An Increasingly Popular Way for organizations to demonstrate their environmental stewardship is through carbon offsets. Essentially, groups acknowledge their carbon footprint — the total tonnage of greenhouse gases emitted into the atmosphere by their activities, including travel — and then buy “offsets” or “verified emission reductions” (VERs) to bring them to carbon “neutrality” or “balance.” One “offset” reduces one ton of carbon dioxide in the atmosphere when your offset purchase price funds a project such as tree planting (trees absorb CO2).

But let's back up. Environ-mentalists would call offsets the third step. First, reduce emissions as much as possible. Second, get some or all of your electricity from renewable energy sources. Then consider offsets.

Sustainable Travel International estimates that offsetting the carbon emissions of an event can cost $250 to $2,000, depending on the event's size. Including offsets for attendee hotel stays and air travel adds $25 to $50 per person

But questions arise. Who calculates your footprint? Who sells you the offsets? Who verifies that your money goes to a viable project? What about “double counting”? (That is, are you being sold the same offsets that someone else is buying?) Do your offsets meet the “additionality” test? (That is, are you buying emissions reductions that were going to happen anyway, even without your investment?)

The following organizations certify or vet carbon providers, offering starting point for organizations wanting to purchase offsets.

www.cleanair-coolplanet.org CA-CP commissioned the first report vetting 30 carbon-offset providers. Because the marketplace of offset providers has expanded since the research was done, CA-CP considers the specific vendor assessments in the report outdated. Still relevant and available, however, is CA-CP's comprehensive review methodology, which organizations could use to assess their own potential vendors.

www.fightglobalwarming.org A Web site created by the Environmental Defense Fund. Recommends four providers selling offsets for $4 to $8 per ton of CO2.

www.cdmgoldstandard.org The Gold Standard certification, developed by several international nonprofits, is given only to renewable energy and energy efficiency projects — in other words, those that seek to reduce emissions in the first place.

www.green-e.org certifies renewable energy credits. A word of warning: Some organizations consider RECs, which are most often used to buy wind power and “add it to the grid,” problematic. That's because of the challenge of meeting the “additionality” test — the test of whether this renewable energy would have been produced anyway, in the absence of the RECs.

www.ghgprotocol.org offers the Greenhouse Gas Protocol Corporate Standard, which helps companies to prepare a GHG inventory that represents a true account of their emissions.

Offset Providers

www.conservation.org Helps companies create sustainability plans.

www.nativeenergy.com Offsets help build American Indian-owned renewable energy projects.

www.drivinggreen.com Offsets support projects to reduce methane and nitrous oxide in agriculture.

www.atmosclear.org Offsets support collecting landfill gas from a facility outside Chicago and using it as fuel for generating electricity.

www.atmosfair.com Offsets support projects in developing countries.

www.carbonneutral.com Read the CarbonNeutral Protocol, an exhaustive guide to evaluating projects.

www.carbonfund.org You can choose your project.

www.terrapass.com Projects happen the same year that you buy your offsets.

www.climatecare.org Read project case studies.

www.climatetrust.com Wide variety of projects

www.ebluehorizons.net Offshoot of The Conservation Fund; focus is on reforestation.