Ammonia Control in Anaerobic Digester to Improve Profitability
Using an additive from FM BioEnergy, specialists in AD nutrition and plant optimisation, AD operator Ynergy has achieved its CHP run time target of 96.6% and saves £20k+ annually on unnecessary feedstock costs.
Using BC.ATOX.Ncon, an additive supplied by FM BioEnergy for high-protein based AD plants, Ynergy is achieving their optimum efficiency of 96.6% of total possible CHP run time at their Great Ynys Farm plant. The 125 acre arable farm in Hereford, also has a 90,000 broiler chicken operation. “As well as using maize, grass and some cereals, we use 800 tonnes a year of broiler litter to fuel our 250kW plant. Although a farm by-product which can be used in AD, broiler litter has a high nitrogen content. Without careful management and the use of the Ncon supplement, nitrogen loading can dramatically hinder gas production, as we found just 5 months post commissioning,” explains plant owner Susan Shakesheff from Ynergy.
“Getting to grips with AD plant biology and diet isn’t easy,” explains Tim Elsome, Business Development Manager at FM BioEnergy. “During the degradation process, every feedstock has differing biological traits and trends. If plant biology is left to its own devices, bacteria and archaea can become imbalanced and unhealthy, resulting in poor gas yields. Plants looking to achieve their optimum gas output require careful monitoring along with a bespoke prescription of additives and supplements for the methane producing bacteria to remain healthy,” adds Tim.
Any high protein based feedstock, such as broiler litter, has a high nitrogen content. Consequently, high concentrations of ammonia are generated during the feedstock breakdown, which in turn inhibits the natural production of methane forming bacteria resulting in lower gas yields. The Great Ynys Farm plant found that their broiler litter contained 27kg N/tonne. They have successfully used Ncon to reduce ammonia’s inhibitory action: “Broiler litter, a feedstock we generate freely at the farm, currently stands for 26% of dry matter in our plant’s diet. If we were to reduce the broiler feed with a substitute feedstock, the annual additional cost to the business would be around £20k+,” remarks Susan. “Importantly, Ncon enables us to use the farm’s available by-product and still achieve our optimum performance,” adds Susan.
Supplied in digestible bags the product is easy to use. “Around 5 months after commissioning the plant, the gas yield dropped significantly. We quickly determined the knock-on effect caused by our high nitrogen feedstock and dosed 75kg of NCON for 3 consecutive days, followed by 10kg on a daily basis ever since. Free ammonia levels were reduced and the plant was back on track within days. Supplied in convenient digestible bags, we simply add one 10kg bag on a daily basis to our digester,” concludes Susan.
Creating a stable biological environment inside an AD plant delivers all round success adds Tim: “It leads to more methane, a faster return on investment and prevents bacterial disasters – no AD operator wants to be faced with having to re-seed and re-commission their plant due to biological failure.”