Each year an average of 2.12 billion tonnes of waste is thrown away globally, with a large portion of this ending up in landfill. When this waste decomposes, landfill gases are released into the atmosphere. These gases are not only harmful to human life, but they also pose a great risk to our environment too.
In this article, we look at the kinds of greenhouse gases produced by landfill sites, why this happens and what can be done to reduce these emissions in the long run.
Yes, landfill gas is actually made up of around 50% methane and 50% carbon dioxide, two of the main greenhouse gases which are responsible for climate change. In 2010 alone, nearly 800 million metric tonnes of CO2 were released from around the world, with 11% being human-generated methane. The USA was responsible for the largest number of methane emissions at a staggering 130 million metric tons.
In order to understand why landfill sites produce these greenhouse gases, we must first look at the conditions of the landfill sites themselves. These sites are located underground, lined in clay and then covered in a flexible sheet of plastic. Drains and pipes are installed which collect the liquid that seeps from the waste – this is then disposed of as wastewater. Each day, landfills are covered in fresh soil until the waste cell reaches its maximum volume and is eventually closed.
Once a site is closed, anaerobic conditions are reached after about a year – meaning there is no more oxygen. this anaerobic state necessary for bacteria to decompose the waste. As it rots, organic waste such as food, paper, card and wood releases methane. This greenhouse gas is between 28 to 36 times more potent than carbon dioxide at trapping heat in the atmosphere over a 100-year period.
Aside from contributing to global warming, the gases produced from landfill pose various health concerns. For example, the gases contribute to the formation of smog which can worsen health issues like asthma.
One of the biggest causes of methane emissions from landfill is food waste. In the UK, around 20 million tons of food is wasted per year. This waste alone is associated with an average of 25 million tons of greenhouse gas emissions. However, this wastage is not just at a household level; farmers are responsible for a large amount of waste as the best-looking produce is selected and the rest is thrown away. Supermarkets often overstock to keep up with demand, with a great deal of expired product ending up in the bin as they struggle to sell the large quantities of products they stock.
Yes, there are a number of ways to reduce the amount of greenhouse gases produced in landfill. In many modern landfill sites, methane is collected through pipes and is then recycled for fuel, manufacturing and electricity. The good news is that methane has a much shorter life than CO2, therefore, reducing the amount of this in the atmosphere by collecting and reusing it can drastically reduce the impact of climate change.
There are three main options for reducing greenhouse gas emissions coming from landfill. These involve creating less waste, sending less waste to landfill and capturing more of the methane that is released from these sites. Some options could include:
This is a method which involves organic waste degrading in the absence of oxygen in a controlled environment. The end product of anaerobic digestion is biogas, an energy source that can be used for energy and fuel. A nutrient-rich, organic biofertilizer can also be created from the leftovers, so nothing is wasted.
Composting involves degrading organic waste to produce compost that can be used on the land. This compost is nutrient-rich and helps reduce the need for chemical fertilizers.
Mechanical biological treatment is where recyclable materials are removed, the waste is broken down via shredding and then composted or digested to create biogas.
With this method, the waste is fed directly into a furnace or boiler, and the energy created in the combustion process is then harnessed and reused.
For more information on landfill gas monitoring and management, read our article on how landfill gas emissions are estimated.
