“Our two projects in Tartu and Vinni give us an important foothold in the Baltic market for our EnviThan technology,” says Lars von Lehmden, managing director of EnviTec Anlagenbau GmbH & Co. KG. While the German plant engineering company has already completed seven biogas plants in neighboring Latvia, gas upgrading plants are a new kind of venture for the Baltics.
Both gas upgrading units will be built as extensions to existing biogas facilities. During the roughly six-month construction project, customer AS EG Ehitus-a subsidiary of gas network operator AS Eesti Gaas-completed the necessary pipe laying work themselves.
“We're now delivering the raw gas components, including the purification and gas upgrading systems, all of which are pre-fabricated as custom parts at our Saerbeck facility and are now ready for shipping,” said von Lehmden.
Before biogas can be fed into an existing natural gas network, the gas must first be purified and conditioned. This step will be handled by the two plants using the innovative EnviThan biogas upgrading technology. For this environmentally friendly and exceptionally cost-effective process, EnviTec Biogas equips its gas upgrading plants with membrane modules from Evonik Fibres.
“These hollow fiber membranes clean the raw biogas generated in the biogas plants exceptionally well, resulting in a final methane content of 97% purity by volume,” explains von Lehmden.
The process exploits differences in gas permeation rates and solubility. Carbon dioxide (CO2) molecules are smaller than methane molecules: they are more soluble in polymers and therefore pass through the polymer membrane more rapidly. While most of the CO2 and water vapor pass through the molecular screen, the valuable methane is concentrated on the high-pressure side of the membrane. The upgraded methane is then piped to the feed-in station, where, thanks to a sufficiently high outlet pressure, it can be fed directly into the natural gas grid. The biomethane can then be used as an environmentally friendly fuel by the transport sector, for example.
Rated at 465 Nm3/h, the gas upgrading plant in Vinni is scheduled to be operational by the end of June, and will run on biogas from wet and solid manure, flotates, and vegetable, harvest and food residues. In Tartu, the 425 Nm3 EnviThan plant will operate using biogas produced from wet and solid manure, and harvest residues. Both plants will feed their biomethane into the existing natural gas network.
The Republic of Estonia is the smallest Baltic state, with just 1.3 million inhabitants-roughly the same population as Lower Saxony in Germany. Estonia joined the European Union in 2004 and also has the lowest national debt of any EU member state: this gives it a positive entrepreneurial climate that also benefits investors in the renewable energy sector.