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To convert biomass to liquid fuels, three platforms are compared: thermochemical, sugar, and carboxylate. To create a common basis, each platform is fed "ideal biomass," which contains polysaccharides (68.3%) and lignin (31.7%). This ratio is typical of hardwood biomass and was selected so that when gasified and converted to hydrogen, the lignin has sufficient energy to produce ethanol from the carboxylic acids produced by the carboxylate platform. Using balanced chemical reactions, the theoretical yield and energy efficiency were determined for each platform. For all platforms, the ethanol yield can be increased by 71% to 107% by supplying external hydrogen produced from other sources (e.g., solar, wind, nuclear, fossil fuels). The alcohols can be converted to alkanes with a modest loss of energy efficiency (3 to 5 percentage points). Of the three platforms considered, the carboxylate platform has demonstrated the highest product yields.

In whatever measure liquid biofuels are produced, they avoid the use of politically and economically unstable petroleum. However, there has been much debate regarding their environmental impact and sustainability. Corn ethanol manufacturing uses large quantities of fossil fuels, which, although locally produced, create doubt on whether its continual use will bring any clear economic and environmental benefits. On the other hand, biodiesel, because it enjoys a simpler and thus efficient manufacturing process, shows more clarity as to the environmental benefits it provides, but its sustainability at a significant scale is not clear due to the low productivity of its crops. Brazil's ethanol industry, which is based on sugarcane, has shown that it is possible to be efficient, both environmentally and economically in the implementation of a biofuel infrastructure. Very akin to sugarcane ethanol technology is cellulosic ethanol. A cellulosic ethanol infrastructure can make use of crops that have higher productivities and lower environmental impact. In addition, the conversion process uses very little fossil fuels, which makes it even more sustainable and environmentally benign. This article describes the infrastructure necessary for the implementation of sustainable biofuels, discusses their projected benefits, their environmental impact, and the logistics needed for their sustainability. © 2007 American Institute of Chemical Engineers Environ Prog, 2007

The MixAlco process employs a mixed culture of acid-forming microorganisms to convert biomass to carboxylate salts, which are concentrated via vapor-compression evaporation and subsequently chemically converted to other chemical and fuel products. To make alcohols, hydrogen is required, which can be supplied from a number of processes, including gasifying biomass, separation from fermentor gases, methane reforming, or electrolysis. Using zeolite catalysts, the alcohols can be oligomerized into hydrocarbons, such as gasoline. A 40-tonne/h plant processing municipal solid waste ($45/tonne tipping fee) and using hydrogen from a pipeline or refinery ($2.00/kg H(2)) can sell alcohols for $1.13/gal or gasoline for $1.75/gal with a 15% return on investment ($0.61/gal of alcohol or $0.99/gal of gasoline for cash costs only). The capital cost is $1.95/annual gallon of mixed alcohols. An 800-tonne/h plant processing high-yield biomass ($60/tonne) and gasifying fermentation residues and waste biomass to hydrogen ($1.42/kg H(2)) can sell alcohols for $1.33/gal or gasoline for $2.04/gal with a 15% return on investment ($1.08/gal of alcohol or $1.68/gal of gasoline for cash costs only). The capital cost for the alcohol and gasification plants at 800 tonne/h is $1.45/annual gallon of mixed alcohols.

Two suggestions can be found in the literature to improve the reproducibility of the Mandels' filter paper assay: add supplemental cellobiase and increase the boiling time for color development. Here we provide data that strongly supports adding supplemental cellobiase. Adding supplemental cellobiase increased assay response by 56%. Cellulases from different sources have different cellobiase activities, which would cause significant variation in the assay response. There is no need for additional boiling time-5 minutes is sufficient. For maximum reproducibility, it is essential that the water bath vigorously boil so that temperature excursions are minimized.