Researchers to develop on-farm technology to recover nutrients from slurry

The technology uses filtration and electrocoagulation to remove suspended solids from manure

Picture: Harper Adams

A UK research project to remove and recover phosphorus from cattle slurry has been awarded a prestigious research award by the UK government.

The 18-month project, worth almost £250,000, will test technology by Elentec Ltd and Merigan Ltd on the Harper Adams University dairy farm, alongside grass crop trials of the treated slurry using both glasshouse and field experiments.

The technology uses filtration and electrocoagulation - a treatment that adds an electrical charge to water - as a way of removing suspended solids from manure.

The process will allow sustainable fertiliser products to be produced from slurry, benefiting the environment both through changes to slurry management and through the reduced use of inorganic fertiliser.

As part of a combined effort to move towards net-zero on dairy farms, it is hoped the technology will aid the recovery of phosphate, enhance the sequestration of carbon, and produce ‘grey’ water, which can be used for purposes such as irrigation.

The maintenance, installation and cost of the systems and their scalability on farms will be assessed as part of the project. Recovery of ammonium and nitrates, pollutants that can be repurposed into organic fertilisers, will also be a target for future programme development.

Elentec’s technology will be designed to be retrofitted to existing slurry equipment with a modular design to allow it to fit any size of farming enterprise.

The technology has already been demonstrated to work in other industrial applications. However, the research project at Harper Adams will now seek to find ways to make it practical for a typical dairy farm.

It comes at a time when slurry spreading practices are under scrutiny in both the UK and Ireland, with tougher rules on nitrates loading proposed in Ireland’s Draft Nitrates Action Programme.

"Further benefits include carbon sequestration and a new revenue stream from the recovered phosphorus for wider use in agriculture and horticulture," Dr Marie Kirby, senior lecturer at Harper Adams University, explained.

“There are many potential benefits from slurry, but its application to farmed land is problematic in areas with increased susceptibility to pollution.” 

“The idea behind this application means, if successful, we can turn slurry from a residue product into something which is potentially valuable.” 

UK government figures suggest a 100-cow dairy herd produces 1,700m3 of slurry over the typical 26-week housed period.

Elentec chief executive John Bostock said: “We are delighted to receive this award, co-funded by Innovate UK and Defra.

 "The electrocoagulation technology will deliver a compact, robust, scalable process for efficient fractionation of dairy farm slurry into three parts: A concentrated, phosphorus-rich sludge for spreading as a fertiliser on cultivatable land; a carbon-rich solids fraction for soil improvement and carbon sequestration and a phosphorus-reduced liquor from which nitrogen can be harvested, to be accomplished in a follow-on project. The resultant greywater can be reused or safely discharged.” 

Mike Theodorou, project manager for the consortium at Merigan Ltd and Emeritus Professor at Harper Adams University, added: “End-user input into the technology design and implementation is essential for effective uptake by the industry, so we will ask farmers how best to retrofit the technology to pre-existing slurry handling facilities, and how best to design and implement the most appropriate business model – or models - for their farm.”