A new analysis from the Union of Concerned Scientists downplays the decade-long federal "Billion Ton Study" that led to a national debate about what role biomass could play in biofuel production in coming decades.
The UCS analysis released this week said the study conducted by Oak Ridge National Laboratory may be overly "optimistic" and did not take into account the need to produce biomass for energy in a sustainable and environmentally friendly way.
The Oak Ridge National Lab analysis estimates that about 767 million dry tons of biomass would be available. The Union of Concerned Scientists analysis said, however, that when factoring in biomass produced sustainably, about 677 million dry tons could be produced by 2030. That volume of biomass would be enough to produce more than 54 billion gallons of ethanol by 2030, UCS said, or 732 billion kilowatt-hours of electricity.
The UCS study was less optimistic about the potential of agriculture residues, including corn stover. The latest Oak Ridge analysis places the ag residues number at about 180 million dry tons. The Union of Concerned Scientists said when factoring in sustainability, the number is more like 129 million dry tons with a potential to produce up to 155 million dry tons.
The majority of that biomass would be generated in the heart of the Corn Belt -- Nebraska, Iowa and Illinois -- and includes corn stover and the straw or stems left from harvesting barley, oats and wheat.
"Since these residues are a natural byproduct of the primary crop, they can be used to generate energy without reducing the availability of food crops or expanding the footprint of agriculture," the study said.
"However, only a portion of the residues can be removed, because some must be left behind to protect the soil from erosion and degradation. Sustainable use of crop residues at the scale described here will require the adaptation of farm management techniques to minimize potential environmental harm."
PRESERVING LANDS
The Union of Concerned Scientists' analysis said because biomass would be produced in areas that already have existing crop production, forestry and other goods and services, expanded biomass production would have to take place in a way that would not alter those systems.
"To protect these essential goods and services we must limit the amount of land devoted to producing biomass," UCS said. "Exceeding the limits of sustainable biomass utilization will trade our current fossil fuel problem for problems in our food system and forests, and will do nothing to reduce heat-trapping emissions.
"So, while the economic and environmental benefits of bioenergy are often measured in terms of its displacement of fossil fuels, a more realistic assessment must include its impact on our farms, forests, water, wildlife, and soils."
The Oak Ridge lab's most recent analysis includes a county-by-county assessment of more than 30 potential biomass sources ranging from tall prairie grasses to construction and demolition debris. The purpose of that study was to determine whether a billion tons of biomass is available to produce bioenergy.
"After a thorough review of (Oak Ridge) assumptions and sustainability thresholds, we concluded that its analysis is too optimistic in some areas, and lacks adequate safeguards to protect the environment," the UCS analysis said.
"We opted for a stricter threshold that would protect the fertility of agricultural soils, and also excluded certain categories of biomass, such as whole trees, that are unlikely to result in low-carbon power or fuel production. Our criteria are designed to establish a level of biomass utilization consistent with protecting land needed to grow food, and supporting healthy farms and forests."
ENERGY CROPS
The UCS study points to energy crops as the "largest long-term opportunity" when it comes to expanding bioenergy production, primarily in Kansas, Oklahoma and Texas.
The most promising feedstocks include tall grasses including switchgrass, miscanthus and hybrid poplar and willow trees, and could lead the way in producing as much as 400 million tons of biomass by 2030.
"Energy crops are attractive because they produce energy efficiently, requiring only modest amounts of fertilizer and pesticide, and less fertile soil than is needed for other types of agriculture," the UCS study said.
"Most are perennials, which can be harvested for many years after planting, and expanding the role of perennial crops in agriculture can provide important environmental benefits compared with the food crops currently used for biofuels (primarily corn and soybeans). Energy crops can be integrated into the agricultural system in various ways: as buffer strips or wind breaks, on highly erodible soils or floodplains, or on land being cycled through longer planting rotations."
Source: Pioneer