(603c) Use of a Carbon Budget Model to Calculate Land Use Change Greenhouse Gas Emissions Associated with Forest-Based Biofuels Production in Michigan

Michigan is heavily forested with 19.4 million acres of timberland, and the large volume of timber resources are potential feedstocks for biofuel and bioenergy production. To truly understand the environmental impacts of biofuels production in Michigan, it is essential to evaluate the land use change (LUC) impacts associated with the biomass production practices in this area, namely sustainable harvesting from natural regeneration forest land, and short rotation forestry (SRF) plantation. These two practices are not likely to cause indirect land use change (iLUC) emissions because forest products are not used in the food market.  However, the impacts of direct LUC (dLUC) should be examined. The Carbon Budget Model of Canadian Forest Sector (CBM-CFS3) is applied in this study to estimate the dLUC impact associated with the biomass production in Michigan. The CO₂ flux between the atmosphere and soils due to dLUC are quantified and incorporated into the LCA study of the biofuels. We consider three cases for this model; 1. Afforestation of MI forests, 2. Increased harvesting above a business as usual harvest level to satisfy a certain level of biofuel production, and 3. Establishment of SRF plantation on abandoned agricultural lands to satisfy a certain level of biofuel production.  A business as usual (BAU) harvesting scenario is first established based on the current harvesting acreage and intensity, a case in which MI forests continue to accrue carbon as forests recover from historic harvest practices (Afforestation case). Because the carbon budget model simulates over a several decade time period, we will also include estimates of changes in fossil greenhouse gas emissions due to changes in extraction practices, for example by relying in inputs from high greenhouse gas intensity crude oils, such as tar sands, using literature values.  SRF species, such as poplar, can be planted on abandoned or marginal agricultural land, but tillage at the land preparation stage will disturb the carbon balance and microbial activity in soil, while the growing biomass can sequester carbon from atmosphere into the root system as it grows. Finally, we include these landscape level carbon dynamics into life cycle assessments of biofuels that can be produced from forest feedstocks, for example cellulosic ethanol, to understand the potential impacts on product-based LCA results.