How Is Landfill Gas Turned Into Electricity?
We all know that the world produces a lot of waste (billions to trillions of tonnes each year) and this waste has to go somewhere – it doesn’t magically disappear (as much as we may want it to). There are various places this waste can go, but a portion of it will make its way to landfills and waste disposal areas in cities and states across the globe. This waste potentially takes decades to decay and, during this decomposition period, produces what’s known as landfill gas. This gas is not a great addition to the environment, and various initiatives are now in place to try and decrease the levels of landfill gas being released from landfills in Australia. Some clever people decided why not turn landfill gas into something we need – electricity – so let’s talk about how that process occurs.
What is a landfill?
A landfill is a waste disposal area where waste is generally buried below ground. A landfill is one of the oldest and most common waste disposal options utilised around the world and ensure that rubbish is separated from the surrounding areas.
What type of gas is released in landfills?
A variety of gases are released in landfills, however the major one (over 50% of the total amount) is methane, a contaminating greenhouse gas. Methane is around 21 times more powerful than carbon dioxide and the major concern when it comes to landfill gas, with man made waste being the third largest source of methane.
To produce methane, waste that is deposited into a landfill first undertakes an aerobic (or ‘with oxygen’) decay stage which results in very low methane levels. Generally after less than a year, anaerobic (or ‘without oxygen’) circumstances are created and methane-producing bacteria begin their decomposition of the waste, which produces methane.
How does landfill gas electricity generation work?
The basic steps for landfill gas electricity generation is as follows :
- Landfill waste is deposited into a landfill area
- The landfill waste begins to decay and emit landfill gas, namely methane
- The landfill gas rises to the top of the landfill and is collected in pipes located in/around the landfill
- The captured landfill gas is then directed to a treatment phase, being dealt with in accordance with its final purpose (ie. burning, electricity etc)
- Once treated, the gas can then be used as fuel for a combustion engine, in order to create electricity for various purposes
When it comes to converting landfill gas to electricity, the combustion engine is one of the major components to the process. Otherwise known as a biogas generator, a combustion ene does all the hard work when it comes to converting landfill gas to electricity.
The Inoplex difference is that we use inverter technology to convert the electricity from our cogenerators into the type of electricity that you need; whether it’s to run computers, industrial machinery or be fed into the grid. This is combined with a variable speed engine that runs on a range of fuel types and quality (eg. low quality Biogas). This varying speed produces raw power that our electronics converts to smooth DC power and then three phase AC power, synchronised with the grid at all times.
Australian carbon credit units
Australian carbon credit units, or ACCUs, are credits that can be earned through various projects approved under the Emissions Reduction Fund. In the case of landfill gas, ACCUs are earned for the levels of methane that is collected and then burnt off through different devices. For every tonne of carbon dioxide equivalent (tCO2-e) stored or avoided by a project, an ACCU is earned. For the creation of electricity, landfill gas can be burnt off through a combustion engine (as opposed to a flare or other combustion device) and ACCUs can still be earned.
Why convert to landfill gas electricity generation?
If you are responsible for a landfill that is already capturing landfill gas produced to be burnt off for ACCUs and are considering the change to landfill gas electricity generation, here are a few things to consider :
The advantages of a system like this are huge, especially for the environment, including :
- Reduction in greenhouse gas emissions
- Efficient use of waste
- Earn ACCUs
- Reduction of air pollution by offsetting the use of non-renewables
- Relatively cost effective
- Improvement to overall air quality
- Reduction of landfill odour
- Potential Green Energy credits
Although there are very few disadvantages to consider, the big one is the quality of landfill gas. A lot of landfill gas can be very low quality, which makes it very difficult (and sometimes impossible, as well as being potentially damaging) for biogas generators to run and generate electricity. When this occurs, the gas needs to be flared anyway – so it sounds like you are merely ‘doubling up’ on technology. In saying this, there are companies which have placed generators on the market which can deal with methane gas levels as low as 45% (see the Inoplex Landfill Gas Generator as an example).
If you have any questions regarding how landfill gas electricity generation works, or how it can be utilised in your business, contact us on 1300 113 782 or complete an online enquiry form now. We are experts in landfill gas to electricity plants and can assist in arranging the best plant for your circumstances, including the best ways to utilise your system for carbon credits.