Anaerobic digestion key to food and drink’s waste and energy challenge

 In Blog

Published on 31 May 2024

Our Sector Director for Waste & Circular Economy Gavin Ramsey’s opinion piece first appeared in Volume 24, Issue 06 of the Food and Drink Network Magazine.

As the UK appears to be moving towards mandatory food waste reporting coupled with a focus on landfill diversion (and a Scottish landfill ban on biodegradable municipal waste next year), the food and drink sector could be well served by investing in anaerobic digestion, says Synergie Environ Sector Director Gavin Ramsey. This, he says, ensures that waste becomes a valuable resource, powering renewable energy and driving greater self-sufficiency and compliance.

The food and drink industry is one that has evolved to gain a much greater appreciation of the waste it creates and it has achieved considerable success in minimising this. However, despite the achievements and greater clarity, challenges remain. This is particularly evident in the dairy and distillery sectors. What is true across the entire food and drink industry, however, is that producers, their clients, consumers and shareholders have a strong preference for a process that puts any waste that cannot be avoided to work, generating renewable energy. These are enviable green credentials to highlight on any annual report or tender document.

Anaerobic digestion is a process that enables carbon-rich biodegradable wastes to be broken down into a less degradable solid or semi-solid matrix (known as digestate). The technique involves degradation of the waste with the use of bacteria in a low-oxygen environment, which in turn produces heat and biogas.

Biogas is a methane-rich gas that can either be cleaned and injected into the national gas grid network as a non-fossil-fuel gas or used directly on-site to generate renewable electricity. When used for the latter, this enables some or all of the electricity and heat requirements for manufacturing or industrial processes that produce high-organic-content wastes or by-products to be met, as well as significantly reducing the costs of waste disposal to landfill.

This is, of course, not the only benefit of the digestate created. It is also valued, depending on the original feedstock, as an agricultural improvement and renewable fertiliser. It is equally important to note that digestate from feedstock that has been segregated at source (such as organic waste from a food manufacturing process or spent lees from whisky distillation) is capable of achieving a recognised quality standard (PAS 110), meaning that it is no longer considered a waste but rather a fully recycled product, opening up its use to a much wider range of applications.

Creating an on-site green waste management system with such an anaerobic digestion plant has many benefits, especially for businesses in more remote areas, such as distilleries, that wish to process their waste close to the source. This is, of course, also in line with the European Waste Framework Directive. But regardless of location, the legislative direction of travel strongly indicates greater regulatory attention to how all food waste is managed and, in an industry with significant energy requirements, it makes sense to invest in technology that can deliver in this way. Should future regulatory change close the door to biodegradable waste at municipal and other landfill sites and introduce mandatory food waste reporting, the investment offers a future-proof and compliant resource management system.

The beauty of anaerobic digestion feedstock is that it can accommodate a range of materials – meaning one plant can offer cross-sector use, such as the food and drink and agriculture industries – with the power generated offering self-sufficiency, multi-business shared use or an injection of power to the grid.

Suitable feedstocks that can be co-digested in an anaerobic digestion plant include the following:

  • agricultural slurry/manure
  • sewage sludge
  • municipal food waste
  • dairy manufacturing wastes
  • organic chemicals and solvents
  • biomass/energy crops.

In the case of one anaerobic digestion plant designed to serve the needs of a distillery in the Scottish Highlands, the facility diverted 20,000 tonnes of waste from landfill each year, while generating 95% of the business’s annual heat and energy requirements (1.2 GWh of electricity, which is the equivalent of that required to power 100 homes, and 1.4 GWh of heat). This was achieved on a 0.1 hectare site staffed by one person with an eight-year return on a £2.8 million investment. The co-located plant also helped the business to achieve a £600,000 saving on waste disposal costs annually. Subsidies are available as part of the introduction of anaerobic digestion and this avenue should be fully explored as part of the project planning process.

Food and drink businesses are in a unique position to lead the energy transition for the manufacturing sector, owing to the nature of the wastes and by-products they produce and the requirement for heat and power in production processes. By harnessing the benefits of anaerobic digestion, companies in this sector can create their own circular economy of producing their own heat and power, reducing their waste disposal costs and minimising their carbon emissions.

Gavin Ramsey is the anaerobic digestion, waste and circular economy sector director for decarbonisation and energy efficiency specialists Synergie Environ, part of the PD&MS Group, and has 23 years’ experience in delivering environmental and sustainability solutions across numerous industries. A Chartered Resource & Waste Manager, Gavin has held key roles across the waste management, construction, minerals and utilities sectors. Find out more about Gavin here.

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