Could sewage save our salad?

11 May 2023 by Jonathan Goldsmith
blog author

​The combination of fresh salad and sewage isn’t the most appetising concept, but a breakthrough in technology may hold the key to safeguarding the UK’s supply of greenhouse vegetables.

Rather than physically mixing the two, Oasthouse Ventures is extracting heat from sewage at local treatment works and transferring it to heat pumps at their sites.

The company owns two high-tech greenhouses on 70 acres of land in Bury St Edmunds and Norwich, capable of extracting enough heat to produce an abundance of tomatoes, cucumbers and peppers.

Electricity for the ground source heat pumps will be provided by the grid and Combined Heat and Power (CHP) units. The latter have the added benefits of providing waste heat which further supplements the greenhouse heating, providing carbon dioxide to enrich the greenhouse atmosphere and promote plant growth.

Oasthouse Ventures develops businesses that have a positive impact on the world, and its three founders believe utilising heat from wastewater treatment works could provide the solution to the salad shortage, which has seen growers impacted by unprecedented increases in wholesale gas prices since 2019.

Ed Moorhouse, Business Development Manager at Oasthouse Ventures, said: "Our greenhouses are not subject to geopolitics and global fluctuations in the hydrocarbon market that have shut many greenhouses in the UK and abroad, one of the key reasons we had shortages this spring."

"We're also largely immune from the effects of climate change. When you decouple your day-to-day operation from gas prices and grow fresh produce in a country with ample rain and good levels of sunshine, you largely deliver food security and provide assurances of supply to supermarkets."

British supermarkets are rationing fresh peppers due to being in short supply as a result of cold weather conditions in Europe and the National Farmers' Union (NFU) has warned Britain is facing its lowest year for salad production since records began.

NFU President, Minette Batters, said: “There are three cornerstones on which a prosperous farming sector must be built and which any government should use to underpin its farming policy. They are boosting productivity, protecting the environment and managing volatility."

“But the clock is ticking. It’s ticking for those farmers and growers facing costs of production higher than the returns they get for their produce. It’s ticking for the country, as inflation remains stubbornly high, and the affordability and availability of food come under strain."

“It’s ticking for our planet, as climate change necessitates urgent, concerted action to reduce emissions and protect our environment. And it’s ticking for government – to start putting meaningful, tangible and effective meat on the bones of the commitments it has made."

“Commitments to promote domestic food production, to properly incentivise sustainable and climate-friendly farming, to put farmers and growers at the heart of our trade policy, and to guarantee our food security. It really is time to back British farmers and back British food.”

UK supermarkets experienced fruit and vegetable shortages earlier in the year, resulting in a huge dependence on imports for salad and fresh produce. The combination of bad weather in Europe and north Africa, and inflated electricity costs, were the main culprits.

Oasthouse Ventures has driven innovation to help ease this.

The business founded Low Carbon Farming in 2016 to develop a distinctive set of world-first greenhouses in the UK. The company then raised £120m from renewable energy investor Greencoat Capital (now Schroders Greencoat), and the first one million plants went into the cutting-edge greenhouses in January 2021.

The downside is costs are high to operate the greenhouses and buy the required equipment and while the government’s Renewable Heat Incentive Scheme initially helped boost the firm, this period has now finished.

Schroders Greencoat presented the government with a plan for 40 potential sites last year, but no support has been received yet. Some sectors benefit from the government's Energy and Trade Intensive Industries (ETII) scheme, which provides a tax relief on energy bills but businesses that grow crops in greenhouses are yet to become eligible.

Jonathan Goldsmith, Head of Transport & Infrastructure at Acre, said: “Food scarcity is a major global threat and the combination of high energy costs coupled with unpredictable weather conditions has put the production of our favourite salad staples at risk."

“Tech innovation, such as heat extraction from wastewater treatment works, to rectify these challenges may well be a key driver to effecting change but it needs longer-term financial backing and support to scale it up.”

Johnny works in Acre’s Sustainable Business team, with responsibility for delivering all Executive-level and strategic searches for clients operating in the Built Environment, Infrastructure & Transportation sectors. He also leads a small team of Consultants to support organisations on operational sustainability hires across the UK & Europe.

Johnny holds a BSc in Environmental Science and, following a brief spell working for a global environmental consultancy, joined Acre in 2015. Since then, he has partnered with major corporates, multi-stakeholder initiatives and SMEs to help shape their sustainability functions. He has an honest and transparent approach to the industry and enjoys working in partnership with ambitious clients to continually drive change.

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