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.
