BEYOND CO2 Lifecycle assessments typically focus on “biogeochemical” effects; that is, net fluxes of greenhouse gases to and from the atmosphere. We are now moving towards including “biogeophysical” effects in lifecycle assessments. These are the changes in the radiation balance of the planet due to physical changes. For example, large-scale biomass cultivation for fuel production results in changes to the average planetary albedo. Our research indicates that this effect is usually cooling, and of a similar order to the biogeochemical effects. A second example relates to contrails — the line-shaped clouds that aircraft sometimes leave in their wake. These are thought to significantly contribute to the climate warming attributable to aviation. Our latest research indicates that combustion of alternative fuels may result in contrails that are optically thinner, so may result in less warming than contrails produced by combustion of conventional jet fuel. We are also assessing the air quality and human health implications of alternative jet fuels, which typically burn cleaner than their conventional counterparts. Beyond the potentially significant benefits of many alternative jet fuel A non-competitive fuel will not options, there are also a range of downsides, some of which penetrate the market and the we are investigating. In particular, fresh water use in biomass lowest cost environmental miticultivation and fuel production is a potential concern. Our gation measures will enable the calculations indicate that use of unirrigated biomass for alternative fuel production results in a water intensity about the greatest reduction in emissions. same as conventional jet fuel. However, maximizing biomass yield would result in many times more fresh water consumption than regular Jet A — in some cases hundreds of liters of water per liter of fuel. A second potential disadvantage is the “environmental opportunity cost” of using biomass for alternative jet fuel production; that is, the extent to which more GHG emissions could have been offset if the biomass were used for a different purpose. For example, rather than expending energy on converting biomass to a tightly specified high quality fuel like Jet A, it could be directly burned in a combined heat and power plant, potentially offsetting CO2-intensive coal-fired generation. Finally, we are assessing the production costs of different feedstock-to-fuel pathways. This is critical for both economic and environmental reasons — a fuel that is too expensive will not be adopted and, thus, will result in no environmental benefit.
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AEROASTRO 2012-2013