Wrong waste jeopardising AD power potential

A lack of certain chemicals in Britain's rubbish is jeopardising the chances of progressing the technology, according to new academic research.

Speaking at the UK Anaerobic Digestion and Biogas conference yesterday (July 7), professor Charles Banks, explained the UK’s waste contained the wrong sort of chemicals.

According to the Southampton University based academic, who was explaining results of small-scale field tests, certain chemical needed to reduce Volatile Fatty Acids (VFAs) were not in waste produced across Europe.

VFAs, which are created through the fermentation process in anaerobic digesters, were the subject of a 500+ day trial at the university funded by Defra.

Professor Banks explained his trials showed how Cobalt (co) and Selenium (Se) were needed to break down the VFAs to keep the anaerobic digestion process working well.

Professor Banks said: “Selenium and Cobalt massively reduced the VFAs as a result there is a need for long term stability.”

However, the professor went on to explain that while 0.22mg of co and 0.16mg of Se per kilogram of waste would help the digestion process, overdoing it could kill the digester.

According to the academic just 1.5mg of se could kill the digester, professor Banks added: “It can’t be added earlier.

“You’ll have to re-inoculate at a later stage.”

Luke Walsh

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