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date: 16 October 2019

Food Waste and Biomass Recovery

This is an advance summary of a forthcoming article in the Oxford Research Encyclopedia of Environmental Science. Please check back later for the full article.

Agricultural and food processing residues, and discarded food are largely organic and biodegradable, and may include important nutrients other than carbon. Inappropriate disposal of these have caused considerable adverse environmental impacts on air and water and continue to do so in 21st-century Asia. While water pollution issues have often been local or national in nature, air pollution arising from the burning of post-harvest crop residues have caused trans-boundary concerns.

Pollution control by means of treating wastes for safe disposal need not be the only approach, however, since such an approach, seen as costly by parties required to manage their wastes, may not engender enthusiasm. Given the nature of the wastes under discussion, a shift in mindset—toward viewing these wastes as another resource—may make waste management more attractive, since there is a possibility for economic gain.

One approach is the conversion of such wastes into added-value products through thermo-chemical processes (e.g., pyrolysis, gasification, and hydro-thermal action), resulting in products such as fuel gas, pyrolytic oil, and biochar. Biotechnology can be a suitable technique for such resource recovery. In addition, the argument, for conversion of waste to added-value products, is possibly more attractive than conversion to CO2 and H2O. Agricultural and food-processing residues, given their high organic content, have been fermented to yield fuel gases such as methane (anerobiosis and methanogenesis) and hydrogen (dark fermentation), and liquids such as butanol and ethanol. Biodiesel, produced from biomass by transesterification, is already used as a fuel to power vehicular engines. Bio-methanol is another biofuel with promise, given its high energy content. These represent opportunities for recovering energy.

Derivable from the organic content of waste is a spectrum of other products that can include useful microbes, phytohormones and antibiotics, enzymes, and polyhydroxyalkanoates (PHAs). Application of fermentation technologies to the wastes, for production of added-value materials, in itself results in residues. The latter, with its still high organic carbon content and possibly significant quantities of phosphorus, potassium, and nitrogen can be used as a delivery platform (with some fertilizing value) for beneficial microbes to apply to agricultural land damaged by excessive use of chemical fertilizers and pesticides, and so rebalance the soil’s microbial ecology. Soil ecology has become an issue requiring urgent attention, as damaged farm soils have resulted in lower crop yields in parts of Asia. This is an issue not only in rural farming or large-scale industrial farming, but also in urban farming, where the bioactives biologically recovered from resources such as discarded food can be used in hydro- and aeroponics. The application of recovered resources from residues represents a tangible example of the circular economy.