(619c) Life Cycle Carbon Footprint of Renewable Electricity Generation from Aspen Forest Intensive Harvest in Wisconsin, USA

The Renewable Portfolio Standard mandates increased production of electricity from renewable sources. There are large quantities of timber net growth in excess of removals in the Great Lakes region. The excess timber wood can be a promising feedstock to address the forest products industry while also providing renewable feedstock for energy production. In this study, we aim to evaluate the life cycle greenhouse gas (GHG) emission of renewable electricity produced from cogeneration of aspen biomass in Wisconsin. The typical harvest age for aspen is 40 years. We propose that one way to provide biomass for electricity generation is to intensively harvest aspen by shortening rotation cycles. First, soil carbon (0-60cm depth) was measured from 4 age classes of aspen, namely, 10yr, 20yr, 30yr, and 40-60yr. CO₂ emissions due to intensive aspen harvest were estimated based on differences in soil C levels of various age classes. Next, the optimal biomass supply chain will be determined by minimizing the economic, environmental and social cost of shipping biomass from forest to the cogeneration facility. Finally, a life cycle assessment model is used to quantify the cradle-to-grave GHG emission of renewable electricity, including soil C change, wood harvest, trans-loading and transportation, and combustion in fluidized bed boiler. The life cycle GHG emissions of renewable electricity will be compared with that of Wisconsin grid mix.