Pop Quiz: What provides Americans more energy, Solar or Trash?

The answer?  Trash, by a mile.

According to the U.S. Energy Information Administration’s most recent Renewable Energy Annual, waste is responsible for 0.452 quadrillion Btus (quads) of renewable energy consumption while solar thermal and PV combined account for only .098 quads.  In other words, waste provides nearly 5 times the energy as does solar.   Looking at just electricity generation, the difference is even greater: 0.272 quads for waste and only 0.009 quads for solar, a difference of 30 times!1

Source

Energy Consumption for Electricity Generation (quads)

Geothermal

0.146

Hydroelectric

2.669

Solar Thermal/PV

0.009

Waste

0.272

Wind

0.721

Wood and Derived Fuels

0.320

Source: EIA Renewable Energy Annual 20091

Energy is produced from waste in two main ways: landfill gas and waste-to-energy.  Gas pockets build up within landfills as bacteria break down the municipal solid waste (i.e. trash), producing methane.  This landfill gas can be harvested and used to generate power.2  For example, Waste Management, North America’s largest provider of environmental services, gathers landfill gas from 130 of its landfills, producing 550 MW of power.3

Waste-to-energy is a more direct means of producing energy from waste.  Instead of being dumped into a landfill, Municipal solid waste (MSW) is directly burned to generate electricity.  According to the EPA, there are 87 MSW-fired plants in the U.S., generating 2,500 MW.  Burning MSW, however, shares many of the same drawbacks as conventional fossil fuel generation including air emissions, water use and water contamination.4

This month Wired Magazine featured S4, a company that is developing an emissions-free alternative to traditional incineration – plasma gasification.  In the first stage of S4’s process, the majority of the MSW input is transformed into syngas within a 1,500o F furnace.  A blast of 18,000o F plasma then breaks the remnants into gas products that can be made into fuel or other products.   This is an amazing, but energy-intensive process and commercial success will depend on producing more power then is consumed.

We typically don’t think of our refuse an energy resource, but maybe it is about time that we should.

References:

  1. Renewable Energy Annual 2009, U.S. Energy Information Administration, January 2012. http://www.eia.gov/renewable/annual/pdf/rea_report.pdf
  2. Landfill Gas, U.S. Environmental Protection Agency.  http://epa.gov/lmop/faq/landfill-gas.html
  3. Renewable Energy. Waste Management. http://www.wm.com/sustainability/renewable-energy.jsp
  4. Municipal Solid Waste. U.S. Environmental Protection Agency.  http://www.epa.gov/cleanenergy/energy-and-you/affect/municipal-sw.html
  5. Wolman, David. High-Powered Plasma Turns Garbage Into Gas. Wired Magazine, February 2012. http://www.wired.com/magazine/2012/01/ff_trashblaster/
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2 Comments

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2 responses to “Pop Quiz: What provides Americans more energy, Solar or Trash?

  1. sarobinson

    Waste to energy (WTE)/landfill gas is a great opportunity to capture resources that would otherwise be wasted, and thus, is a notable component of a national energy strategy. While it is worth noting that waste to energy (WTE) currently is responsible for more electricity generation in the United States than Solar (CST + PV) it is unlikely that this will be the case for much longer:

    As of 2009, the planned generating capacity additions through 2015 for Solar was listed by EIA as 8,295MW compared to 478MW for all “Other Biomass” which includes WTE and several other sources. That is a factor of 17.

    This planned installed capacity can be expected to rise considerably given the recent freefall of solar PV panel prices.

  2. katelyncolwell

    Both harvesting landfill gas and waste to energy are proving to be very viable options. However, with waste to energy, unsorted trash is burned to create electricity. This means that potential recyclables will be lost. I found a Canadian company, Enerkem, that has found a way to first sort the trash and then create a move valuable product. They remove metals, recyclable plastics, paper, and glass and then use the remaining non-recyclable plastics to create a synthetic hydrocarbon gas. Through their proprietary thermodynamic process, they convert this gas into methanol and ethanol. They first prep the feedstock (sorting). Then they gasify the non-recyclable plastics. This synthetic gas (syngas) is then cleaned and conditioned. Finally, the gas undergoes a catalytic synthesis, producing ethanol and then methanol.
    This seems to me like a great way to recycle carbon. It would reduce the size of our landfills and also increase our supply of natural gas and biofuels. Enerkem has three of these plants in construction and development.

    Resources:
    http://www.enerkem.com/en/facilities/plants.html
    http://green.blogs.nytimes.com/2009/10/05/quebec-company-turns-trash-into-fuel/

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