Abatement cost of GHG emissions for wood-based electricity and ethanol at production and consumption levels

Replacing coal in Georgia's power plants with woody biomass to increase carbon benefit: A mixed integer linear programming model

To combat climate change, reducing carbon emissions from coal consumption in the power sector can be an effective strategy. We developed a price-exogenous mixed integer linear optimization model satisfying both traditional timber demand in Georgia and its neighboring states (Alabama, Florida, North Carolina, South Carolina, and Tennessee) and additional bioenergy demand to replace coal in the power plants of Georgia for 50 years, maximizing social welfare. We used Forest Inventory & Analysis unit level yield of five forest types (planted softwood, natural softwood, upland hardwood, bottomland hardwood, and mixed forest), timber demand, and price information, and developed three scenarios. In the Baseline scenario, traditional annual timber demand (152 million tons of wood) was satisfied with no coal replacement. In Scenario 1, 100% coal (7.34 million tons annually) was replaced using pulpwood only, along with traditional demand. In Scenario 2, also with traditional demand, 100% coal was replaced using pulpwood and logging residues. It would require approximately 336 and 98 thousand acres of additional annual timberland harvested in Scenario 1 and Scenario 2, respectively, compared to Baseline (1280 thousand acres). During 50 years, a total of 9.3, 10.2, and 9.6 billion tons of timber was produced in Baseline, Scenario 1, and Scenario 2, respectively. About one-third of all torrefaction plants would be located in the central region of Georgia. The net change in stand carbon was positive in all three scenarios-the highest in Baseline (1330 million tons C), followed by Scenario 2 (1261 million tons C), and the lowest in Scenario 1 (872 million tons C). About 240 million tons of carbon was avoided by using biomass instead of coal in Scenario 1 and Scenario 2. In Baseline, with continued emission from coal usage in the power plant for 50 years (285 million tons C), net carbon benefit was 1046 million tons C. Replacing 100% of coal with both pulpwood and logging residues provided a net benefit of 1501 million tons C, about 43% higher compared to baseline.

Cost of abating greenhouse gas emissions with cellulosic ethanol

We develop an integrated framework to determine and compare greenhouse gas (GHG) intensities and production costs of cellulosic ethanol derived from corn stover, switchgrass, and miscanthus grown on high and low quality soils for three representative counties in the Eastern United States. This information is critical for assessing the cost-effectiveness of utilizing cellulosic ethanol for mitigating GHG emissions and designing appropriate policy incentives to support cellulosic ethanol production nationwide. We find considerable variations in the GHG intensities and production costs of ethanol across feedstocks and locations mostly due to differences in yields and soil characteristics. As compared to gasoline, the GHG savings from miscanthus-based ethanol ranged between 130% and 156% whereas that from switchgrass ranged between 97% and 135%. The corresponding range for GHG savings with corn stover was 57% to 95% and marginally below the threshold of at least 60% for biofuels classified as cellulosic biofuels under the Renewable Fuels Standard. Estimates of the costs of producing ethanol relative to gasoline imply an abatement cost of at least $48 Mg(-1) of GHG emissions (carbon dioxide equivalent) abated and can be used to infer the minimum carbon tax rate needed to induce consumption of cellulosic ethanol.