Last updated on November 19th, 2019
Using our waste to power our homes sounds like a great idea. However, there are some added complexities involved in the process. Here we highlight exactly how waste-to-energy works and how you can benefit from it.
Waste-to-Energy Guide: I Give You My Garbage, You Give Me Energy
A few years ago, news stories circulated about Sweden ‘running out of garbage.’ This caught my attention and I began to research Sweden’s ‘Garbage to Energy’ program. As of 2018, Sweden had 34 waste to energy (WtE) plants operating, though it is still a small component of the country’s total energy production.
On the surface, this technology seems to be an obvious choice to resolve several key environmental issues: energy production, a reduction in methane that would be produced by waste decomposition, reducing the amount of fossil fuels being imported, and eliminating the environmental impacts of landfills.
It was a wonder that the rest of the world didn’t immediately follow suit! As it turns out, WtE plants are more common than the general public likely realizes with 431 operating across Europe as of 2005 and more than 86 operating in the US.
However, there are varying technologies, some better for the environment than others. Supporters of this idea see the technology as a win-win, but the industry does have some downsides and a lot of disinformation.
Detractors see this technology as little more than ‘greenwashing’, citing emissions of not only greenhouse gasses, but also toxic chemicals in their rationale.
The Process of Waste-to-Energy
There are many variations on the process, but at the most basic level WtE revolves around diverting municipal solid waste (household trash) from the landfill to the WtE plant. At the plant it is loaded into a processor.
From this point there are three main technologies: burning the waste and using the heat to boil water and turn a steam turbine (Figure 1), converting the waste to synthetic gas (Figure 2) as fuel for electric generators, or processing the synthetic gas into fuel for vehicles or planes.
For all available technologies, there are byproducts. Some of the byproducts are marketable, while others may need special treatment to dispose of safely.
Considered by itself, the efficiency of WtE electricity facilities may not be that good. The Sweden facilities operate at about 40% efficiency. This is seen as a detractor by some, but there are many opportunities to increase the efficiency rating.
In Sweden for example, the waste is burned, and the heat used to turn turbines to generate the electricity. To increase efficiency, the residual heat is then used to heat water. This water is then piped throughout the area to provide hot water for taps and hot water for radiator heating.
This is an excellent example of synergistic design and engineering, however, it required years of planning and adding the infrastructure to pipe the hot water throughout the service area.
Comparing the efficiency rates of WtE to more traditional thermal energy producers shows us that 40% really isn’t that bad.
- Conventional coal power plants in the US range from 35-38%. Natural gas facilities range from 32-38%,
- Hydro power ranges from 85-90%,
- Wind ranges from 30-45%,
- Nuclear operates at 38%, and
- Diesel engines range from 35-42%.
Check out the meaning of capacity factor to learn more about these efficiency ratings.
In the field of super clean coal technology, Japan has managed an average operational efficiency of 41.6%. This data is about 9 years old. Solar is not included as substantial gains in efficiency have been made in this time period.
In conventional incineration facilities, one ton of waste can produce 500-600KW of electricity per ton of waste. Newer gasification technology, one tone of waste can product up to 1,000KW of electricity.
Gasification technology has the added benefit of making byproduct separation more efficient and reliable.
Clearly, the environmental impacts from a waste-management perspective are significant. The environmental impacts from an air quality standpoint are more complicated.
Figure 1. Process diagram of Waste to Electricity Incineration Plant in Maine. clink link to go to the original source of this image.
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Sweden is doing it, why doesn’t the US?
In a word: oil. Big oil. The US is one of the largest oil producers in the world. The oil industry provides hundreds of thousands of jobs across the US in extracting, transporting, and refining. Because the US is such a major oil producer, the costs of using it are much lower than areas that rely on importing – such as Sweden.
The US political system is also inextricably intertwined with the oil industry with many politicians fighting any effort that could undermine this lucrative industry.
Sweden had another motivation lacking in the US – no room for major landfill operations. Whereas the US has an abundance of cheap, wide-open land.
In short – landfilling our waste and powering with oil is the path of least resistance, and it is familiar.
It should be noted that though Sweden has been getting most of the limelight for their efforts, many other countries around the world are also adopting WtE technologies. Denmark, Germany, Japan and, in particular, China have invested in such plants.
As of 2016, China had more than 300 WtE facilities operating with another 100 more under construction.
Despite the hurdles, there are a few WtE plants burning across the US. Beginning in the 70’s WtE plants began to be built and many thought they were a good answer to the accumulating trash problem.
Grassroots movements focusing on stopping such projects began to spring up as the public began to have easier access to technical information about the process and react to poor location choices that seemed to target disadvantaged and vulnerable communities.
Some also thought that WtE plants would jeopardize efforts to establish and grow a strong recycling culture to reduce waste.
The industry response to the public backlash and controversy in acquiring permits was to co-cite with other industries who add waste into their manufacturing kilns.
This is problematic. Such industries are not regulated the same way energy production industry is and are not required to report their emissions to the same level. This makes comparative studies to quantify and characterize emissions from the process difficult.
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The Problem: Is it Greenwashing?
