Working with FM Bioenergy BioWatt has solved ongoing biological inhibition problems at the Katharos AD Facility in Essex.

Having achieved stable biological and mechanical performance at 60% of installed capacity, further feed increases were resulting in sudden drops in output and of the percentage of CH4 in the biogas. Once dropped, it would take several weeks of careful management to build performance back to a stable 60%.

Using their partners and facilities in Germany, FM undertook a suite of detailed tests on samples from the digester. It was determined that a micronutrient deficiency was preventing bacteria from responding to increases in feed rate resulting in high FOS/TAC results and lowering pH which inhibited growth.

” The trial was a two-stage process. We began with a correctional or ‘impulse’ dose, which involved feeding 45 days worth of BC.MICROcon5 into the digester within just 30 minutes over three feed batches. This dose rate was calculated using the original trace element levels, the size of the tank and the volume of feedstock being processed by the plant each day”


The second stage of the trial – the maintenance phase – then began, which saw operators feed one tab of the product into the 1MW digester each day, for a period of nine weeks.

In addition to their expertise, FM were appointed because their additive is much like a dishwasher tablet, small, hand sized, individually wrapped and coated with a water-soluble film, meaning they are safe to handle.

After using the product for just a few days, the CH4 increased rapidly as the excess sugary acids were burnt off. Once the CH4 had returned to a stable 52% and FOS/TAC below 0.4 feed was slowly increased to above that previously limited and the plant was able to run consistently at over 850KW output without trouble and at lower than previous feeding rates.

BioWatt & FM Bioenergy Solve Performance Issues
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