Within only twelve months after the award of the turnkey extension of the Topinoja biogas plant, BTA won another GASUM tender - the design and construction of the Lohja biogas plant. This plant processes approximately 40.000 tons of biowaste, commercial waste and food waste from ferries & ships, as well as 20.000 tons of various sludges annually.

Four separate receiving lines ensure the plant's high substrate flexibility: grease separator contents are pumped directly into the suspension buffer. Industrial sludges are first diluted before being pumped into the digesters. Two further reception lines - a deep bunker and a reception tank for liquid food waste - enable separate reception of these waste streams with impurities. These are first fed to the BTA® hydromechanical treatment unit before the purified organic suspension also passes on to the digestion unit.

The anaerobic digestion stage consists of two fully mixed digesters with a reactor volume of 4.000 m³ each. The digestate passes through a hygienisation step (70°C, 1 hour), which is equipped with a heat recovery system for optimal energy utilisation. A partial stream dewatering by means of a centrifuge enables the recovery of the process water required for the previous processes. The remainder is stored as liquid fertiliser in a digestate tank on which a double-membrane gas holder is installed. Before the biogas is handed over to GASUM for further utilisation (purification), the H2S is removed in a biological desulphurisation unit.

The Lohja biogas plant produces about 50.000 tons of organic fertiliser and more than 40 GWh of biogas per year. GASUM expects that the portfolio expansion through the Lohja project will further boost the Finnish biogas market and promote the use of biogas as a fuel for transport.