Background Decomposing organic waste in landfill sites generates large quantities of biogas containing methane (CH4) and carbon dioxide (CO2), greenhouse gases that contribute significantly to the global problem of climate change. However, due to its methane contents, biogas is also a potential source of renewable energy, and can be used for generating power and heat. Today, Combined Heat and Power (CHP) systems are the most common technology for exploiting biogas as an energy source. However, the installation of this technology is currently not technically and economically viable for landfill sites with a low output of biogas. Objectives The project aimed to demonstrate the technical, economic and environmental viability of a system using micro-turbines for recovering biogas from landfill sites in which biogas production is too low to apply conventional technology. The project targeted the use of micro-turbines because of several perceived advantages over conventional CHP systems: i.e., that they can be adapted to landfill sites with low biogas production, operate with low levels of methane concentration in the biogas, and have lower maintenance costs. Two pilot plants would be built to upgrade the biogas recovered from the landfill sites, in order to reduce its levels of hydrogen sulphide and siloxanes, which are corrosive and thus harmful to the equipment. Results The MICROPHILOX project met its overall objective and demonstrated important technological innovations including the use of micro-turbines for biogas recovery, an innovative biological biogas upgrading system and the development of a proven methodology for siloxane analysis. At the start of the project, the most commonly used technology for landfill gas energy recovery was based on CHP engines. However, such systems are only technical and economically feasible when the generated power is over 600 kW (kilowatt) and where biogas has a methane content of at least 40%. Landfill sites with low biogas flow and low methane content cannot profit from this source. The project showed that micro-turbines are a possible option for types of landfills where the installation of CHP engines is not feasible, either due to low biogas flow or to low methane content, or even landfill sites where there is a high biogas production that is being used in cogeneration engines, but where there is a biogas surplus that the engines can’t consume so the energy is flared. The project demonstrated the capacity of the micro-turbines to work with a biogas with a methane concentration of only 31%, Appropriate examples could be small landfills, or those at initial or final life stage. In order to use micro-turbines, the biogas needs to be upgraded due to the presence in the biogas flow of trace elements such as sulphuric acid or siloxanes. (These can damage recovery equipment, thus increasing maintenance costs and reducing the efficiency and economic viability of the whole system.) There are several biogas upgrading technologies. But the one most favoured is activated carbon due to its simplicity of operation and high efficiency. However, it has a high cost and the drawback of the formation of a final waste that must be properly managed. Recently, biological upgrading methods have greatly improved so that today they can achieve similar efficiencies to physical-chemical methods. The project showed that using biological filters for the removal of biogas impurities can help to reduce operating costs, either by the complete replacement of the activated carbon filter or as a pre-treatment of this filter, with the subsequent increase of activated carbon replacement periods. Biotechnological systems use microorganisms to degrade biogas contaminants. In particular, Thiobacillus sp is the bacterium used for the removal of sulphuric acid from biogas and Pseudomonas fluorescens for the removal of siloxanes. Among the different biotechnological upgrading methods, biofilters, bioscrubbers and biotrickling filters are the most important. Among them, biotrickling filters have some advantages in comparison with the other technologies, as for example that they do not present medium acidification problems. As already mentioned, the presence in biogas of trace concentrations of siloxanes can cause serious problem for energy recovery, since combustion of these compounds causes a substance with characteristics similar to those of glass, which damages equipment. For this reason, and also to evaluate upgrading process efficiencies, it is therefore important to know the quantity of siloxanes that are contained in biogas. The project successfully piloted a methodology to capture and analyse sulphuric acid and siloxanes in biogas in a reliable manner. The LIFE funded biofilter will be able to process 15m3/h, as foreseen in the proposal, meaning that 50% of the biogas will be treated using a scale up factor of 15 (from 1m3/h to 15m3/h). The MICROPHILOX project also won the following awards: The IX Garrigues Medio Ambiente-Expansión Awards, in the Innovation, Development and Application of Best Technologies category. The award was presented by the Spanish Minister of Environment on 29 November 2006. The objective of these prizes is to raise awareness amongst the public on how Spanish companies have contributed towards the environment; The Energy Globe Award. Last 10th April, Mr. Paul Rübig, Member of the European Parliament and also member of the Industry, Research and Energy European Committee, presented the MICROPHILOX project with the Energy Globe Award in the national category of 2007 Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).