Friday, May 04, 2007

Explaining Offsets

I decided to renew my car’s TerraPass for another year. For those of you unfamiliar with TerraPass, they sell annual carbon offsets for cars, homes, and frequent flyers in a range of convenient chunks.

A carbon offset is a term that combines several concepts into one. Carbon, technically carbon dioxide, as everyone must know by now, is a greenhouse gas implicated in climate change. It is released from a variety of natural and man made sources, and scientists have noted in recent decades that CO2 is rapidly exceeding historic levels in the atmosphere. A staggering amount of CO2 is released from people burning fossil fuels for power and transportation. But there is also a massive natural cycle of CO2 emission and absorption, analogous to the evaporation/precipitation water cycle. Because there is such a variety of sources and “sinks” or methods of absorbing CO2, there is a corresponding wide range of actions that can be taken either to reduce sources or increase sinks. Some actions will be very disruptive (a.k.a costly) and other actions will be trivial (a.k.a. cheap).

For example, I drive my car about 6,000 miles per year (~half the national average) emitting on the order of 6,000lbs (3 tons) of CO2/year. For me to stop driving entirely would be extraordinarily disruptive to me personally, but there are actions I (or other people) can take, like installing a solar panel (or wind turbine) to produce electricity without CO2 emissions which would not be disruptive to any of us, which could easily result in 3 tons less CO2 being emitted each year. Nearly any investment to improve energy efficiency, increase recycling, or burn less fossil fuel (system wide) will cause less CO2 to be emitted. There are also “natural” emission streams of CO2 and equivalent gases that can be reduced. Methane, for example, is frequently released from the decay of plant and animal waste. A farmer can collect cow and pig manure, capture the methane gas this manure releases as it breaks down and burn it to generate energy, reducing both the amount of methane emitted (a more potent greenhouse gas than CO2 lb for lb, although it breaks done leaves the atmosphere much faster) and the demand for burning other fossil fuels. Landfills frequently capture the methane emitted from municipal waste streams and use it to generate power. Reforestation, or at the very lest slowing deforestation, can also increase the amount of CO2 “sunk” in any given year. There is still some debate about how effective planting trees is in terms of mitigating climate change, although most people would agree that trees “store” CO2 outside the atmosphere for as long as they live.

So getting back to the TerraPass example, they purchase credits (wholesale) from non-fossil energy producers or large efficiency initiatives that cause less CO2 to be emitted each year and resell the credits (retail) to people like me, which allows me to offset my 3 tons of CO2 for about $10/ton of CO2. TerraPass does nothing to reduce my gas bill, but I consider balancing out this slice of my personal pollution a valuable service. This transaction requires the small leap of faith that TerraPass is doing what it says it is…but I’m willing to take that leap/risk along the lines of “trust but verify” until I learn they are not performing at least as well as their competitors (or some damning evidence that the entire offset industry beats puppies). The system is entirely voluntary (in the US) and there are many other vendors of offsets, Drive Neutral (cars), Native Energy (electricity), RenewableChoice (electricity) are a few I’m familiar with.


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