Carbon Neutrality

There's a simple equation. Burn carbon, you get energy. That's good. You also get the greenhouse gas carbon dioxide. That's bad. Since coal, oil, and natural gas provide 86% of all America's energy, that's a lot of CO2. Everybody has a carbon footprint – the amount of CO2 your energy-use creates. It used to be, you want less CO2, you burn less carbon. Now there's a new option – carbon neutrality. That's when someone makes sure that, however much CO2 he produces, he pays for the same volume to be removed from someone else's footprint.

Under its Climate Protection Plan, Austin plans to go carbon neutral. People and businesses will be able to calculate their carbon footprints online; then the city will give them advice on achieving carbon neutrality. Even visitors will be able to buy carbon credits. It's not as good as producing no CO2, but it's a start.

Here's how it works: Say a factory uses enough energy to account for a ton of CO2; meanwhile, an oil company pumps a ton of CO2 underground to increase the pressure in its oil field. That CO2 that the oil company removes from the atmosphere becomes a carbon credit or "offset credit" – effectively, clean air it can sell. The oil company sells the credit to the factory – one ton goes into the air; one ton comes out. That's carbon neutrality.

This is done through a regulated market. Members set an agreed target for their CO2 emissions. Some reduce their carbon footprints, through conservation, buying renewable energy, building "green" buildings, or by storing or sequestering CO2. This can be done artificially, such as by pumping it underground, or by natural methods, like planting trees that absorb CO2. Members who miss their agreed targets can buy this excess capacity or "carbon credit," offsetting their own CO2 production. While critics say the carbon-credit market lets big polluters clean up without cleaning up, it still means the total carbon output of all members will drop. Some ecological groups even buy credits to force the price up – making actual emission cuts more appealing to polluters.

While other pollutants like nitrogen dioxide are traded in the U.S., and there's a CO2 market in Europe, there is currently no federal carbon market here. Under the Bush administration, the EPA says CO2 is not covered by the Clean Air Act, so it is unlikely to support a market. A voluntary private market, the Chicago Climate Exchange, has attracted companies like Austin-based Freescale Semiconductor Inc., which pledges to cut its emissions of CO2 and five other greenhouse gasses by 6% of its 1999-2001 levels, before 2010.