Biogas refers to a gas produced by the anaerobic breakdown of organic matter (in the absence of oxygen). This type of fermentation is produced through natural processes in marshes, for example. In a landfill site, where organic matters are buried and trapped in an anaerobic space, biogas is released (also called landfill gas).
Biogas is a mixture of several gases in variable proportions depending on the nature of the waste from which it is released. It comprises primarily of methane (CH4), a very harmful greenhouse gas. It contributes to the effects of global warming and is 20 times more potent than is carbon dioxide (CO2).
By using the landfill gas (LFG) released from landfill sites and converting it into energy, we are taking a step further in preserving the natural balance of the Earth.
Did you know?
The methane released from the Montagne-de-la-Croix landfill produces enough energy to feed more than 500 houses in electricity.
Facts related to the landfill gas (LFG) collection and recovery system at the Montagne-de-la-Croix landfill site
- Since 1997, the NWRSC Solid Waste Service buries wastes. In 2010, the site is ready to extract LFG (whose primary constituent is methane) that is released from landfill cells composed of solid wastes.
- In 2010, LFG is recovered from 6 landfill burial cells that each contains 100,000 tonnes of wastes. LFG that is extracted from the cells is drawn up by vacuum through 8 vertical gas wells (large vertical cylinders skirting the cell’s outline) (see picture below).
- LFG is routed towards the filtration system where impurities are extracted. A pipe carries the gas, that has been transformed into fuel, from the filtration system towards the engine.
- The engine makes the turbine rotate and produce energy. The Jenbacher engine was designed inAustria, the company is now affiliated to General Electric (GE).
- The heat produced by the cooling system of the engine (a glycol base fluid at a temperature of 900C) is recuperated and directed by subsurface ducts to heat the facilities (buildings and offices). This fluid circulates in a closed circuit system.
- This surprisingly highly efficient system can produce 633 kilowatt-hours of energy (kWh) all year long. The engine will be out of use for maintenance only, which should not exceed 40 hours a year.
- If the turbine engine stops for any reason, during maintenance for example, a valve system will direct the LFG directly to the burner. The latter is heated automatically by a propane cylinder.The combusted methane gas pollutes far less than when it is released directly into the atmosphere. When burnt, it becomes an almost neutral gas (near 99%).
- Energy produced by this system exceeds the need of the Solid Waste Service facilities. The excess is distributed in the NB Power network.
This project of almost $2.5 million has been made possible thanks to a funding of $900,000 from Climate Action Network Canada (CAN Canada). This system is the second of its kind established in the province of New Brunswick, the first being at the Fundy Solid Waste landfill site in St. John.
Facilities for LFG recovery at the Montagne-de-la-Croix sanitary landfill site
This photo shows a generator used one site to transform LFG into energy. When the system needs to be stopped due to maintenance, the methane gas will be burnt in order to be destroyed instead of being released in the atmosphere.
Vertical gas well used for LFG collection from a burial cell