The role of waste-to-energy in renewable power
Waste-to-energy (WtE) is the process of generating energy from waste that can’t be recycled, usually by burning it and recovering the resulting thermal energy. It’s a form of energy recovery, helps reduce CO2 emissions from power generation and supports the circular economy.
In this article, we examine the role of waste-to-energy in the renewable power generation sector and its contribution to the goal to have a functioning circular economy.
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How it works: energy generation from waste
Energy generation from waste is achieved through the process of waste-to-energy (WtE). Waste that can’t be recycled is burned as fuel, similar to coal in coal plants. The heat produces steam, which in turn drives a turbine in a generator, producing electricity for energy companies such as National Grid.
Waste-to-energy reduces the volume of waste by 87% and helps to reduce methane emissions.
Sterling TT is a UK expert in heat exchangers, and designs and manufactures heat exchangers for use in such generators.
After combustion, the ash is sorted to remove any metals that can be recycled. The remaining ash is very similar to gravel or sand. The construction industry can use it for making roads, for example. WtE plants will also send some to a landfill, where it is processed through a filtering system to prevent groundwater contamination.
The supply of high-temperature heat produced by WtE systems isn’t always turned directly into electricity. It can be used in nearby industry processes, such as factories. Depending on the WtE system infrastructure, hot water can be sent to the local district heating/cooling network to heat or cool buildings, offices, hospitals and so on.
Is waste to energy renewable?
Waste to energy is partially renewable. Only the waste in the mixture from recently grown materials is classed as renewable. However, it does have other benefits, such as reducing methane emissions.
In lower-income countries, the Municipal Solid Waste that is burned tends to have a higher proportion of food and green waste compared to higher-income countries, where it usually has more plastic. This means a higher proportion of the energy is renewable in lower-income countries.
However, while waste-to-energy is only partially renewable, it does have other benefits in the drive for renewable and sustainable energy. For example, it offsets how much energy people need from fossil-fuel sources.
In more detail, waste-to-energy produces energy that would take 49 million tonnes of fossil fuels through fossil-fuel energy production. This would emit up to 49 million tonnes of CO2. The precise amounts depend on which type of fossil fuel you compare against hard coal, lignite, gas or oil.
WtE does still produce CO2, but less than fossil-fuel alternatives.
Therefore, while waste-to-energy is not completely renewable, it does play an important role in reducing CO2 emissions from power generation. It’s an important companion in the move towards renewable energy.
The role of waste-to-energy in the circular economy
The circular economy centres around reusing and recycling to reduce waste. Therefore, in a circular economy, is there a place for waste-to-energy?
The answer is yes.
Recycling or reusing waste sits in the first tier of a renewable, sustainable system. However, waste-to-energy is a vital companion.
WtE helps to tackle waste that cannot be recycled or reused – for example, sanitary items. Other items that have been previously recycled and reused several times can degrade. They may reach a point where they are no longer viable for recycling. WtE solutions will transform the non-recyclable waste into a usable form of energy that is a high-value renewable energy source for the circular economy.
For a circular economy to be successful, waste that is still produced needs to be handled in environmentally-conscious ways. WtE is one of these ways that reduces the volume of waste going to landfills and uses it to produce energy.
Waste-to-energy, therefore, has multiple functions within the circular economy, working hand-in-hand with recycling and reusing.
Read about how Sterling TT is supporting the circular economy.
Advantages of waste-to-energy in a circular economy
1. Reduced methane emissions
Waste-to-energy reduces the volume of waste that goes to landfills (by around 87%). It, therefore, reduces the methane emissions produced by anaerobic decomposition in landfills.
Over 100 years, methane’s impact on global warming has been 28 times higher than CO2. A UN report suggested that reducing methane emissions has arguably the greatest potential of any strategy that decreases global warming.
Waste-to-energy, therefore, has an important role in reducing global warming and working alongside the circular economy to support renewable initiatives.
