Modern waste incineration plant in Denmark

What Should We Do About Garbage? A Burning Question

The Waste-to-Energy plant “Amager Bakke” in Copenhagen, Denmark. Photo credit Niels Quist/Alamy stock photos.

Most people do not enjoy talking, or reading, about garbage. For one thing, it’s boring. But it’s also disturbing: garbage imposes great costs on our economy and our society. The biggest problem is simply the amount of garbage we produce. For example, in 2015, two kilograms (4.4 pounds) of Municipal Solid Waste was generated per citizen of the USA every day (MSW is the fancy name for garbage). This number includes industrial and commercial waste. For the country as a whole that comes to 260 million tons a year, as reported by the Environmental Protection Agency, EPA.

(The following abbreviations will be explained, and used: MSW – municipal solid waste; WTE – waste to energy, i.e. burning garbage directly to produce energy; LFGTE – landfill gas to energy, i.e. collecting methane from landfill and using it to generate energy; EPA – the US Environmental Protection Agency)

The mountain of garbage

The following quote from the web site SaveOnEnergy conveys the magnitude of MSW waste:

[In the USA the garbage produced includes. . .] 22 billion plastic bottles every year. Enough office paper to construct a 12-foot-high wall from Los Angeles to Manhattan. It is 300 laps around the equator in paper and plastic cups, forks, and spoons. It is 500 disposable cups per average American worker – cups that will still be sitting in the landfill five centuries from now.

Let me add to this image: 59 billion coffee pods, the devilish little conveniences for making pretty good coffee with the push of a button, are used worldwide each year. Those empty pods, laid end to end, would circle the equator more than 65 times. From the number used in the USA alone each year (75 million people make at least one cup a day, so this is a conservative estimate), you could build a wall extending from New York City to Los Angeles 1.3 meters high by 1.3 meters wide (4 feet by 4 feet). The Great Wall of America. And that’s just coffee pods.

From dumps to landfill sites

There are several things you can do with MSW. First, you can try to reduce the amount of it, which is always a good idea. We North Americans use the greatest amount of energy per capita of any large countries in the world, and also produce, per capita, the largest amount of MSW. The two are undoubtedly related.

Before the mid-1970s, most municipalities in America threw their municipal waste into holes in the ground called “garbage dumps”. Dumps were less than ideal. When biogenic waste such as food scraps and wood-based material decays under anaerobic conditions it produces methane, which is a much more potent greenhouse gas than carbon dioxide (see my previous post about methane). Dumps also contaminate ground water and soil with toxic materials that leach out of the garbage. And then there is the problem of space: so many dumps, so much land.

The government of the United States passed legislation in 1976 that made the old style of garbage dump illegal. That began a movement to ever larger and better-controlled “sanitary landfill” sites (notice how much nicer “sanitary landfill” sounds than “dump”?). Landfills must control leaching by having plastic and clay linings. The liquids that accumulate are treated as noxious material, and disposed of. Landfills must have systems of pipes to collect methane and burn it off to produce relatively less climate-destructive CO2. Some landfills produce useful heat and electrical energy from the collected methane. This technology is called “Land Fill Gas to Energy”, LFGTE.

Some problems with landfills

As landfills became larger and better equipped, they also became more expensive to set up and maintain. The result has been a drastic reduction in the number of places MSW can be disposed of. From an estimated number of over 10,000 garbage dumps before 1976, there are today fewer than 2,000 landfill sites in the United States. That, plus the increase of MSW, has resulted in many municipalities hauling ever more waste to distant landfill sites.

The transportation of MSW to landfill sites itself presents environmental costs. New York City, for example, has to dispose of about 5.4 million metric tonnes (6 million short tons) of MSW each year. Since there isn’t enough affordable space in the city, about 80% goes to sites in surrounding states and upstate New York. Transportation and landfill access costs are in the order of a third of a billion dollars annually.

Not only major cities are running out of landfill space; according to the Global Citizen website (here), the USA is on pace to run out of room in landfills within 18 years. The Northeast is running out of landfills the fastest, while Western states have the most remaining space.

