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The Green Life: Hey Mr. Green, Can I Sell Carbon Offsets?

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January 12, 2012

Hey Mr. Green, Can I Sell Carbon Offsets?

Ask Mr. GreenHey Mr. Green,

I had a residential geothermal system installed last year. How do you calculate the greenhouse-gas offsets for the system, and how do I go about selling them?

—Betty in Revere, Missouri

The good news is that geothermal heating and cooling systems do reduce greenhouse gasses, carbon dioxide being the most significant. The bad news is that no system exists for selling residential carbon offsets, according to Geoexchange, a trade organization for the geothermal heat-pump industry.

But you can at least enjoy a bit of moral satisfaction by doing fairly reliable estimates of the CO2 offset that your geothermal system is responsible for. Start with a simple “before” and “after,” like those weird weight-loss ads in which a pasty guy who looks like a termite queen with man breasts stands next to his new, tanned, svelte self, all abs and pecs. Just compare your average annual gas, heating oil, and electric use before you installed the system with your annual consumption after the installation.

If you use propane, subtract the gallons burned before geothermal from the gallons burned after, and multiply that number by 12.7 to get the total pounds of reduced CO2 emissions.

If you use heating oil, do the same subtraction of before and after, and multiply by 22 to get your total pounds of reduced emissions.

For natural gas, total up the average annual therms used during your pre-geothermal era, and subtract from that the number of therms used in your post-geothermal era. Then multiply this result by 11.7, which is the number of pounds of CO2 emitted per therm burned. (If you don’t have the records, you can get them from your power company.)

Determining pre-geothermal electrical carbon emissions is even easier: Just add up your annual kilowatt-hour (kWh) electric consumption before you went geothermal, and go to the EPA’s Power Profiler site. There, plug in your ZIP code, the name of your utility, and your total annual kWh usage before your installation. Voila! You get the CO2 emissions from your electrical consumption. Then do the same for the year after which you installed your geothermal system, and subtract it from the first CO2 total.

If you’re an average U.S. household using about 970 kWh per month, your electrical use would have been responsible for emitting 22,000 pounds of CO2. Other areas that rely less heavily on coal than Missouri might have considerably lower emissions for the same amount of power. Missouri is also one of all too many states that need to do more energy conservation: Its average residential consumption is more than 1,150 kWh per month, compared to neighboring Illinois, which is down to less than 800 kWh per month. California's at 560, and even sweltering D.C. has cranked it down to 780, according to the U.S. Energy Information Agency.

The common-sense solution to our energy and emissions problems is simply to use less. You can find abundant how-to-save information at places like the EPA’s site, at the American Council for an Energy Efficient Economy, here at the Green Life, and, of course, in Mr. Green's own stupendous archives.

Got a question for Mr. Green? Submit it here.

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