Biomass — plant material and animal waste — can be used to create transportation fuels and generate electricity, but the key to using biomass resources in a beneficial way is to focus on the right resources and use them at an appropriate scale.
To date, food crops (corn, sugar, and vegetable oil) have been the primary source of biofuels for transportation, but increased use of these fuels has created more problems than solutions: rising food prices and food price volatility, and accelerated expansion of agriculture in the tropics.
This UCS analysis focuses on the four primary non-food sources of biomass — energy crops, agricultural residues, waste materials, and forest biomass — and details the amount of each type of biomass that could be sustainably produced and utilized in the United States without compromising the fertility of agricultural soils, displacing land needed to grow our food, or threatening the health of our farms and forests.
The United States has the potential to dramatically expand biomass use for fuel and power
Biomass resources totaling just under 680 million dry tons could be made available, in a sustainable manner, each year within the United States by 2030.
- This is enough biomass to produce more than 54 billion gallons of ethanol (four times as much corn ethanol as the United States produced in 2010) or 732 billion kilowatt-hours of electricity (19 percent of total U.S. power consumption in 2010).
- Biomass resources are distributed widely across the United States, ensuring that communities across America can benefit both financially and environmentally from increased biomass production.
Energy crops offer the greatest opportunity to expand energy production from biomass
Energy crops include tall grasses like switchgrass and miscanthus, and fast-growing trees like hybrid poplar and willow. As much as 400 million dry tons of these crops could be produced each year by 2030.
- Energy crops produce energy efficiently, requiring only modest amounts of fertilizer and pesticide, and less fertile soil than is needed for other types of agriculture.
- Time and significant changes in agricultural practices are needed to realize the full potential of energy crops, but expanding the role of perennial grasses in agriculture offers important climate and water quality benefits.
Agricultural residues can provide significant biomass without expanding the footprint of agriculture
Agricultural residues left behind after harvest — corn stover (i.s. stalks and leaves) and wheat straw — are a potential source of up to 155 million dry tons of biomass for energy production.
- Since these residues are a natural by-product of the primary food crop, they can be used without reducing the availability of food crops or increasing the amount of land used for agriculture.
- In order to be sustainably produced, agricultural residues can only be removed at a rate that allows soild to maintain their organic matter, which is a key contributor to long-term soil productivity.
Waste materials for bioenergy production benefit from an existing infrastructure for collection
Household garbage, vegetative waste (lawn clippings and tree trimmings), and construction and demolition debris are already collected for disposal and can provide 35 million dry tons of biomass.
- Many sources of waste biomass are mixed with recyclable materials and potentially dangerous contaminants; sorting and pollution control technologies are needed to ensure it is used in an environmentally friendly manner.
- Manure can be used to produce electricity by using anaerobic digesters to extract bioenergy (in the form of biogas). Almost 60 million tons of manure is currently available in the United States.
Forests offer a limited source of new biomass resources
Tree tops and limbs collected during logging operations could provide just under 20 million dry tons of additional biomass for energy production.
- Recent science has raised significant doubts as to whether the use of whole trees for bioenergy is a low-carbon method for energy production. In the absence of a clear emissions benefit, wood from whole trees, including pulpwood and forest thinnings, has been excluded from this assessment.