Turning rubbish into ‘green energy’:

Above - 30,000MWh ReOrganic Energy Facility.
Source - Landfill Management Services Pty Ltd

Landfill gas can be captured and converted into a useful energy source in many ways. This gas can be extracted by inserting perforated pipes into the landfill site. In this way, the gas will travel through the pipes under natural pressure and the gas is then piped into an on-site power station. Inside the power station, the landfill gas is burned to generate electricity and during this process, the methane is converted into water and CO₂. The landfill gas is scrubbed and cleaned before feeding it into internal combustion engines or gas turbines to generate heat and power.

For more information, go to:
http://www.rise.org.au/info/Tech/waste/index.html

In essence, there are five main ways to use energy from landfill gas: For direct heating, electricity generation, chemical feedstock, purification to pipeline-quality gas and heat recovery. The electricity generation applications involve:

• The processing and use of landfill gas in internal combustion engines. Internal combustion engines are the most effective and economical option when the gas supply is enough to produce one to three megawatthours (MWh) of power.
  
  For more information about internal combustion engines, go to:
  http://en.wikipedia.org/wiki/Internal_combustion_engine
  
  
• The processing and use of landfill gas in gas and steam turbines. Turbines are the most effective and economical option when the gas supply is enough to produce more than 3MWh of power.
  
  
• The processing and use of landfill gas in fuel cells. In the future, fuel cells may become more attractive because of their high energy efficiency, their negligible emissions impact, and their suitability for all landfill sites. However, some studies suggest that fuel cells would be more competitive in small to medium projects (less than 1MW to less than 3MW). At present, however, there are economical and technical disadvantages which make fuel cells clearly uncompetitive with more conventional applications.

Above - Clean burn enclosed flares.
Source - Landfill Management Services Pty Ltd

Given that all landfills generate methane, it makes sense to use the gas for the beneficial purpose of energy generation rather than emitting it into the atmosphere. It is estimated that a landfill gas energy project will capture between 60 per cent and 90 per cent of the methane emitted from the landfill, depending on the system design and effectiveness. Generating energy from landfill gas creates a number of environmental benefits. Landfill gas projects help to significantly reduce potentially harmful methane emissions, as well as lessening our reliance on depleting fossil fuels – coal, natural gas and oil. These projects also create jobs, revenues, and cost savings for Australians.

A typical 4MW landfill gas plant will reduce a significant amount of greenhouse gases – it’s about equivalent to the annual greenhouse gas emissions which can be saved by removing 45,000 cars from the road. The amount of energy generated by this same 4MW power plant is equivalent to that produced by 1,000 railcars of coal or almost 500,000 barrels of oil.

It should be noted that landfill gas power plants can generate some emissions of nitrogen oxides (NOx), which are air pollutants. However, these power facilities are far less polluting to the community than allowing the methane gas produced from landfill sites to escape into the atmosphere.

Also, there have been environmental concerns that the combustion of landfill gas can release dioxins, a group of toxic chemical compounds. However, the United States Environmental Protection Authority believes that the potential for dioxin emissions from the combustion of landfill gas is small.

^ back to top ^