Читать книгу Encyclopedia of Renewable Energy - James Speight G., James G. Speight - Страница 64

Propanol and butanol are considerably less toxic and less volatile than methanol. In particular, butanol has a high flashpoint (35°C; 95°F), which is a benefit for fire safety, but may be a difficulty for starting engines in cold weather.

The fermentation processes to produce propanol and butanol from cellulose are fairly tricky to execute, and the Clostridium acetobutylicum currently used to perform these conversions produces an extremely unpleasant smell, and this must be taken into consideration when designing and locating a fermentation plant. This organism also dies when the butanol content of whatever it is fermenting rises to 7%. For comparison, yeast dies when the ethanol content of its feedstock reaches 14%. Specialized strains can tolerate even greater ethanol concentrations -so-called turbo yeast can withstand up to 16% ethanol. However, if ordinary Saccharomyces yeast can be modified to improve its ethanol resistance, scientists may yet one day produce a strain of the Weizmann organism with a butanol resistance higher than the natural boundary of 7%. This would be useful because butanol has a higher energy density than ethanol, and because waste fiber left over from sugar crops used to make ethanol could be made into butanol, raising the alcohol yield of fuel crops without there being a need for more crops to be planted.

See also: Alcohols.