1. Do you agree that it is possible to minimize the destructive effects of burning coal?
Yes, it is possible to minimize the negative effects of burning coal, however, the question arises whether US society is willing to pay the cost.
Coal plants produce a number of environmental pollutants that can negatively affect human and animal life. Negative effects result from the mining, electrical generation, and waste storage phases of the life cycle of coal (Reference 1).
Coal mining has led to numerous incidents of ground collapse, e.g. in Pennsylvania (Reference 2) In some cases the condition was caused by water intrusion from above, e.g. leaking swimming pools (Reference 3) Mining has also caused numerous deaths. Ground restoration is a key concern of the states which allow surface mining of coal (Reference 4)
Key airborne pollutants released from the burning of coal include:
· Sulfur dioxide can produce acid rain with acidification of lakes, forests, and soil
· Nitrogen oxides (NOx) include various nitrogen compounds like nitrogen dioxide (NO2) and nitric oxide (NO). These compounds play an important role in the atmospheric reactions that create harmful particulate matter, ground-level ozone (smog) and acid rain. NOx emissions contribute to the formation of fine particles and ozone smog that cost society billions of dollars annually from illnesses and deaths. NOx emissions also contribute to a suite of year-round environmental problems, from acid rain in the mountain regions to eutrophication (the buildup of nutrients in coastal estuaries), leading to oxygen depletion that degrades water quality and harms fish. NOx emissions also contribute to haze air pollution in our national parks and wilderness areas (Reference 5)
· Particulates result in smog.
· Mercury results in uptake by fish, then humans. Mercury acts as a neurotoxin, interfering with the brain and nervous system. Exposure to mercury can be particularly hazardous for pregnant women and small children (Reference 6).
Ash pollutants include:
· Flyash concentrates lead and cadmium and can pollute groundwater
· Bottom ash has been used as a filler in concrete and road construction. Metals and alkali concentrates are present in such ash (Reference 7).
Coal ash storage has resulted in some localized environmental damage due to failure of storage walls or the dammed ash. It has also led to groundwater pollution.
Counteracting Negative Effects
The United States Congress passed the Clean Air Act, US Code Title 42 Chapter 85 (Reference 8). The related EPA regulations are intended to protect the nation’s air quality and stratospheric ozone layer. The Clean Water Act and National Pollutant Discharge Elimination System (NPDES) are intended to protect the nation’s water. Usually state environmental regulations are expected to protect groundwater.
Methods used to reduce the impact of coal to date include:
· Baghouses, scrubbers, and electrostatic precipitators are used to treat the stack emissions from coal plants.
· Low sulfur coal, primarily from the western United States, is used to reduce the impact of sulfur oxides.
· Use of fluidized bed and pulverized coal can lead to reduction in environmental pollutants.
· Ash pit liners and leachate collection systems have been used somewhat successfully to minimize groundwater pollution.
Clean coal, Coal gasification, Carbon dioxide sequestration have been proposed, particularly over the past 20 years, as methods for reducing impact of coal burning. Coal cleaning can consume huge amounts of water, Gasification can produce huge amounts of chemical, solid, or liquid waste. Personally, I cannot believe that sequestration can be viewed as a final solution. Some benign use must be found for the large amount of carbon dioxide produced. Disposal in the ocean cannot be viewed as an option because there is already concern about ocean acidification as noted in some National Academies Press book recently released (http://books.nap.edu/catalog.php?record_id=12904&utm_medium=etmail&utm_source=National%20Academies%20Press&utm_campaign=NAP+mail+CB+09.30.10+climate+choices&utm_content=Downloader&utm_term=) .
Natural gas could be used, to a limited degree to offset the use of coal. Compared to the average air emissions from coal-fired generation, natural gas produces half as much carbon dioxide, less than a third as much nitrogen oxides, and one percent as much sulfur oxides at the power plant (Reference 9).
Nuclear energy could be used, however, the costs of new plants have risen markedly in the past several years. For many years, the cost of electricity generation by nuclear plants had been close to that of coal.
