BIOGAS processing expert Schmack Carbotech has won a contract to provide a gas upgrading plant at one of the world’s largest underground wastewater treatment plants. Through a process of purification, the facility will produce about 180 million kilowatt hours of natural gas quality biomethane annually from the metropolitan area of Stockholm’s sewage, covering up to 40 per cent of its annual CNG fuel needs.
The Henriksdal plant, owned by municipal water, wastewater and waste management company, Stockholm Vatten AB, currently treats wastewater from around one million inhabitants, extracting biogas from sewage sludge. This will now be purified and upgraded to natural gas quality using the pressure swing adsorption (PSA) process. This method of gas upgrading is characterised by low power consumption, efficient heat extraction and a high methane yield.
The company built a similar plant for upgrading biogas from organic waste in Sofielund, Stockholm in spring 2015.
The plant has a capacity to upgrade 3,000 m³/h of raw biogas. The gas that is produced has a methane content of 97 per cent after purification and is used as biofuel in natural gas vehicles. The need for CNG in Sweden is comparatively high, as 60 per cent of public buses already use fuel from renewable energy sources such as biogas, bioethanol or biodiesel.
The demand for and acceptance of environmentally friendly technologies is said to be high in Sweden: 40 per cent of newly registered cars are powered by biogas or electricity. By using biofuels in its public transport system, Stockholm saves 130,000 tonnes of environmentally harmful CO2 per year.
The Carbotech plants in Sofielund and Henriksdal will enable almost 17 per cent of Sweden’s natural gas vehicles to run on climate-neutral fuel in the future, according to the firm.
