Ensuring clean emissions

Recovering energy from the combustion of solid waste is a key component of the waste management hierarchy for the planned Cayman Islands Integrated Solid Waste Management System. While modern waste-to-energy facilities are a far cry from the smoke-belching incinerators of the past, misconceptions about emissions linger. 

So, what’s the truth? Are waste-to-energy facilities a safe alternative to landfilling, or do they spew dangerous emissions? Dart Engineering Coordinator Martin Edelenbos says the answer might surprise you. 

"Unfortunately, waste-to-energy facilities are still tainted by the reputation of incinerators of the past that would not come close to the modern-day emission standards,” he says. “In the U.S. for example, the implementation of Maximum Achievable Control Technology standards under the Clean Air Act in the early 1990s significantly reduced emissions, in many cases by more than 95 per cent. And similar reductions in emissions were achieved under European standards.”

Data from the United States Environmental Protection Agency shows that vehicles are responsible for the majority of the volatile organic compound, carbon monoxide, and hazardous air pollutant emissions, and fossil fuel electricity generators are responsible for most of the mercury and particulate matter generated.

“When you take into consideration the emissions generated as a result of on-the-road vehicles and fossil fuel electricity generation, the emissions produced by a waste-to-energy facility are negligible,” Edelenbos says. 

Modern waste-to-energy facilities employ a number of chemical and physical mitigation technologies to filter out harmful chemicals and material that cannot be burned, he says.

"Waste-to-energy facilities produce two types of residue: fly ash and bottom ash,” Edelenbos says, adding that a relatively small amount of fly ash is produced by the air pollution control technology, and that it contains toxins such as heavy metals that are removed from the emissions. Bottom ash, which represents about 25 per cent by weight of the incoming waste, is the relatively inert material discharged from the waste combustion furnace, he says.

Although fly ash on its own is classed as a hazardous waste, with further treatment, fly ash can be safely disposed of in an engineered landfill. Bottom ash contains ferrous and valuable non-ferrous metals that can be removed and sold to overseas buyers, while the remaining bottom ash can be used as secondary aggregate in construction.

"Compare this to allowing the waste to be sent to landfill where it releases harmful methane and takes up space,” Edelenbos says.