Relatively large volumes of distillate and residual oil are burned each year in the U.S. These fuels are used by utilities (primarily fired by #6 residual oil), commercial and industrial boilers (which depending on their size may be fired by either residual or distillate oils or a combination thereof) and residential boilers (primarily fired by #2 distillate fuel). Fuel oils contain trace amounts of mercury which occurs naturally in crude oils at levels that are very variable and which may relate to the specific source of the oil. These values range from 0.007 to 30 ppm, with a typical value being 3.5 ppm (USEPA, 1989; USEPA, 1993a). Massachusetts Fuel Oil Use
Aggregate MA usage estimates for these fuel types combined with USEPA derived emission factors were used to estimate total possible mercury emissions from oil combustion in Massachusetts. The total amount of distillate and residual oil burned per year in the Commonwealth equals approximately 1.0 and 1.15 billion gallons, respectively (MADEP, 1995). Due to the large number of oil fired boilers in operation in MA individual source estimates have not been derived and no attempt has been made to identify specific facilities. Estimates for Overall Emissions of Mercury from Massachusetts Oil Combustion
Due to the large amount of variability in measured and predicted emission factors for oil combustion, the potential mercury emissions from this source category were calculated using a range of possible values.
Measured emission factors for mercury from distillate oil combustion have been reported to range from 2.8 to 17.0 lb. per trillion Btu (USEPA, 1989; USEPA, 1993a). These estimates are very uncertain due to variations in the mercury content of the oils and in possible measurement errors associated with the sampling of vapor phase mercury in the stack emission tests (Endnote 17). USEPA recently used a predicted value of 6.8 lb./trillion Btu (based on the average mercury content of this oil type and assuming no mercury removal by APC devices) in their calculations of national mercury emissions from distillate oil combustion. Lacking other more specific data these values were used to derive a range of estimates of overall mercury emissions from this source category in Massachusetts.
Using a heat value of 140,000 Btu per gallon for this fuel, the heat energy equivalent associated with the Commonwealth's overall consumption of 1 billion gallons of distillate oil equals 140 trillion Btu a year. Multiplying this estimate by the range of emission factors noted above (using a minimum value of 2.8 and a maximum value of 17 lb. of mercury per trillion Btu) yields a range of possible mercury emissions from statewide combustion of distillate oil of 392 to 2,380 lb. per year. Using the USEPA predicted emission factor of 6.8 lb. mercury/trillion Btu yields an estimate of 952 lb. mercury/year.
Measured emission factors for residual oil combustion have been reported to range from 0.037 to 1.4 pounds per trillion Btu (USEPA, 1989). Because of the great variability in these measured values as well as the fact that they are believed to be low due to inefficient capture of mercury vapor during sampling of the flue gases during the emission tests, these estimates were not used in the following calculations. USEPA recently used a predicted value (based on average mercury content of this oil type and assuming no mercury removal by APC devices) of 7.2 lb. per trillion Btu in their calculations of national mercury emissions from residual oil combustion. We have used this value as a maximum emission factor in our calculations. Since some control of mercury emissions from APC devices installed on some residual oil-fired boilers is to be expected this USEPA value may be somewhat high. Depending on the exact type of APC devices installed, mercury removal from flue gases may range from less than 10% (for ESPs, mechanical collectors and Venturi scrubbers) to greater than 90% (for carbon injection systems followed by high efficiency particulate capture devices) (USEPA, 1989; USEPA, 1993a).
Since oil-fired boilers are not generally equipped with these systems the maximum overall control efficiency for this source category in Massachusetts is likely to be closer to 10%, or lower, than 90%. To allow for some limited control of mercury emissions from APC devices, a "best" emission factor estimate was derived by reducing the USEPA value of 7.2 lb. mercury/trillion Btu (for uncontrolled facilities) by 10% to yield a value of 6.48 lb. mercury/trillion Btu.
Using a heat value of 150,000 Btu per gallon for residual oil, the heat energy equivalent associated with the Commonwealth's use of 1.15 billion gallons of this oil equals 172.5 trillion Btu per year. Multiplying this value by the USEPA emission factor cited above (7.2 lb. per trillion Btu) yields an estimated emission rate of 1,242 pounds of mercury per year from combustion of residual oil in the Commonwealth. Allowing for some control of mercury stack emissions (using the "best" estimate emission factor of 6.48 lb. mercury/trillion Btu), yields an estimate of 1,118 lb. mercury/year.
