Under pressure from customers and investors, many U.S. companies have pledged to voluntarily reduce their impact on the climate. But that doesn't always mean they're cutting their own greenhouse gas emissions.

A long list of sustainability measures saved School District 43 more than $1.2 million in the past year. But the district will soon need to fork over extra cash for carbon offsets, since the provincial government requires the public sector be carbon neutral by the end of 2010.