
Table 7. Biomass conversion plants as large as 9090 (dry)Mg/day may still be of questionable
practicality for processes other than Hydrocarb because of the large number of plants required.
One must also consider the amount of land in the U.S. that is suitable for the production
of woody biomass as short rotation crops in dedicated energy farms. That area, not essential for
food crops, has been conservatively estimated (Graham el al., 1992) to be 14 x 106 ha which
could yield about 3 EJ of wood energy. An optimistic estimate of the U.S. maximum SRWC
19
-------
TABLE 7. NUMBER OF ENERGY CONVERSION PLANTS REQUIRED TO PRODUCE 30
PERCENT OF U.S. HIGHWAY FUEL REQUIREMENTS IN THE YEAR 2010
Number of plants producing fuel by:
Plant size, Enzymatic BCL biomass
(dry)Mg/day of biomass hydrolysis gasification Hydrocarb
1,700 1705 1110 235
9,090 340 208 44
energy yield is 12 EJ (Lee et al., 1991). Given the projected alcohol yields from the leading
process options, Table 8 shows the percent of highway fuel consumption in the year 2010 that
could be replaced. Should the lower estimate of biomass availability prove correct, the
comparison indicates that no more than 7 percent displacement of petroleum could be obtained
as ethanol, whereas Hydrocarb could displace the full 30 percent with that minimum amount of
biomass. Should the 12 EJ estimate actually represent the total biomass potential, much of that
land will nevertheless be too far from an energy conversion plant to permit its use for biomass
farming. In any case, it is clear that only methanol could meet the projected goal of 30 percent
displacement and, if it were produced by Hydrocarb, could in theory displace all of the
transportation fuel requirement in the year 2010. As a practical matter, it is unlikely that either
the biomass supply or alcohol production capacity for 100 percent displacement could be in place
by the year 2010.
20
-------
TABLE 8. PERCENT OF HIGHWAY FUEL CONSUMPTION IN THE YEAR 2010 THAT
COULD BE DISPLACED BY BIOMASS DERIVED FUEL
Available
biomass supply,
EJ
3
6
12
Biomass
Enzymatic hydrolysis
(current)
5
10
18
(improved)
7
14
28
conversion technology
BCL biomass
gasification
11
21
42
Hydrocarb
36
71
CONCLUSION '
The Energy Policy Act provides a strong incentive for identification of an alternative fuel
that can best meet future demands for displacement of petroleum, improving the national
economy, improving urban air quality, and reducing greenhouse gas emissions. Based on the
assumptions made, this analysis suggests that methanol has greater potential than ethanol for
meeting national goals for alternative fuel production, in terms of both the amount of petroleum
that could be displaced and the cost of production. Among methanol production options, the
Hydrocarb process presents a prospect for maximum displacement of petroleum and greatest
reduction of greenhouse gas emission from mobile sources. The large potential effect of
alternative fuel production on the national economy implies the use of domestic resources as
feedstock to the maximum possible extent and therefore favors biomass produced in a renewable
and sustainable manner such as SRWC. Because of the limitation of biomass supply it will be
essential to leverage that feedstock with another domestically available feedstock to meet the
projected alternative fuel requirements. Since natural gas is a cofeedstock for the Hydrocarb
21
-------
process, the amount of liquid fuel that can be produced from the limiting resource is increased
substantially. This analysis projects that Hydrocarb has the potential to yield methanol at a cost
lower than the future cost of gasoline. Although development of the Hydrocarb process will
challenge the state-of-the-art in several respects, the projected advantages form the basis for the
EPA program to fully evaluate its potential in a systematic development effort.
LITERATURE CITED
Bhat, M.G., English, B., and Ojo, M. "Regional Costs of Transporting Biomass Feedstocks," in
Liquid Fuels from Renewable Resources, J.C. Cundiff (ed.) Am. Soc. of Agr. Engineers, St.
Joseph, MI, pp. 50-57 (1992).
Bruetsch, R.J., and Hellman, K.H. "Evaluation of a Passenger Car Equipped with a Direct
Injection Neat Methanol Engine," Alternative Fuels for CI and Sf Engines, SAE technical
paper No. 920196 (1992).