It is important to note that this value is very uncertain and, for many specific oils, may be high. For example, data generated by the Electric Power Research Institute (EPRI) indicate that the concentrations of mercury in some residual oils may be much lower than those estimated by USEPA. EPRI has reported that the concentrations of mercury in an unspecified number of samples from unspecified oil fields (Chu, 1995) ranged from approximately 0.1-0.3 lb./trillion Btu. EPRI has also reported that measured mercury concentrations in stack flue gases, determined on a limited number of analyses (5), ranged from approximately 0.16-1.4 lb./trillion Btu, with a geometric mean of 0.46 lb./trillion Btu. If this latter emission factor is confirmed to be accurate and applicable to the fuel oils actually utilized by MA utilities, the estimated mercury emissions by this source category would be reduced to approximately 79 lb./year. Coal-Fired Facilities Background
These facilities burn coal to generate heat for commercial or industrial applications or to fire steam boilers used to produce electricity. Mercury emissions from these facilities are of concern because this metal occurs at trace levels in essentially all coal. The concentration of this metal varies considerably depending on the type of coal used, where it was mined and how it is processed prior to combustion. Even though the concentrations of mercury in most ready-to-fire coals are relatively low, the massive amounts of coal combusted on a yearly basis suggested that such boilers might, overall, be a large source of mercury releases into the general environment.
A large fraction of the mercury contained in the coal burned in these facilities is expected to exit the stack in the vapor phase as a component of the flue gases. At the operating temperatures of coal fired boilers (in excess of 1000 degrees C in the combustion zone) essentially all of the mercury present exists in the vapor phase (USEPA, 1989).
Many coal fired boilers are equipped with electrostatic precipitators (ESP) as their primary air pollution control (APC) device. Although ESPs are very effective at removing particulates, gas phase pollutants are not efficiently captured. Thus, one would predict that ESPs would not reduce mercury emissions to an appreciable degree.
Indeed, the efficiency of ESPs in removing mercury from coal utility boiler emissions has been reported to range from 0-70%, with a median value of approximately 10% (USEPA, 1993). This removal is probably attributable to limited condensation of gas phase mercury as the flue gases cool after combustion. Massachusetts Facilities
There are 10 large scale coal-fired facilities in Massachusetts; two additional facilities have been proposed but are not yet in operation. These facilities are summarized in Table 3-12 and their geographic locations are depicted on Figure 3-15. Of the facilities in operation, nine burn bituminous coal and one sub-bituminous coal. Their coal use ranges from 24 tons/year to 2.6 million tons/year. In total, approximately 4 million tons of coal are burned by these facilities each year. Estimates for Overall Emissions of Mercury from Massachusetts Coal-fired Facilities
As direct measures of mercury emissions from MA coal-fired facilities are not available, indirect methods were used to estimate mercury emissions from coal combustion.
Two fundamentally different approaches were used. The first relied on an emission factor for bituminous coal developed by USEPA (USEPA, 1993a). Based on average mercury concentrations in coal, USEPA estimated that uncontrolled bituminous coal utility boilers were likely to emit approximately 16 lb.. mercury per trillion Btu (emissions from subbituminous coal were estimated to be essentially the same).
| COAL TYPE | |||
|---|---|---|---|
| FACILITY | SUB BITUMINOUS |
BITUMINOUS | TOTAL COAL FIRED Tons/Year |
| U-MA Amherst | X | 44,485 | |
|
Norton Co. Worcester | X | 14,650 | |
|
Rielly Stoker Worcester | X | 588 | |
|
Ware Cogen Ware | X | 24 | |
|
Indeck Montague | X | 40,514 | |
|
Monsanto Springfield | X | 41,908 | |
|
Mt. Tom Holyoke | X | 342,699 | |
|
NEPCO Salem | X | 667,046 | |
|
NEPCO Brayton Pt | X | 2,602,920 | .|
|
Montaup Electric Somerset | X | 232,428 | |
| TOTAL | 3,987,262 | ||
|
*Eastern Energy New Bedford | X | 1,161,576 | |
|
*Silver City Taunton | X | 535,236 | |
|
**The Eastern Energy facility was recently approved for construction in New Bedford. Its permit limits mercury emissions to 1.59 X 10-5 pounds per million Btu based on use of best available control technology. Approval of the Taunton plant is pending. *Proposed coal fired facilities. Note: Totals may not add precisely due to rounding. | |||
It is important to note that this emission factor is quite uncertain due to variability in the actual concentration of mercury in combusted coal. For example, measurements of mercury concentrations in typical coal samples have been made by the United States Geological Survey (USGS), USEPA and industry sources. USGS estimated the concentrations of mercury in various coals based on over 3,300 samples. These samples were of coal as mined, prior to any processing. The Electric Power Research Institute (EPRI) recently reported that mercury levels in ready-to-fire coal were up to 50% lower than the levels estimated using USGS data (EPRI, 1995). The EPRI study involved a much smaller set of 154 samples of ready-to-burn coal and the coals tested may have may not have been directly comparable to the coals analyzed by USGS (e.g. from different coal sources). The data does, however, suggest that coal processing after mining and prior to combustion may reduce the mercury content of this fuel. (The degree to which coal "processing wastes" may impact the environment has not been addressed as there are no such facilities in MA). This, in addition to the anticipated 10% ESP mercury capture efficiency suggests that the USEPA value of 16 lb. mercury/trillion Btu for uncontrolled facilities may be somewhat high.
