German biogas technology company, EnviTec, has announced its completion of a third EnviThan gas upgrading plant in Estonia.

The company’s made-to-measure biogas plants feature their environmentally friendly EnviThan biogas upgrading technology.

Completed in just six months from signature to handover, the new plant is located in Oisu and features EnviTec’s tried-and-tested systems.

The combined gas upgrading (capacity 427 Nm3/h) and CNG (compressed natural gas) compressing plant runs on raw gas from wet manure and feed waste.

The Oisu plant will be using tank trailers, whereas the first two fed the biomethane produced into the existing gas grid.

The biomethane will be transported to urban filling stations with the need for a gas grid utilising three filling points.

Stefan Laumann, Head of the Gas Upgrading Department at EnviTec, explained some of the technical challenges that the company had to overcome, 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, saying, “We had a number of technical difficulties to overcome here.”

“This was where our wealth of experience in plant engineering really helped out.”

Before raw biogas can be compressed to become biomethane and later bio-CNG, it first has to be purified and conditioned.

EnviTec uses its EnviThan biogas upgrading in order to purify and condition the raw gas. For over nine years, EnviTec has been equipping its gas upgrading plants with membrane modules from Evonik Fibres.

In order to achieve a final methane content yield of over 97% purity by volume, the hollow fibre membranes purify the raw biogas generated in the biogas plants.

This method also reduces the ‘methane slip’, or the portion of methane that goes unused to well under 1%.

Speaking about the future potential of biogas, Lars von Lehmden, Managing Director of EnviTec Anlagenbau GmbH & Co. KG, said, “As a substitute for diesel in the transport sector, biomethane can make a lasting contribution to climate protection and the existing infrastructure can be re-used for filling vehicles without needing to make large additional investments.”

By 2025, the city of Tallinn aims to have replaced all of its existing diesel buses with environmentally friendly alternatives such as CNG buses and, according to a press release by public transport company Aktsiaselts Tallinna Linnatransport (TLT), 100 CNG buses already serve Estonia’s capital.

In total, the EnviThan plants supply 8.2 million kg of CNG each year, which could, according to Laumann, depending on journey type and bus size, power 400 vehicles for about 20 million km, saving around 26,000 tonnes of polluting CO2 in comparison to Euro VI diesel buses.