Food waste lignocellulose

The unfavorable energy balance notwithstanding, the fermentation of ethanol, as well as other chemicals, from lignocellulose hydrolysate is considered highly desirable by some to avoid competition with food production. We note, however, that the large scale processing of waste lignocellulose runs counter to sensible... 

The choice of the most appropriate technology and process set-up is mainly dependent upon the substrates to be treated. Municipal biowaste includes two distinct fractions green waste from gardens and parks, and food waste from residential and commercial sources. These fractions have a different composition and structure. Green waste has a high structure and total solids (TS) content with a high lignocellulosic and fibrous component. Food waste, on the other hand, usually has a poor structure and TS <30%, and can be conditioned to a pumpable substrate. 

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 next generation of biofuel processes should differ from the first in (a) utilizing the whole plant as a feedstock and (b) the use of non-food perennial crops (woody biomass and tall grasses) and lignocellulosic residues and wastes (woodchips from forest thinning and harvest residues, surplus straw from agriculture). 

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... 

All considerations for the use of lignocelluloses for the production of bioethanol or other platform chemicals should include the overall mass and energy balance as well as the availability through the year and the transportation needed. Regarding a study of IEA/OECD 2010 [9], there is no additional land available in the short term and only 10% of global forestry and agricultural residues are assumed to be available for biofuel or platform chemical production. Therefore, there will always be a direct competition of bioethanol or other platform chemicals production with food production even if so-called plant waste material is used as the real limitation is the arable land available. 

In the future, lactic acid may be produced from biowaste (e.g., cellulose and lignocellulose) instead of starch fi om food crops to further reduce the cost and to increase the sustainability of PLA. A gypsum-free process is also under development to reduce solid waste to make PLA more environmentally friendly. Industrial-scale d-LA is being optimized to produce low-cost PDLA to improve PLA for high-end applications. Extensive efforts have been committed by the enzyme and fermentation industries and research institutes to these topics. 

---