Life cycle environmental and economic sustainability assessment of UK household food waste management

Abstract

Although difficult to quantify accurately, it is estimated that a third of food produced globally is wasted and the value of the resources embedded in the production of wasted food is increasingly being recognised. In developed countries, consumers are the greatest contributors to the loss of edible food; while prevention must remain the primary goal, once generated the waste should be sustainably utilised. This research assesses the life cycle environmental and economic sustainability of managing household food waste in the UK. The treatment routes considered are anaerobic digestion (AD), in-vessel composting (IVC), incineration and landfilling. Life cycle assessments (LCA) and life cycle costing (LCC) have been carried out to assess the impacts of the current UK treatment mix and potential future scenarios for 2030. The latter reflects the target year for both the UN's Sustainable Development Goal to reduce food waste by 50% and the EU's aims for improving recycling rates within a circular economy. A quantitative methodology has also been developed for comparing the environmental impacts of the food waste treatment options within a food-energy-water-health nexus. At present, the majority of food waste managed by local authorities is found within general waste, resulting in 50% being incinerated and 34% sent to landfill. The remaining food waste is in targeted collections where it is treated via IVC (10%) or AD (6%). The LCA results show that per tonne of waste treated AD has the lowest impacts for 13 of the 19 categories assessed, including a net-negative global warming potential (GWP). Incineration performs the second best, while IVC is the least environmentally sustainable option despite conforming to circular economy principles. With current collection rates, incineration has the lowest life cycle costs (£71/t), while landfilling is the most expensive (£123/t). The current treatment of the 4.9 Mt of food waste collected annually from UK households has a life cycle cost of £452 m and generates 340,000 t CO2 eq., while saving 1.9 PJ of primary energy, predominantly through energy recovery from incineration. The most environmentally sustainable future scenario involves collecting 95% of food waste separately, prioritising AD, and using the currently wasted heat from biogas combustion to displace natural gas. It has a net-negative GWP (-140,000 t CO2 eq./yr) and has the second lowest LCC at £181 m/yr. The lowest costs are for the same scenario but with upgrading the biogas to biomethane for grid injection (£114 m/yr), provided government incentives continue. An overall net saving in GWP can only be achieved if heat from incineration and AD can be utilised widely in the future scenarios, as the projected 2030 electricity mix has a lower GWP than the electricity from food waste, used to credit the systems. However, if the UN is successful in halving the consumer food waste by 2030, then the GWP savings of avoiding this food production are fifteen times greater than implementing the best future treatment scenario with no reduction in waste; the savings are equalled with a 2% reduction of food waste. The integration of environmental impacts in the nexus has reinforced the previous findings, with AD having the lowest influence on food, energy, water and health. IVC has the greatest impact on all aspects, except water, for which landfill is the worst option. Therefore, results of this work demonstrate the benefits of collecting food waste separately for treatment via AD and of continued prioritisation of incineration over landfill. However, the benefits of utilising food waste in a circular economy are far outweighed by waste prevention and this must be considered when investing in waste treatments.

Date of Award	31 Dec 2019
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Adisa Azapagic (Supervisor) & Rosa Cuellar Franca (Supervisor)