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Maryland Power Plants and the Environment (CEIR-18)

5.3 Fossil Fuel-fired Generation and CO2

5.3.1 Background

Coal is abundant in the U.S. and coal-fired electric generating units are effective in meeting baseload, intermediate load, and peak demands given their high reliability. Historically, coal-fired power plants have supplied over half of Maryland’s net electricity generation. Since 2012, however, this number has fallen to a little under half while natural gas-fired generation has increased. Energy conversion from traditional coal-fired power plants generates the highest levels of CO2 emissions on a per-unit-of-energy basis of all the fossil fuels available, with the exception of petroleum coke. All fossil fuels contain substantial amounts of fuel-bound carbon that is oxidized into carbon monoxide (CO) and CO2 during combustion. CO2 emissions from conventional coal combustion technologies amount to approximately 1 ton per MWh of electricity generated, compared to 0.4 to 0.6 ton per MWh from natural gas-fired generation (e.g., combined cycle/simple cycle gas turbines). Figure 5-7 shows the approximate level of CO2 formed when combusting various fossil fuels.

Figure 5-7 CO2 Emissions from the Combustion of Fossil Fuels

Bar chart with CO2 emissions for different carbon fuels

For coal to have an environmentally acceptable future, CO2 emissions from new and existing coal-fired power plants will need to be mitigated to as low a level as feasible given regulatory drivers facing the electric utility industry in the upcoming years, especially EPA’s Clean Power Plan (CPP) passed in August 2015. See Section 5.2.3 of the CEIR for more information on the CPP.

CO2 mitigation for coal-derived power is a highly debated topic; however, there are several options that can be effective:

Currently, three general methods are available to capture CO2 from power plants and thus reduce CO2 emissions:

Located in Cumberland, Maryland, the AES Warrior Run power plant has been capturing a small portion of its CO2 emissions for use in the food and beverage industry since 2000. This 180 MW circulating fluidized bed generating unit uses a post-combustion monoethylamine flue gas scrubber system to remove approximately 110,000 metric tons of CO2 annually from a 2 to 3 percent slipstream of the plant’s flue gas. The extracted CO2 is then purified to a 99.99 percent purity level using carbon filters and molecular sieves. The CO2 is stored under pressure in steel tanks until it can be shipped off-site via tanker trucks for beneficial use primarily in the food and beverage industry.

Several carbon capture demonstration projects are currently under various stages of development in the U.S., most of which are funded by the U.S. Department of Energy (DOE) National Energy Technology Laboratory. These projects incorporate the full range of existing carbon capture technologies, as well as test the viability of emerging innovative methods, such as cryogenic, phase-changing, and enzyme-based sorbent capture. A few commercial-scale industrial CO2 capture projects are under construction or have commenced preliminary operations; however, most of the projects involving coal-fired power plants have not yet completed commercial-scale testing. The key barrier to carbon capture technology implementation for new and existing power plants is the substantial capital and operating costs. The beneficial use of captured CO2 prior to storage to create value-added products or services may alleviate some of the economic burden.