Energy demand and carbon footprint of treating household food waste compared to its prevention

The majority of household food waste in the EU is sent to landfill or incinerated; a slowly-increasing fraction is collected separately and utilised for anaerobic digestion (AD) or in-vessel composting (IVC). This study evaluates life cycle environmental impacts of these four options to identify the most sustainable alternatives. The results are compared to waste prevention, inclusive of upstream supply-chain impacts. The results suggest that AD has the lowest, net-negative carbon footprint of -40 kg CO2 eq. per tonne of waste treated and the highest life cycle energy recovery efficiency of 12% with respect to the total primary energy recovered. If all of the heat can be utilised, then both AD and incineration can achieve maximum energy recovery efficiencies of around 25%. Waste landfilling has the highest carbon footprint at 193 kg CO2 eq./t and a recovery efficiency of 3% through the combustion of landfill gas. IVC, credited for the production of fertiliser, has a carbon footprint of 80 kg CO2 eq./t and it has the lowest recovery efficiency at 1%. Under the best conditions, the greatest CO2 eq. savings are achieved by the incineration of food waste, with a net-negative carbon footprint of -221 kg CO2 eq./t. However, this is eclipsed by the 2,800-3,100 t CO2 eq. that can be avoided by preventing the avoidable and potentially avoidable food waste. Thus, while unavoidable food waste may be best treated via AD or incineration, the savings are negligible compared to the benefits of waste prevention. Therefore, food waste may be used within a circular economy to reclaim a limited amount of resources, but it should not be considered an alternative to prevention.