DBE Energy takes food waste and controls the breakdown process of the waste to produce biomethane which can be injected into the national gas grid, and a liquid fertiliser (digestate). This replaces chemical fertilisers on agricultural land.
Anaerobic digestion (AD) is a natural process that occurs where organic material is in an air-free environment e.g. the bottom of ponds. The organic material is consumed by micro-organisms that produce methane gas. Anaerobic (without air) conditions are also found in landfill sites where food waste is typically deposited. Within the landfill site it can release methane, a greenhouse gas.
All pre-treatment of food waste is undertaken in an enclosed building, into which the waste is delivered. It is loaded by a telehandler into a large hopper, which feeds into a Paddle Depacker. Here the food is turned into organic sludge and separated from any packaging, as it is pushed through a screen. We are currently the only facility in England to utilise a Paddle Depacker within our process line.
Plastics from packaging are moved through to a hot water wash drum. These are then washed, and the water is pumped directly back into the process. The washed plastics are compacted, collected and taken away for disposal, as they cannot currently be recycled.
The organic material is transferred into one of four buffer tanks. From there, it is pumped through the pre-pasteurisation heat exchanger, where it is pre-heated to a minimum of 72°C.
The material passes into one of two heated and insulated pasteurisation holding tanks, where it resides for at least one hour. This ensures that any pathogens are destroyed in compliance with the Animal By-Product Regulations.
After this, material is pumped from the pasteurisation tanks to horizontal underground anaerobic digestion (AD) tanks.
Within these tanks, the organic material is digested by microbes which then produce biogas.
The biogas generated in the AD tanks is collected in a large gas collection bag. The stored gas is then drawn forward for upgrading, where the pressure is increased and the gas is cooled. Next, it goes through a set of carbon filters, to strip out unwanted Hydrogen Sulphide (H₂S) and other unusable gas content.
The remaining Methane (CH4) and Carbon Dioxide (CO2) within the biogas is then increased in pressure and forced through cleaning membranes, leaving biomethane. The biomethane is pushed forward to the network entry unit for the national grid, and odorant is added to make it smell like the gas we are familiar with in the domestic environment.
Following completion of the anaerobic digestion process, the digested material (digestate) is pumped from the AD tanks to holding vessels, and then to an off-take vessel, prior to it being removed by tanker. The digestate which is removed can be applied under licence to agricultural land.
Where are waste comes from
Our waste collection
partners bring food waste to the facility from a wide variety of sources including:
Packaged food waste, such as surplus or out of date products from supermarkets.
Restaurant and catering waste.
Food waste from local amenities, such as schools.
Food waste from local specialist food suppliers.
Kerbside collected food waste.