Rummaging through trash to find clean energy

Gepubliceerd op 21/08/2019

Landfills around the world are filling up. In 2016, humanity generated over 2 billion tonnes of waste. In the next 30 years, that figure is expected to grow to 3.4 billion.

 

Where will all this waste end up?

A recent report by UN Environment’s International Environmental Technology Centre outlines one technology that has the potential to reduce the volume of waste entering landfills by up to 90 per cent.

Waste-to-energy plants have been around for over 100 years, but today their use is on the rise, with many seeing the plants as a quick-fix solution to growing waste challenges. This phenomenon is especially apparent in Asia, where some 1,200 of the 1,700 plants worldwide are found. Japan alone maintains over 700. China is on track to increase the number of their plants by over 50 per cent, according Yuanyang Ou of SUS Environment, a Chinese investor and operator of waste-to-energy plants.

The core concept remains largely the same as a century ago. Burn solid waste at high temperatures so that the waste is eliminated and use the excess heat to power turbines and create electricity.

Historically, this would also produce significant amounts of ash and toxic gases. Today’s waste-to-energy plants, however, are much cleaner. Advanced technologies help to burn waste at extremely high temperatures, which ensures complete combustion. Emissions are also specially treated, which leaves minimal amounts of toxic byproducts like flue ash. Some tests have even shown that the air emitted by certain waste-to-energy chimneys can be cleaner than the air flowing in.

“Removing waste is the primary benefit of these plants, but not the only one,” says Ou. “Energy capture mechanisms ensure that excess heat can be used for electricity generation.”

Globally, 1 per cent of renewable energy already comes from waste.

Keith Alverson, director of the UN Environment Programme’s International Environmental Technology Centre, points out that the climate benefits of waste-to-energy extend beyond renewables.

“Waste-to-energy plants can also reduce greenhouse gas emissions compared to open burning and landfills,” he says.

“Open burning does not happen at a high-enough temperature for complete combustion, so emissions are dirty. And in landfills, biomaterial will decompose and emit methane, a powerful greenhouse gas.”

While they are typically clean, a mismanaged plant will produce unsafe byproducts, even with advanced emission control technologies. In countries where there are detailed regulations governing waste-to-energy plants, it’s less of an issue. But where countries don’t have strategies for maintenance and monitoring or guidelines on health and safety, there is a much higher risk.

The plants are also hungry beasts. A large-scale modern thermal waste-to-energy plant requires between 100,000–300,000 tonnes of municipal solid waste per year over, delivered daily over its lifetime. If an operator can’t procure enough waste, some plants could potentially drop below their optimal operating temperature. When that happens, efficiency drops, and the risk of toxic emissions is increased.

In an extreme scenario, operating a plant may mean a government has to import waste, or add coal to the waste stream, just to feed the fires.

And while a waste-to-energy plant may significantly reduce the amount of waste going to landfill, it does not eliminate the need for them entirely. The residues that such a plant does produce are hazardous and require safe disposal.

Even with all of the downsides, the increase in the number of waste-to-energy plants is not slowing down. While the refrain used to be NIMBY—“not in my backyard” —these days it’s just as likely to be PIMBY—“please in my backyard”.

“The benefits of the plants are clear, but the technology is not without its problems,” says Alverson. “For those countries eyeing the technology, getting the regulations and the legislation right will ensure the technology does more good than harm.”

Learn more about UN Environment’s work on chemicals and waste.

 

Source: © United Nations Environment Programme