I found an interesting article on what some companies are pursuing to make the fracing process more environmentally friendly: http://www.drillingcontractor.org/technology-advances-push-greener-...

I'm not usually one for posting links, but this has some good information in it as well as touching upon what occurs behind the monitors in the frac vans.

The opening paragraph: Hydraulic fracturing has been an area of aggressive research and development over the past several years, with operators and service companies introducing a number of “green” technologies as a response to public concerns and as part of the effort to improve well economics. Hydraulic fracturing to restore or enhance well productivity is performed in all types of formations and reservoirs and has become a high-profile operation as a result of its increased use in the prolific shale plays in North America and in other unconventional reservoirs.