Identifying key drivers of greenhouse gas emissions from biomass feedstocks for energy production

•Production emissions dominate transportation and processing emissions.•Choice of feedstock, geographic location and prior land use drive emissions profile.•Within scenarios, emissions variability is driven by uncertainty in yields.•Favorable scenarios maximize carbon storage from direct land-use change.•Similarly, biomass production should attempt to minimize indirect land-use change.

Many policies in the United States, at both the federal and state levels, encourage the adoption of renewable energy from biomass. Though largely motivated by a desire to reduce greenhouse gas emissions, these policies do not explicitly identify scenarios in which the use of biomass will produce the greatest benefits. We have modeled “farm-to-hopper” emissions associated with seven biomass feedstocks, under a wide variety of scenarios and production choices, to characterize the uncertainty in emissions. We demonstrate that only a handful of factors have a significant impact on life cycle emissions: choice of feedstock, geographic location, prior land use, and time dynamics. Within a given production scenario, the remaining variability in emissions is driven by uncertainty in feedstock yields and the release rate of N2O into the atmosphere from nitrogen fertilizers. With few exceptions, transport and processing choices have relatively little impact on total emissions. These results illustrate the key decisions that will determine the success of biomass programs in reducing the emissions profile of energy production, and our publicly available model provides a useful tool for identifying the most beneficial production scenarios. While model data and results are restricted to biomass production in the contiguous United States, we provide qualitative guidance for identifying favorable production scenarios that should be applicable in other regions.

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