Biomass Energy in Context: Coal, Natural Gas, Other Renewables, Liquid Fuels and Greenhouse Gas Reduction

摘要

As fuel for electric power generation in the U.S., biomass could grow to supply as much as 40% of the electricity now generated from coal, i.e., about 800 billion kWh (TWh), which would be 20% of current US electricity generation. Or, as transportation fuel, biomass could expand to as much as 35% of the heat content of the gasoline now going into automobile and truck transportation. These are maximum estimates and assume that the biomass goes 100% to one or the other. Today biomass generates about 1.2% of US electricity and also supplies the energy equivalent of approximately 2% of US gasoline. In addition to these roles in electricity and transportation, biomass wastes and byproducts supply process heat in the pulp/paper and forest product industries. In total, biomass accounts for approximately 3% of the primary energy input into the US economy. The potential role could be 5 to 10 times larger. The most efficient use of biomass would be via combined heat and power (CHP, or cogeneration) with biomass-to-ethanol plants being the heat users. These ethanol plants fueled and powered by solid biomass and/or gasified biomass would also be producing fuel to replace something on the order of 20% of today's gasoline use. This combination could allow biomass to supply perhaps 25% of all of US primary energy needs, and account for over 35% of the greenhouse gas reductions needed at mid 21st Century. This paper develops these estimates based on (a) biomass resource types, (b) crops and their potential yields, and (c) wastes as potential biomass fuels. Next, the major technologies are identified and characterized. These are the technologies that would be considered for use in any scenario that envisioned a major role for biomass in the US. The following are the biomass energy technologies included here: (1) direct solid fuel combustion for heat, steam and power, (2) cofiring with coal, (3) cofiring with natural gas, (4) gasification combined cycle, (5) CHP, (6) corn-to-ethanol, (7) sugarcane-to-ethanol, and (8) cellulosic biomass to ethanol.