The National Industrial Symbiosis Programme, an organization promoting
cross industry resource efficiency, is working with Severn Trent Water,
the largest independent water company in the United Kingdom, to divert
industrial food waste from landfills to Severn Trent Water's anaerobic
digestion plants across the U.K.
"There is a big move in the U.K. for companies to build new
anaerobic digestion plants to process food wastes," James Woodcock, a
practitioner with NISP said. "Being familiar with Severn Trent and the
water industry in general I thought there are a lot of these plants in
existence already treating sewage mixed with industrial waste."
Severn Trent Water utilizes anaerobic digestion to treat over
700,000 gallons of wastewater and sewage a day. Biogas produced by the
digesters fuels combined heat and power units generating 154,000
megawatt-hour (MWh) of electricity, representing 17 percent of the
company's electrical requirements. Process heat from the Combined Heat
and Power generation (CHP) systems is used to warm the digesters.
Woodcock talked to Severn Trent Water about setting up a program to
identify companies with organic waste streams near its anaerobic
digestion plants. NISP maintains data on each of its member businesses,
which includes the quantity and type of waste material sent to landfills
and where the waste is produced.
Adding industrial organic wastes to Severn Trent Water's anaerobic
digestion systems will increases biogas production and renewable energy
generation, improving the sustainability of the treatment process.
Producers of industrial food waste will benefit by cutting waste
disposal costs by as much as two-thirds over landfill costs, Woodcock
said.
As part of the project, NISP is working with Severn Trent Water to
identify the specific types of feedstock that could prove most
beneficial in boosting biogas production. Certain types of wastes, like
glycerol, have been found to significantly increase biogas production
in sewage systems, Woodcock explained.
NISP is also grappling with legal issues that might prevent
anaerobic digestion systems treating sewage sludge from accepting food
wastes.
"The U.K. is on record saying that their preferred methodology for
the treatment of food wastes is anaerobic digestion and are looking at
commercial anaerobic digestion plants," Woodcock said. Standards are
under development to specify operating methodologies to insure the
byproducts of these anaerobic digestion plants, the digestate, can be
classed as a product and sold for uses such as fertilizer for specific
applications.
Sewage treatment plants and the water industry are facing a new
standard specifically excluding sewage as one of the waste product that
can be added to anaerobic digestion plants processing food wastes.
Sewage is excluded because laws already are in place in Europe that
apply to the treatment of sewage in anaerobic digestion plants and
regulate the land application of the digestate from the process,
Woodcock explained.
"From our point of view, sewage sludge is just another organic waste
going to the anaerobic digestion plant," he said. NISP is working with
the government and the Environmental Agency to enable sewage treatment
plants to utilize the same standards as new anaerobic digestion plants
built to handle food wastes.
Woodcock said he is hearing from many food companies that are
interested in sending their wastes to the treatment plants instead of
landfills. Offsite treatment is appealing to many of these companies
that don't have sufficient waste to run their own anaerobic digestion
plants or don't want to manage a waste treatment process.
"At some point you go from managing your food process to managing
your waste process," Woodcock said. He also questions if food-processing
firms want to colocate waste treatment systems on their production
sites.
For more information on Severn Trent Water, visit
http://www.stwater.co.uk/. For more information on NISP, visit
http://www.nisp.org.uk.