EPRI AND USGS ESTIMATES OF MERCURY IN COALEPRI argues that the higher USGS levels are due to mercury containing rocks and minerals which would be at least partially removed by processing. Additional coal washing would also be expected to remove some trace elements such as mercury. The extent to which such processing would affect mercury concentrations is open to question and would clearly be dependent on the degree to which non combustibles are removed and the actual distribution of the mercury in the mined material. Depending on the geological nature of the contaminating rocks and minerals, it is possible that they might actually contain less mercury than the coal itself. In this case removal of the rocks would actually lead to an increase in the concentration of mercury in the coal. |
Unfortunately, sufficient information is not available on the mercury concentrations of as-burned coal purchased by Massachusetts facilities nor on the exact processing of such coal. Mercury concentrations in coal have not generally been determined on a per-shipment basis nor are they routinely measured prior to combustion. Such information could be valuable to any source reduction efforts, allowing utilities and other facilities to identify low mercury coal sources or to optimize pollution control device utilization to cost effectively reduce post combustion mercury emissions.
In any case, lacking such information, the USEPA mercury emission factor estimate of 16 lb. per trillion Btu cannot be readily adjusted to account for the specific conditions experienced by the Massachusetts facilities. If this value is applied, unadjusted, to all coal usage in Massachusetts, a total mercury emission estimate of 1,658.7 pounds/year is obtained (3,987,262 tons/year X 26 X 106 Btu/ton) X 16 lb. mercury/1012 Btu= 1,658.7 lb. mercury/year).
Due to the inherent uncertainties in this predicted emission factor, measured emission rates based on stack test results from bituminous coal-fired utility boilers equipped with ESP APC devices (as summarized in USEPA, 1989), were also used to estimate mercury emissions from the coal-fired Massachusetts facilities. These measured mercury emission factors were reported to range from 0.41-22.3 lb. mercury per trillion Btu with an average of 11 (based on 13 boilers; 42 data points) for facilities with ESP pollution control devices (USEPA, 1989). EPRI has estimated that mercury emissions from coal-fired utility plants ranged from 4-14 lb./trillion Btu based on direct measurements (Chu, 1995).
Based upon these emission factors, the potential range of mercury emissions attributable to currently operating coal fired boilers in MA spans from 42.5-2,311.7 pounds of mercury per year. An estimate of 1,153.1 pounds/yr. results when the average emission value of 11 lb. mercury/trillion BTU is used (Table 3-13). Of this total 744.46 lb.. (65%) and 190.76 lb.. (17%) are attributable to the NEPCO Brayton Point and Salem facilities. Using the midpoint of the EPRI emission values cited above (which equals 9.0 lb. mercury/trillion Btu) yields an estimate of 934 lb./year for the State as a whole. Limited trace metals analyses of the coal burned by New England Power (NEP) has been provided to MADEP. Data from two rounds of testing, with from 1-2 analyses reported for each specific coal source tested, suggest that the as-fired coal currently used by NEP may be very low in mercury content. The values from this data set ranged from less than 0.0004 to 0.0045 parts per million of mercury. If confirmed and demonstrated to be consistent with a more robust sampling program these results suggest that the mercury emissions by the NEP Salem and Brayton Point facilities may be more than 1-2 orders of magnitude lower than the estimates presented above (i.e. from 2-22 lb./year for Brayton Point and from 0.5-5.6 lb./year for Salem Harbor).
Using the EPA derived average emission factor of 11 lb./trillion Btu, the proposed facilities at New Bedford and Taunton would emit, if operational, approximately 332 and 153 pounds of mercury per year, respectively.
