Massachusetts-based Executive Charter Services (ECS), in a joint program with an organization that promotes alternative energy, is giving its passengers an option it says helps offset the carbon dioxide emissions from corporate jets. Depending on the type of jet chartered, passengers can opt to pay an additional $20 to $42 per hour, on top of the hourly charter rate. TerraPass will use this money to help buy alternate energy sources, such as wind farms. ECS estimates that it will initially be offsetting about 500 hours of private jet travel, equaling an estimated 1.7 million pounds of carbon dioxide emissions.