Buckingham, P.A., Cobb, D.D., Leavitt, A.A., and Snyder, W.G. "Coal-to-Methanol: An
Engineering Evaluation of Texaco Gasification and ICI Methanol-Synthesis Route," Fluor
Constructors and Engineers, Inc., prepared for the Electric Power Research Institute, EPRI
Report No. AP-1962 (1981).
Dreyfus, D.A., and Koklauner, A.B. "Description of the Global Petroleum Supply and Demand
Outlook," Strategic Planning and Analysis Division, Gas Research Institute, Chicago, IL, p.
5 (1992).
Graham, R.L., Wright, L.L., and Tufhollow, A.F. "The Potential for Short-Rotation Woody Crops
to Reduce U.S. CO2 Emissions," Climate Change, pp. 223-238 (1992).
22
-------
Hebden, D., and Stroud, H.J.F. "Coal Gasification Processes," in Chemistry of Coal Utilization,
Second Supplementary Volume, M.A. Elliott (ed.), John Wiley & Sons, Inc., New York, NY,
pp. 1701-1706 (1981).
Ismail, A., and Quick, R. "Advances in Biomass Fuel Preparation, Combustion, and Pollution
Abatement Technology," Energy from Biomass and Wastes XV, pp. 1063-1100 (1991).
Jones, K.W. "Operational Case Histories of the South Port Ethanol and Kentucky Agricultural
Energy Corporation Fuel Ethanol Plants," Energy from Biomass and Wastes XII, p. 1365
6
(1989).
Kenney, W.A., Gambles, R.L., and Zsuffa, L. "Energy Plantation Yields and Economics," Energy
from Biomass and Wastes XV (1991).
Larson, E., and Katofsky, R. "Production of Hydrogen and Methanol via Biomass Gasification,"
in Advances in Thermochemical Biomass Conversion, A.V. Bridgwater (ed.), Elsevier, New
York, NY (1992).
Lee, K.H., Johnston, S.A., Stancil, W.D., andByrd, D.C. "Biomass State-of-the-Art Assessment,"
Research report GS-7471, Volume 1, Electric Power Research Institute, p. 3-7 (1991).
Perlack, R.D., and Ranney, J.W. "Economics of Short-Rotation Intensive Culture for Production
of Wood Energy Feedstocks," Energy, pp. 1217-1226 (1987).
Pohlenz, J.B., and Scott, N.H. "Method for Hydrogen Production by Catalytic Decomposition of
Gaseous Hydrocarbon Stream," Universal Oil Products, U.S. patent No. 3,284,161 (1966).
Reed, T.B. (ed.) "Biomass Gasification, Principles and Technology," Noyes Data Corp., Park
Ridge, NJ, p. 360(1981).
23
-------
Steinberg, M, Grohse, E.W., and Tung, Y. "A Feasibility Study for the Coprocessing of Fossil
Fuels with Biomass by the Hydrocarb Process," Research report EPA-600/7-91-007 (NTIS
DE91 -011971), U.S. EPA, Air and Energy Engineering Research Laboratory, Research Triangle
Park, NC (1991).
Steinberg, M., Kobayashi, A., and Dong, Y. "Rates of Reaction and Process Design Data for the
Hydrocarb Process," Research report EPA-600/R-93-020 (NTIS PB93-155976), U.S. EPA, Air
and Energy Engineering Research Laboratory, Research Triangle Park, NC (1993).
Strauss, C.H., Grade, S.C., Blankenhorn, P.R., and Bowersox, T.W. "First and Second Rotation
Cost Evaluation of Biomass from SRIC Populus Plantations," Energy from Biomass and
Wastes XII, pp. 211-225 (1989).
Strauss, C.H., Grado, S.C., Blankenhorn, P.R., and Bowersox, T.W. "Economic Evaluation of
Optmum Rotation Age for SRIC Plantations," Energy from Biomass and Wastes XIII, pp. 295-
307 (1990).
U.S. Congress, Energy Policy Act of 1992, Public Law 102-486, Washington, DC, U.S. Govt
Printing Office, Title V, Sec. 502 (1993).
