Consider AD biology when commissioning biogas facilities

The biogas industry boom has begun and it’s great to read of new sites coming on stream in the UK, USA and Europe. In all this positive news there is little mention of anaerobic digester (AD) inoculum or AD biology for that matter. Given the amount of time, not to mention millions invested in biogas plant infrastructure it perhaps warrants more attention and a higher profile.

After all, Anaerobic Digestion (AD) is a biological system. I compare it to Formula 1 racing where the teams focus on the engineering whilst recognising the impact of fuel and lubricants on track performance. Everything that can potentially improve performance is considered in the pursuit of marginal gains. With this is mind there are 3 aspects of AD biology worthy of greater focus when commissioning a biogas plant.

1. Digester Inoculum – start right & achieve full production more swiftly

Starting your digester off in the right way is important to digester stability and performance. Typically, a new anaerobic digester’s biology is started with a tanker load of sludge from an adjacent facility. This is often convenient and inexpensive but is it the optimal approach?

As we know digester biology varies and performance with it. Research studies indicate that the type, quality and volume of inoculum effects digester performance from the outset. Suboptimal sites will correct themselves overtime but after spending £25million on infrastructure do investors want to hear “don’t worry we’ll get there eventually”. Bespoke inoculum is now available, along with the biological expertise to deploy it. So, help is available to those looking for it.

2. Feedstock Characterisation – understand potential & reduce risk

Characterise the biological potential of your feedstocks and understand their interactivity with others. Some substrates can enhance each other when combined in a digester but in the wrong ratios they can also inhibit optimal biological performance. Short term this can reduce gas output, but long-term incomplete digestion can lead to maintenance issues, silting and reduced tank volume. Feedstock characteristics also helps feedstock managers and plant managers objectively assess value. Striking a balance between gate fees and COD with the potential for organic loading rate (OLR) fluctuations and gas quality.

3. Biological monitoring – optimise the digester ecosystem & anticipate change

Biogas plants are not short of monitoring equipment. With SCADA the control room can appear like the starship enterprise to the uninitiated. However, lab equipment and onsite biological resources vary widely. A biological monitoring programme, based on a rigorous lab testing (inhouse or out), provides an additional layer of management insight into the efficiency and effective operation of a biogas plant. The biological indicators in combination within operational measures provide a holistic picture of the digesters. Providing the opportunity to fine tune biological performance or anticipate problems as biology evolves with changing feedstocks or chemical imbalance.

There is no revelation in these suggestions however by focusing on AD biology there is an opportunity to achieve optimal performance from the get-go. Something that biogas plant owners and their operators will appreciate on the bottom line. To learn more about the opportunity for biological system optimisation in new or existing anaerobic digesters please message or complete a contact form.

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