Tuesday, May 17, 2011

The Challenges of Finding Truly ‘Clean Energy': The environmental impact of wood stoves compared to solar, wind, oil and gas

Some peope think the smoke from biomass stoves (wood, corn, pellet) should take this technology out of the “clean energy” basket. However, biomass stoves are like every other energy source, renewable or not, in that they have both obvious and hidden environmental impacts.

One of the biggest fallacies of emission charts comparing wood and pellets with oil, gas and electric is that they only compare emissions at the point of combustion. The pollution generated by extracting and refining oil and gas, as well as generating electricity, is too often outsourced and not visible to the consumer. By not counting the emissions those fuels create in other communities and other countries, we are only reinforcing the classic not-in-my-backyard argument.

Even wind turbines and solar panels have negative environmental impacts associated with the energy and chemical intensive processes required to manufacture them. These issues, however, are often overlooked by the consumer. In a way, the obvious negative effect of biomass heat - wood smoke – forces us to demand that it be made cleaner. If we didn’t see it, there would be less pressure to design cleaner-burning stoves. Even domestic issues in energy production, such as mountaintop removal, can take a long time to gain a widespread movement calling for cleaner and greener practices.

Solar is a great technology in many ways, one which will hopefully continue to gain widespread use. It offers one of the cleanest sources of electricity around. Unlike the relatively simple process of releasing the solar energy stored in trees through direct combustion, photovoltaics require a much more complex transformation. The components of solar cells (dependent on type) commonly include lead, cadmium, nitrogen triflouride (a potent greenhouse gas), arsenic, hexafluoroethane and polyvinyl fluoride, among numerous other chemicals. The production process of solar cells and modules is very energy intensive and often involves the emission of a complex mix of compounds including heavy metals, SOx, NOx, Particulate Matter (PM), and CO2. Furthermore, there is currently no widespread infrastructure to deal with recycling old solar cells before these chemicals are released into the ecosystem.

Wind is another promising renewable energy source that has already begun to meet a portion of the U.S’s electricity needs and to decrease our reliance on fossil fuels. However, even wind energy also comes with environmental drawbacks. The heavy reliance on the rare earth metal, neodymium—used in the wind turbine magnets—comes with a host of negative environmental impacts. The typical mining process involves large quantities of powerful acid pumped into the earth and the processing of rare earth, which results in emissions of toxic chemicals such as fluorine, sulfur, acid and radioactive thorium). Further, over 96% of rare earth metals on the market today are mined and refined in China, a country notorious for its lax environmental standards. Numerous Asian environmental disasters have already been recorded from the mining of neodymium. However, most Americans never see the environmental impacts of rare earth mining, so they are easily left out of the discourse on green energy.

The impacts of fossil fuels are better known, but on a day-to-day basis are still well hidden to the average consumer who merely needs to flick on a light switch or an electric heater. In comparison, wood stoves are virtually carbon neutral; they emit is no more carbon than the carbon the tree originally absorbed, and the next generation will reabsorb with sustainable forestry practices. Fossil fuels on the other hand add to the mobile carbon pool by releasing carbon stored in the ground. However many people who are very skeptical of wood stoves appear to simply accept the inevitable issues with electricity production - almost half of which comes from coal that emits particulate matter, CO2, ozone, SOx, NOx, and toxic heavy metals such as arsenic and mercury. In addition some coal mining practices, such as mountain top removal, can be devastating to both the ecosystem and to human health.

Oil and gas extraction also can lead to dangerous environmental practices, and notable disasters such as the Exxon Valdez oil spill and the Deep Water Horizon oil platform explosion. A third of the greenhouse gas emissions in the U.S come from the transportation sector (gasoline use). The particulates and other pollutants emitted from the transportation of fossil fuels over very large distances, even when the fuel is domestically sourced, are another a large source of pollution. The long distance transportation is an issue with natural gas as well. Natural gas extraction techniques, primarily shale fracking, are known to wreck havoc on ecosystems and drinking water quality. The entire southern coast of Louisiana for example was horrifically contaminated when hurricane Katrina flooded gas drilling refuse pools and polluted the gulf water shed. Additionally unlike wood stoves, most fossil fuel appliances don’t allow for energy efficient space heating practices.

Biomass fuel has its drawbacks as well. Both EPA certified stoves and old uncertified ones can create dangerous levels of particulate matter when operated poorly, which can damage the lungs. Wood also suffers from a knee-jerk reaction among the public that conjures up images of industrial clear-cutting, where in the worst case scenario (think Amazon basin) over-harvesting means carbon can’t be re-sequestered by new forest growth. Wood however can be harvested sustainably, and in America wood for residential heating is primarily collected locally and on such small scale that it is almost always part of a very healthy, sustainable process. Corn produced in the conventional manner is often a bad energy investment due to the high levels of nitrogen fertilizer inputs, but sustainably and locally grown corn can avoid this issue. Many pellet producers operate sustainably by using waste products such as the excess sawdust produced in saw mills. Biomass can be an excellent source of clean, renewable energy with the right equipment and sustainably grown fuel.

While many energy systems may produce ‘clean’ energy in your immediate vicinity, there may be dirty impacts felt elsewhere. With biomass heat, what you see is what you get. Even if it was possible to make the extraction, processing and long distance transportation of fossil fuels exceedingly clean; they would still release vast quantities of new carbon into the carbon pool. And while solar and wind power are one of the cleanest options available, every form of energy production has pros and cons. Local air quality officials may not want to consider particulates or other forms of pollution from energy production that are not at the point of combustion, but as environmentalists, world citizens or green heat advocates, shouldn’t we?

Relevant articles:

Bradsher, Keith. U.S Called Vulnerable to Rare Earth Shortages. Dec. 15, 2010


Energy Information Administration

U.S. Energy Information Administration, Form EIA-63B, "Annual Photovoltaic Module/Cell Manufacturers Survey."


Environmental Protection Agency


Fthenais et al. Emissions from Photovoltaic Life Cycles. Environment, Science, Technology. Jan. 4, 2008. Pg 21


Harkinson, Josh. Solar Panels: Tomorrow’s Toxic Waste. March 23, 2010


Hilsum, Lindsey. Chinese Pay Toxic Price for a Green World. The Sunday Times. Dec. 6, 2009


Margonelli, Lisa. Clean Energy’s Dirty Little Secret. The Atlantic. Dec. 7, 2010


McDermott, Matthew. Solar Panel Toxic Manufacturing Byproducts, Product Disposal Needs Greater Oversight, Report Urges. Treehugger. Jan. 1, 2009


Pasternack, Alex. China Tightens Grasp on Rare Earth Metals Vital for Green Technologies. Sept. 1, 2009


Woody, Todd. Solar Energy’s Dirty Little Secret. The Grist. Jan. 6, 2010


1 comment:

  1. Thanks for presenting a well written piece on how to make a meaningful comparisons on emission impacts of various energy types.

    In the book "Planning and Installing
    Bioenergy Systems" published by James&James 2005, the energy requirements for processing a wood pellet to its final form is equivalnet to 2% of the energy content of the end product whereas the energy consumed to refine fossil fuels is typically 10-12% of the energy content of the end product. Undoubtedly the energy used to refine fossil fuels results in signifcant emissions.