East Anglian farms will test efficiency of energy plant by-products as organic fertilisers

A tour of the anaerobic digester at JF Temple & Son in Wighton, north Norfolk. Picture: Agri-Tech Ea

A tour of the anaerobic digester at JF Temple & Son in Wighton, north Norfolk. Picture: Agri-Tech East - Credit: Agri-Tech East

A consortium of six East Anglian farmers will undertake field trials to assess the optimum use of organic fertilisers, generated as by-products from anaerobic digestion (AD) energy plants.

Euston Biogas plant: Euston Estate director Andrew Blenkiron

Euston Biogas plant: Euston Estate director Andrew Blenkiron - Credit: Archant

Agri-Tech East, supported by the "Innovative Farmers" network, has set up a field laboratory to measure the impact on crop nutrition from liquid and fibre digestate - left-over from the microbial process of turning organic materials into biogas.

The farmers will be investigating how to ensure the maximum nitrogen is available to feed crops, while preventing it being lost through the soil profile, causing diffuse pollution, or escaping as ammonia gas.

The project originated from discussions at the Royal Norfolk Show, where many farmers with AD plants said they wanted to maximise their value.

The farms involved in the project are: Holkham Estate in north Norfolk; Upton Suffolk Farms, near Bury St Edmunds; Boxford Suffolk Farms near Sudbury; Allpress Farms at Chatteris in Cambridgeshire; Euston Estate near Thetford; and JF Temple at Wighton, near Wells in north Norfolk.

"We want to get back to the soils of 20 years ago," said Patrick Allpress, farm director at Allpress Farms, which invested in a 500kW AD plant in 2014, feeding it 50% onion waste and 50% leek waste.

The plant is fed 12,000 tonnes of this feedstock a year, producing around 11,500 tonnes of digestate while generating a potential 4.4m kilowatt hours of electricity.

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"The first point is getting the value out of digestate - we know what it costs, but measuring the value of it as a farm input is difficult," said Mr Allpress. "By doing the trials we hope to use digestate like a regular fertiliser; an alternative to inorganic fertilisers."

Andrew Blenkiron, estate director at the Euston Estate near the Norfolk-Suffolk border, is also taking part in the trial.

He said: "It is a big challenge to work out the economic benefits of spreading 30,000 tonnes of organic material from the anaerobic digester, compared to the cost of artificial applications - but I know that the organic material will have the longer-term benefit on the soil health."

Experts from Cranfield University and scientists from the National Institute of Agricultural Botany (NIAB) in Cambridge are also lending their expertise.

Dr Belinda Clarke, director of Agri-Tech East said: "By bringing together farmers and researchers for these on-farm trials, we hope to improve the efficacy of digestate and understand the costs."