This survey provides up-to-date information about the capacity and throughput of the AD and composting industries in England and compares this data to that gathered in previous survey exercises
This research has covered all AD activity in England apart from sewage-based AD, Mechanical Biological Treatment (MBT) or transfer facilities; and all permitted composting of all types (open windrows and in vessel composting) but not exempt small scale composting operations.
The report summarises data that was collected from survey respondents for the calendar year 2018.
Main findings for the AD industry
- There has been growth in all types of AD (farm, commercial, industrial) but growth has been highest in the farm sector. Growth of the industry is expected to continue with the development of further sites.
- The majority of sites reported using continuous, wet, mesophilic AD systems (as they did in 2012). A higher proportion of sites (88%) are now undertaking some processing of digestate compared to in 2012.
- The operational capacity of AD sites in England has grown to 3.2 million tonnes for food waste within a total operational capacity for all feedstocks of 9.6 million tonnes in 2019 when farm sites and dedicated industrial sites are included.
- An estimated 7.5 million tonnes of digestate was produced in 2018. About half of survey respondents said they separated the digestate into fibre and liquor, but this was more common amongst farm sites than commercial sites.
- Nearly all respondents (irrespective of the type of AD operation) said that digestate (whole, fibre and liquor) was applied to agricultural land. Small numbers of respondents gave a price for digestate in its different forms but the evidence available indicates that digestate is generally a low value product.
- A total estimate of 1,231 million m3 of biogas was produced. Amongst both commercial and farm sites, approximately a quarter of this was being directly injected into the national grid which represents a considerable increase compared to 2012 when nearly all gas was used for CHP.
- The majority of commercial and farm AD site operators surveyed expected their output for 2019 to be similar to 2018.
Findings on the composting industry
- An estimated 272 permitted composting sites were identified in 2019. The number of permitted composting sites has been relatively stable over time, 271 permitted sites were reported to exist in 2012 and 291 in 2010.
- The operational capacity of the composting industry (the maximum working capacity taking into consideration planning, regulatory and physical constraints) was estimated to be 6.8 million tonnes in 2018.
- The estimated grossed composting feedstock in England for 2018 was 5.1 million tonnes. The majority of composting feedstocks in 2018 were local authority (84%). This is similar to 2012. The majority (72%) of all feedstock was green or garden waste.
- Reported levels of rejections were low, although anecdotal evidence from stakeholders suggests these may be higher than reported. Just under half of operators said that growth in the use of compostable packaging was having an impact upon their business.
- The grossed estimated compost produced was 2.7 million tonnes in 2018. About two thirds (66%) of the compost produced was sold to users off-site.
- In 2019, there were 137 PAS 100 certified composting processes These sites produced 1.6 million tonnes of certified compost.
- Almost half (43%) of operators expected their output to increase over the next five years and half (50%) expected their output to stay the same. The most frequently cited barriers to expansion related to regulation; costs; and limited space.
A review of technologies to optimise the value of digestate
The use of anaerobic digestion to treat food waste and other materials is now a well-established technology in the UK. The industry has grown over the last 10 years to have the capability to treat millions of tonnes of separately collected food waste from our homes, factories and businesses. This provides us with renewable electricity and gas which are a vital part of the UK transition to lower carbon energy sources.
However, the AD process also generates a nutrient rich digestate product. This is currently applied to our agricultural land as a valuable fertiliser, but industry, regulators and policy makers are now increasingly aware of a number of issues that could compromise markets for digestates going forwards such as plastic contamination and high levels of potential ammonia emissions when spread, and there is a real need to consider how to make digestate into a higher value product that is easier for operators and farmers to handle and use.
In 2020 Wrap updated the 2015 work to look again at the technology that is potentially available to treat and add value to digestate. The resulting brief report summarises a number of technologies that have emerged and indicates where those have now reached commercial viability and where they still require some work to bring them fully to market.
This report is a summary update and is not therefore a definitive list of all potential technology providers operating now. It does however indicate an increasing number of options that could be available to change the way digestate is handled and could therefore enable development of more robust future solutions for digestate management.
The report is intended to be a starting point for those interested in digestated treatment. It contains links to source reports and data which users can follow for further information on the identified technologies.
The last report available on this page is a review of the impact of a series of nitrogenous materials that are applied to land that provides evidence and context for the comparison of composts and digestates with other materials.
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