Circular fertiliser: The use of digestate in indoor farms

Added on 31 August 2023

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Circular fertiliser: The use of digestate in indoor farms

Synthetic fertilisers are a significant contributor of greenhouse gases in agriculture, and tackling them is vital. In June Nicholas Pitts from the Scotch Whisky Research Institute, India Langley and Lilly Manzoni from LettUs Grow, and Dr Alexandros Stratakos, Associate Professor in Sustainable Agri-Food Production at UWE Bristol, came together at the AFN Network+ Crucible event in Bristol to develop a project on this theme. Their idea, developed over two days, was one of two selected to win funding. Here they explain why assessing the use of digestates in indoor farming is so important.

LettUs Grow designs and builds aeroponic technology and farm management software for greenhouses and vertical farms. The farms require fertiliser all year round, with many growers reliant on synthetic versions, which are a significant source of greenhouse gas emissions. Developing more climate friendly fertilisers is critical. One possible alternative to synthetic fertilisers is to use digestate from anaerobic digesters. Digestate is in surplus due to the growth of the anaerobic digestion sector, and is rich in nitrogen, phosphorus and potassium - vital for plant growth. But although digestate has been used as a fertiliser for arable crops, it hasn’t been used significantly in indoor farming systems.

“As a technology provider we’re doing research on behalf of growers who have a high reliance on synthetic fertiliser,” says Lilly. “That’s generally quite problematic because it’s a by-product of a chemical process and has quite a significant emissions profile. We can reduce our reliance on synthetic fertilisers by using digestate but one of the challenges with that is establishing whether to use plant or animal based digestate, as each have different nutritional profiles and safety consideration.”