| "BEST" ESTIMATES OF Hg EMISSIONS* (pounds/year) | |||
|---|---|---|---|
| FACILITY | ESTIMATED RANGE (minimum to maximum) OF Hg EMISSIONS (pounds/year)* |
EPA Data | EPRI Data |
| U-Mass Amherst | 0.47 - 25.78 | 12.72 | 10.30 |
|
Norton Co. Worcester | 0.16 - 8.46 | 4.18 | 3.38 |
|
Rielly Stoker Worcester | 0.006 - 0.34 | 0.17 | 0.13 |
|
Ware Cogen Ware | 0.0002 - 0.014 | 0.007 | 0.005 |
|
Indeck Montague | 0.43 - 23.48 | 11.58 | 9.37 |
|
Monsanto Springfield | 0.45 - 24.28 | 11.98 | 9.70 |
|
Mt. Tom Holyoke | 3.65 - 198.60 | 97.98 | 79.36 |
|
NEPCO Salem**** | 0.5 - 386.70 | 190.76 | 154.51 |
|
NEPCO Brayton Pt.**** | 2 - 1,509.20 | 744.46 | 603.01 |
|
Montaup Electric Somerset | 2.48 - 1,348.00 | 66.50 | 53.86 |
| TOTAL | 10.14 - 2,311.7 | 1,153.1** | 934.01*** |
|
* Based on a range of mercury emission factors, (0.41-22.3 lb./trillion BTU) as measured in 13 ESP equipped utility boilers, as reported in USEPA, 1989. ** Using average emission factor (11 lb. mercury/trillion BTU) from data cited in footnote above. *** Based on EPRI midpoint emission factor of 9 lbs. mercury/trillion BTU (estimate based on EPRI measured emission factors of 4 - 14 lb. **** The lowest values presented for Brayton Point and Salem facilities are based on the limited data provided to DEP by NEP on the mercury concentrations of their as burned coal. | |||
The above estimates only consider stack emissions of mercury. Although this route of release is likely to predominate, some loss (volatilization; leaching) of mercury may occur following APC capture during ash storage, transport and disposal or from volatilization or direct discharge of contaminated APC liquids.
Quantitative estimates of mercury releases via these pathways cannot be determined at this time due to a lack of information. However, if the ESP mercury capture efficiency is approximately 10% then the maximum quantity of mercury in the ash would not be expected to exceed 10% of the stack emission estimate or approximately 115 pounds per year (based on "best" estimate using method 2 above). This provides a likely upper bound on potential losses from these pathways.
In conclusion, emissions from MA coal-fired facilities are highly uncertain at this time. This uncertainty can best be reduced by more extensive testing of as-fired coal and/or by additional stack emission testing (Endnote 18). Releases from Wastewater Background
Mercury may be released to the general environment from wastewater treatment and disposal operations via sludge disposal/incineration and wastewater effluent discharge. MADEP has been working with the Massachusetts Water Resource Authority (MWRA) and other municipal systems to identify and reduce mercury sources to wastewater. A large body of information exists on wastewater mercury discharges in MA due to the considerable efforts made by MWRA to reduce levels of this metal to its system. Stack monitoring results of potential air emissions of mercury also exist for five operational municipal sewage sludge incinerators in MA.
The MWRA presently serves 43 cities and towns by removing wastewater from homes and businesses. MWRA provides this service to approximately 2.5 million people and 5000 businesses. Wastewater is conveyed to the Deer Island and Nut Island treatment plants. At Deer Island, a new primary treatment plant has partially come on-line and will be fully operating in a few years to improve wastewater treatment and effluent quality. The effluent outfall pipe from the new Deer Island plant is currently being constructed and will extend 9.5 miles from shore. Sludge generated from these treatment facilities is sent to a pelletizing plant in Quincy where it is processed into fertilizer and marketed all over the country.
The MWRA has extensive information on mercury discharges into the MWRA sewer system, as well as several databases on other toxic compounds. Mercury contamination of wastewater and sludge has been carefully considered by MWRA which has made significant efforts to reduce mercury inputs into the system. Mercury may enter the wastewater from a number of sources including process chemicals, laboratory and clinical reagents, and from residual mercury in sewers and plumbing from wastewater discharges that occurred many years in the past.
MWRA has collected information on mercury concentrations in a variety of industrial discharges to the sewer system and in the influent and effluent of the treatment plants. Sludge and sludge pellets have also been routinely tested for mercury content.
Several industries/facility types have been identified by the MWRA as discharging the majority of the industrial load of mercury into the sewer system, with hospitals being one important source. The industrial load is based on information gathered from permitted industries only. (The MWRA is in the process of identifying which other non-permitted facilities may be contributing mercury to the sewer system. At this point, the only significant non-permitted source that has been identified is the dental industry.) The primary contributors include:
Other MWRA permitted sources comprise a smaller contribution of mercury discharges. These include:
Mercury is sometimes detected in discharges into the system from sources such as septage sites, dental offices, contaminated ground water, contaminated water supplies and stormwater runoff. In order to assist industries and other facilities to identify mercury sources and options to reduce mercury discharges, the MWRA has established a mercury products workgroup. This group met initially in June, 1994, with over 51 industries being represented.
