August 30, 2014, by Alex Kirby
Waste not, want not: a maize anaerobic digester on a farm in the UK
Image: Alex Marshall/Clarke Energy Ltd via Wikimedia Commons
Scientists are developing a way to squeeze the last vestiges of value from renewable energy processes by combining their waste products to produce eco-friendly fertilisers that could help slow food price rises. LONDON, 30 August 2014 − Researchers in the UK think they may have found a way to produce fertilisers that should cut farmers’ costs and at the same time boost some types of renewable energy. Their scheme, which involves using waste material from anaerobic digesters and ash from burnt biomass, would also cut fossil fuel use and save natural resources. The team, based at the Environment Centre at the University of Lancaster, says their fertiliser would help to slow the rise in food prices. And they believe it would work worldwide. The three-year project has received more than £850,000 (US$1.4 m) in funding from the UK’s Natural Environment Research Council. Research, due to start this year, will take place in labs at the university and in field trials. The project, which includes several partners working with the university, aims to produce a sustainable, environmentally-friendlier source of soil conditioner and crop fertiliser.
It builds on research originally conducted by one of the partners, Stopford Energy and Environment Ltd consultancy, which investigated using a mixture of digestates − the waste left over after material has been through an anaerobic digester − and ash, from burnt biomass, as an alternative to existing fertilisers. Most fertilisers now in use, such as phosphorous-based and nitrate-based products, are made using energy-intensive methods that involve the consumption of oil and gas. Phosphate-based fertiliser relies as well on the mining of phosphate, a finite and unsustainable resource, and on a production process using various toxic chemicals. There are already projects in several countries − including the UK − that use waste from digesters to make fertiliser. But Professor Kirk Semple, of the Lancaster Environment Centre, who leads the project, said: “It is the mixing of anaerobic digestate with biomass ash that is important. . . This would reduce pressure on natural resources and develop a new market for problematic by-products of the bio-energy industry. “Although the project is based here in the UK, we believe there is exciting potential to produce a sustainable alternative to existing fertiliser use across the globe.”
A successful digestate-ash fertiliser would reduce costs and provide additional income to biomass and anaerobic digestion operators. The Lancaster team says this could make these forms of renewable energy − which could meet more than 15% of UK energy demand by 2020 − more appealing to investors, as at the moment ash has to be expensively dumped in landfills. They say it could help to improve food security and reduce costs to farmers as production of the new fertiliser would not be linked to the global price of oil and gas. Previous studies by Stopford show that biomass ash and digestate can be useful nutrient sources for crops in conditions which lack them. Professor Semple told the Climate News Network that he and his colleagues were working to ensure that the new fertiliser was entirely safe. He said: “Part of the grant will be used to chemically analyse the materials, individually and together, for metals and potentially other chemicals.” He says commercial-scale production of a successful digestate-ash fertiliser “is some way off”. But he adds: “This project offers the first detailed interrogation of this type of soil amendment. If successful, we would then look to develop this for the commercial sector.” − Climate News Network
Alex Kirby is a former BBC journalist and environment correspondent. He now works with universities, charities and international agencies to improve their media skills, and with journalists in the developing world keen to specialise in environmental reporting.