Because of its abundance and high-energy value coal powered the industrial revolution and early mass transportation. Today, coal provides the base-load power for most U.S. utilities. The problem with coal is that the bacteria and fungus that created it 300 million years ago used sulfur, nitrogen and metals, most notably mercury, to build enzymes to break down the plants into usable molecules such as sugar. So, when coal is burned it produces pollutants that need to be scrubbed from the air emissions. One molecule that isn't scrubbed from coal plants is carbon dioxide. As the world concentrates on reducing carbon dioxide pollution, interest in biomass, which can be considered the new coal, has peaked. Since the carbon dioxide in biomass comes from the current atmosphere it is not considered "pollution" like the carbon dioxide from coal that has been sequestered in the earth for millions of years.
To reduce their carbon footprints, utilities and entrepreneurs are investigating opportunities to convert small coal power plants to use biomass. Once converted, the majority of these facilities will produce 20 to 50 megawatts of electricity, which is small in comparison with typical coal power plants. Energy density is one reason biomass power plants are smaller than coal power plants. Coal on a unit-weight basis contains three times the energy of green wood and more than twice that of dry herbaceous materials. This makes it more economical to transport coal a long distance when compared with wood and other biomass. So, on one level water content and bulk density can be considered a problem for biomass. But is it really an issue? While power plants often use coal mined half a country away, a biomass power plant would use locally produced fuel making it a local economic generator.
Coal was once the cheapest energy source around and still is inexpensive compared with other fossil fuels. But the price of coal has risen rapidly, similar to petroleum, because of global demand and the cost of transportation. The increase in the price of coal makes locally produced biomass competitive at smaller, less efficient plants. Furthermore, as the U.S. government gets more serious about reducing greenhouse gas emissions, possibly with the next administration, moving existing coal assets to biomass would be a way to reduce a greenhouse gas footprint, earn renewable energy credits and be a champion of local economic development. That is definitely a win, win, win alternative to coal.
Art Wiselogel is manager of BBI International's Community Initiative to Improve Energy Sustainability. Reach him at email@example.com or (303) 526-5655.