UK biogas pioneer on solid ground

London -- Holsworthy Biogas is home to the UK’s first Biogas plant, which processes 75 kilotonnes per annum of food waste and animal manure and uses the anaerobic digestion gases to generate electricity and pipe hot water for the local community. To reinforce the efficiency of its Devon plant and comply with animal by-product disposal regulations, Holsworthy operates a special high torque grinder unit to ensure that food waste is reduced to a particle size of 12mm.

The company’s digestion process requires waste to be in a mostly liquid form when it is pumped into the digestion tank. The waste is pumped to a TR Muncher grinder – a twin-shaft, low speed unit from Mono -- which macerates and reduces it to a homogenous product for digestion processes. Biodegradable waste passes through a series of cutters, which revolve at differential speeds to pull apart, crop and shear any solids, such as bones, flesh, offal and vegetable waste. Liquid passes through the cutter stacks, whilst the solids are trapped and macerated to a small, consistent particle size.

The grinder has an intelligent auto reverse sequence controller, which enables it to unblock itself and restart automatically. The cutter stacks are inclined at 25º from the vertical axis to allow any solids that are difficult to grind to drop clear of the cutters into the trash trap, on reversal of the cutter stacks. A trash trap is fitted with a large diameter access port to enable easy removal of any rejected debris. The design also features a cantilever drive shaft that eliminates the need for bottom seals and bearings, so reducing wearing components and offering cost savings on replacements.