The old phrase that “where there’s muck, there’s brass” seems to ring true to an occasionally controversial part of the energy market.
Most homes and businesses accumulate garbage despite the best efforts to recycle. As if proof was needed of our throwaway society, humankind has created the floating Great Pacific Garbage Patch. This island, made up of 1.8 billion plastic pieces, has been dubbed the eighth continent.
One solution to our enormous trash problem is waste to energy (WTE), which essentially uses trash to create viable energy. It addresses energy production in a slightly different way from traditional fossil fuels or renewable energy systems. With waste to energy, waste disposal becomes an active part of the energy system. But is it the right way to approach our cast-offs?
Let’s roll up our sleeves, put on our protective gloves and goggles, get knee-deep into the development of waste management, and consider the pros and cons of turning waste to energy.
What Is the Waste-to-Energy Process?
The world produces about two billion tonnes of rubbish annually, with at least a third not disposed of or treated correctly. More than a third is dumped into a landfill, and just under 20% is recycled. Just over a tenth is incinerated, which is where waste-to-energy steps in.
WTE technology means municipal solid waste (MSW) no longer heads to landfill but becomes part of a circular economy of energy transference. Authorities turn trash into electricity, and there are sometimes other valuable byproducts.
There are three principal processes that occur at waste-to-energy plants. These are:
- Incineration
- Pyrolysis
- Gasification
The first, waste incineration, takes place at waste-to-energy power plants, also called WTE plants. The basic process takes the following steps:
- Garbage trucks dump trash or MSW into a pit
- Machines move the material into furnaces to be burned at high temperatures
- The released heat produces steam, which turns a turbine
- The turbine produces electricity
The process produces ash and also a gas called flue gas, which is reused to power the furnaces. In theory, any smoke from the burning rubbish is treated to remove pollutants and harmful particulates before being released into the surrounding environment through a smoke stack.
The second waste-to-energy method is called pyrolysis. This heating technique degrades plastics and other materials at high temperatures without oxygen. Residues from the process include oil that can be refined into petrochemical replacements, synthetic gases that are later burned, and a solid called biochar. Some solids left behind after pyrolysis can be used in building materials.
Finally, there is gasification. MSW materials are converted into synthetic gas called syngas. This syngas can then go through chemical processes to become chemicals, fertilizers, or transportation fuels. Syngas can even substitute natural gas for heating homes or powering natural gas vehicles.
What Do They Burn at Waste-to-Energy Incinerators?
Humankind has often burned materials considered waste, going as far back as the Stone Age. Back then, people burned animal droppings for heat or cooking. Fast forward 13,000 years, and we are still burning waste products, albeit with slightly different aims and for changing reasons.
Waste-to-energy incinerators have been around for a long time. New York built its first on Governer’s Island in 1885, burning almost a third of the city’s garbage for decades. Previously, some 75% of New York’s waste had been dumped in the Atlantic.
Nowadays, waste-to-energy power plants are capable of burning many fuels, also called feedstocks or biomass. Materials to burn include:
- Any residential or commercial waste previously intended for landfill, or MSW
- Organic waste, from food to paper to pharmaceuticals
- Manure slurries or sludges from municipal wastewater-treatment processes
So there really is brass where there is muck.
Why Do Waste-to-Energy Power Plants Burn Municipal Waste?
Greenhouse gas emissions causing climate change are big news, and landfill sites are part of the issue. Composting trash produces methane and carbon dioxide as a byproduct of a process called anaerobic digestion.
During its first 100 years in the atmosphere, methane is about 30 times more warming to the Earth than carbon dioxide. That ratio grows to methane being 85 times more potent than CO2 over the first 20 years of its release into the atmosphere.
Looking at the United States, municipal solid waste is the third-largest source of human-produced methane. Some landfill sites capture and reuse this methane, also called biogas, for burning to create electricity or purifying it into biomethane for use in adapted vehicles. However, uncaptured methane may escape into the atmosphere.
Some see WTE plants as a form of pollution control because they stop the garbage at the source. Regular trash doesn’t enter landfill sites and, ergo, can’t produce methane there. Instead, the waste treatment process sees garbage head to a WTE power plant where its burning produces electricity.
According to research, every ton of waste burned in a WTE plant saves a ton of carbon dioxide emissions had that trash gone to landfills.
Commissioning a rash of WTE plants to burn all our trash is not a panacea for our waste management systems. The toxic ash produced by incineration does still find its way back to landfill, albeit as a smaller mass.
Are Waste-to-Energy Plants Environmentally Safe?
Waste-to-energy plants offer a way to deal with potentially hazardous waste by burning it and making the most of the energy released. Industry leaders are keen to point out that WTE plants bring clean energy and many advantages:
- Reducing the amount of trash entering landfill sites
- Recovering energy from discarded materials (20-25% energy return at best)
- Reducing greenhouse gas emissions through the prevention of methane creation at landfills
- Residues like ash require less space in a landfill than trash and won’t produce methane once buried
- Metals in the garbage that melt during incineration can be recycled (700,000 tonnes of metal annually worldwide).
