by Emil Morhardt
Seems like a good idea. Yael Rebecca Glazer just suggested it in a Masters Thesis in Engineering at the University of Texas at Austin. A major issue with fracking is that sometimes a lot of the fracking fluid that was pumped down the well to create the fractures comes back up, sometimes along with additional “produced” water, sometimes twice as much as was pumped down in the first place. On top of that, it is often so contaminated that it exceeds the capabilities of industrial treatment facilities, so it gets trucked to a nearby injection well and is reinserted. But injection wells are not always handy, and anyway, the water itself would be valuable if it weren’t so polluted. Meanwhile, although a fracked well might producing mainly oil, there is also often a fair amount of natural gas produced; but if there isn’t enough gas to make it economical to capture it and sell it, it is commonly flared—burned right there at the wellhead. This converts the natural gas to CO2 without using the energy released for anything at all. Maybe, thought Ms. Glazer, that free energy could be used onsite to power wastewater cleanup technologies that normally wouldn’t be considered because of their high energy costs. It also occurred to her that since lots of these wells are in the sunny, windy southwestern US, local photovoltaic panels or wind turbines might supply energy as well. This latter option is attractive when there are no convenient transmission lines to take the power offsite, even though solar or wind energy is abundant.
So the first idea is to channel the heat from burning the otherwise flared gas to heat-powered water treatment technologies like multi-stage flash distillation, multi effect distillation, and mechanical vapor recompression. Heat could also come from a solar thermal facility. Alternatively, if not enough gas were available for producing the heat, electricity from photovoltaics or wind turbines could pressurize the wastewater for membrane separation, or the related reverse osmosis. Reverse osmosis is the most energy-efficient of the treatments considered here, so it would be preferable if energy were limiting.
Ms. Glazer uses a series of equations to do a formal engineering analysis of the feasibility of her suggestions, and figures they could reduce overall water requirements for fracking by 11–26%, and reduce the energy use for freshwater trucking by 16%. If renewable energy were used there would need to be at least four 100 kW wind turbines (much smaller than the ones we are accustomed oto seeing at wind farms) or between 1000 and 4000 250 Watt PV panels. She thinks she’s on to something, and I’d agree. But even though the fuel is free, the equipment and maintenance sure are not, so this probably won’t happen without a mandate, and unless there’s a full-scale demonstration of the feasibility and cost, no mandate is likely either. Maybe DOE or EPA should fund a demonstration project.
Glazer, Y.R., 2014. The potential for using energy from flared gas or renewable resources for on-site hydraulic fracturing wastewater treatment. Thesis, Master of Science in Engineering, Graduate School. University of Texas at Austin, 83 page. Full thesis available at: http://repositories.lib.utexas.edu/handle/2152/26020