Utilization of low-calorific landfill gas: Landfill site becomes energy source

Up until 2005, organic waste was deposited in landfill and is today still producing landfill gas, which is initially comprised of up to 55 per cent by volume of methane. It has long been state of the art to generate power and heat by utilising this so-called “good gas” in conventional gas-powered combustion engines. As the materials in landfill age, the methane content of the landfill gas drops. Once the methane content falls below around 35 per cent by volume, the gas can no longer be recovered using the available technology and the engine ceases to operate. By using the Stirling-engine CHP unit from gas-technology company LAMBDA Gesellschaft für Gastechnik mbH, even landfill gas with only 18 per cent by volume of methane can be used to generate power and heat. This means that the time frame for recovering landfill gas is considerably extended, with the result that landfill gases from organic waste can continue to be used for decades to come.

Germany’s main environmental agency, the Umweltbundesamt (UBA), estimates that in 2015 – ten years since landfill of organic materials ceased – over 500,000 tonnes of methane were still being produced annually and need to be captured and processed. UBA calculations also reveal that less than 25 per cent of the landfill gas being produced is removed through conventional methods of landfill gas extraction (use in gas-powered combustion engines, for instance). As a consequence, methane – which is 28 times more damaging to the climate than CO2 – is escaping into the atmosphere.

Engine for progress:

  • over 240,000 kilowatt-hours of electricity and heat saved per engine
  • the equivalent of approx. 700 tonnes of CO2 saved
  • can also be used for sewage and mine gas

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Photo: Lambda Gesellschaft für Gastechnik mbH

Solution: the Stirling engine

By using Stirling-engine CHP units, landfill gas with only 18 per cent by volume of methane can be used to generate power and heat. This is possible because Stirling engines are powered by an external heat source. In the Stirling-engine CHP unit from LAMBDA, this heat source is provided by a flameless gas burner in continuous operation. If the power from Stirling-engine CHP units is used to operate a landfill degassing system or for landfill aeration, the operation of this degassing or aeration system can be almost climate neutral.

A climate-friendly solution

In addition to the savings in CO2 resulting from the use of Stirling-engine CHP units, preventing methane emissions from landfill sites also has an impact in terms of climate protection. A Stirling engine can produce up to 61,000 kilowatt-hours of electricity and 185,000 kilowatt-hours of heat from low-calorific landfill gas each year. By substituting power and heat from fossil energy sources, each engine installed can therefore prevent the equivalent of around 85 tonnes of CO2 from being emitted in the production of power and heat. In addition, capturing and processing low-calorific landfill gas containing methane prevents the equivalent of around 600 tonnes of CO2 from being generated. According to these figures, running a Stirling engine on low-calorific landfill gas saves the equivalent of up to 690 tonnes of CO2 in total per year. Furthermore, according to LAMBDA, there is also significant potential in Germany, and also elsewhere, to use Stirling-engine CHP units to exploit waste gases in perhaps several hundred systems.

Stirling-engine CHP units in operation at four locations in Germany

The Stirling CHP unit at Göritz landfill site in Brandenburg was provided by the Herten-based company and went into service at the beginning of September 2015. It is the first Stirling-engine CHP unit using landfill gas as its energy source to be deployed in Germany. There are two more in Baden-Württemberg and there are plans to install a fourth unit in North Rhine-Westphalia. The Stirling engine can also be used with other organic gases, such as sewage gas. Around ten systems are scheduled to be installed in the landfill- and sewage-gas sector at various locations in 2016.

Photo: Lampda

“In 2016, Stirling-engine CHP units developed by us will save around 10,000 tonnes of CO2 across Germany. And, in addition to the obvious advantage in terms of climate protection, the systems can have a positive economic impact for landfill operators, too.”

Benedikt Preker, Managing Director of LAMBDA Gesellschaft für Gastechnik mbH

Partners and sponsors

  • LAMBDA Gesellschaft für Gastechnik mbH
  • EU-Förderung

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