Repsol YPF
Ruta
Recovery of energy in solid urban waste dumps
Biogas, or refuse dump gas, is generated naturally during the decomposition of organic solid waste that is contained in rubbish. This biogas, obtained in the degasification systems of the controlled refuse dumps whose methane content is of around 50%, is used as fuel in cogeneration units.
Previously, the dump's biogas is collected through a series of wells and a channelling network. The biogas undergoes a dehumidifying treatment and is passed on to the engine-alternator units, that convert it into electricty that is exported into the grid once the amount that the facilities themselves consume has been removed. The surplus of biogas is taken to the flare, where it is burned.
LPG can be used as back-up fuel for biogas engines that regulate the percentage of methane and CO2 with which they can function, making it possible to ensure that the engine will work for 100% of the hours, although with propane, as a result of its self-detonating power, the pressure under which it works must be reduced, resulting in the engine working at 50% of its capacity.
The biogas produced by the effluents that are treated in the purifiers, whose methane content reaches 65-75%, can also be used as fuel in gas-fuelled electric generators that turn it into electricity. Part of this energy is self-consumed in the plant itself, and
the rest is exported to the grid, with the resulting decrease of operating costs.