The environmental impacts of this technology are not to be ignored. The residual ash remaining from waste incineration contains dioxins – cancer causing pollutants. The ash can also contain heavy metals, depending on what was in the waste.
A recent online post (February 2018) Ana Baptista, Assistant Professor of environmental Policy and Sustainability Management ad The New School) stated that WtE facilities in New York State produced up to 14 times the mercury, twice as much lead, and four times as much cadmium per unit of energy compared to coal power plants.
These toxins were released in spite of the facility fully complying with state air quality regulations. This is clearly a problem for the health and safety of those who live and work near the facilities. Industry and government regulators assert that emissions data touted by WtE opponents is outdated.
The EPA has approved emissions calculations from recent project proponents and approved projects. Opponents to the technology in Australia have stated that to burn a petroleum product (plastics) into energy should not be considered ‘green.’
The ecomaine plant has published its emissions stack test results on their website since 2000 in 4-year intervals. The test results clearly show a reduction in all pollutant emissions over the past 16 years for nearly all pollutants. This facility has managed to ensure that the long-term statistical average concentrations of measured pollutants is non-hazardous.
As with every industry, early pioneers face many hurdles, while subsequent developers reap the benefits of learning from the pioneer’s mistakes. More is now known about the rate of Co2 emissions from WtE plants and can compare these rates to the amount of Co2 created and released by methane at landfill sites.
The finding is that WtE is the only energy-producing technology that actually prevents Co2 from being created and released, while wind, solar and other renewables merely avoid creating new emissions.
Other industry opponents express concern that WtE plants will detract from local recycling programs. If the public knows their garbage is being turned into energy why should they take the time to sort out recyclables?
Careful planning in design and process can alleviate many of the pollutant concerns. The ecomaine WtE plant near Portland has been operating since 1998. This facility has state of the art emissions controls and has earned awards from the International Standards for Operation (ISO), an OHSAS 18001 certification for health and safety excellence in the workplace. The success of this facility is attributable to several factors.
The facility is co-sited with a recycling facility to streamline feedstock processing and ensuring that local communities maintain and improve their efforts at recycling. Although the public has been educated in what items should not be put in the trash, sometimes mercury containing items such as thermometers, fluorescent light bulbs and other things find their way into the facility.
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The ecomaine process was created to handle these types of contaminants. The facility also operates an aggressive community education and involvement campaign and strives for transparency.
To judge the environmental impact of different energy technologies based on its efficiency rating would not show the full picture. To consider the full environmental impact one must include issues such as location, emissions, and waste streams from each technology.
Nuclear is considered clean energy; however, natural gas has emissions at the extraction site as well as in energy generation and fracking technology impacts are only beginning to be understood, and the waste is the most dangerous of the industry.
Coal may have decent efficiency, especially considering the newest clean coal technology, however, there are still dangerous polluting emissions, environmental impacts of mining operations and even air current and microclimate changes where mountaintop removal is being used.
These lines have been creating huge fire hazards, particularly in the western US.
The Co2 emissions and other pollutants associated with forest fires such as the Paradise fire in northern California last year are not included in the emissions calculations of each technology.
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The Future Outlook for Waste-to-Energy
The US is becoming more focused on the concept of sustainability. Some of the main tenets of this movement include finding synergistic uses for bi-products and waste streams with other industries. In this capacity, WtE fits very well.
The renewable energy industry has been booming for more than a decade and will continue to grow with California’s 2018 mandate to be fully powered by renewable energy by 2050.
As California gets closer to that goal the limitations of renewable energy are in the spotlight – even with a mix of renewable technologies the flow of power into the power grid is uneven and at times unreliable.
Backup solutions are required to stabilize the flow of power. Energy storage technologies are progressing, however, are not economically efficient at this point.
WtE has the potential to help California reach its lofty goals. Another upside to the WtE industry is the potential to decentralize energy production.
Every community has a waste stream and every community has the potential to provide a portion of its power from WtE.
As always, it is the process that determines the outcome. Any power plant that that doesn’t pay attention to proper siting, environmental mitigation, supply chain, and climate resiliency is a lost cause, and can do as much harm as good regardless of their emissions.
While early WtE facilities may have had greenhouse gas and emissions issues newer technologies have come a long way to not only being able to separate emissions and byproducts from the finished product, but also finding ways to market many of the byproducts or ensuring for their safe and environmentally responsible disposal.
WtE is certainly not ‘clean’ energy, but it is a superior alternative to coal and other polluting alternatives, and with proper design can be made to be nearly as clean as natural gas – all while preventing our landfills from filling up.
This is a technology to watch out for.
There is great potential for expansion and advancement of the industry. And with developer commitment to transparency, collaboration with environmental groups, and public education there is potential to create a supportive environment to siting and permitting facilities.
What do you know about waste-to-energy? Please let us know in the comments below. I’d love to hear from you.
Sandra Pentney, MA, RPA, ENV SP
Sandra started her professional life as an archaeologist. Her career evolved into preparing environmental reviews of renewable energy projects across the United States. She has a passion for renewable energy and sustainability and has recently completed her certification as an Environmental Specialist through the Institute for Sustainable Infrastructure. As an archaeologist her concern with waste to energy plans includes seeing a shortage of work for archaeologists in 200 years!