Coal: An Old Source Facing New Challenges

1. Coal: An Old Source Facing New Challenges Daniel Cohan Rice University October 4, 2014

2. Outline • Overview of coal and its use • Emissions from coal • Controlling emissions from coal • Other impacts of coal • Costs of coal

3. Overview of Coal and its Use

4. How Coal Forms • Plants die in swamp forests and are buried by sediment as peat • Heat and pressure expel water and gases • Coal becomes more carbon and energy rich over millions of years Graphic from Univ of Kentucky

6. Western coals becoming increasingly prevalent • Thick seams in West for large-scale mining • Appalachian coals heavily utilized before, most accessible reserves already tapped • Western coals have lower sulfur content, lower price • Transportation costs, bottlenecks are issue US EIA, AEO 2012

7. Powder River Basin Coal supplies many TX power plants http://www.wildearthguardians.org/images/content/pagebuilder/Powder_River_Basin_distribution_legend-2.jpg

8. U.S. uses 1,045,878,000 tons of coal for electric generation each year • 3.5 tons/person/year (~50 times our weight) 12 tons 360 tons 100 tons 1 ton

9. U.S. Coal Use Trends • Historically, large use by industry, homes, transportation • Now power plants predominate US EIA, AEO 2006

10. Coal supplies 34% of electricity for the Texas ERCOT grid

11. Coal is big share of US electricity capacity, but most growth is natural gas & renewables

12. Most U.S. coal-fired electricity is from decades-old power plants Cohan and Douglass, 2011

13. Emissions from Coal

14. IPCC

15. Projected climate change depends on CO2 emissions IPCC, WGI SPM, 2013

16. Electricity Generation: Biggest source of greenhouse gases in U.S.

17. Highest CO2 emissions from coal(This is life cycle CO2equivalent basis, so includes CH4 leaks, etc) Greenhouse gas impact per kWh: Coal >> Natural gas >> Solar, biomass, wind, nuclear Weisser, “A guide to life-cycle greenhouse gas emissions from electric supply technologies.” Energy, 2007

18. Old coal plants emit far more NOx than other options in Texas Emissions from Texas power plants Cohan, 2013

19. NOx contributes to excess ozone in Texas cities (standard is 75 ppb) Cohan, 2013

20. Ground-level Ozone Impacts • Health effects • Strong oxidant, irritates lungs • Linked to asthma and other respiratory illnesses • Recently linked to mortality • Damage to vegetation & crops • Greenhouse gas • Non-attainment of EPA standards

21. Old coal plants emit far more SO2than other options in Texas Emissions from Texas power plants Cohan, 2013

22. SO2 contributes to fine particulate matter • Particulate matter: airborne particles composed of a variety of chemical compounds • Particulate matter is likely the leading cause of illness and mortality from air pollution

23. Controlling emissions from coal-fired electricity

24. Timeline of US cap-and-trade policies for air pollutants http://www.epa.gov/airmarkets/progress/ARPCAIR10_01.html

25. U.S. Power Plant Emissions Trends NOx Emissions SO2Emissions http://www.epa.gov/airmarkt/progress/datatrends/index.html

26. US EPA Policies for CO2 from Power Plants • Historically, CO2 was not regulated • 2007: Supreme Court in Massachusetts v. EPA ruled Clean Air Act can cover CO2 • 2013: Proposed New Source Performance Standards of 1000-1100 lbCO2/MWh • Attained by new natural gas plants • Would require partial capture of CO2 from coal • 2014: Proposed Clean Power Plan, with CO2 targets for each state • For Texas: 39% reduction by 2030

27. Clean Power Plan CO2 Reduction Targets

28. US Power Plant CO2 Trends http://www.epa.gov/airmarkt/progress/datatrends/index.html

29. Power Plant NOx Control:Selective Catalytic Reduction (SCR) • Ammonia is injected after boiler to convert NOx to N2 and water • Requires catalyst • Specific temperature range • ~85% NOx reduction 29 www.de-nox.com

30. Flue Gas Desulfurization (“Wet Scrubber”) for SO2 US DOE National Energy Technology Laboratory

31. Rainfall Acidity, 1994

32. Rainfall Acidity, 2009(Note the reductions in acidity in regions where coal is heavily used for electricity; results from SO2 & NOx controls under Acid Rain Program)

33. Post-combustion carbon capture Reverse Reaction @ 100-120°C (needs steam; hurts efficiency) Forward Reaction @ 40-65°C (flue gas must be cooled) FIGURE 12.1Flowsheet of the monoethanolamine(MEA) process for CO2 capture. • Reaction of liquid solvent MEA with CO2 • C2H4OHNH2 (“MEA”) + H2O + CO2 ↔ C2H4OHNH3+ + HCO3- • Need 1 mole MEA per mole CO2 captured • Huge material flows: 400 kg/s MEA for 500MW plant Fay & Golomb textbook

34. CO2 Transport • Pipelines • Some CO2 pipelines already exist for enhanced oilfield recovery • Similar impacts as other hydrocarbon pipelines • Ships • CO2 could be liquefied for ship transport • Road or rail • Probably not cost-effective

37. Geological Storage Capacity • For comparison, global anthropogenic emissions are about 28 GtCO2/year IPCC, 2005

38. Cost of CCS vs. other CO2 control options

39. Coal Impacts beyond Air and Climate

40. Mountaintop Removal Mining • In much of Appalachia, coal seams may be hundreds of feet beneath surface • 500 feet or more of a mountain summit may be removed to access coal

41. Coal Ash Pond Spill, Kingston (TN) Power Plant, December 2008 Associated Press

42. Ash from Coal Power Plants

43. Coal Ash • Ash from coal combustion: 10% of original volume of coal (U.S. EPA) • Fly ash (74%): Mixed with exhaust gas; captured by various technologies • Bottom ash (20%): Large, settles to bottom • Boiler slag (6%): Ash that melts by heat • 1,300 coal ash dumps in U.S. • Mercury, lead, arsenic, and selenium in ash • Lack of federal regulation • $5-11 billion/year estimated clean-up costs N.Y. Times, “Hundreds of Coal Ash Dumps Lack Regulation,” 1/6/2009

44. Solid Wastes from Coal Power Plants • Coal combustion generates ~129 million tons/year of wastes in US; ~35% reused US EPA Coal Combustion Products Partnership

45. Cost of Coal Electricity

46. New coal costs more than gas, wind, or geothermal; with carbon capture, it costs more than solar

47. Alternatives to coal in Texas Costs per MWh generated Cohan, 2013

48. Externality costs of coal(National Research Council, 2009) • 3.2 cents/kWh due to health and other impacts of air pollution • 1.7 cents/kWh by 2030 as emissions are cut • Natural gas impacts are ~0.2 cents/kWh • Other studies estimate much higher impacts from coal • Wide uncertainty on climate impacts (up to 10 cents/kWh) • Additional impacts from coal mines and transport

49. Projections of coal use depend on climate policy GHG15 scenario: US sets CO2 emission price, rising to $44/ton by 2035 US EIA Annual Energy Outlook 2012

50. Summary of challenges to coal • Old coal plants provide affordable electricity, but: • Need to control NOx, SO2, and mercury • Retrofit carbon capture is very expensive • EPA Clean Power Plan will require CO2 cuts • New coal plants aren’t cost competitive with natural gas or some renewables • Need carbon capture to meet EPA’s proposed New Source Performance Standards • Impacts to air, climate, land, and water