Improving the sustainability of biofuels through modification of the biomass production subsystem: Application to corn and lignocellulosic ethanol

摘要

Concerns about dwindling fossil fuel reserves and climate change, energy independence, and depletion of ecosystêm goods and services have driven the development of alternative technologies such as biomass-based fuels (biofuels). Although biofuels may be a step towards alleviating the aforementioned concerns due to the renewable nature of the biomass feedstock, there are several drawbacks associated with them. Food crop-based fuels such as corn ethanol, which comprise the majority of the current biofuel mix in the US, require large amounts of fossil-based inputs purchased from the economy in order to grow the biomass. These inputs, such as fertilizers, pesticides, and fossil fuels greatly diminish the renewable nature of the plant itself and force the production of biofuels to be reliant on nonrenewable fossil-based inputs. In addition to reliance on non-renewable inputs, biofuels are heavily reliant on ecosystem goods and services. Current large-scale farming practices result in the runoff of nutrients from fertilizers into rivers and streams, which can overwhelm the carrying capacity of the nitrogen (N) and phosphorous (P) cycles of these aquatic ecosystems with devastating results. Freshwater for irrigation is needed if natural precipitation is not sufficient. Topsoil, a vital local npn-renewable resource, is, also depleted through erosion in traditional monocultural row cropping. Ecosystem goods andservices are also indirectly consumed through the life cycle of the inputs used in farming.