Under the MWRA's regulatory program, mercury is prohibited in wastewater entering the system. Enforcement action against a source contributor of mercury is taken when the mercury concentration of the input wastewater stream reaches or exceeds a level of 1 part per billion (ppb), a level five times the analytic detection limit, which allows MWRA to demonstrate that mercury is actually present in the wastewater. This is a very low level, even falling below the 2 ppb level established by the USEPA for mercury in drinking water.
Although it may seem strange that less mercury is acceptable in wastewater inputs than drinking water there are several reasons why this is the case. First of all it is important to note that mercury in water or wastewater exists primarily as less toxic inorganic forms. Once discharged into the general environment mercury may, however, be converted by microbial action to the more toxicologically potent methylated form. Secondly, in addition to considering human health impacts MWRA discharges must also meet ambient water quality standards that protect sealife. Thirdly, mercury may enter MWRA wastewater from many sources, such as stormwater runoff, that are difficult to control; lower levels from controllable sources are therefor needed to insure that MWRA effluent and sludge meet acceptable mercury levels.
These factors, in part, explain why the MWRA mercury limit for input wastewater is lower than that for drinking water. In cases where discharges into the MWRA sewer system exceed the 1 ppb enforcement limit, the MWRA sends out a notice of violation. The notice of violation calls for additional mercury monitoring and submission of a report to the MWRA showing how any existing problem will be corrected. MWRA Monitoring and Mercury Release Information
The MWRA extensively monitors mercury concentrations in the influent wastewater entering the Deer and Nut Island Treatment Plants and effluent water leaving these facilities. A mass balance of mercury for the MWRA system is presented in Figure 3-16, which includes specific sources and influent and effluent mercury concentrations and loadings for both facilities.
The figure shows that the level of mercury in the influent to Deer Island was below 1 ppb with a mean value of 0.22 ppb. The total influent load was 0.469 pounds per day, with much of it from the residential sector (0.21 pounds per day) and background load (0.282 pounds per day) and a smaller amount from industry (0.0286 pounds per day). The effluent load was 0.235 pounds per day.
At Nut Island the level of mercury in the influent was also below
1 ppb with a mean value of 0.25 ppb. The total influent load
was 0.278 pounds per day, with much of it from the residential
sector (0.076 pounds per day) and background load (0.0585 pounds
per day) and a smaller amount from industry (0.0143 pounds per
day). The Nut Island effluent load was 0.174 pounds per day.
For both facilities the effluent meets state and federal standards
(Gold Book Standards) for mercury to protect human health and
aquatic life.
The sludge from the waste water treatment plants is also monitored for mercury content. Data on the mercury levels in the MWRA sludge pellets show that the mercury concentrations averaged less than 6 ppb and thus meet all federal and state regulatory limits for fertilizer application. However, the concentrations of mercury in the MWRA's sludge pellets are high enough to be of substantial concern to the MWRA, which has accordingly embarked on an aggressive mercury source reduction program.
The daily mercury load figures can be used to estimate yearly mercury inputs to the environment from sludge pelletizing, the sludge pellets themselves and effluent water. These total approximately 0.747 pounds per day (the total of influent loadings to Deer Island and Nut Island treatment facilities) or 272.66 pounds per year. Sewage Sludge Incineration and Extrapolated Total Statewide Sewage-related Mercury Releases
Sewage sludge incinerators are used primarily to reduce the volume of sludge prior to final disposal. They are used by a relatively small percentage of US municipalities. USEPA estimated that, nationwide, a total of 210 such facilities are in operation and that these emit a total of approximately 1.82 tons of mercury per year. There are a total of six sewage sludge incinerators in Massachusetts. Stack tests for mercury and several other pollutants have been performed on 5 of these facilities. Results of these tests are presented in Table 3-14. The highest mercury emission rate was 96.0 grams per day, well below the current USEPA standard of 3,200 grams per day (USEPA NESHAPS 40 CFR 61).
Based on these results estimates of yearly mercury emissions were determined. These ranged from a low of less than 2 pounds per year to a high of 77.09 pounds per year. Cumulatively, these five facilities are estimated to emit a total of approximately 126 pounds of mercury per year (Table 3-14). Stack test results were not available for the Upper Blackstone facility. Assuming that the emission rate of this incinerator is similar to the average emission rate for the five tested facilities, it would be anticipated to emit approximately 27 pounds of mercury a year. The estimated total emissions from all six incinerators would therefore equal 151 pounds of mercury per year.
