Biomass - Energy Policy Analysis: A Conceptual Framework - page 160

can be converted into synthetic gas (syngas), a mixture of hydrogen and carbon monoxide. Mi-
croorganisms can break down biomass from human sewage, animal manure, or poultry litter in
anaerobic digesters to produce methane and carbon dioxide (UCS 2010).
Through gasification, biomass can also be cofired at natural gas-powered electric generating
plants. Syngas is often refined to remove contaminants and carbon dioxide and can then be burned
directly in a gas turbine or burned in a steam turbine to produce electricity. Biomass gasification is
generally cleaner and more efficient than direct combustion. Syngas can also be further processed
to make liquid biofuels or other useful chemicals (UCS 2010). Liquid biofuels have great potential
to help supply our transportation needs (Luque et al. 2008).
To assess the global warming impact of transportation fuels, we must measure their full life
cycle emissions per unit of energy delivered. Emissions vary depending on the feedstock and
refining process. A study by the Union of Concerned Scientists found that liquid coal (gasoline or
diesel made from coal) may produce emissions more than 80 percent greater than conventional
gasoline. Gasoline produced from tar sands may produce emissions about 14 percent greater
than conventional gasoline, depending on the feedstock and refining process used. Corn ethanol
can produce higher emissions than conventional gasoline or cut emissions more than 50 percent,
depending on how it is processed. Cellulosic ethanol, which is made from woody plants, may be
able to reduce emissions more than 85 percent, as compared to conventional gasoline (UCS 2007).
The range of findings suggests great caution is warranted when analyzing the environmental costs
of biomass technologies.
COSTS OF BIOMASS UTILIZATION
Environmental Costs of Utilizing Biomass
The fuel cycle for biomass is twofold, depending on whether one wishes to use it for biopower
or biofuel. The fuel cycle for biopower includes growing and harvesting the fuel, transportation,
processing, combustion in a power plant, decommissioning and reclamation of the generating site,
and disposal of waste by-products, as illustrated in Figure 9.1. The basic components of biopower
generation facilities include a nearby source for fuel, a processing facility, a combustion turbine,
and electrical grid interconnection equipment. Suitable areas must be evaluated, processing and
generating facilities constructed and operated, and eventually generating equipment must be
decommissioned. Potential environmental costs of using biopower technologies include land
disturbance and major ecosystem changes, adverse effects on water quality and quantity, and
climate-changing air emissions.
The fuel cycle for biofuels includes growing and harvesting the fuel, processing, transpor-
tation, combustion, decommissioning and reclamation of the processing site, and disposal of
waste by-products, as illustrated in Figure 9.2. The basic components of biofuels production and
consumption include a nearby source for fuel, processing equipment, and combustion. Suitable
areas must be evaluated, processing facilities constructed and operated, and eventually process-
ing equipment must be decommissioned. Potential environmental costs of using biofuels include
land disturbance and major ecosystem changes, adverse effects on water quality and quantity, and
climate changing air emissions.
Biomass can be grown and harvested in ways that protect soil quality, avoid erosion, and maintain
wildlife habitat. However, biomass for energy can also be harvested at unsustainable rates, damage
ecosystems, produce harmful air pollution, consume large amounts of water, and produce increased
net greenhouse emissions, affecting climate change. The Union of Concerned Scientists main-