Process data monitoring is key to optimising the performance of anaerobic digestion. Learn more about how you can maintain the ideal environment within your vessels by taking a trip to the UK AD & World Biogas Expo, taking place on 3rd - 4th July at the NEC


s famed American management author and professor W Edwards

Deming once said: “You can’t control something that you don’t measure.” That is why the anaerobic digestion (AD) industry takes process data monitoring so seriously. “AD operators must follow the

evidence,” says Angela Cronjé of Roots Organics. “Only when you methodically gather, and clearly present data, do patterns emerge. And only then do things that were hidden suddenly become clear and make it hard to ignore potential issues arising within the anaerobic digestion process.” Avril Banks, an AD consultant and

member of the Anaerobic Digestion and Bioresources Association advisory board emphasises the point. “Understand your results, understand your feedstock, monitor regularly, monitor the parameters which suit your plant. Better understanding results in better rewards.” AD is both a simple, centuries old

technology and hugely complex beast. In principle it is simple; you put a load of organic matter into a reception vessel and it will naturally produce methane. That is why it is often likened to a concrete cow. The more you seek to optimise this

dynamic living structure and its methane production, however, the more complex and sophisticated the system becomes. This makes it more like Goldilocks, everything has to be ‘just right’ to achieve the desired results, increasing profit while safely optimising the system. David Woolgar is a specialist AD

consultant and chair of the ADBA Training, Safety and Environment group. “Methanogens are the bacteria and archaea

due to the limiting factor in their absence - growth is not controlled by the total amount of nutrients available but by the rarest resource available; • gas quality and output, to assess the

quality and mix of gases being produced; • temperature, if the digester is too hot

or too cold it can impact the biological process and severely inhibit the process if feedstock temperatures are not controlled in relation to feedstock inputs; • and finally, digestate, which takes us

full circle. If there is a high proportion of biomethane in the digestate it means something has gone wrong earlier in the process. Process data monitoring allows operators

that produce the methane and they are fussy buggers,” he said, drawing the Goldilocks analogy. “If it’s too hot or too cold they don’t like it. If the environment is too acid or has too little acid they don’t like it. And if the diet is too much or too little they don’t like it. If you keep everything ideal for them the system will produce methane and give you money.”

REGULAR, ROUTINE MONITORING Keeping things ideal requires regular and routine monitoring along the process. There are myriad measurements that can be taken but the fundamentals are considered to be: • the organic loading rate of the

feedstock; FOS/TAC (alkalinity ratio), which describes the relationship between VFA content and the buffer capacity. It is highly advisable to look at FOS and TAC as a ratio and separately. FOS/TAC is German for VFA/TIC; VFA means volatile fatty acids, which indicate the decomposition and gas generation, and TIC means total inorganic carbon (buffer/alkali); • ammonia and ammonium levels, which

can inhibit the production of gas; • trace elements, a dietary requirement

As in previous years, the extensive exhibition will once again enable visitors to view the latest AD and biogas technologies, products and services and hear success stories from around the world

to understand what’s going on in the receptor vessel and along the system. Equipment and laboratory services for process and biogas monitoring grow ever more sophisticated by the day, with digitalisation and mobile monitors allowing ‘live’ observations and alerts to be received if parameters are being breached. Several ADBA members supply them and

are detailed in the ADBA Directory and on the ADBA website, and many will be among the 160 exhibitors at the UK AD & World Biogas Trade Show being held at the NEC, Birmingham on July 3rd and 4th. The event is the largest international exhibition dedicated solely to anaerobic digestion and biogas. The International Energy Agency

forecasts that the AD industry will experience the greatest growth of all renewable energies over the next few years, recognising the myriad of services it can deliver in the fight against climate change. The industry is uniquely positioned to help achieve emissions reduction and mitigate many of the impacts of climate change through capturing organic wastes, producing renewable energy, and returning nutrients and organic content to the soil. It has the ability to reduce global greenhouse gas emissions by 18-20% across the waste, agricultural, energy, and transport sectors. Process data monitoring is integral to

A dedicated seminar and workshop will give delegates the opportunity to discuss current market and policy trends and operational issues with industry leaders


achieving this. So critical is it to plant optimisation that the latest edition of ADBA’s quarterly magazine Anaerobic Digestion & Bioresources News carries a Big Summer Data Quiz for readers. And the issue will be a key feature of the UK AD & World Biogas Expo and World Biogas Summit. For further information and to register

for free, visit

UK AD & World Biogas Expo


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