City College of New York: Waste-to-energy can alleviate landfilling but misinformation is rife
27 May 2021 --- A new report by the City College of New York’s Grove School of Engineering has identified thermal conversion, also known as waste-to-energy (WTE), as an important component of US municipal solid waste (MSW) recycling.
The report highlights WTE facilities can offer significant environmental protection and reduce greenhouse gas (GHG) emissions.
However, “significant confusion and misinformation” around WTE practices runs parallel to growing interest in circular waste management solutions.
“The main misconception is that everything cannot be reused, composted or recycled for technical and economic reasons,” study author Professor Marco Castaldi, chemical engineering department at the City College of New York, tells PackagingInsights.
Despite WTE’s decade-long “proven method,” incorrect perceptions and dated information of facilities that operated nearly 30 or 40 years ago still preventWTE from becoming a mainstream complementary recycling aid.
“Local policymakers are struggling to manage daunting waste management challenges with outdated or erroneous information,” Castaldi adds.
“This report is an effort to provide officials with a single source of reliable information. My hope is that officials will be well-positioned to make policy decisions based on established facts rather than unsubstantiated claims.”
(Credit: Scientific Truth About Waste-To-Energy report)Counting up the costs
The US alone generates nearly 300 million tons of annual MSW, managed in the US in three ways. WTE treatment makes up just 12.8 percent of MSW, followed by primarily landfill (52.5%) and recycling and composting (34.7%).
According to the report, every ton of waste processed in a WTE facility avoids a ton of CO2 equivalent emissions when the GHG savings from recycling recovered metals are included.
Processing MSW in a WTE facility costs approximately US$90 per ton, Castaldi estimates. In contrast, landfilling MSW averaged US$54 per ton in 2020.
Castaldi’s report notes WTE could reduce the amount of waste sent to landfill by up to 90 percent. Currently, there are 76 WTE facilities in the US processing nearly 94,000 tons of MSW daily.
“China has built nearly 300 facilities in the last decade, which is about the number of facilities needed in the US to reach [the 90 percent] target,” says Castaldi.
Overall, WTE is estimated to be a US$10 billion industry, employing approximately 6,000 US workers and growing worldwide.
WTE differs by capturing energy
Significant differences between thermal conversion technologies have developed over the years. One of the main differences is the amount of oxygen used during the conversion process and therefore the achieved commensurate temperature.
These technologies span the range of air usage with pyrolysis operating without any air, gasification using near stoichiometric amounts of air, and combustion using excess air or a quantity of air greater than the stoichiometric requirement.
Using excess air led to combustion systems becoming the predominant thermal conversion technology. WTE differs from combustors that are classified as incinerators because of its energy recovery component.
In WTE facilities, the heat generated by waste combustion is transferred to steam that flows through a turbine to generate electricity. In some installations, there also is a direct sale of the steam to commercial customers for heating, cooling or other purposes.
(Credit: Scientific Truth About Waste-To-Energy report)WTE facilities and incinerators both use a high-temperature combustion process followed by air pollution control systems, but only WTE captures the energy released from combustion to produce power and steam while recovering additional materials for recycling.
Environmental benefits
Castaldi’s report highlights numerous studies that have quantified how WTE can reduce GHG emissions. For example, a recent UN report highlights how Paris avoids 800,000 tons of carbon emissions through its three WTE facilities. These savings are possible because the low-carbon electricity produced from WTE offsets electricity production from facilities that rely on fossil fuels.
Moreover, WTE plants currently recover nearly 700,000 tons of ferrous metal for recycling annually. This avoids CO2 emissions and saves energy compared to the mining of virgin materials for manufacturing new metals.
In terms of health impacts, the report affirms there is no scientific evidence WTE facilities adversely influence human health. Well-operated WTE facilities also destroy and remove viruses, enteric bacteria, fungi, human and animal parasites at a 99.99 percent efficiency.
Professor Marco Castaldi maintains waste-to-energy should be part of a holistic solution to sustainably manage municipal solid waste.Chemical recycling technology boom
Next to purification and depolymerization, thermal conversion is one of the three main chemical recycling technologies.
Rabobank predicts advanced recycling plants will double to around 140 plants globally by 2025 as regulatory and public demand for recycled plastics packaging drives “huge” investment.
For example, Plastic Energy has begun collaborating with ExxonMobil to convert post-consumer plastic waste in France into raw materials.
Innova Market Insights crowned “The Carbon Catalyst” as its second top packaging trend for 2021, highlighting packaging’s carbon footprint as a key indicator of environmental sustainability.
“Until global manufacturing and packaging practices change dramatically, we will have to contend with significant amounts of unrecyclable waste,” comments University of Maryland Professor Ashwani Gupta, a member of the peer-review panel.
In the meantime, landfill disposal and energy generation remain as the two main systems to manage unrecycled waste. “Every credible study conducted on this subject has concluded converting waste to energy is preferable to landfill,” she concludes.
By Anni Schleicher
