Like all combustion processes (e.g., cars, trucks, fossil-fuel power plants, landfill gas to energy) and nearly all waste management processes (e.g., landfilling, composting, anaerobic digestion, recycling), Energy-from-Waste (EfW) facilities have air emissions. To minimize emissions, EfW facilities employ a carefully controlled combustion process with temperatures in excess of 2,000°F and sophisticated air pollution control equipment. Emissions are monitored both continuously and with periodic testing performed by regulator-approved third parties. 99.9% of what comes out of the stack is comprised of normal components of air, including water vapor, nitrogen, oxygen and CO2.

 

Since the implementation of stringent air pollution standards, such as the Clean Air Act Amendments of 1990, emissions from the industry have dropped dramatically, as the result of both closing outdated facilities and installing new air pollution control equipment. Emissions from Covanta’s facilities continue to decrease. Since the start of the company’s sustainability program in 2007, emissions of pollutants at Covanta operated facilities, as measured over the three-year period from 2016–2018, have decreased by up to 69% (Figure 1). In addition to our continued focus on operations and system optimization, our capital improvements are paying dividends in reducing emissions. The new baghouse installation we completed at our Essex County facility in 2016 continues to perform well, having reduced pollutants by up to 90%. Our proprietary low nitrous oxide system (Low NOx™), already installed in 24 units, helps us control NOx emissions and reduce reagent consumption. We are currently planning on installing the technology in nine additional units.

View Detailed 2018 Performance by Facility

These emissions reductions support Covanta’s strong record of consistently falling well below federal regulatory limits for emissions (Figure 2). More information is available in our white paper on EfW Emissions.

Covanta Americas 2016–2018 EfW Emissions Compared to 2007

Figure 1. Since Covanta launched its sustainability program in 2007, emissions of pollutants at Covanta-operated facilities, as measured over the three‐year period from 2016–2018, have decreased by up to 69%.

Covanta Americas 2016–2018 EfW Emissions Compared to Federal Standards

Figure 2. In the U.S., air emissions from Covanta usually operate at 60 to 90 percent or more below permitted parameters.

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Detailed Facility Performance

Select an individual U.S. facility to see detailed 2018 environmental performance on life cycle GHG emissions, electricity generation, metals recycling, emissions performance relative to federal guidelines and emissions compared to total emissions in the local county.

Our facilities use state-of-the-art control technologies to remove air pollutants associated with the EfW process.

Boiler Design:

Our boilers are specifically designed to ensure complete combustion, thereby recovering as much energy as possible out of the waste resource, including volatile organic compounds (VOCs) and other organic compounds.

Nitrogen Oxides (NOx) Control:

Most boilers are equipped with selective non-catalytic reduction (SNCR) systems, which inject ammonia or urea into the furnace to chemically convert NOx into gaseous nitrogen, a harmless gas that makes up the majority of our atmosphere. In addition, we have installed Covanta’s proprietary low nitrous oxide system (Low NOx™) in 24 units, which helps us control NOx emissions and reduce reagent consumption.

Carbon Injection:

After leaving the boiler, combustion gases travel through an extensive air pollution control system. At many of our plants, activated carbon is added to the flue gas stream as it exits the boiler. Gaseous phase contaminants such as mercury and dioxins adsorb to the surface of the carbon so it can be removed downstream in the baghouse.

Scrubber:

A scrubber neutralizes acid gases, including sulfur dioxide and hydrochloric acid, by spraying a lime slurry into the exhaust stream.

Baghouse:

Operating like a very efficient vacuum cleaner, the baghouse removes over 99.5 percent of the particulate matter from the combustion gases. As air is drawn through the baghouse, particulate matter and fly ash are caught on the surface of the bags. Periodically, the bags are cleaned by temporarily reversing the airflow or, in other designs, pulsing the bags with a strong jet of air. The particulate and fly ash are removed from the bottom of the baghouse.

Emission Monitoring:

All of our facilities operate under strict air pollutant control limits. To demonstrate compliance, we use a combination of continuous emission monitoring systems and stack tests performed at least annually.