Jump to a frequently asked question:
Why does the county use waste-to-energy to manage garbage?
There are two choices for managing waste that cannot be recycled – you can bury it in a landfill or you can burn it for energy.
Processing waste at a waste-to-energy facility is environmentally and economically preferable to sending waste to landfills. Using waste-to-energy also helps Hennepin County comply the Waste Management Act, a state law that establishes a hierarchy for waste management practices. The waste management hierarchy places preference on using waste-to-energy technology over sending waste to landfills.
Read more about the environmental and economic benefits of HERC.
How are air emissions controlled at HERC?
HERC has an air emission permit from the Minnesota Pollution Control Agency (MPCA). The MPCA permit imposes strict air emission limits, outlines monitoring and testing requirements, and requires that facility operators undergo annual training. HERC’s air permit requires it to operate under very stringent U.S. EPA and even more restrictive State of Minnesota air pollution regulations.
Air emissions from HERC have consistently been below the MPCA permitted limits.
HERC is a state-of-the-art facility that is designed and operated to minimize air emissions. The flue gases from waste combustion pass through a series of air emission control devices.
- Air is injected into the boiler to control nitrogen oxide emissions.
- Activated carbon is injected into the exhaust gases to control mercury.
- Flue gases then pass through a dry scrubber, where a lime slurry is injected to control sulfur dioxide and hydrochloric acid.
- Combustion gases pass through a baghouse containing a series of fabric filters to remove particulate matter, metals and dioxins.
Only after this thorough filtration process is air emitted from the facility. Air emissions are monitored on a continuous basis for multiple pollutants.
How does waste-to-energy reduce greenhouse gas emissions?
Burning garbage at HERC reduces greenhouse gas (GHG) emissions in four ways.
- Generating electricity from solid waste reduces the need to generate electricity in conventional power plants that use fossil fuels such as coal and oil. An average Midwest power plant generating the same amount of electricity as HERC would produce 33,000 metric tons of carbon dioxide equivalent more each year than HERC.
- Metal is separated for recycling, which is more energy efficient than mining virgin materials for the production of new metals such as steel. More than 11,000 tons of metal is recovered and recycled each year.
- Less garbage is sent to landfills. Garbage in landfills create methane, which is a greenhouse gas that is 21 times more potent than carbon dioxide. The emissions saved each year by not landfilling the material sent to HERC amounts to 120,000 metric tons of carbon dioxide equivalent.
- Haulers bringing garbage to HERC travel a shorter distance compared to those bringing waste to a landfill, resulting in avoided vehicle emissions.
Is waste a renewable resource?
Minnesota defines waste-to-energy as a renewable energy source to help meet the state's goal of producing 25 percent of energy from renewable resources by 2025. Hennepin County has registered HERC with the Midwest Renewable Energy Tracking System to sell or trade renewable energy credits. HERC produces the equivalent electricity for about 220,000 renewable energy credits per year.
How does waste-to-energy affect recycling?
Statistics compiled for more than a decade have proven that waste-to-energy and recycling are compatible.
According to a report from the MPCA, residential recycling rates have typically been higher in communities with contractual commitments to waste-to-energy facilities than those without. Although this may seem counterintuitive, one reason may be that committing to waste-to energy facilities encourages those communities to pay more attention to their waste rather than relying on distant landfills that are “out of sight and out of mind.”
According to a report from the Integrated Waste Services Association, communities with waste-to energy facilities tend to have higher recycling rates because waste-to-energy is employed as a part of a fully integrated waste system that also includes waste reduction efforts, extensive recycling opportunities and the collection of household hazardous waste. Waste-to-energy also provides an opportunity to recycle ferrous metals that would otherwise end up in landfills.
Instead of sending garbage to HERC, can't we just reduce waste and recycle more?
Hennepin County is a national leader in recycling and waste reduction, and the county is continuously looking for ways to develop new, innovative programs. The county supports curbside recycling programs, operates drop-off facilities for proper disposal of household hazardous wastes, and has programs to encourage waste reduction and reuse opportunities. The county has also worked on developing recycling opportunities for new materials such as organics and mattresses.
The county’s Solid Waste Management Master Plan outlines strategies the county will implement to achieve a 45 percent recycling rate by 2015. But even with an increased recycling rate, there will still be some waste that will require disposal through waste-to-energy or landfilling. Garbage not delivered to HERC must be hauled out of the county to landfills. Even with recycling and waste-to-energy, Hennepin County sent 27 percent of the waste produced in the county in 2011 to landfills.
While Hennepin County works with partners to remove barriers to improve recycling in the future, we still need to manage the waste being generated today in the most environmentally preferable manner. That means reducing the amount of waste generated in the first place, recycling as much as possible, and processing garbage at HERC to produce renewable energy.
How is the ash managed?
Burning garbage to generate energy reduces the volume of the waste by 90 percent and the weight by 75 percent. The material remaining after combustion is a non-hazardous ash that is sent to an industrial landfill.
Because organic materials that were present in the garbage have been thermally destroyed, ash from HERC does not decompose and is more stable than landfilled garbage.
What is done to monitor and control odors at HERC?
County staff, known as Nasal Rangers, use a portable odor detecting and measuring device to monitor odors on and around the HERC site. The Nasal Rangers monitor every weekday from April through November.
A variety of measures are in place to keep odors in the building:
- Traffic patterns for trucks entering and exiting HERC were changed in 2009. Trucks now enter and exit the building through the one door on the 7th Street side of the building (rather than the side that faces Target Field). The pavement closest to Target Field was removed and replaced by landscaping.
- High speed doors have been installed on the waste tipping hall, minimizing the length of time the doors are open.
- The tipping floor has negative air pressure. Fans pull air from the tipping floor to be used in the boilers, helping to keep odors inside the facility.
- A product containing natural ingredients is used to neutralize odors.
- Roadways are swept and kept clean of debris from trucks.
- An air lock has been constructed at the entrance to the tipping hall