Incineration of solid waste

The little town I grew up in many decades ago had no garbage collection service. So we burned garbage in a barrel out back. Of course, this was terrible for the environment; used on the waste produced by a modern city it would be devastating. But a lot of garbage is burned today, albeit using much better technology. This is done at facilities where household and other waste is burned and the energy produced is used to provide heat or electrical energy. This technology is “Waste to Energy” (WTE), and is quite different from LFGTE.

Waste to energy is more popular in several European countries than in North America, for several reasons. For one thing, Europeans have much less space for landfill. For another, there has been a great deal of opposition to WTE in North America by environmental organisations such as Greenpeace, and in my own country, the David Suzuki Foundation. The basis for that opposition will be explored in the following sections.

Epitomizing the European embrace of waste to energy is the plant “Amager Bakke”, designed by Bjarke Ingels Group, located in Copenhagen, Denmark (the picture at the top of this post). It produces electricity and hot water for heating, and is considered to be safe enough that it is located next to a leafy suburb, less than a kilometer from the Opera House and downtown Copenhagen. The sloping roof has been developed into a ski run.

One frequent criticism of WTE in North America is that it produces the greenhouse gas CO2, as indeed it does. But when waste to energy is used on biogenic waste it is pretty much greenhouse gas neutral, as the carbon in biogenic materials originates from CO2 captured from the atmosphere. The only net greenhouse gas production comes from the combustion of petrochemical-based materials like plastics, and these should not be in the waste flow. All parties interested in reducing our impact on the environment agree that we need to reduce plastic use and recycle it after use. There’s really no alternative on that issue.

Methane can be collected from landfill sites by LFGTE technology, sp why not just do that, and forget about WTE, at least in places where space for landfills is still available? One reason is that LFGTE is less efficient. This is measured by the CO2e yield per amount of electrical energy produced (the CO2 equivalent factor is explained in a previous post; it relates the effects of all gases, including methane, to the amount of CO2 in terms of greenhouse effect). The CO2e per million kilowatt-hours of electricity generated for WTE (direct burning of waste) ranges from 0.4 to 1.5 million tonnes. The best for LFGTE is 2.3. In other words, LFGTE produces far more greenhouse gases than WTE (1). It also results in higher nitrogen oxide emissions.

The Green objections to WTE

In 2011, Dr. Heather Youngs of Berkeley University wrote a report for the California Council on Science and Technology. It listed the possible benefits and risks of WTE. (It can be downloaded here) The benefits include the decreased need for landfill sites. Also, less greenhouse gas emission, because WTE replaces conventional fossil fuels in generating energy. (There is a misleading claim floating around the anti-WTEsphere that WTE produces less electrical energy per CO2 emitted than coal. This is not true if petrochemical products are excluded from the waste stream, as they should be. And the CO2 released by burning coal has been sequestered for millions of years; its release contributes global warming. The CO2 from burning biogenic materials has recently been captured from the atmosphere.) Reduced transportation costs, both in dollars and CO2 emission, are also among the benefits, most of which are either self-evident, or have already been described. The negative effects will be examined individually.

From the Youngs report

Possible benefits of WTE Possible negative impacts
Decreased landfill burden Disincentive to waste reduction and recycling programs
Decreased greenhouse gas emissions through offset of fossil fuels Increased air and water impacts with a disproportional effect on already stressed urban areas
Reliable, local, low-carbon electricity that could fill response gaps of intermittent renewable like wind and solar High costs may force scaling and lifetime of facilities that is contradictory to overall conservation goals – potentially exacerbated if companies receive renewable credits
Local energy source (fuels or electricity) Financial risk for communities if technology is unreliable
Little transportation required to process waste It’s inefficient and expensive (DTS Foundation)

Will WTE be a disincentive to recycling solid waste?