U.S. Congress, Office of Technology Assessment "Replacing Gasoline: Alternative Fuels for
Light-Duty Vehicles," OTA-E-364, Washington, DC, U.S. Govt Printing Office, p. 76 (1990).
U.S. Department of Energy "National Energy Strategy," First Edition 1991/1992, Washington,
DC, U.S. Govt Printing Office (1991).
U.S. Environmental Protection Agency "Analysis of the Economic and Environmental Effects of
Methanol as an Automotive Fuel," Research report 0730 (NTIS PB90-225806), Office of
Mobile Sources, Ann Arbor, MI (1989).
24
-------
Wright, J.D., Power, A.J., and Bergeron, P.W, "Evaluation of Concentrated Halogen Acid
Hydrolysis Processes for Alcohol Fuel Production," Research report SERI/TR-232-2386, Solar
Energy Research Institute, p. 56 (1985).
Wright, J.D. "Ethanol from Biomass by Enzymatic Hydrolysis," Chemical Engineering Progress,
p. 69 (August 1988).
Wright, L.L., Graham, R.L,, Turhollow, A.F., and English, B.C. "Opportunities to Mitigate
Carbon Dioxide Buildup using Short-Rotation Woody Crops," in Sampson, R.N. and Hair, D.
(eds.), Forests and Global Change, Vol. 1, American Forestry Assoc., Washington, DC, pp.
123-156 (1992).
Wyman, C.E., Bain, R.L., Hinman, N.D., and Stevens, DJ. "Ethanol and Methanol from
Cellulosic Biomass," in Renewable Energy: Sources of Fuels and Electricity, T.B. Johansson,
H. Kelly, A.K.N. Ruddy, R.H. Williams (eds.). Island Press, Washington, DC, pp. 865-923
(1992).
25
-------
AEERL-P-1084
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before compi
1. REPORT NO.
EPA/600/A-93/298
2.
4. TITLE AND SUBTITLE
Reduction of CO2 Emissions from Mobile Sources by
Alternative Fuels Derived from Biomass
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7-AUTHORls)R.H. Borgwardt (EPA), M.Steinberg (BNL),
and Y. Dong (Hydrocarb)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Brookhaven National Laboratory, Upton, NY 11973.
Hydrocarb Corporation, New York, NY 10018.
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
IAG DW-89934598 (BNL)
68-D1-0146WA/9 (Hydrocarb)
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Air and Energy Engineering Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Published paper: 4/9Q-1/93
14. SPONSORING AGENCY CODE
EPA/600/13
15. SUPPLEMENTARY NOTES AEERL project officer is Robert H.
919/541r2336. Presented at AIChE, Seattle, WA, 8/15-
Borgwardt, Mail Drop 63,
18/93.
16. ABSTRACT,
\\The paper discusses process options forjutilizing biomass to obtain great-
est reduction of carbon dioxide (CO2) emissions from motor vehicles at least cost. -
(NOTE: The Energy Policy Act of 1992 seeks to displace 30% of the U. S. petr'oleum
requirement by the year 2010 with an alternative that, among other things, has great-
est impact on reduction of greenhouse gas emissions. An alternative fuel derived
from biomass is probably the most practicable method of achieving, that objective.)
The paper emphasizes the Hydrocarb process, currently under evaluation by EPA for
production of methanol from short-rotation woody crops using natural'gas as cofeed-
stock. It"is compared with other process options in terms of feedstock availability,
cost of conversion to liquid fuel, amount of petroleum that can be displaced,. and com-
petitiveness with gasoline price.- The analysis indicates that, for a given supply of
biomas-s, more petroleum can be displaced through methanol production processes
than through those for ethanol^If performance projections can be achieved, the Hy-
drocarb process should displace, more than three times as much gasoline as the
other options. Assumed trends invfeedstock costs are expected to favor methanol,
relative to the equivalent price of)gasoline.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution
Motor Vehicles
Biomass
Carbon Dioxide
Greenhouse Effect
Carbinols
Natural Gas
Ethanols
Gasoline
Pollution Control
Stationary Sources
Hydrocarb Process
Methanols
13 B
13 F
08Ar06C
07B
04A
07C
21D
13. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)'
Unclassified
21. NO. OF PAGES
25
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
------- |