Food Waste Treatment & Associated Costs
This week we will be exploring the second part of our two part blog series on the status of food waste in England. In our first blog we addressed the food waste hierarchy, key legislation and food waste collection. In our second blog we will be covering treatment processes and associated costs.
Food waste transfer & anaerobic digestion (AD) treatment
The Department for Energy and Climate Change (DECC) and the Department for Environment, Food and Rural Affairs (DEFRA) have an Anaerobic Digestion (AD) Strategy and Plan which is a commitment to increasing energy from waste through AD(1). AD is the preferred method for the treatment of food waste although In-Vessel Composting (IVC) is not excluded.
AD is a process in which bacteria break down organic matter such as food waste, without oxygen. It is undertaken for food waste in a sealed digestion tank which operates much like the human stomach. The bacteria in the tank consume the food waste and give off biogas, primarily methane, which rises to the top of the digester. From there it is extracted and combusted in engines to generate electricity. The electricity may be used locally or fed to the grid. The residue digestate is drawn off from the bottom of the tank and may be spread to land as a fertilizer if it passes the PAS110 standard(2).
Digesters come in a wide range of shapes and sizes and each one is slightly different. Getting the precise mix of nutrients to keep the micro bacteria well-nourished ensures that the plant maximises the energy recovered from the food waste.
There are currently some mumblings within the AD business regarding the use of biodegradable (compostable) food waste bags. These bags should have the word ‘compostable’ on them along with the Seedling logo and EU standard EN1343Z on them.
Frith Resource Management (FRM) understand that use of these bags has caused some blockages at AD facilities and some operators prefer non-degradable plastic bags which can be removed from the food waste before digestion.
The median gate for food waste AD in 2023-24 was around £20/t(3). This was up from £13/t in 2022-23. In recent years food waste AD companies/contractors have had a low gate fee, some accepting food waste with no gate fee (£0/t) or even a rebate, and some including transfer in the gate fee. A reason for this was the energy price hike from 2021/22 where significant income could be realised from the renewable electricity produced in the process(4).
Comment
The instruction for the collection of food waste should be a no-brainer for Waste Disposal Authorities (WDAs). The 2023-24 median cost of the collection and treatment of residual waste is £116/t around(5), while costs for collection of food waste is likely to range from around £8/t to £21/t(6), plus the AD gate fee. Therefore, it is much more cost effective to collect, transfer and dispose of food waste than residual waste. The issue is going to be whether there is sufficient food waste AD treatment capacity in England to treat all of the food waste that has to be collected from April 2026. AD gate fees in England are likely to increase as demand exceeds capacity.
FRM provides advice to local authorities and businesses on the collection and treatment of food waste. FRM may act as a Critical Friend providing advice on the delivery of food waste services. Alternatively, we can lead on the provision of food waste services for public and private sector organisations.
(1) https://assets.publishing.service.gov.uk/media/5a7968b4e5274a2acd18c991/anaerobic-digestion-strat-action-plan.pdf (2) https://www.wrap.ngo/resources/guide/bsi-pas-110-producing-quality-anaerobic-digestate (3) https://www.wrap.ngo/resources/report/gate-fees-report-2023-24 (4) https://assets.publishing.service.gov.uk/media/63a2e8c78fa8f53911cfcd2c/quarterly-energy-prices-december-2022.pdf (5) https://www.wrap.ngo/resources/report/gate-fees-report-2023-24 (6) From FRM modelling, depending on household numbers
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