The production chain of biogas in landfills
The exploitation of the biogas produced in landfill sites makes it possible to reach important goals: the first is the use of biogas as a renewable resource to produce energy by means of a cogeneration plant that generates heat and electricity. The second is its contribution to reducing the greenhouse effect, through the elimination of methane that is formed by the fermentation of waste and has an extraordinarily high global warming potential, 25 times that of CO2 .
Verdesis, a pioneer enterprise in the biogas industry
Verdesis recently joined the French group Dalkia specialising in energy services and has been operating in the biogas sector since 2002. Specialised in methanation - the production of biogas from agricultural and food products - and the exploitation of the energy generated by biogas, Verdesis chose the Mattei Group to develop its compressors used in the final biogas processing phase for energy purposes.
The biogas generated by the anaerobic fermentation of waste is in fact recovered and treated to eliminate water and waste pollutants; it is then compressed so it can be used as fuel for the cogeneration plant engines and microturbines.
Mattei, a well targeted choice
“The compressors supplied to Verdesis were developed exclusively for the company in collaboration with its technical office - explains Philippe Cluchague, General Manager of Mattei France - It is a customised solution that meets the specific requirements of this type of plant system: it can compress up to 9,000 litre a minute of biogas containing up to 300 ppm of hydrogen sulphide, in accordance with the microturbine specifications”.
The Mattei VCG 55s variable speed compressors have a nominal power of 55 kW and operate at a pressure of 8 bar. “They are designed to operate 24/7 outdoors, at temperatures of between -15°C and 45°C - continues Philippe Cluchague - They are machines that require high levels of efficiency and reliability: and this was the reason that prompted Verdesis to choose Mattei, together with the low maintenance costs of our compressors”.
The La Crau site
After designing and realising the first model of this special compressor, Mattei supplied other thirteen units to Verdesis, which were installed and put into operation in six different sites in France.
Among them is also the biogas production plant in the waste storage centre of La Crau, near Marseilles. Opened in 1912, this landfill collected the waste of the city of Marseilles and other boroughs in the region until 2010.
Then the centre was revamped with an energy production project where Verdesis realised a cogeneration plant: the electricity generated by the plant is sold and fed into the grid, while the heat is used on site for the treatment of leachates, which are then concentrated into sludge and disposed of. The La Crau plant was inaugurated in October 2015, has a capacity of 5 MW and will generate 36,000 MWh of green energy in its first year of operation, avoiding 3,000 tons of CO2 emissions a year: “The La Crau biogas production plant is the largest realised by Verdesis inside a landfill facility - commented the President and CEO of Dalkia, Jean-Michel Mazalérat - and slots perfectly into our plans for the development of renewable energy and energy efficiency in this area. Projects such as this are the heart of the energy transition process in the territories and will increasingly become the cornerstones of the development of the circular economy”