IGPN - International Green Purchasing Network

December 15, 2016

New system to convert food waste into fertiliser for greenhouse use gives potential 95% reduction in CO2 emissions

A new method of processing food waste into fertiliser has been outlined in a recent study. The process uses a digester system with microorganisms to break down organic waste into fertiliser. The resultant fertiliser was used in a low-energy greenhouse to produce a range of food crops. The method is a potential way to utilise food waste and reduce the energy consumption of food production as part of a circular economy.

Globally, food waste accounts for 6–10% of human greenhouse gas emissions. In the EU, an estimated 88 million tonnes of food is wasted annually, which is around 20% of food produced, or 95–115 kilograms of food per person each year. The EU is attempting to reduce the environmental impact of waste through the Circular Economy Strategy, which aims to maintain the value of materials in the economy for as long as possible and to reduce waste by promoting the reuse and recycling of materials; this programme includes food waste as a priority sector.

Anaerobic digestion — the breakdown of organic material using microorganisms in the absence of oxygen — is a good way of allowing resources in food waste to be used rather than disposed of at landfill. This method also reduces carbon dioxide (CO2) emissions from composting or landfills. The biogas — gaseous fuel, such as methane – produced from the process can also be used as a substitute for fossil fuels. However, the treatment and handling of digestate — the material remaining after anaerobic digestion — is still a cause of CO2 emissions, or equivalent emissions from methane or nitrous oxide, even when sustainably used as a substitute for mineral fertiliser. Utilising digestate directly in a closed greenhouse system can, therefore, improve the sustainability of this process. However, digestate is toxic to plants and needs to be treated if it is to be used directly on plants as a fertiliser. Greenhouses can also produce high CO2 emissions due to artificial heating, transportation of produce grown for commercial sale and the cooled storage of vegetable crops grown.

Read more at "Science for Environment Policy": European Commission DG Environment News Alert Service, edited by SCU, The University of the West of England, Bristol.

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