Oil & gas companies that have postponed getting on the clean tech train – usually because they don’t believe there are enough proven technologies on the market – should think again about getting the journey started. Now that what we call the “eco-nomics” of clean tech solutions actually makes good business sense, we’re seeing more oil & gas companies adopt processes such as capturing the energy used in gas processing. In fact, three of the 10 most active investors in clean tech startups happen to be among the world’s largest oil & gas companies, according to research firm Cleantech Group. By Audrey Bold