Farm biogas plant overcomes feedstock solids problem to keep renewable energy output on track

A remote farm-based biogas plant on Hokkaido, the northernmost of Japan's main islands, has resolved a recurring mixing failure that was threatening its ability to convert agricultural waste into renewable energy.

High-solids manure and farm feedstock had been overwhelming the plant's original digester mixers, and any maintenance work required the digester to be drained down completely – a costly process that repeatedly interrupted energy generation.

To keep the plant running reliably, the operator installed an externally mounted GasMix system from Landia, built around the company's Chopper Pump technology, first developed in 1950, which continuously breaks down heavy solids before they can build up inside the digester.

Two floor-mounted Landia Chopper Pumps, each rated at 18.5kW and operating for only 15 minutes per hour, work with venturi nozzles to recirculate and homogenise digester sludge, increasing the surface area available to anaerobic bacteria through vertical and horizontal mixing. With no moving or wearing parts inside the digester itself, all maintenance can now be carried out externally, without taking the plant offline.

Fergus Clark, from Landia (Asia/Pacific), said: "In such a remote, rural area, reliable equipment is essential. Many mixers are just fine in other, gentler applications, but at a biogas plant, unless they are designed for purpose, cannot deal properly with the grit, straw and solids that you always have to contend with in an agricultural feedstock."

He added: "Now, with an efficient and highly dependable mixing system, the farmer has a perfectly healthy biogas plant that can utilise the much-needed excess heat for his cow sheds in Hokkaido's very cold winters – and sell excess renewable energy to the grid."