For on-farm biogas plants using crop-based feedstocks, the quality of the harvesting and ensiling processes can make or break the efficiency of the plant and the anaerobic process for the following year, impacting on gas output and profit.

Having experienced issues with bought-in silage feedstock outside his control, Nick Cowie, of Gloucestershire-based JJ Power, now uses a silage additive from FM BioEnergy to ensure that the quality of his feedstock and the performance of his digester remain high.

JJ Power operates a 435 kW biogas plant within a larger 700 ha farming operation, based around a single 2750m3 digester. The feedstock is a mixture of chicken manure and maize silage, together with some liquid waste from the animal feed industry.

However, when plant manager Mr Cowie bought in external silage feedstock from an unfamiliar source, the plant soon hit problems. The digester biology became upset, resulting in a drop in gas output.

Nick was keen to ensure this never happened again. Already a customer of specialist AD consultancy, FM BioEnergy, which provides JJ Power with a biological support and trace element supply service, he attended a workshop on best silage practice and learnt about the science behind biological silage additives.

A new product, Silasil Energy XD, seemed to be the obvious solution. “The way that our clamp is arranged means that we have quite a large, open face, which can result in a significant proportion of the silage being exposed to the air before use,” he said.

Tim Elsome, general manager of FM BioEnergy, explained how the product worked: “This is a biological additive which contains bacteria that help preserve the crop during storage, reducing aerobic losses. It also reduces losses when removing material from the open front of the clamp by preventing re-heating and thereby increases the amount of gas produced per tonne of crop harvested.”

Tested and certified by the German agricultural society, DLG, it is specifically formulated for use on crops destined for anaerobic digestion, boosting the population of beneficial bacteria and suppressing the multiplication of problematic species.

As well as the benefits to feedstock storage and quality, the additive can also provide an insurance against issues such as poor fermentation: “Poor fermentation, or a build-up of antibiotic-producing moulds, can have severe effects on digester biology.

"Once the crop is in the clamp, if you haven’t applied an additive you will have to live with that decision for the rest of the season. Given the benefits in terms of quality that it provides, it really does make sense to use it as a standard treatment when harvesting silage for use as AD feedstock.”

JJ Power is hosting a silage for biogas training day for on-farm AD operators at their Gloucestershire site on March 18, 2020. To attend, contact info@fmbioenergy.