United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-01/066 October 2001
Mercury in Petroleum and
Natural Estimation of
Emissions from Production,
Processing, and Combustion
S. MarkWilhelm
The report is intended to assist in the
identification of those areas that require
additional research, especially the
needs associated with measuring the
concentrations of the various chemical
species of mercury (Hg) in the various
feedstocks and waste streams associ-
ated with the oil and gas industry. Ac-
quisition of additional information will
be necessary if the magnitudes of Hg
emissions associated with U.S. petro-
leum and natural gas are to be esti-
mated accurately.
This Project Summary was developed
by the National Risk Management Re-
search Laboratory's Air Pollution Pre-
vention and Control Division, Research
Triangle Park, NC, to announce key find-
ings of the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Discussion
Mercury (Hg) extracted from the earth
in oil and gas, including that in associ-
ated waste streams, contributes to the
global Hg cycle. While the amount of Hg
that derives from burning coal can now
be estimated with reasonable confidence,
the amount that derives from petroleum
cannot be estimated with equal confidence
at present. The report provides a compi-
lation of currently available data on the
concentration of Hg in oil and gas and in
the various waste streams associated with
petroleum and gas production, transpor-
tation, and processing. From these data,
estimates are compiled of the contribu-
tion of Hg to the U.S. (and global) envi-
ronment. The estimates are incomplete
due to lack of data, but they do provide a
framework from which one can gain a
rough, but preliminary, idea of the
amounts that may be involved. With addi-
tional data inputs to the estimates, it even-
tually may be possible to estimate the
total amounts of Hg emissions from oil
and gas with greater accuracy. Table 1
summarizes the estimates compiled and
discussed in the report.
The report and cited references gener-
ally use a material balance approach to
estimating Hg emissions to air, water, and
solid waste streams. A material balance
can be applied to oil and gas production
by examination of Hg in produced fluids
including discharged water and drilling
waste. Note that not all of the Hg in waste
streams originates with the Hg in the res-
ervoir. In production, some of the Hg origi-
nates from cuttings (rock not necessarily
associated with the reservoir) and from
the chemicals (barite) used to add weight
to the drilling fluids. When a material bal-
ance is applied to a refinery, a small por-
tion of the Hg originates with treatment
chemicals, but the majority comes from
the oil that is processed.
Currently available data for total Hg
(dissolved and suspended) in petroleum
and fuel products, when applied to a
mass balance for Hg in the U.S. refining
system, provide an order of magnitude
estimate of the contribution of Hg in oil
and gas to U.S. anthropogenic emissions.
The model finds the mean amount of Hg
in petroleum refined in the U.S. to be
close to 10 ppb and predicts that the
amount of Hg in fuel products burned in
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Table 1. Summary of Estimates for Hg Emissions from Oil and Gas Production and Processing
Type
Water
Subtotal
Solid Waste
Subtotal
Air
Subtotal
TOTAL
Industry Segment
Oil and Gas Production
Oil Refining
Oil Transportation
Oil and Gas Exploration
Oil Refining
Oil Production
Oil Production
Gas Production and Transmission
Oil
Gas
Category
Produced Water
Refinery Water
Tanker Ballast
Drilling Waste
Refinery Waste
Flared Gas
Fugitive
Fugitive
Fuel Combustion
Fuel Combustion
Amount of
Discharge (106kg/y)
500
250
?
50
30
4.5
1
5.9
790
341
Total Hg
(PPb)
1?a
1?
1?
100?
50?
1.5?
185
?
<8
<0.3?
Estimated Emission
Rate (kg/y)
500
250
?
750
5,000
1,200
6,200
10
185
?
6,000
100
6,300
13,250
the U.S. is less than approximately 6,000
kg/y. The amount of Hg in U.S. fuel oil
was estimated to be no greater than ap-
proximately 1,500 kg/y. This number is
somewhat in conflict with current U.S. EPA
estimates of Hg in fuel oil (10,000 kg/y).
While the estimates compiled in this
report are useful in the present time frame,
they are insufficient to answer some ma-
jor issues and questions that are impor-
tant in determining the contribution of Hg
in petroleum to global pools and fluxes.
For example, data on refined products
are scarce and undocumented as to the
refineries from which they originate. Thus
it remains uncertain as to whether the Hg
in crude oil is accounted for mainly by the
amount in products (> 50%) or if it distrib-
utes more prevalently to other avenues of
egress from refineries (solid waste, waste-
water, fugitive emissions).
It does appear that, based on currently
available data, approximately half of the
entire amount of Hg associated with oil
and gas (exploration, production, trans-
portation, processing) enters the atmo-
sphere in fuel combustion. Some
unknown portion of this amount is cap-
tured by pollution control equipment, but
the total is likely to be less than approxi-
mately 6 Mg/y (if the mean amount of Hg
in crude oil is 10 ppb as expected). This
would suggest that, while oil and gas
account for approximately the same mass
of fossil fuel burned yearly in the U.S., the
amount of Hg in combusted petroleum
and gas is about 10 times less than that
which derives from coal (66 Mg/y).
The distribution of Hg to effluents and
air emissions in the refining process is
important, and only limited data are avail-
able upon which any definite conclusions
can be drawn. Insufficient data are avail-
able for many of the major refinery streams
including wastewater, solid waste, still
gas, treatment fluids, and products. To
obtain a firm understanding of the fate of
Hg in refineries, it would be necessary to
examine the individual unit processes (de-
salting, distillations, hydrotreating, and
catalytic cracking). In each case, the at-
tempt to determine the distribution of Hg
would require tracking not only total Hg
but also its various species (volatile, oxi-
dized, inert) by measuring concentrations
of each species in all of the streams that
enter and exit the process.
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S. Wilhelm is with Mercury Technology Services, Tomball, TX 77375. D
David A. Kirchgessner is the EPA Project Officer (see below). D
The complete report, entitled "Mercury in Petroleum and Natural Gas: Estimation^
of Emissions from Production, Processing, and Combustion," (Order No.
PB2001-109026; Cost: $29.50, subject to change) will be available from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161-0001
Telephone: (703) 605-6000
(800) 553-6847 (U.S. only)
The EPA Project Officer can be contacted at:
Air Pollution Prevention and Control Division
National Risk Management Research Laboratory
U. S. Environmental Protection Agency
Research Triangle Park, NC 27711-0001
United StatesD
Environmental Protection Agency D
CenterforEnvironmental Research InformationD
Cincinnati, OH 45268D
PRESORTED STANDARDD
POSTAGES FEES PAIDD
EPAD
PERMIT No. G-35D
Official Business
Penalty for Private Use
$300
EPA/600/SR-01/066
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