Methane from AD plants could fuel tractors
Farmers operating anaerobic digestion (AD) plants should consider converting a proportion of the methane produced into biomethane fuel for their tractors and farm vehicles.
A pioneering project led by the Royal Agricultural Society of England – RE-fuelling the countryside – is looking at ways farm businesses and rural communities can integrate renewable fuels into their transport systems.
Fuel options being explored in the project include: biomethane, electricity, hybrids and dual fuels, biodiesel, bioethanol and hydrogen.
However, the most easily accessible to farmers are likely to be biomethane – linking up to farm-based AD – and electricity, linking up to farm-based solar and wind projects, said Greenwatt Energy project manager Mike Woollacott, who is involved in the project.
The project will be completed in December this year with findings published at the beginning of next year.
UK farm trials
UK AD supplier and installer Evergreen Gas is involved in a research project to look at the feasibility of fitting an upgrader to an AD plant to convert a proportion of the methane produced into biomethane for fuel.
Trials have proved successful so far, and according to director Will Llewellyn, biogas as a vehicle fuel produces three times more km/ha than first-generation biodiesel or bioethanol.
“The incentive is fossil fuel displacement – 1kg of biomethane has the same value as one litre of diesel. You can get 100 miles from 100 litres of slurry or 100kg of food waste.”
Will Llewellyn, Evergreen Gas director
The company has fitted an upgrader – kit to convert methane into fuel – to its own AD plant in Shropshire, using a water scrubbing system to remove any impurities from the biogas. This creates a gas with around 96% methane – the remainder carbon dioxide – which is then compressed to improve efficiency and allow for easy gas storage in a vehicle.
The upgrader has the capacity to produce the equivalent of 90 litres of diesel in a 24-hour period, from only a small proportion of the methane produced from the AD plant.
CNG (compressed natural gas) vehicles can be bought from dealers – Valtra has a CNG tractor, for example – and vehicles can also be retrofitted to run on gas, explained Mr Llewellyn, speaking at the Nextgen energy event in Stoneleigh, Warwickshire held on 9-10 October.
The company would be prepared to stock and install similar upgrader units in the future, with the likely cost of one unit no more than £140,000, he said.
“The incentive is fossil fuel displacement – 1kg of biomethane has the same value as one litre of diesel. You can get 100 miles from 100 litres of slurry or 100kg of food waste,” he added.