Competitive liquid biofuels from biomass

摘要

The cost of biodiesels varies depending on the feedstock, geographic area, methanol prices, and seasonal variability in crop production. Most of the biodiesel is currently made from soybean, rapeseed, and palm oils. However, there are large amounts of low-cost oils and fats (e.g., restaurant waste, beef tallow, pork lard, and yellow grease) that could be converted to biodiesel. The crop types, agricultural practices, land and labor costs, plant sizes, processing technologies and government policies in different regions considerably vary ethanol production costs and prices by region. The cost of producing bioethanol in a dry mill plant currently totals US$1.65/galon. The largest ethanol cost component is the plant feedstock. It has been showed that plant size has a major effect on cost. The plant size can reduce operating costs by 15-20%, saving another $0.02-$0.03 per liter. Thus, a large plant with production costs of $0.29 per liter may be saving $0.05-$0.06 per liter over a smaller plant. Viscosity of biofuel and biocrude varies greatly with the liquefaction conditions. The high and increasing viscosity indicates a poor flow characteristic and stability. The increase in the viscosity can be attributed to the continuing polymerization and oxidative coupling reactions in the biocrude upon storage. Although stability of biocrude is typically better than that of bio-oil, the viscosity of biocrude is much higher. The bio-oil produced by flash pyrolysis is a highly oxygenated mixture of carbonyls, carboxyls, phenolics and water. It is acidic and potentially corrosive. Bio-oil can also be potentially upgraded by hydrodeoxygenation. The liquid, termed biocrude, contains 60% carbon, 10-20 wt.% oxygen and 30-36 MJ/kg heating value as opposed to <1 wt.% and 42-46 MJ/kg for petroleum.