| Summary: | Life cycle assessment is an important tool to evaluate the impact of 2nd generation lignocellulosic ethanol, and its potential greenhouse gas (GHG) emissions benefits relative to gasoline. The choice of feedstock, process technology, and co-products may affect GHG emissions and energy metrics. Co-products may improve both the financial and environmental performance of the biorefinery. 26 well-to-wheel models of future lignocellulose-to-ethanol pathways were constructed, considering corn stover, switchgrass, and poplar feedstocks, three pre-treatment technologies, four co-product options, and the use of ethanol in a light-duty vehicle. Model results showed that all pathways with lignin pellet co-production had significantly lower net GHG emissions relative to gasoline and corresponding pathways producing only electricity. Pathways co-producing xylitol had at least 66% greater GHG emission reductions relative to pathways co-producing only lignin pellets. All feedstock/pretreatment/co-product combinations led to GHG reductions of at least 60%, meeting the threshold stipulated under the Energy Independence and Security Act.
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