In addition to incinerator emissions some mercury releases will occur from discharge of wastewater effluent from other MA municipal treatment systems as well as private systems. As no data on mercury discharges from these pathways was available an estimate of statewide sewage related mercury was made by extrapolating the MWRA estimates to the rest of the state on a per-capita basis. This estimate equals {272.66 lbs/year/2.5 million citizens served by MWRA} X 3.5 million citizens not served by MWRA= 381.72 lbs/year statewide (note: Since MWRA does not incinerate sludge this extrapolated value is for all wastewater related mercury releases including the incinerator related emissions noted above).
| NAME OF FACILITY | EMISSION RATE (gr/day) |
VOLUMETRIC FLOW-RATE (dscm/sec) |
APC DEVICE | IN-STACK CONC. (µg)/(dscm) |
AIR EMISSIONS POUNDS PER YEAR |
|---|---|---|---|---|---|
| Lynn WWTP | 2.18 | 0.70 | VS/WS/ESP | 36.0 | 1.75 |
| East Fitchburg | 38.88 | 4.5 | WS | 100 | 31.22 |
| Brockton | 96.00 | 2.73 | WS | 407.0 | 77.09 |
| New Bedford | 4.32 | 1.45 | WS | 34.48 v3.46 | |
| Fall River | 15.83 | 2.29 | WS/ESP | 80.0 | 12.71 |
|
FF - Fabric Filter VS - Venturi Scrubber WS - Wet Scrubber PF - Particulate Filter |
C - Cyclone AB - After Burner ESP - Electrostatic Precipitator | ||||
Wood may be burned for residential heating or as a commercial energy source. Commercially, wood is used as a fuel source to fire industrial and utility boilers or as a general heating source. Most systems using wood as a fuel operate at temperatures sufficiently high to vaporize mercury. Thus, any mercury present will exit the facility in the vapor phase. Mercury is expected to be present in wood in trace amounts attributable to root uptake from soil and deposition of airborne mercury to leaves, buds and bark. Some waste wood may contain mercury or other metals in paints applied to their surfaces. Massachusetts Facilities and Emissions Information
A total of 20 commercial wood burning facilities were identified in Massachusetts. These are identified in Table 3-15. These facilities consume from one to 151,517 tons of wood per year. Most of the wood burned is bark (89%) with the remaining 11% constituting other waste woods, mostly being comprised of unpainted material. Estimates for Overall Emissions of Mercury from MA Wood Burning
Based on emission test results (from seven tests) USEPA has recommended that an emission factor of 0.67 X 1-5 lb. mercury/ton of wood be used when estimating mercury emissions from commercial wood-fired boilers (USEPA, 1993a). This factor was applied to each facility listed in Table 3-14 to generate an estimate of mercury emissions from this source category. Only one facility, Pinetree Power, is estimated to emit in excess of one pound of mercury per year and all facilities combined are estimated to emit less than 1.5 lb. of mercury a year. Table 3-15. Existing Wood Fired Facilities
ANNUAL ESTIMATED
WOOD USAGE Hg
FACILITY NAME CITY/TOWN TYPE (Tons) (lb.)/yr.
EMISSIONS
Cooley Dickinson Hospital Northampton Waste 8,000 0.0536
St. Joseph's Abbey Spencer Waste 2,300 0.0154
Rex Lumber Acton Waste 77 0.0005
Livingston Mfg. Co. Winchendon Waste 5 0.0000
F.W. Lombard Chair Co. Ashburnham Waste 150 0.0010
Eustis Enterprises Ashburnham Waste 63 0.0004
Conant Ball Co. Gardner Waste 60 0.0004
Design Showroom Gardner Waste 600 0.0040
Nichols & Stone Co. Gardner Waste 2,300 0.0154
S. Bent & Brothers Gardner Waste 3,864 0.0259
Ipswich Industries Winchendon Waste 67 0.0004
M.H. Parks Co. Winchendon Waste 300 0.0020
Keyes Wholesale Flws. Hadley Waste 1,000 0.0067
Montgomery Company Hadley Bark 6,632 0.0444
Mohawk Plastics, Inc. Turner Falls Bark 15 0.0001
Cummington Mfg. Co. Cummington Waste 90 0.0060
J.P. Bartlett Inc. Sudbury Waste 1 0.0000
Holt and Bugbee Co. Tewksbury Waste 6 0.0000
Pinetree Power Westminister Bark 151,517 1.0152
TOTAL 1.5
* Using Emission Factor of: 6.7 x 10-6 lb. mercury per ton of wood burned. Other Industrial, Commercial and Miscellaneous Sources Overview
Where possible quantitative estimates were generated for other possible emission sources in Massachusetts. These were extrapolated from USEPA national estimates on a per capita basis as discussed below. These additional sources are estimated to emit approximately 145 pounds of mercury per year in Massachusetts. Lamp Breakage
USEPA estimated that 8.8 tons of mercury was lost to the atmosphere nationwide due to breakage of mercury containing lamps in 1991 (USEPA, 1993a; USEPA, 1993b). This total was based on estimates that 20% of the mercury present in indoor lights and 33% in outdoor lights is released due to lamp breakage each year and that 32 tons of mercury were used in lamp production in 1991 (USEPA, 1993a). Extrapolating this value to Massachusetts based on a per capita loss rate yields an estimate of 422.4 pounds of mercury released from lamp breakage per year. A subsequent assessment of this pathway by the Research Triangle Institute (Truesdale, 1993) suggested that considerably less mercury would be released due to lamp breakage. Based on this RTI assessment approximately 1.54 tons of mercury can be estimated to be released per year, on a nationwide basis, from this pathway. This equates to approximately 74 lb./year in MA, when extrapolated on a per capita basis (Endnote 19).
