Читать книгу Encyclopedia of Renewable Energy - James Speight G., James G. Speight - Страница 165

Bioenergy crops are low-cost and low-maintenance crops grown solely for energy production by (for example) combustion. The crops are processed into solid, liquid, or gaseous fuels, such as pellets, bioethanol, or biogas. The fuels are burned to generate electrical power or heat. The plants are generally categorized as woody or herbaceous. The former – woody plants include willow and poplar while the latter – herbaceous plants – include miscanthus and these crops, while physically smaller than trees, store (approximately) twice the amount of carbon dioxide (in the form of carbon) below ground, compared to woody crops.

Thus, bioenergy crops include fast-growing trees such as hybrid poplar, black locust, willow, and silver maple in addition to annual crops such as corn, sweet sorghum, and perennial grasses such as switch grass. The first-generation bioenergy crops include corn, sorghum, rapeseed, and sugarcane, whereas the second-generation bioenergy crops are comprised of switchgrass, miscanthus, alfalfa, reed canary grass, Napier grass, and other plants.

Briefly, switch grass is a thin-stemmed, warm season, perennial grass that has shown high potential as a high yielding crop that can be readily grown in areas that are also suitable for crop production. In fact, there are many perennial crops (grass and tree species) that show high potential for production of cost-competitive cellulosic biomass. Switch grass can be viewed as a surrogate for many perennial energy crops when estimating biomass supply and availability.

Bioenergy crops increase soil carbon and fix atmospheric carbon. In addition, bioenergy crops (miscanthus, sorghum, and poplar) could also be used for the phytoremediation of heavy metal-contaminated soils. The bioenergy crops include specific plants that are grown and maintained at lower costs for biofuel production. Many other crops are possible, and the optimal crop will vary with growing season and other environmental factors. Most fast-growing woody and annual crops are high in hemicellulose sugars such as xylose.

See also: Bioenergy, Biofuel, Biomass.