Pioneering AD Plant

Permission secured for pioneering AD plant

Engineering and environmental consultancy Wardell Armstrong has helped to secure planning permission from Devon County Council for an innovative £15 million sustainable waste treatment facility using autoclave processing and advanced anaerobic digestion at the Imerys Minerals china clay works at Lee Moor, near Plymouth. AAD (South West) Limited, an Aero Thermal Group company, will process up to 75,000 tonnes per annum of municipal and commercial/industrial waste to produce renewable energy for export to the National Grid, as well as digestate for use in local restoration as a soil conditioner. The site could save up to 20,000 tonnes of CO2emissions annually.

The use of Aero Thermal’s state of the art autoclave technology upstream of the AD plant is an innovative approach using high temperatures (160oC) and pressures to break down otherwise unsuitable paper, cardboard, packaging and woody plant wastes. This means that totally unsorted municipal waste and high organic fraction supermarket and kitchen food waste can be processed simultaneously, while also making the AD process up to four times faster and enhancing biogas production rates. The quality of recyclates removed at the screening stage such as metals, plastics, glass and textiles is also higher since these are effectively cleaned and sterilised.

The biogas will be combusted in a CHP plant to produce up to 3.2MW of renewable electricity for export to the National Grid. It will also generate 3.8MW of heat which will be used to raise steam for use in the autoclaves and to provide heat for the AD tanks, significantly reducing the amount of energy the system requires. The digestate, an organic rich soil conditioner containing nutrients such as nitrogen, potassium and phosphorus that are essential for plant growth, will be used in the restoration scheme for the nearby Lee Moor china clay pits.

The site will incorporate a high level of site controls, process technology and abatement equipment. Incoming waste loads will be deposited in an enclosed building before being processed, while the entire system will be enclosed to prevent fugitive odour emissions. Air within the building will be extracted to a scrubber and biofilter system. The CHP plant will meet strict emission standards set and regulated by the Environment Agency.

The planning application and supporting Environmental Impact Assessment were prepared by Wardell Armstrong, as well as the Environmental Permit Application which is currently being determined by the Environment Agency. Areas assessed in detail included land use and soils, hydrology and hydrogeology, traffic and access, air quality, noise, ecology and wildlife, landscape and visual impacts, and socio-economic effects.

“It has been exciting to be involved with such an innovative, state of the art facility,” said Stephen Barnes, Associate Director at Wardell Armstrong. “Both the EIA and Environmental Permit Application included detailed air dispersion modelling, noise calculations, water quality assessments and health assessments which demonstrated that strict controls and high standards of waste management technology will ensure that there is no harm to the public or the environment.”

Tristan Lloyd-Baker, AAD (SW) Ltd’s Managing Director, said, “We are delighted to receive the green light by way of planning consent for our proposal and I would like to thank Wardell Armstrong for their support throughout the successful planning and ongoing environmental permit application work. Our intention is to begin construction in early 2012 with a view to being fully operational from April 2013.”