2. Reduces waste dumping
Waste-to-energy plants help to reduce the amount of waste dumping by providing a viable alternative.
Today, over 33% of global waste is openly dumped (source), contributing to pollution and groundwater contamination. In developing countries, two thirds of waste is dumped in open landfills, which not just threatens the environment, but also public health.
3. Bottom ash recycling
In addition, the bottom ash that remains in the furnace following the burning of waste is filtered to recover metals. These can then be reused or recycled, contributing to the circular economy.
While a circular economy seeks to eliminate waste, it needs to have solutions for when products do expire or it is not sanitary to recycle them. This is where waste-to-energy is a viable and helpful tool. It helps the world to move closer to functioning within a renewable and sustainable system.
Risk to recycling
There are concerns from environmental campaigners who think uptake of waste-to-energy would lead to a reduced focus on recycling. (Source)
Waste-to-energy shouldn’t be an alternative to recycling, but a way to use non-recyclable waste as fuel.
When used to its best, waste-to-energy works in tandem with recycling initiatives. It reduces waste going to landfills while materials that can be recycled continue to be so.
Challenges and barriers to waste-to-energy
If waste-to-energy has so many advantages and works so well within a circular economy, why isn’t it more widely adopted?
Currently, there are almost 2,500 waste-to-energy plants operating globally. According to a report by Tolvik, in 2020, there were 54 fully operational plants in the UK. The Digest of UK Energy Statistics (DUKES) 2020 reported that energy generated through the UK’s waste-to-energy plants contributed 2.5% of the UK’s overall energy output.
However, a common challenge, in seeing more uptake of waste-to-energy is not due to the technology itself but the public opinion. Known as the ‘not in my backyard’ (NIMBY) phenomenon, the public has a significant impact on whether or not a planned waste-to-energy plant can go ahead.
The public is often misinformed when it comes to waste management, and energy-to-waste plants in particular, with concerns including pollution, bad odours, increased traffic and other factors. Often, these concerns are unfounded but still mean locals vote against new waste-to-energy plants.
A key example is the reception to the Spittelau waste-to-energy plant in Vienna, which became a topic within political debates and public conversations.
In this case, public awareness of the risks of dioxins emitted by waste-to-energy plants grew, but with limited understanding of the actual science.
The mayor, Helmut Zilk consulted Green Party members on how to make this technology better perceived in the eyes of the people and had a local artist design the appearance of the plant to help it be better received.
A critical factor in improving the uptake of waste-to-energy is public education. There are a lot of assumptions and misconceptions in the public opinion that can lead to proposals for new plants being rejected by local residents.
Aside from public opinion, a common challenge is, unsurprisingly, cost.
Developing countries, in particular, have to be mindful of the lifecycle costs of waste-to-energy plants. They often have high capital and operating costs, which often puts them beyond the budgets of local and national governments’ abilities to finance.
However, even in higher-income countries, the cost is considerable. For example, the Amager Bakke waste to energy plant in Copenhagen is estimated to have cost around 500 million euros. It then experienced issues with the technical installation of combustion furnaces, leading to an additional cost of 13 million euros.
As technology advances, it is hoped that WtE plants will become more cost-effective, making them more viable.
The current regulation associated with waste-to-energy is the EU 2010/75/EC. It’s one of the strictest standards for waste management in the world.
Due to how highly regulated this waste management method is, it’s particularly difficult for developing countries to meet this standard – at least without significant additional costs.
Some advocates call for standards to be lowered to allow for increased uptake of waste-to-energy in developing countries. Once plants are established and have gained operating experience, standards can gradually be made stricter. (Source)
The future of Waste to Energy
Waste-to-energy can play a helpful role in the world’s move towards cleaner, renewable energy sources. By off-setting fossil-fuel power generation and supporting the circular economy, it can support efforts for a sustainable future.
However, there are obstacles still to overcome, from public opinion to better enabling uptake in developing countries, if waste-to-energy is to fully impact upon our move to a sustainable, renewable future.
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