Maximising biogas feedstock potential through digester flexibility

Feedstock availability has been a significant issue for the biogas sector since the start of the COVID-19 pandemic. The lack of availability of commercial food waste during lockdown periods has constricted supply, forcing Anaerobic Digestion (AD) plants to substitute, ration or scale back production.

Some such as Lanes Farm Energy have found it easy to adapt. In the February 2021 edition of bioenergy news they reported, that the flexibility of their plant design had paid off during the pandemic. According to the article they were able to adapt to changing supply as the biogas plant accepts packaged food waste, solid and liquid food waste, agricultural waste, and crops.

Others have been less fortunate due to supply agreements, legislative frameworks and planning or infrastructure constraints. With a 15% to 20% reduction in feedstock availability some biogas businesses’ have found it hard to make money. However, the AD industry is resourceful and resilient.

Adapting to new digester feedstocks

Feedstock optimisation has become the buzzword and a new area of focus within the industry. As well as a friction point between feedstock procurement and plant operations. For example, sudden availability of waste beer might appear attractive, but this sugar rich liquid can easily unbalance a digester at the incorrect loading. Likewise, low cost but high lignocellulosic crop waste can constipate, leading to erratic gas supply and digestate issues.

Historically, the solution to flexibility was increased capital expenditure. Involving reconfiguring the biogas plant-infrastructure or purchasing pre or post treatment equipment to breakdown substrates or extract ammonia.

Embracing innovation in AD

However, the feedstock emergency, has provided a welcome boost to AD industry innovation. Encouraging biogas plant teams to consider new solutions. One’s which offer the flexibility to adapt feedstocks whilst maintaining balanced productive anaerobic digesters.

The use of bio-organic catalysts (BOC) is one such example. Considered “out there”, 5 years ago this patented branch of organic chemistry is gaining acceptance by delivering results. The action of this unique compound enables digesters to accept a greater diversity of feedstocks whilst remaining balanced. BOC is unique in its ability to harmonise dissolved feedstocks and provide greater access to their cell structure. This creates optimal conditions for hydrolysis.

The result is faster and more complete digestion providing sites with greater commercial flexibility. Gas to Grid (G2G) biogas facilities tend to take to the resultant increase in CH4 yield (+15%) and the higher OLR too (+20%). Non G2G plants, flex according to their commercial circumstances. Some ration expensive feedstock by controlling OLR, others accept a greater diversity of substrates, safe in the knowledge that the digester will remain balanced and energy consumption stable.

Other emerging trends in Anaerobic Digestion (AD)

Several other AD trends have emerged through 2020/21, and we at Alps Ecoscience believe some will remain post pandemic
• Greater focus on biology and sampling
• Feedstock classification and load rate balancing
• Substrate pre-treatment processes
• Digester efficiency and optimisation programmes

Another trend that has emerged is the availability of biogas specific managed services. Such as biology and sampling service, digester optimisation or end to end plant management. It appears that the added security offered by a managed service is resonating with site owners. Afterall, it provides operational and financial security in uncertain times and expertise on demand. Not to mention fixed price additives in a world of increasing raw material cost.

As we emerge from lockdown and the hospitality sector scales up, feedstock availability will likely rise. However, we believe the newly acquired understanding of feedstock adaptation will benefit the industry as it looks to deliver green energy transformation.

To learn more about the commercial results of Alps Ecoscience’ managed services or feedstock pre-treatment programme please request a case study from or use complete a contact form

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