Summary:

Global population growth and rising food consumption have led to an increase in the generation of food waste. Inappropriate waste management has been recognized and proven to be a major cause of serious health problems due to harmful air pollution and environmental degradation. For instance, conventional processes such as landfills often produce methane emissions due to anaerobic digestion and the decomposition of organic waste in landfills. The escape of methane into the atmosphere generally contributes to a warming climate because it is a greenhouse gas 25 times more potent than CO2. In addition, the leachate produced during the decomposition of food waste is a major source of underground water pollution. Nearly 2.3 million tonnes of edible food is wasted each year, costing Canadians more than $20 billion, according to a study by the National Zero Waste Council on household food waste in Canada. This shows that local municipalities spend huge budgets on management, making food waste disposal a heavy burden on society.

Biogas, a natural metabolic by-product of microbial metabolism, can be used to reduce energy costs. The City of Ottawa has successfully collected biogas from food waste-induced landfill and created sufficient electricity to power 6,000 homes. However, the quality of the collected biogas is not high enough, as the methane content should be above 60% for maximizing its profit margin. This is mainly due to the fact that the rough sorting process of food waste does not accurately divide the organic material, as a range of C:N ratios is required for high-quality methane production. Too high or too low C:N ratios, caused by different ratios of carbohydrates and nitrogen-containing chemicals, inhibits methane production but promotes CO2 emissions. While it is well known that leachate contains a large number of nutrients in plant-available forms and is a potential substitute for fossil fuel-derived synthetic fertilizers, there is still a lack of sufficient evidence directly from field studies, especially for nutrient availability and different cropping regimes and safety assessment in different environments.