Spain captured landfill methane from 700 tonnes of daily waste; the result generated 4.4 million kWh of electricity in one year at Bilbao’s Artigas landfill project

What happens when the gas produced by a large landfill is treated as an energy source rather than just being allowed to escape? At the rubbish dump in Bilbao, Spain known as Artigas, a system was used which was intended for gathering the biogas produced as a result of urban waste decomposing. The site received every day about 700 tonnes of waste from Bilbao and the neighbouring towns, the amount being equivalent to a population of about 800,000 people, as per a report by CORDIS - EU.

The project was intended to show that landfill gas could be collected and then used as a source of electricity, and in its first year of operation, from November 1992 to October 1993, the plant produced 4.4 million kWh of electricity.




The entire amount was sold to Iberdrola, which is the electricity company that bought and used the power.

Turning landfill gas into electricity

The Artigas plant had 21 collection wells linked to 12 gas lines; the depth of the wells ranged from 10 to 18 metres and the pipes carried the gas to a main collector which was situated inside the motor house.

The biogas obtained on average had about 52 per cent methane in it, and the plant could collect roughly 600 cubic metres of biogas each hour while the motors used about 500 cubic metres per hour.

The gas was initially passed through some machinery which sucked out the particles and helped it to get through the system, together with the use of a flare to burn the extra biogas that the motors did not need.

The gas had to go through a dehumidifying system before it reached the engines since the water in the gas would damage the motors.

The plant had two internal combustion engines, each operating a 450 kW alternator, and the combined capacity of the units was about 900 kW.

The electricity was sent through a 2,000 kVA booster transformer and then injected into the Iberdrola grid.

The landfill gas also helped deal with waste problems

It involved more than just the generation of electricity from biogas.

The project also aimed at dealing with the problems resulting from gas building up inside a landfill; the report says that the collection and removal of the gas helped to reduce the risk of explosive mixtures and also avoided damage to vegetation because methane is capable of displacing oxygen around the roots of plants.



This also contributed to getting rid of the unpleasant smells around the landfill.

The gas was regularly monitored, and since 1990 the Institute of Renewable Energies has been analysing the biogas and the condensates which pass through the collection system.

The results indicated that the methane levels averaged about 50 per cent, the oxygen levels varying between 0.72 and 8.65 per cent.

The gas also contained a number of other compounds. Specifically benzene, toluene and ethylbenzene, and hence the plant employed some equipment for preparing the gas before it reached the engines.

In the first year the system produced 4.4 million kWh of electricity, after which Iberdrola bought 4.1 million kWh at an average rate of 10.6 pesetas per kWh.



The Artigas project showed that waste that had already been sent to a landfill could be turned into a second useful resource. Instead of seeing the gas merely as something that had to be controlled, the plant collected it, cleaned and prepared it and then used it to generate electricity for the power grid.