Anaerobic digestion’s potential as a renewable energy option for Scottish farm businesses is believed to be in jeopardy unless Westminster reinstates the feed in tariff (FiT) rates available for those considering installation.
The UK Government has recently proposed a 20% reduction in FiTs for anaerobic digesters. This is likely to stall the positive impact the technology could have on Scottish livestock farms, according to NFU Scotland.
Anaerobic digestion (AD) plants are now common across Europe, especially in Germany.
Animal slurries are an ideal feedstock but often need to be supplemented by crop products such as maize silage.
Food waste, such as bakery products past their sell by date, can also be fed into the system.
There is a considerable capital cost in setting up an AD plant.
At its heart is a large gasometer which has the dual function of containing the feedstock as it is digested and storing the resulting methane gas.
The gas is then normally used as a fuel for an internal combustion engine coupled to an electricity generator.
Apart form the green energy produced, the digestate left at the end of the process is a useful fertiliser and soil conditioner.
There is also the potential for the heat from the process to be used, for example for community heating schemes.
The reductions in FiT are targeted mostly at plants of below 250kW capacity. These smaller units are of the type that would typically be found on farms, hence the NFUS anger.
The union argues that while wind energy, both at commercial and farm level, has been the main driver of the growth in renewables in Scotland, the development of a more diverse portfolio of renewable technology would add value to the economy while contributing to a balanced energy flow into the grid.
Writing to Climate Change Minister Greg Barker, NFUS president Nigel Miller said: “Although anaerobic digestion is yet to mature as a technology in the UK and Scotland, it has real potential to contribute to and balance renewable energy targets while utilising waste. That is why we are so disappointed to see FiT rates have been rolled back by Westminster.
“Anaerobic digestion has been widely adopted on German farms. We can build on this technology in Scotland, integrating it into modern dairy units and utilising cattle slurry as the principal feedstock.
“This smart approach to anaerobic digestion utilises a waste stream to generate power, heat and fertiliser while also minimising water quality risks associated with conventional slurry management.
“Clearly the technology fits with ambitions on renewable energy, zero waste and environmental targets.
“Adapting anaerobic digestion to a cattle slurry feedstock is a challenge and there are costs to introducing a smart, second- generation technology like AD. That is why underpinning AD output through the use of defined FiTs, and perhaps supplementary renewable heat incentives, is fundamental to creating the platform for the required investment.
“NFU Scotland is firmly of the belief that if FiT rates for plants up to 250KW in size were reinstated at the levels they previously held, there would be a generous return.
“Indeed, the 20% reduction for FiTs on anaerobic digesters is likely to put the technology’s uptake in Scotland and the UK into reverse.”