One criticism is that WTE facilities will need a constant stream of waste, which will reduce efforts to recycle and re-purpose it. While there is a potential logic to this, in practice there is no evidence for it where WTE plants are currently operating in Europe. Countries with high levels of WTE also have high levels of recycling, much higher than in the United States. This is probably because those European countries have taken a comprehensive approach to waste management, which includes intensive recycling. The means of treating MSW in several European countries and the United States are shown in the followig graph, taken from “Why Not Burn Waste”, by Shawn Lawrence Otto, available here.

Waste to energy conversion in Europe and the USA
Levels of different modes of waste disposal in European countries and the USA in 2013. Data are from Confederation of European Waste-to-Energy Plants, European Environmental Agency, and Columbia University. By kind permission of Shawn Otto.

Germany, for example, sends 38% of its MSW to WTE facilities, and recycles 62% – and no landfill! The comparable numbers for the USA are 7% WTE, 24% recycling and composting, and 69% landfill. And within the USA, communities with WTE facilities typically recycle more than those that don’t; in 2004, the rates were 34% for WTE communities and 31% for those lacking WTE (see the article). The data shown are for 2013; the USA has increased its level of recycling somewhat since then.

The financial questions about waste incineration

The answers to some questions about the financial costs of WTE depend on a number of external variables — for example, how effective recycling efforts become, and the costs of other forms of energy. But the relative cost effectiveness under present day circumstances is being proven daily at WTE facilities in Europe. For example, in Sweden, the plants that generate electricity and heat by burning waste generate operational profits. But the calculation of total costs and benefits is complex, and includes estimations of the lifetime costs of facilities and their operation.

Toxins in incinerated waste

Probably the most important critique of WTE is related to its safety. This is the issue raised most often by organizations such as Greenpeace and the David Suzuki Foundation. And in fact, toxins were present at significant levels in flue gases from incinerators when Greenpeace first put out its anti-WTE statements twenty years ago. But the technology for removing toxic materials has improved profoundly in the past 20 years, and has led to greatly reduced emissions. The levels of the metals mercury, cadmium, and lead in flue gases has been reduced by more than 96% in the USA, according to the EPA.

The metals present in incinerated waste are condensed into solid ash, or trapped by scrubbing flue gas. These trapped solids can be handled more safely than the same metals in the leachate of landfill.

Toxic substances in the environment arise from many sources. For example, in a study of urinary levels of chromium, manganese, and platinum in people living near a WTE site in Italy (2), these were found to be higher near high vehicular traffic and certain industrial sites than near the WTE site. Arsenic and cadmium were affected more by fish intake and tobacco smoke, respectively.

A group of compounds known as dioxins are of great concern in municipal waste. These are organic compounds that are known to cause cancer in animals and probably in humans. They’re bad actors, no doubt. Because WTE facilities operate at such high temperatures, dioxins are destroyed during combustion. However they are produced in small amounts within the flue gas in the presence of certain chlorinated materials. So, in modern plants they are “scrubbed” from the emitted flue gas.

But it is still important to measure the concentrations of toxins actually emitted and present in the environment. This has been done. In 1987 municipal waste combustors in the USA produced about 18 pounds of dioxin, and medical waste incinerators added another 5 pounds. In 2005 the total emission was estimated to be less than a quarter ounce annually, a reduction of greater than 99.9% (EPA).

Another study, in France (3), showed that dioxins and furans (another toxic organic substance that is considered dangerous to human health) were at levels well below those considered unsafe. The major source of dioxins in 2012 was residential woodburning, which produced more than 250 times as much of these toxins as all of the WTE and medical incineration facilities together. In North America, exposure to dioxin in the air contributes less than 2% of our exposure from eating foods such as meat and eggs, as documented here.

Landfill keeps metals and organics that are known hazards to human wellbeing in the biosphere. Leachate must either be stored on the landfill site in dilute form, or treated with still emerging, expensive, technologies, or disposed of through sewage. WTE facilities either eliminate them (dioxins, furans, other organic substances such as antibiotics) or condense them into compact, solid ash that can be handled and stored more safely.

