Taking root: Our AD plant is starting to grow

March 21, 2011

It’s been a long journey to get here, but building work on Local Generation’s first Anaerobic Digestion (AD) plant is under way! The building team is working closely with all the relevant agencies and supervising bodies, to ensure that the project operates to the highest professional and sustainable standards. “It’s really exciting to see the plant going up – you can see the progress we’re making every day’” says Nick Waterman.

The concrete bases are already in place for the hydrolysis, pasteurisation and digester tanks. Once depackaged, food waste will be liquidised and moved into the hydrolysis tank where the digestion process will start. Pasteurisation will be used to treat the waste so it meets stringent quality requirements. Finally, in the oxygen-free digester tank, the slurry will be converted by micro-organisms into methane which is a ‘biogas’, similar to natural gas.

So far, the project has already used almost 800 cubic metres of concrete, 84 tonnes of steel and over 300 concrete pilings each 14 metres long. Sustainability is at work here too with 8040 tonnes of reclaimed stone and 240 tonnes of reclaimed road surface which has been used around the site.

The beginning of any building project is exciting, but some unusual features of the AD plant pose especially interesting challenges to our engineers and builders. For example, the hydrolysis tank isn’t being built from the foundations upward, but from the top down. That means manoeuvring the 10 huge rings into position (see photo) using equipment that looks and works like a giant car jack.

“It’s an exciting time for the whole team and for our customers as we see the plant taking shape,” said project engineer Neil Hunter. “Last winter’s weather made it even more interesting – concrete can only be poured at temperatures above 4ºC, and no-one expected it to hit -13ºC!”

With winter successfully weathered, Neil and his team will now move on to the next stage of the build, when construction begins on the other tanks.