|
(1.54 ton/250 million 1991 US population) x 6 million Massachusetts
population x 2,000 lb./ton = |
USEPA estimated a national emission of 0.6 ton of mercury in 1991 due to losses during use of mercury containing materials (amalgam fillings) in dental applications (USEPA, 1993a; USEPA, 1993b). This estimate was used to calculate a Massachusetts specific emission estimate of approximately 28.8 lb./year for this source based on a per capita emission estimate as follows:
|
(0.6 ton/250 million US 1991 population) x 6 million Massachusetts
population x 2000 lb./ton = |
USEPA estimated a national emission of 0.4 ton of mercury in 1991 due to losses during laboratory use of mercury and mercury containing reagents (USEPA, 1993a; USEPA, 1993b). This estimate was used to calculate a Massachusetts specific emission estimate of approximately 24 lb./year for this source based on a per capita emission estimate. As noted below this per capita emission estimate was adjusted upward by 25% to account for the relatively high density of research facilities in MA.
|
(0.4 ton/250 million US 1991 population]) x 6 million Massachusetts population x 2000 lb./ton X 1.25= 24 lb.. mercury emission from general lab use per year in Massachusetts. |
USEPA estimated the number of cremations in Massachusetts in 1990 to equal approximately 8,104. Given that the Massachusetts population has not significantly changed since that time, this value is believed to provide a reasonably accurate estimate of the current cremation rate in Massachusetts. Additionally, since this is a relatively minor source of mercury emissions it was felt that efforts to update this estimate were not warranted. Each cremation has been estimated to release, on average, 1 gram of mercury, largely due to vaporization of mercury containing amalgam dental fillings (USEPA, 1993a; USEPA, 1993b). (This estimate is based on European data which may not accurately reflect US dental practices and thus is somewhat uncertain). Applying this emission rate to the 8,104 cremations yields the following estimate of mercury releases via this practice:
|
(8,104 cremations x 1 gram mercury per cremation)/ 454.54 grams
per lb. = |
USEPA estimated that up to 7.4 tons of mercury might have been released in 1991 from five major mercury recycling facilities (none in Massachusetts) during efforts to collect and recycle this metal. This estimate was viewed by USEPA as being highly uncertain as it was based on an unverified emission factor developed in 1973. No Massachusetts specific emission estimates or monitoring data were available to allow for meaningful predictions of possible mercury emissions from Massachusetts enterprises that are focused on collection and recycling of mercury containing products. Some release of mercury from these facilities, however, would be anticipated to occur. Petroleum Refining
No reliable emission factors are available for this source. Potentially significant emissions may, however, be anticipated to occur from refining facilities given the presence of mercury in crude oil at levels of up to 30 ppm. However, Massachusetts has no petroleum refineries, so emissions from this source in the state do not occur. Pesticides
As recently as 1990, two turf product fungicides were marketed that contained substantial amounts of mercuric and mercurous chloride. USEPA estimated that in 1990, 54,158 pounds of mercury were contained in these pesticides nationwide. Currently all registrations for mercury containing pesticides have either been officially or voluntarily canceled. Although continuing inputs are expected to be minimal, the potential use of existing stocks of these and other mercury containing pesticides may still result in some continued mercury inputs into the environment Mobile sources
Mobile sources include cars, trucks, trains, and boats. We have not estimated mercury contributions from mobile sources because the only available emission estimate is based on an ambient sampling study conducted in 1977, which is felt to be inappropriate for current use. Natural Gas Combustion
No estimate was derived as an appropriate emission factor is not available. However, emission via this source are likely to be low; mercury concentrations in natural gas are expected to be low and the processing steps applied prior to distribution are likely to further remove any trace levels of mercury from the gas. Paint Use
Due to discontinuation of domestic production of mercury-containing pigments in 1988, inputs of mercury due to new paint application is currently believed to be negligible. Electrical Apparatus and Instrument Manufacture
Current, reliable emission factors are not available. Thus, no source estimates were determined. Mercury Compound Production
No specific information is available on potential mercury releases by Massachusetts industries producing specialty chemicals. USEPA has, however, identified one industry (Morton International Inc., Specialty Chemical Group, Woburn Massachusetts) that is reported to produce highly purified dimethyl mercury for chemical vapor deposition (CVD) of thin films. Other
Other potential sources of mercury emissions are:
Cement Manufacturing
Lime Manufacturing;
Primary Metal Smelting;
Battery Production; and
Chlor-alkali Plants.