Renewables could be used, however, they cannot necessarily be considered acceptable for base load generation.
Hydro is limited by the number of areas that can still be dammed. As an example, the Klickitat River has suitable topography for locating a dam. However, use of the Klickitat, a wild river, with scenic beauty, is highly unlikely.
For 2008, the most recent year of complete DOE data in the Electric Power Annual Report, fossil fuels represented 77.6% of the net electrical energy generated by fuels (fossil, nuclear, wood, wastes). Approximately 9.1% of the BTUs were generated by non-fuel sources as hydro and renewables. In that year, coal costs were 2.07 cents per million BTU, natural gas was 902 cents per million BTU, and the average for fossil fuels was 4.11 cents per million BTU. Fuel expenses were 17.7% of the utility operating expenses. If it were possible to exchange natural gas for coal for electricity generation, it is estimated that increased fuel costs would raise utility operating costs by at least 25%. It is questionable whether consumers would tolerate a rapid rise in electricity costs of that amount. It should be noted that 25% would be a minimum average. Some utilities are highly dependent on coal and their customers would be heavily affected. Other utilities depend more on nuclear and hydro and would have little impact. In addition, use of natural gas as a fuel for electricity would greatly reduce the amount available for home heating which would force consumers to look for other sources. Use of natural gas does not eliminate the carbon dioxide emission issue. (References 10 through 16).
A number of methods can be used to minimize the detrimental effects of coal. However, use of carbon dioxide and/or sequestration must be proven as viable methods for dealing with coal plant emissions. Cost is a major issue if the decision is made to place increased reliance on natural gas.
2. In spite of the side effects, should we still consider coal as an energy source?
Yes, we have no option but to consider coal. The US has greatly increased the natural gas generation capability between 1990 and 2010 by 314 Gw, or 82% of the capacity added during that period (Table 4). However, natural gas fuel cost is typically over twice that of coal (Table 5). In 2008, natural gas produced only 21.4% of the country’s energy needs even though natural gas capacity was 41%. Coal produced 48.2% of the energy demand even though coal capability represented only 30.5% of the total available (Tables 2 and 3).
Consumers have often been irate at the slight escalation in electricity costs that have occurred to date. Utilities respond to that anger by only using gas as a last resort.
A well balanced grid must be able to respond to customer demand when needed. Utilities must be able to respond to conditions as:
A well balanced grid must have multiple sources with adequate fuel available. Coal has been, and should continue to be, considered as part of the fuel mix. No energy source is without impact. A gradual shift should be made away from coal or reliable methods developed to eliminate the adverse environmental effects of coal. Improved energy storage technologies could make increased use of renewables a dependable option. Expansion of reservoirs could improve the capability of hydro. Increased reliance on natural gas or nuclear could result in dependence on imports, an undesirable option. Consumer cost will drive any action taken.
1 Statements not referenced are based on information obtained during my work experience as a utility engineer and manager.
2 Ground Collapse Over Abandoned Mines, Paul E. VanDorpe, Iowa Geological & Water Survey, http://www.igsb.uiowa.edu/Browse/minecoll/minecoll.htm
3 Miner Subsidence , PA Bureau of District Mining Operations, http://www.dep.state.pa.us/dep/deputate/minres/districts/homepage/california/Underground/Mine%20Subsidence/mine_subsidence.htm ).
4 Worst US Mine Disasters, Historical Data on Mine Disasters in the United States, United States Mine Rescue Association, http://www.usmra.com/saxsewell/historical.htm .
