The landfilled waste contains a high percentage of organic compounds. The break-down of these compounds produces methane or biogas. It is important that no methane escapes into the environment, because this would contribute to global warming.
At the Hooge Maey landfill site the landfill gas is efficiently extracted. It is pumped into gas engines through gas collectors and pipelines. As the landfill site is brought into a state of low pressure, methane emissions are drastically reduced. In order to prevent any biogas from escaping through the flanks, the banks have been re-profiled and solidly sealed.
The generated green power is partly used for its own needs and partly supplied to the electricity grid. The residual heat from the engines is used for heating the Hooge Maey offices.
By re-profiling the banks, they now have a perfect angle of inclination for an additional useful application, more in particular solar panels, which also produce green energy.
The remediation project mainly focuses on valorising the biogas that is present in the landfill waste. Gas shafts were drilled vertically through the landfill in order to extract the methane from the landfill. The gas is pumped towards gas engines through gas pipelines.
In order to guarantee a long-term gas extraction, we keep looking for new technologies that may further optimize our system. These were found in a system where vanes are inserted into the landfill up to a depth of 30 metres, thus constituting a finely-meshed network. This way all parts of the landfill become available for direct degassing. Thanks to the short distance in-between the vanes build-up of water and gas is prevented and ideal circumstances for gas production are created at the landfill site. Early 2010 a trial installation was set up covering 1 ha of the surface. After a positive evaluation this has been extended so as to cover the entire surface area (3.5 ha).
In order to ensure a maximum valorisation of the methane gas, 4 gas engines were gradually installed. The first two gas engines were installed in 2004 and 2005. As from the middle of 2007 the Intermunicipal Association Hooge Maey had 3 engines of 943 kW each. That is why the production of green energy substantially increased in 2008. In 2008 the Intermunicipal Association Hooge Maey produced 18,833 MHw of sustainable energy. In 2009 a 4th engine was installed with a power of 1,260 kW.
Today the production of electricity corresponds with the electricity consumption of almost 4750 households.
The largest former landfill zone of Hooge Maey ("zone C") was abandoned in 2009. In the meantime this zone has already been fully capped. Although no more waste is dumped there, the potential of landfill gas is still substantial. In order to ensure an optimum inertisation, approximately 30 additional shafts were drilled in 2009. After several years the gas production will gradually decrease. According to the forecasts, in 2020 one gas engine will remain operative.
On 19 January 2011 a planning permission was granted for the construction of a solar panel installation. The work was started on 19 May 2011, and on 27 January 2012 the installation was put into operation. The solar panels are mounted on a landfill site slope and cover a surface area of ± 550m². They produce 68,475MWh per year. Since an average household consumes 3.5MWh on an annual basis, this means that our solar panels provide sufficient energy to power about 20 households.