Indeed, some states recognize WTE plants as renewable energy sources, with waste treated as a type of feedstock or biofuel.
However, burning garbage is not a new energy technology. For years, incinerators and WTE plants have been subject to scrutiny by local residents and authorities. Many worry about their environmental impact, including:
- The increase in air pollution releasing dangerous dust, dioxins, and smells
- Creating a risk to human health from exposure to fly ash and bottom ash
- Releasing lead and mercury into the air
- Producing higher levels of greenhouse gas emissions compared to trash reduction and reuse practices
One new waste-to-energy incinerator in Holland, built in 2011, often contradicted its “state of the art” label. It regularly broke EU laws on pollutant levels as it burned everything from waste to sewage sludge.
WTE plants produce two types of toxic ash — fly ash and bottom ash. In Europe, the less-toxic bottom ash is reused in construction materials like building roads. In contrast, the two ashes are mixed and sent to landfills in the United States. Either way, lots of trash still ends up in landfill, just in a different form.
Other issues include people and authorities recycling less when they know the solid waste management system is just to burn garbage. For example, paper or plastics that may have been recycled are taken out of the energy system. Perfectly good materials go up in smoke.
WTE plants are not always top of the energy efficiency charts, either. Sales from electricity generated may not cover the expensive construction and running costs.
Finally, some large companies have also been accused of sending goods, returned via online shoppers, directly to incinerators rather than reselling or recycling them.
Can We Generate Renewable Trash?
There are more than 2,600 waste-to-energy power plants globally with more growth expected in the coming years. But is burning rubbish really renewable energy?
By definition, renewable energy is something that doesn’t run out and is replenished at least as quickly as it’s consumed. Humankind currently produces more rubbish than it burns, so one could argue that trash for burning is renewable. However, this ignores the fact that garbage only exists because we create it. The world has finite resources, so waste is limited and not renewable.
That hasn’t stopped some countries from aggressively pursuing a waste-to-energy policy. One state has even shown why renewable trash is an unachievable goal.
The European Union doubled its trash incineration capabilities between 1995 and 2019. The United Kingdom now burns half of its garbage. But it is Denmark that cancels the idea of renewable trash. The country built so many WTE plants that it needed to import waste from other countries to keep them working — the antithesis of renewable.
Can Landfills Be Used for Energy?
We can and do use landfill gas (LFG) to provide energy. Rotting waste in landfills undergoes a process called anaerobic digestion, which, in turn, produces biogases like methane and carbon dioxide. Landfill gas digestion occurs underground, meaning the methane must be sought out.
Perforated pipes wind their way through the deeply buried sections of landfill sites, collecting gas. The gas is then returned to a collection area of sealed tanks. From here, the gases can be compressed or added to the natural gas supply, completing the energy recovery journey from trash to gas.
The methane from landfills is considered biogas, which puts it under the bioenergy umbrella. Bioenergy sources are often classified as renewable energy sources. But it’s controversial. The methane from landfills is a greenhouse gas that causes global warming, and it would be hard to award it the renewable energy ticket.
What Is Renewable Natural Gas (RNG)?
Renewable natural gas (RNG) refers to gases sourced from the decomposition of organic matter.
All RNG has to be of high-enough quality to substitute standard natural gas as an energy source. That means RNG, also known as biomethane, needs to be pure enough for natural gas vehicles or as a fuel feeding people’s furnaces and stoves.
Landfill gas (LFG) is a renewable natural gas. According to the EPA (Environmental Protection Agency), “As of August 2022, there are 538 operational LFG energy projects in the United States and 470 landfills that are good candidates for projects.”
Waste-to-Energy Incinerators, Not Trash Talkers
Waste-to-energy as a concept has accompanied humankind since the Stone Age. Modern cities have burned trash on an industrial scale for a long time. Worldwide population growth means more garbage will be produced. The question is more about what we do with it. Do we recycle more or burn it?
There is an energy value contained within the trash. Leave it in a landfill, and the valuable but useful gas methane escapes. Burn it and release energy for electricity production and salvage useful metals. It’s also worth noting that the $10 billion waste-to-energy industry employs around 6,000 American workers and provides electricity to 2.3 million homes.
The flip side is that burning garbage may reduce the government’s and public’s appetite for recycling. Throwing trash in an incinerator seems as easy as throwing all the waste down the chute, out of sight and out of mind. The environmental impacts are many, from air pollution to burying toxic ash in the ground.
There are several MSW processing sites for various materials across Texas, so some of your power may come from burning trash. If you prefer your electricity to be clean energy, consider switching suppliers to one with renewable energy elements.
Brought to you by amigoenergy
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