5 Fact Sheet Air Quality , http://www.edf.org/documents/2551_FactSheet_NOx.pdf
6 Mercury Contamination in Fish , Natural Resources Defense Council, http://www.nrdc.org/health/effects/mercury/effects.asp
7 Monitoring the species of arsenic, chromium and nickel in milled coal, bottom ash and fly ash from a pulverized coal-fired power plant in western Canada , Fariborz Goodarzi and Frank E. Huggins, J. Environ. Monit., 2001, 3, 1±6, http://www.rsc.org/delivery/_ArticleLinking/DisplayArticleForFree.cfm?doi=b006733o&JournalCode=EM
8 Clean Air Act , US EPA, http://www.epa.gov/air/caa/
9 Natural Gas , US EPA Clean Energy, http://www.epa.gov/cleanenergy/energy-and-you/affect/natural-gas.html
10 Table 4.5 Receipts, Average Cost, and Quality of Fossil Fuels for the Electric Power Industry 1996 through 2007 , US Energy Information Administration, http://www.eia.doe.gov/cneaf/electricity/epa/epat4p5.html
11 Figure ES 4. Fuel Costs for Electricity Generation, 1997- 2008 , http://www.eia.doe.gov/cneaf/electricity/epa/figes4.html
12 Table 2.1. Net Generation by Energy Source by Type of Producer, 1997 through 2008 (Thousand Megawatthours) , http://www.eia.doe.gov/cneaf/electricity/epa/epaxlfile2_1.pdf
13 Figure ES 1. U.S. Electric Power Industry Net Generation , http://www.eia.doe.gov/cneaf/electricity/epa/figes1.html
14 Table 1.2. Existing Capacity by Energy Source, 2008 (Megawatts), http://www.eia.doe.gov/cneaf/electricity/epa/epat1p2.html
15 Electricity Generating Capacity ,
16 Existing Electric Generating Units by Energy Source, 2008 , http://www.eia.doe.gov/cneaf/electricity/page/capacity/existingunitsbs2008.xls
17 US EPA Executive Summary on Utility Emissions of Hazardous Air Pollutants http://www.epa.gov/ttn/oarpg/t3/reports/utilexec.pdf
18 Toxic Substances from Coal Combustion – A Comprehensive Assessment , October 1996, http://126.96.36.199/technologies/coalpower/cctc/resources/pdfsmisc/haps/M97051055.pdf
19 Major Demonstrations: Clean Coal Technology Demonstration Program (CCTDP) , http://188.8.131.52/technologies/coalpower/cctc/cctdp/index.html
20 Innovations for Existing Power Plants , US Department of Energy, http://www.fossil.energy.gov/programs/powersystems/pollutioncontrols/
Table 1 Summary Table – Energy Source and 2008 Cost
|2008 Cost (cents per mmBtu)|
References 9 and 10
Table 2 Net Generation by Type in 2008
References 11 and 12
Table 3 Existing Capacity by Energy Source, 2008
|Energy Source||No. of Generators||Generator Nameplate Capacity (MW)||% of Total|
|Solar Thermal and Photovoltaic||89||539||0.00%|
|Wood and Wood Derived Fuels||353||7,730||0.70%|
Table 4 Capacity Additions by Type between 1990 and 2008 (Data Extracted and Summarized from References)
|Energy Source||No. of Generators||MW rating of Plants||Wind Turbines||%||Avg MW|
|Wood & Wood Derived Fuels||82||2,351.80||NA||0.60%||NA|
References 14 and 15
Table 5 Figure ES 4. Fuel Costs for Electricity Generation, 1997- 2008
|Year||Coal Cost||Natural Gas Cost||Petroleum Cost||Average Fossil Fuel Cost|
Carbon Dioxide Sequestration
Oil and gas have remained buried until wells were drilled. The material used to plug the formations containing the carbon dioxide would have to last forever. The rock formations overlying the carbon dioxide vaults would also have to never fracture. Hopefully, the Department of Energy (DOE) research programs thoroughly evaluate all of the potential event paths and human and environmental risks associated.
