EnviTec Biogas commissions third plant in Estonia
Following the construction and commissioning of two EnviThan facilities in Tartu and Vinni, the third facility in Oisu was completed on schedule, taking just six months from signature to handover.
“Our customer here again was AS EG Ehitus, a subsidiary of gas network provider AS Elenger, who had previously commissioned us to build the two plants in Tartu and Vinni,” said Lars von Lehmden, managing director of EnviTec Anlagenbau.
The combined gas upgrading (capacity 427 Nm3/h) and compressed natural gas (CNG) plant runs on raw gas from wet manure and feed waste. Although the first two plants completed by EnviTec feed the biomethane produced into the existing gas grid, the Oisu plant will use tank trailers. With a total of three filling points for these 'swap-body' trailers, the biomethane will be transported to urban filling stations without the need for a gas grid.
Stefan Laumann, head of EnviTec’s gas upgrading department, said: “We had a number of technical difficulties to overcome here. From connectivity with the CNG unit to the integration of various customers’ components, such as a gas chromatograph or flow rate meters with EnviTec’s containers – effective solutions were needed throughout.
“This is where our wealth of experience in plant engineering really helped out.”
To ensure raw biogas can be compressed into biomethane and later to bio-CNG, it is first purified and conditioned. As with the other facilities, the Oisu plant also uses EnviThan biogas upgrading for this step.
For over nine years, EnviTec has been equipping its gas upgrading plants with membrane modules from Evonik Fibres. The hollow fibre membranes purify the raw biogas generated in the plants to yield a final methane content of over 97% purity by volume. This also keeps methane slip (methane that goes unused) to under 1%.
“As a substitute for diesel in the transport sector, biomethane can make a lasting contribution to climate protection, and the existing infrastructure can be reused for filling vehicles without needing to make large additional investments,” said Von Lehmden.
Tallinn-based public transport company Aktsiaselts Tallinna Linnatransport recently revealed that 100 CNG buses are already serving Estonia’s capital, with the acquisition of another 100 buses planned for this year. The city is also inviting bids to supply up to 150 methane-powered buses. By 2025, the city aims to have replaced all of its existing diesel buses with environmentally-friendly alternatives, such as CNG buses.
EnviTec’s three plants could play a key role in Estonia’s local public transport network. In total, all EnviThan plants supply 8.2 million kilograms of CNG annually, which could, depending on the journey type and size, power 400 vehicles for around 20 million kilometres, according to Laumann, while also saving around 26,000 tonnes of CO2 compared to Euro VI diesel buses.