Either no facilities of these types are known to exist in Massachusetts (primary metal smelting, chloralkali, cement) or no specific data was identified on mercury use or emissions from operating facilities. Summary of MA Mercury Release Estimates
Table 3-16 presents a summary of the yearly release estimates for all sources considered. This data is graphically presented in Figure 3-17. We estimate that these Massachusetts sources may release a total of 10,845 pounds of mercury to the environment each year with the most significant sources being combustion facilities. Municipal solid waste combustion appears to be the largest source category emitting approximately 6,040 pounds of mercury per year (56%). Medical waste incinerators may emit up to 780 pounds of mercury per year (7%).
| SOURCE | ESTIMATE (1) (pounds/year) |
|---|---|
| Municipal Solid Waste Combustors | 6,0402 |
| Medical Waste | 780 (780 - 3,735) |
| Coal Combustion | 1,153 (10 - 2,312) |
| Residual Oil Combustion | 1,118 (79 - 1,242) |
| Distillate Fuel Oil | 952 (392 - 2,380) |
| Municipal Wastewater Releases | 502 |
| Lamp Breakage | 74 (11 - 422) |
| Sludge Incinerators | 153 |
| Dental Applications | 29 |
| General Lab Use | 24 |
| Crematories | 18 |
| Commercial Wood Burning | 2 |
| TOTAL | 10,845 (8,040 - 16,859) |
| |
The considerable uncertainty in all of these estimates must be kept in mind. This is due in part to a lack of monitoring data on mercury emissions from several potential source categories, uncertainties in the mercury content of the fuels/materials combusted, and differences in the effectiveness of installed APC devices. Nonetheless, we believe that the estimates presented provide reasonable bounds on the likely emissions and that the "best" estimates are reasonable approximations of current emissions. The potential magnitude of these emission sources and their associated uncertainty suggest areas where additional monitoring and source reduction efforts and research/investigation may be most productive. In particular the estimates for coal and oil combustion are highly uncertain and require additional analytical work on stack emissions and fuel mercury content.
Because of the monitoring required by MADEP, mercury emission estimates for municipal solid waste combustors are probably the most accurate. The estimated yearly emission of mercury from this source category is approximately 6,040 pounds. Although this is considerably less than that estimated by USEPA for Massachusetts MSWCs (based on data reported by USEPA (USEPA, 1993a; USEPA, 1993b) MA MSWCs would be predicted to emit approximately 10,787 lb. mercury/year), it still remains the largest probable source category of ongoing emissions in MA. Since the estimate presented here is based on actual emission monitoring data of the facilities in question we believe it provides a more accurate picture of MSWC emissions in Massachusetts than the USEPA-derived figure, which was extrapolated from other facilities.
The estimates of possible emissions from Medical Waste Incinerators in Massachusetts suggest that they, in total, emit approximately 780 pounds of mercury per year. Although still a significant source of potentially avoidable mercury emissions, this estimate places this category as the third or fourth largest source in MA. This stands in contrast to USEPA's national estimates, where Medical Waste Incinerators were identified as the largest source category.
Combustion of distillate oil (primarily #2 oil used in home heating furnaces and by smaller boiler units of up to approximately 3 million BTU/hour output) and residual oils (heavier oils such as #6 oil that are primarily used in larger boilers including those found in electric utility plants) are estimated to emit 952 and 1,118 pounds of mercury per year, respectively. Together these rank as the second largest source category. Our calculations indicate that coal combustion may contribute approximately 1,153 pounds of mercury per year. Due to a lack of specific monitoring data on facilities burning these fuels in MA these estimates are highly uncertain.
Statewide, sewage-related releases of mercury to the environment are estimated to be approximately 502 pounds/year (including air, sludge and effluent water related releases). Approximately 273 pounds of this total are attributable to MWRA effluent and sludge, 153 lb. to air emissions from sewage sludge incineration at 6 municipal facilities and the remainder to non-MWRA effluent related releases statewide.
Miscellaneous sources are estimated to release a total of approximately 147 pounds of mercury per year. These include releases attributable to: breakage of certain electric light fixtures/bulbs (approximately 74 lb./year); cremations (approximately 18 pounds per year); commercial wood combustion (less than 2 pounds per year); and non-point source releases of mercury attributable to its use in dental applications (29 pounds per year) and in laboratories (24 pounds per year).