Investing in anaerobic digestion (AD) plants as a means of diversifying farm businesses should be approached with care, those involved in the sector have warned.
UK farmers were far slower in taking up AD than their German counterparts – who embraced the technology wholeheartedly about 10 to 15 years ago.
The technology, which will be discussed at an Agri-Tech East event in May, has its challenges, with a perception among those involved in the agricultural sector in the UK that it was over-sold in the early years.
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Jon Duffy, boss at farm co-operative Anglia Farmers, who will be speaking at the afternoon event at Hethel Innovation, Norwich, on May 23, said farmers had encountered problems, including in not realising the amount of effort and expertise required to run a plant successfully.
“The perception is that AD has been oversold in the main, with some AD plants not performing as expected either due to construction, design or feeding issues,” he admitted.
“One of the main concerns, highlighted by our members, is that the systems do require quite a lot of time and effort to keep the systems running, from monitoring pH levels through to maintenance of the Combined Heat and Power (CHP) engine.
“Originally it was expected to fit in with other farming practices, but it has becomes a role in itself to achieve the expected output and associated revenue.”
There were also issues related to the disposal and use of AD plants’ by-product, digestate, especially in nitrate vulnerable zones (NVZ), he added.
There are a variety of options, with some AD plants near urban areas feed gas directly into the national grid, while others convert the gas into electricity.
Jon Myhill, technical lead at AD specialist Future Biogas, which has five of its crop-based 13 AD plants located in Norfolk – at Coltishall, Holkham, Swaffham, Methwold and Taverham – and a workforce of around 100, agreed the idea had been over-sold.
His company’s plants are run on maize, whole-crop cereal, grass, beet or chicken manure, with maize providing the best energy return per tonne.
Plants can work well with good financial benefits, and do offer agronomical benefits through the digestate by-product produced, which can be used to feed crops and improve soil health, he said.
But he advised farmers to ‘do their homework’ before opting for AD, looking at costs, including of clamps to store silage, maintenance, and lagoons for storing liquid digestate.
“It was over-sold that it was a couple of hours’ job a day to feed and do a bit of maintenance, but actually, it’s a full-time job for one or two people,” he said. These needed to have an understanding of mechnical and electronic engineering and a grasp of biology, as the ‘feeding’ balance right was an art, he said.
While farmers tended to opt for plants of less than 0.5MW, costing up to £1m, his range in size to 1.5MW to 4.5MW operations, usually costing in the range of £8-10m.
Germany had become over-saturated, with every other farm taking up the technology, resulting in a backlash over the amount of fuel crops grown, and problems with operating them, he said. But while numbers there were on the decline, they were “very slowly creeping up” in the UK.
Suffolk farmer George Gittus, of Symonds Farm, Risby, near Bury St Edmunds, now supplies energy to neighbouring agricultural machinery firm CLAAS UK and his own business park through his AD plant, which has been operational since January 2012 and is fed by crops grown on his farms and others. For him, it’s been a success story, with healthy returns, but it’s not for everyone, he said, and had not been “a complete bed of roses” for him.
“Like so much else, everybody rushing in thinking it was easy-peasy, and I suppose it was over-sold,” he said. “But I would say that’s pretty much the same with anything these days. Anyone will sell you anything. You have to monitor it: if you put rubbish in, you’ll get rubbish out.”
He added: “It’s providing us with a very sensible return, and we are aiming to get more retail sales and wholesale sales as well. The market will keep changing – probably to make it harder.”
Norfolk dairy farmer Stephen Temple, of Wighton, at Wells-next-the-Sea, said his £800k investment 10 years ago in a 170kW plant had worked for him, but felt it was only suitable if the farmer had, like him, a by-product. “I don’t think there’s any future in a purely crop-fed digester.”
In his case, he uses his livestock slurry, the sides of the silage clamp not fed to the cows, and energy beet which they grow on farm. The heat generated from the plant heats the farm and three quarters of the electricity is exported.
He advised farmers interested in AD to look at their feedstock and the costs involved in grid connection, and also at planning and Environment Agency red tape first.
“When we put ours in, solar panels were very much more expensive than they are now,” he said.
Running an AD plant can be hard work, he added. “There are days when it takes five minutes and another day when there’s a breakdown and it’s all hands to the pump.”
The Agri-Tech East Pollinator, entitled We’ve Got the Power; On-Farm Solutions to Energy Demands, is on May 23 from 1.30pm to 5pm at Hethel Innovation, NR14 8FB. Visit here to book a place.
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