Praxair Inc. has begun offering oil and gas producers a waterless system for use in hydraulic fracturing (fracking) operations. According to the Danbury, CT-based company, its DryFrac system blends liquid carbon dioxide (CO2) with proppant. Praxair said it can separate CO2 returned from the well, enabling faster natural gas production, adding that much of the CO2 is captured from industrial off-gas and purified.