Making a meal of it

The Doncaster plant will handle 45,000 tons of food waste a year, and will produce 2.8MW of power and heat. In PDM's idealized Vision 2020 world that food waste would come from sorted trade and municipal refuse. And indeed in the medium term that may very well happen. The fluidized bed combustion plant, built a decade ago, is a legacy from the foot-and-mouth and BSE mad-cow diseases of that time. It was designed to put the equivalent of a fire-break in the food chain to stop these diseases from recurring. The output from Widnes, though, is energy, and only energy. Combustion is good technology where the feedstock has to be destroyed. But with most food waste there is a potential second end-product in the fertilizer that is produced, and this could tip the balance towards AD plants. These are essentially wet processes and in Biogen Greenfinch's early food-waste AD trials it used the animal slurries both to add moisture to the waste material and to transfer some bacteria cultures back into the mix.