The point about fuel cells is well taken. In the mid-1980’s I had reviewed fuel cell status for a report. At the time, DOE and the Electric Power Research Institute were funding research and applications using the molten carbonate fuel cells. Some applications included shopping centers and industrial facilities. Fifty five (55) percent energy recovery was anticipated through extensive use of heat recovery heat exchangers. A coal gasification front-end had been proposed, however, the downside was the type of wastes produced by that process. I am disheartened by progress in fuel cells since that time (25 years). I was hopeful about 10 years ago when Plug Power, producer of a proton membrane fuel cell, was at 150 in the stock market. I had seriously considered use until confronted with the high cost. Today, PLUG is at 0.48 in the stock market. Other fuel cell manufacturers and small standalone generators (http://www.google.com/finance?q=NASDAQ:PLUG) appear to be in the same condition. It’s a neat concept but sure is slow in coming to market.
Power Plant Cycle Efficiency
A typical 35% efficiency for steam turbine power plants (Rankine Cycle) can be a drawback unless one seriously tries to improve the process. One approach, the Kalina Cycle, uses ammonia as part of the process (http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JERTD2000129000003000243000001&idtype=cvips&gifs=yes&ref=no).
Cogeneration can also improve efficiency, although that is rarely done in large scale central generation plants. The key would be to locate power plants in energy parks with heavy users located nearby. By doing so, one could improve energy recovery to over 50%. High efficiencies could be achieved today if sufficient impetus was provided by state utility regulators to force utilities to invest in avoiding lost energy. Use of cooling towers further degrades the efficiency. Five (5) percent is lost on the pumps used to push the water to the towers.
Russian nuclear plant design usually includes a heat supply to the adjacent town. The concept is good. However, utilities need to ensure maintenance of the heat supply and condensate return lines is done to keep decent cycle efficiency.
Recently, increased attention has been given to concept of small self contained nuclear reactors (http://www.world-nuclear.org/info/inf33.html) for remote areas. Considering the concern still expressed over reactors that have operated safely for 35-40 years, the industry would still have to overcome public apprehension.
Spent nuclear fuel, which still release heat and energy, could be considered a potential resource rather than as waste only.
While we tend to focus on generating more electricity, perhaps energy efficiency improvements could be achieved by rethinking the processes by which we refrigerate, cook or bake, heat, or even light our homes. Use of solar cells for providing lighting after dark is a really decent concept.
We do need to think outside the box. As a nation, we have some fantastic energy assets (e.g. coal, hydro, nuclear, wind). We need to concentrate on how we can use them better and more efficiently in the future than we have in the past.
Do not think I am necessarily a fan of coal generation. I just believe that we cannot afford to throw away any energy source (My preferred order for sources: Dams > Wind > Nuclear > Municipal Solid Waste > Solar > Coal). Likewise, we should not throw away billions of dollars in capital investment and completed or partially completed construction. Rather, it is generally cheaper, in the long run, to improve processes or facilities so they work better than to build anew.
It bothers me to see waste such as the uncompleted former WPPSS plants at Hanford and Satsop, premature shutdown of Trojan, Rancho Seco, Maine Yankee, Connecticut Yankee, among others, or dismantling of the Snake River dams.
As an example of improvements, a natural gas supplement or gas re-burning could be used to improve boiler combustion to reduce emissions. Wood- or biomass co-firing could be used to reduce carbon dioxide emissions. The disadvantage that I see with biomass is the low heat content and high moisture content which can lead to incomplete combustion and harmful emissions.
Reducing Emissions from Coal Plants, http://www.canadiancleanpowercoalition.com/index.php/download_file/-/view/40/
Natural gas can help coal burn cleaner, http://pubs.acs.org/doi/abs/10.1021/es60169a006
Co-Firing Wood In Coal-Fired Industrial Stoker Boilers: Strategies for Increasing Co-Firing in New York and the Northeast, http://www.nrbp.org/pdfs/pub18.pdf
Gas Re-burn Demonstration, DOE NETL, http://www.netl.doe.gov/technologies/coalpower/cctc/summaries/eerco/gasreburndemo.html
Renewables Home - Virtual Nuclear Tourist - Tuesday March 29, 2011