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The goal of this study was to estimate the greenhouse gas (GHG) emissions and fossil energy requirements from the production and use (cradle-to-grave) of bioethanol produced from the indirect gasification thermochemical conversion of loblolly pine (Pinus taeda) residues. Additional impact categories (acidification and eutrophication) were also analyzed. Of the life-cycle stages, the thermochemical fuel production and biomass growth stages resulted in the greatest environmental impact for the bioethanol product life cycle. The GHG emissions from fuel transportation and process chemicals used in the thermochemical conversion process were minor (less than 1 percent of conversion emissions). The net GHG emissions over the bioethanol life cycle, cradle-to-grave, was 74 percent less than gasoline of an equal energy content, meeting the 60 percent minimum reduction requirement of the Renewable Fuels Standard to qualify as an advanced (second generation) biofuel. Also, bioethanol had a 72 percent lower acidification impact and a 59 percent lower eutrophication impact relative to gasoline. The fossil fuel usage for bioethanol was 96 percent less than gasoline, mainly because crude oil is used as the primary feedstock for gasoline production. The total GHG emissions for the bioethanol life cycle analyzed in this study were determined to be similar to the comparable scenario from the Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation model. A sensitivity analysis determined that mass allocation of forest establishment burdens to the residues was not significant for GHG emissions but had significant effects on the acidification and eutrophication impact categories., ********** The United States is the largest bioethanol producing country, with 49.2 billion liters as of 2010 (Renewable Fuels Association [RFA] 2010). Controversy around conventional biofuels, which are usually produced [...]

The heightened interest in biofuels addresses the national objectives of reducing carbon emissions as well as reducing dependence on foreign fossil fuels. Using life-cycle analysis to evaluate alternative uses of wood including both products and fuels reveals a hierarchy of carbon and energy impacts characterized by their efficiency in reducing carbon emissions and/or in displacing fossil energy imports. Life-cycle comparisons are developed for biofuel feedstocks (mill and forest residuals, thinnings, and short rotation woody crops) with bioprocessing (pyrolysis, gasification, and fermentation) to produce liquid fuels and for using the feedstock for pellets and heat for drying solid wood products, all of which displace fossil fuels and fossil fuel-intensive products. Fossil carbon emissions from lignocellulosic biofuels are substantially lower than emissions from conventional gasoline. While using wood to displace fossil fuel-intensive materials (such as for steel floor joists) is much more effective in reducing carbon emissions than using biofuels to directly displace fossil fuels, displacing transportation fuels with ethanol provides the opportunity to also reduce dependence on imported energy. The complex nature of wood uses and how wood fuels and products interact in their environments, as well as the methods needed to understand these impacts and summarize the relative benefits of different alternatives, are discussed herein. Policies designed to increase biofuel use by subsidies or mandates may increase prices enough to divert biomass feedstock away from producing products, such as for composite panels, resulting in increased emissions from fossil fuel-intensive substitutes. Policies that fail to consider life-cycle implications are discussed, identifying their unintended consequences., The life-cycle inventory (LCI) data for the many different uses of wood reveal a hierarchy of different opportunities to reduce carbon emissions or increase energy independence, both being current national [...]