Bio-methanol: How Energy Choices In The Western United States Can Help Mitigate Global Climate Change

摘要

Converting available biomass from municipal, agricultural and forest wastes to bio-methanol can result in significant environmental and economic benefits. Keeping these benefits in mind, one plausible scenario discussed here is the potential to produce energy using bio-methanol in five states of the western United States. In this scenario, the bio-methanol produced is from different biomass sources and used as a substitute for fossil fuels in energy production. In the US. West, forest materials are the dominant biomass waste source in Idaho, Montana, Oregon and Washington, while in California, the greatest amount of available biomass is from municipal wastes. Using a 100% rate of substitution, bio-methanol produced from these sources can replace an amount equivalent to most or all of the gasoline consumed by motor vehicles in each state. In contrast, when bio-methanol powered fuel cells are used to produce electricity, it is possible to generate 12-25% of the total electricity consumed annually in these five states. As a gasoline substitute, bio-methanol can optimally reduce vehicle C emissions by 2-29 Tg of C (23-81 % of the total emitted by each state). Alternatively, if bio-methanol supported fuel cells are used to generate electricity, from 2 to 32 Tg of C emissions can be avoided. The emissions avoided, in this case, could equate to 25-32% of the total emissions produced by these particular western states when fossil fuels are used to generate electricity. The actual C emissions avoided will be lower than the estimates here because C emissions from the methanol production processes are not included; however, such emissions are expected to be relatively low. In general, there is less carbon emitted when bio-methanol is used to generate electricity with fuel cells than when it is used as a motor vehicle fuel. In the state of Washington, thinning "high-fire-risk" small stems, namely 5.1-22.9 cm diameter trees, from wildfire-prone forests and using them to produce methanol for electricity generation with fuel cells would avoid C emissions of 3.7-7.3 Mg C/ha. Alternatively, when wood-methanol produced from the high-fire-risk wood is used as a gasoline substitute, 3.3-6.6 Mg C/ha of carbon emissions are avoided. If these same "high-fire-risk" woody stems were burned during a wildfire 7.9 Mg C/ha would be emitted in the state of Washington alone. Although detailed economic analyses of producing methanol from biomass are in its infancy, we believe that converting biomass into methanol and substituting it for fossil-fuel-based enerev production is a viable option in locations that have high biomass availability.