If you really want to negate the carbon emissions of your transportation, consider purchasing carbon offsets, or greentags, for your trip. The money you spend on carbon offsets will be used to plant trees or support a renewable energy project, thereby offsetting the carbon emissions generated during your travel.

The important thing to remember about carbon credits is that you need to purchase them from a trustworthy company to ensure that they will actually be used to support a green project. So do your homework. Before you spend your hard earned dollars on carbon offsets, check out a carbon credit buying guide such as Clean Air-Cool Planet to get a better idea of what to look for in a carbon-credit company.

Look for carbon credits that are certified and audited by a third-party such as Environmental Resources Trust or the Climate, Community, and Biodiversity Alliance.

Good companies to choose from include Carbon Neutral, Carbon Fund, or Green-e.