Safety of waste incineration plants

Some of the toxins in MSW are still present after it is processed even through a modern WTE plant. Are they present at unsafe levels? Measuring them in the ash or flue gas doesn’t prove that they don’t accumulate in the environment around such a plant, or in the bodies of people working there, or living nearby. Studies that measure such accumulations are now beginning to appear. Most have been done in Europe, understandably, since incineration of MSW is more common there than in North America.

Although some earlier studies (4) suggested that workers at MSW incinerators had an elevated level of mutagens in their bodies compared to the general population, these conclusions (published in 1992) were found not reliable on retesting, and in any case, involved plants with older technology, before the remarkable reductions in toxins noted already.

Studies in the “modern era” suggest WTE plants do not significantly contaminate their surroundings. One study, comparing levels of toxic metals before, and one year after, the start of operations of such a plant in Turin, Italy concluded, “at current knowledge, living near the Turin incineration did not significantly influence the exposure status of the population” (2). Another survey found that between 1997 and 2016 the environmental concentrations of dioxins and furans near a hazardous waste incinerator in Spain actually decreased significantly. Presumably because of better waste disposal generally. The study concluded that the local population was not at increased carcinogenic or non-carcinogenic risk (5). A similar assessment at a (different) Spanish hazardous waste incineration site came to the same conclusion. (Again, the overall levels had decreased with time, presumably because of an improving environment generally.) (6) Areas close to the site were no higher in these toxins than those further away.

Another kind of analysis, also carried out in Italy, estimated the lifetime risk of lung cancer due to the buildup of Polycyclic Aromatic Hydrocarbons, heavy metals, dioxins, and furans near an incinerator (7) (all of these agents have been designated as potential carcinogens by the International Agency for Cancer Research). No increased risk was found.

Although the available evidence indicates that modern WTE plants are safe, continued monitoring and further studies are needed as new technology takes hold. It isn’t enough to monitor air quality or the levels of toxins in surrounding land; what is also needed are careful, longitudinal studies on the people who work at such plants and live near them. Both body burdens of toxins, and long-term health outcomes need to be measured.

The leaders of the city of Copenhagen clearly accepted the safety of the modern WTE plant when they located it near the city centre.

The perfect is the enemy of the good

In a perfect world we would not need to employ either landfill or WTE — we would reduce our use of materials, and recycle waste that couldn’t be avoided. However, municipal waste will be around for the foreseeable future. The question then is how best to deal with it. Arguments against WTE abound on the Internet, almost all of them “adjective-based” and non-quantitative in nature. But quantitative arguments show that WTE is, in the words of the late Lewis Thomas, a useful “half-way technology” which, for now, can help us get to the best future.

Sources cited (a number of sources are on-line, and these have been linked in colour in the text)

  1. Kaplan, Decarolis and Thorneloe, “Is it Better to Burn or Bury Waste for Clean Electricity Generation?”, Environ. Sci. Technol., 43:1711 (2009).
  2. Ruggieri et al: “Human Biomonitoring Health Surveillance For Metals Near a Waste-to-Energy Incinerator: The 1-year Post-Operam Study”, Chemosphere, 9:225:839 (2019).
  3. Nzihou, Themelis, Kemiha and Benhaou, “Dioxin Emissions From Municipal Solid Waste Incinerators (MSWIs) in France”, Waste Management, 32(12): 2273 (2012).
  4. Ma et al., “Mutagens in Urine Sampled Repetitively From Municipal Refuse Incinerator Workers and Water Treatment Workers”, J. Toxicol. Environ. Health 37(4):482 (1992).
  5. Marques et al., “Concentrations of PCDD/Fs in the Neighborhood of a Hazardous Waste Incinerator: Human Health Risks” Environ. Sci. Pollut. Res. Int. 25(2):26470 (2018).
  6. Zubero et al., “Changes in Serum Dioxin and PCB Levels in Residents Around a Municipal Waste Incinerator in Bilbao, Spain” Environ. Res. 156:738 (2017).
  7. Scungio et al.,”Lung cancer risk assessment at receptor site of a waste-to-energy plant”, Waste Manag. 56:207(2016).

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