Background Methanisation technology has been used as a waste management treatment in bio-methanisation plants for many years. The methanisation process transforms organic carbon to methane, which can then be used to produce electrical and/or thermal energy as a substitute for fossil fuels. By-products from the methanisation process also offer carbon sink benefits. Bio-methanisation plant operations are vulnerable to a range of factors including: changes in the content and quality of waste raw material; availability and access to profitable markets for the energy produced; increases in maintenance costs and other overheads; and technical operational difficulties. Objectives The objective of this METHAPI EXPERTISE LIFE project was to develop a methodology that optimised the operation of bio-methanisation (anaerobic digestion) plants in Europe. A two pronged approach was carried out to determine optimum operating conditions. Initial work focused on analysing and comparing the effectiveness of methanisation for a range of waste sources, as well as examining the potential uses for different by-products. Conclusions from this work then informed the development and operation of a pilot-scale methanisation plant and results from this were intended to provide guidance for full-scale bio-methanisation plant operators. Key LIFE targets included: reduced liquid effluent discharges to the environment; lower levels of noise pollution; and savings in operating costs from improved preventive knowledge regarding maintenance causes. Results The project partially achieved its objectives. The full test programme was not completed and so only partial guidelines could be produced for the operational management of methanisation installations. Work included both, pilot-scale tests and monitoring of an industrial installation. A pilot methanisation plant of 21m2 was built, scaled down to 1/100 of a standard size plant, and four batch tests were conducted, along with a semi-continuous test, using innovative co-digestion methods on household waste, wastewater treatment sludge and slaughterhouse wastes. Tests were conducted in thermophile and mesophile conditions. Results included the treatment of household waste to produce a satisfactory biogas yield (149 Nm3 per fed tonne) with a CH4 content of 54 %. Variables such as the shape of the digester, treatment duration and waste characteristics proved difficult to define during the elaboration of a homothetic ratio. These and other lessons learnt during the LIFE project have been incorporated within the guidance that was produced covering mechanical aspects of plant installation, preparation of the waste, management of the installation and monitoring of the process. Despite the project set-backs, the beneficiary remains committed to fulfilling the original LIFE objectives and continues to invest in gaining further knowledge about optimal operational parameters for bio methanisation plants. Tests were planned for 2008 and the pilot will continue to be used for several years. Beside the methanisation and composting tests, the pre-treatment of the waste will be improved. New information is to be included in the methodological guide, that will also be integrated in new decision support software for industrial exploitation according to the beneficiary.