Lignocellulosic crops, food production

Both in the USA and the EU, the introduction of renewable fuels standards is likely to increase considerably the consumption of bioethanol. Lignocelluloses from agricultural and forest industry residues and/or the carbohydrate fraction of municipal solid waste (MSW) will be the future source of biomass, but starch-rich sources such as corn grain (the major raw material for ethanol in USA) and sugar cane (in Brazil) are currently used. Although land devoted to fuel could reduce land available for food production, this is at present not a serious problem, but could become progressively more important with increasing use of bioethanol. For this reason, it is important to utilize other crops that could be cultivated in unused land (an important social factor to preserve rural populations) and, especially, start to use cellulose-based feedstocks and waste materials as raw material. 

The list of plants, by-products and waste materials that can potentially be used as feedstock is almost endless. Major resources in biomass include agricultural crops and their waste by-products, lignocellulosic products such as wood and wood waste, waste from food processing and aquatic plants and algae and effluents produced in the human habitat. Moderately dried wastes such as wood residue, wood scrap and urban garbage can be directly burned as fuel. Energy from water-containing biomass... 

Lignocellulose, which comprises the main construction material of plant biomass, accounts for up to 90% of all biomass and is formed in amounts of approximately 1.5 trillion tons per year [12]. Consequently, lignocellulose is much more abundant than available amounts of vegetable oils, starch, and sugar crops. In addition to the high abundance of lignocellulose, it is inedible, and its utilization as feedstock for production of biofuels and chemicals could drastically reduce challenges of food versus fuel production. 

The current ethanol supply is, in the large part, derived from starch. Nevertheless, vast amounts of agricultural residues and other lignocellulosic biomass can serve as the feedstock for ethanol production. Theoretically, enough ethanol can be produced from cellulosic biomass to meet most of the liquid fuel requirements in the US. The expanded utilization of lignocellulosic biomass for ethanol production can also free starchy crops for food and other uses. In addition, less carbon dioxide emission can be realized if more ethanol can be produced from lignocellulosic biomass and if the market for ethanol as a transportation fuel can be expanded beyond the current level. 

Agro-based lignocellulosics suitable for composites come from two main sources. The first is agricultural residues and the second is those lignocellulosics grown specifically for their fibre. The first source includes rice husks or cereal straws, which are by-products of food or feed crops and can be used for everyday purposes such as animal bedding or fuel or alternatively are simply left on the field or burnt to reduce mass. Two examples of the second source are jute and kenaf. These plants also have residues, which are often used for bedding or fuel as well. 

The advantages connected with the use of material from renewable resources as filler in blends with synthetic degradable polymers have promoted the interest for a wide series of polymers from non-food crops or over production, such as lignocellulosic materials, pectin, proteins, and oils from vegetal sources. 

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