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| Fig. 1: Management of municipal solid waste in the United States, 2008. [1] |
In 2010, Americans generated nearly 250 million tons of municipal solid waste (MSW). Of that waste, 65 million tons were recovered through recycling and 20 million tons were composted. 136 million of the remaining 165 million tons of waste were discarded in landfills. The rest, 29 million tons (12%), was combusted for energy recovery. [1] Although this number has been growing, it still lags behind many European countries. Denmark converts about 30-40 percent of their waste into energy, and Sweden converts an astounding 45 percent. [2,3] We will look at why the United States lags behind these numbers, and how this catching up would reduce our dependence on fossil fuels.
The most common form of waste to energy is incineration. Trash is burned, creating steam to rotate turbines and provide electricity and heating. The amount of energy created by waste varies depending on the content, which in the United States is mainly composed to paper, yard trimmings, food scraps, and plastics. [1] According to the Danish Energy Agency, it is generally estimated that MSW produces 10.5 Mj/kg, or about 2600 kWh/ton. This means that 4 tons of waste produces roughly the same amount of energy as 1 ton of oil or 1.6 tons of coal. [4] However, the incineration plants only recover 20-25% of the energy, which is consistent with data showing that the average plant in the United States generates 563 kWh per ton of MSW combusted. [5]
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| Fig. 2: Total municipal solid waste generation by material, 2008. [1] |
The US has been making gains in reducing the amount of waste sent to landfills. In 1960, 94% of our waste went to landfills; today the number has been reduced to just 54%. Still, Denmark sends about 10% of its waste to landfills, and Sweden both sends just 4% of their waste to landfills. [2,3] Not only are we depositing our trash in landfills, we are shipping it to other places in the world. In 2010 our biggest export to China was "Scrap and Trash", totaling $8 billion. [6] Individual cities also ship waste to landfills, with New York City alone sending 10,500 tons of trash every day to landfills as fat away as Ohio and South Carolina. It is estimated that these transportation costs were over $300 million a year. [7] As of 2005, there are just 89 waste to energy plants in the USA, while Europe has 431. [8] If the United States could reduce the amount of trash sent to landfills to 10%, that would leave 140 million tons to be incinerated. Those 140 million tons, multiplied by 563 kwh, gives us approximately 79 terawatt hours of electricity.
When people think about burning waste, the first problem that comes to mind is pollution. It's easy to imagine that burning all this garbage will release toxins into the air, and when incineration plants were built in the 1980's, it was true. But the reality today is quite the opposite; emissions have been reduced by more than 90 percent since then. Waste sent to landfills actually generates more pollution though the release of methane gases than waste that is incinerated. [3]
Another argument made against incineration is that it decreases the incentive to recycle. If we look at the example of Denmark, we see that not only are they converting a larger percentage of their waste to energy, they are also recycling much more than us. [4]
Of course, the real reason that over 50% of our waste goes to landfills is because it is cheaper. A waste to energy facility costs hundreds of millions of dollars to build, while landfills, at least in the United States, are cost-effective. Unlike our European counterparts, the United States has an abundant supply of cheap land and cheap energy, so much so that even shipping garbage hundreds of miles from cities is still the most cost effective method. Prices are different in Europe, energy and landfilling costs are higher. Per kilowatt hour, Denmark pays roughly 40 cents, and Sweden pays about 25 cents. [9] This is in comparison to the United States where the average price is 11 cents per kilowatt-hour, Europe is 2 to 4 times more expensive. [10] The other important factor is the "tipping price" at landfills, or the cost to dump garbage. In the United States, it costs only $44 per ton, while the price in Sweden is $175 per ton. [11] The combination of these two factors is the real reason Sweden and other European countries are more advanced.
Europe is more advanced than the United States in terms of waste management, and has derived benefits fin terms of energy production. However, similarly to other issues in energy, it's economics that are at play. It's still cheaper for the United States to truck waste to landfills, and use fossil fuels for electricity and heating. When prices rise however, our trash may become energy treasure.
© John Gold. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] "Municipal Solid Waste Generation, Recycling, and Disposal in the United States: Facts and Figures for 2008," U.S. Environmental Protection Agency, EPA-530-F-009-021, November 2009.
[2] A. W. Larsen, C. Petersen and T. H. Christensen, "Bulky Waste Quantities and Treatment Methods in Denmark," Waste Manag. Res. 30, 147 (2012).
[3] "Towards a Greener Future with Swedish Waste to Energy," Avfall Sverige, 2008.
[4] "Waste-to-Energy in Denmark," RenoSam, 2006.
[5] N. Themelis, "Energy Recovery from Global Waste-to-Energy," Earth Engineering Center, Columbia University, 10 May 06.
[6] J. Allen, "America's Biggest Trade Export to China? Trash," US News and World Report, 3 Mar 10.
[7] E. Rosenthal, "Europe Finds Clean Fuel in Trash; U.S. Sits Back," New York Times, 13 Apr 10.
[8] "Energy from Waste: State-of-the-Art-Report, 5th Edition," International Solid Waste Association, August 2006.
[9] "Key World Energy Statistics, 2012," International Energy Agency, 2012.
[10] "Electric Power Monthly with Data for August 2012," US Energy Information Administration, October 2012.
[11] "Waste Management Benchmarking Study," Forfás, June 2006.