People searching the web are now be able to contribute to carbon offset schemes run by US non-profit organisation Carbonfund.org after the organisation inked an agreement with recently launched green search engine provider Greenback Search.

Launched earlier this year, Greenback Search is based on Google's search engine but any searches that generate revenues will see the company's operators donate half to carbon offsetting schemes.

Greenback Search said the new service also allows users to monitor how much carbon has been offset as a result of their online searches and provides them with functionality for displaying the information through their profile on social networking site Facebook.

Meanwhile, a Greenback Search widget for bloggers allows users to provide the search functionality on their blogs and display the environmental contribution made from any searches undertaken on the blog.

Eric Carlson, executive director of Carbonfund.org, welcomed the partnership, adding that with Greenback Search expected to donate around half a cent per click the alliance should help finance a wide range of offset schemes.

"It's such a fantastic idea," he said. "It's completely free, has much the same functionality as Google, and you can offset carbon while you search."