AskPablo: Coal-Fired Power Plants

This week I am going to examine the world of coal-fired power plants. Coal is an energy-dense substance found deep underground. Like oil and natural gas it is made from prehistoric organisms and biomass under intense heat and pressure. The living precursors to these fuels sequestered CO2 from the atmosphere, as plants do today, and have locked it away for millions of years, making the atmosphere conducive to life as we know it. In extracting and combusting these fuels we are returning that CO2 into the atmosphere. Is one fuel just as bad as the others or is coal just evil? Let’s look at some numbers and find out.

In addition to vast amounts of carbon, coal also contains trace amounts of toxic substances such as heavy metals. These heavy metals include mercury, which I discussed in a previous column (“AskPablo: Mercury in Compact Flourescent Bulbs”). When burned, coal releases between 200 and 230 pounds of CO2 per MMBtu (One Million British Thermal Units, or 10 Decatherms). Compare this to natural gas, which releases 116 pounds of CO2 per MMBtu, or gasoline at 155 pounds of CO2 per MMBtu. For your reference, every 3,412 Btu represent one kWh of delivered electricity.
So, a coal-fired power plant emits roughly twice as much CO2 as a natural gas-fired power plant. According to the US EPA E-Grid the average coal-fired power plant has a capacity of 600 MW but only operates at 75% capacity, resulting in 4 million MWh/year. Electricity production from all sources in the US average 3 pounds of NOx per MWh, 6 pounds of SOx per MWh, and 1,515 pounds of CO2 per MWh (delivered). For coal the emissions factor is around 2,000 lbs per MWh. At this emissions factor and 4 million MWh/year, the average US coal-fired power plant emits 4 million US tons of CO2 per year.
smog_beijing.jpeThe average US passenger vehicle emits 12,100 pounds of CO2 per year. The average coal-fired power plant is equivalent to 660,000 cars. If every person in the US had a car, or 300 millions cars, this would be equal 454 coal-fired power plants.
From a previous AskPablo: If every household in the US replaced one incandescent bulb with a CFL we could turn off 1 coal-fired power plant, assuming 3 hours per day of use. How did I get this? Well, if you replace one 60W incandescent bulb with a 23W CFL you are saving 37W. 37W x 3 hours/day x 365 days/year x 110,000,000 households in the US = 4,456,650,000 kWh/year, or $668,497,500! A typical coal fired power plant generates 4,000,000MWh/year. To find out how many power plants we could eliminate we simply divide the energy savings by the energy generated by a power plant (4,456,650MWh / 4,000,000MWh). This shows that, if every household in the US replaced one incandescent bulb with a CFL, we could turn off 1 coal-fired power plant.
In another previous AskPablo (“AskPablo: Phantom Power”) I calculated that households in the US probably waste around 34,913,913 MWh/year to phantom energy losses from power supplies and appliance on standby mode (TV, VCR, Microwave Oven, etc.). If we could unplug all of these it would eliminate the need for almost 9 coal-fired power plants (34,913,913 MWh / 4,000,000 MWh). Amory Lovins frequently states 11 coal-fired power plants, so his assumptions must be similar to mine.
This is all great information to know but the sad thing is that China is currently building around 1 coal-fired power plant per week! In fact the Chinese government doesn’t even know the full extent of new power plant construction. What they do know is that there is a near-permanent cloud of smog of vast past of the country, part of which even impacts air quality in the Western US. Coal is clearly not the solution to our problems. Not even so-called “clean coal” can save us. To prevent the further accumulation of bad stuff in the air we need to keep it locked away safely underground where it belongs and instead rely on abundant and clean renewable energy available on the surface.

Pablo Päster

Sustainability Engineer