The European LIFE Biogasnet project has validated a new biogas purification technology, which allows improving the quality of this resource produced in urban solid waste treatment plants and wastewater treatment plants, as well as reducing the carbon footprint of the cycle energy and promote the circular economy concept.
Specifically, the solution “is based on the application of biological, efficient and low-cost technologies, and allows to increase the quality of biogas to promote its use as an alternative energy source”, explains the project coordinator, Xavier Gamisans, professor at the Polytechnic University of Catalonia in Manresa.
The developed system has been tested for a year in an urban solid waste treatment plant located in Cádiz (Spain) and, subsequently, in a municipal solid waste treatment plant in the Attica region, in Athens (Greece), two facilities in which that have been used with different sources of effluents rich in ammonium to desulphurize biogas with the aim of validating the technology and its operation in diverse environments and conditions.
At the same time, “exhaustive studies on the environmental impact of the technology have been carried out to objectively demonstrate which are the most favourable scenarios for its implementation”, explains the director of the Waste, Energy and Environmental Impact Unit from the Eurecat technology centre, Frederic Clarens. In this sense, “scaling studies have been carried out for installations other than those where the project system has been installed and operated, for example, in wastewater treatment plants”.
According to the director of Eurecat’s Water, Air and Soil Unit, Xavier Martínez, this project “is a clear example of how biological technologies for gas treatment are becoming more robust and attractive for its implementation in industry”.
Validation in two real waste treatment facilities
For its validation, the technology installed in Cádiz has included an anoxic bioreactor for the elimination of hydrogen sulphide from biogas with yields greater than 97%. The elimination of hydrogen sulphide is carried out using nitrate and/or nitrite, which is obtained in a nitrification bioreactor using the landfill leachate itself as a source of ammonium. Hydrogen sulphide is mainly oxidized to elemental sulphur, a re-valuable byproduct.
Regarding the installation in the Athens plant, the process has initially consisted of capturing the ammonia present in the extraction gases of a composting plant in a liquid stream by a bioscrubber. This stream has been nitrified to nitrite and/or nitrate to be used in an anoxic trickling biofilter to eliminate hydrogen sulphide through its majority oxidation to sulphate. Finally, this sulphate has been combined with some of the ammonium-rich liquid to produce ammonium sulphate in a CSTR reactor, effectively converting waste gases into a useful product.
The LIFE Biogasnet consortium has included the Polytechnic University of Catalonia, project coordinator, the Eurecat technology centre, the University of Cadiz and the National Technical University of Athens, and the companies AERIS Tecnologies Ambientals and Bioreciclaje de Cádiz.