Filter May Be a Match for Fracking Water

Superhydrophilic Membrane Cleans Fluids for Reuse

Date: September 25, 2017
Source: Rice University
Summary: A superhydrophilic filter has proven able to remove more than 90 percent of contaminants from water used in hydraulic fracturing operations at shale oil and gas wells.

A superhydrophilic filter produced at Rice University can remove more than 90 percent of contaminants from water used in hydraulic fracturing operations. In this image, 'produced' water from a Marcellus shale fracturing site is at left, the retentate (carbon removed from the feed) is at center, and filtered 'permeate' water is at right. The hydrophilic treatment keeps the filter from fouling and restricting flow while rejecting contaminants.
Credit: Barron Research Group/Rice University

A new filter produced by Rice University scientists has proven able to remove more than 90 percent of hydrocarbons, bacteria and particulates from contaminated water produced by hydraulic fracturing (fracking) operations at shale oil and gas wells.

The work by Rice chemist Andrew Barron and his colleagues turns a ceramic membrane with microscale pores into a superhydrophilic filter that "essentially eliminates" the common problem of fouling.

The researchers determined one pass through the membrane should clean contaminated water enough for reuse at a well, significantly cutting the amount that has to be stored or transported.

The work is reported in Nature's open-access Scientific Reports.

The filters keep emulsified hydrocarbons from passing through the material's ionically charged pores, which are about one-fifth of a micron wide, small enough that other contaminants cannot pass through. The charge attracts a thin layer of water that adheres to the entire surface of the filter to repel globules of oil and other hydrocarbons and keep it from clogging.

A hydraulically fractured well uses more than 5 million gallons of water on average, of which only 10 to 15 percent is recovered during the flowback stage. "This makes it very important to be able to re-use this water," Barron said.

Not every type of filter reliably removes every type of contaminant, he said.

Solubilized hydrocarbon molecules slip right through microfilters designed to remove bacteria. Natural organic matter, like sugars from guar gum used to make fracking fluids more viscous, require ultra- or nanofiltration, but those foul easily, especially from hydrocarbons that emulsify into globules. A multistage filter that could remove all the contaminants isn't practical due to cost and the energy it would consume.

"Frac water and produced waters represent a significant challenge on a technical level," Barron said. "If you use a membrane with pores small enough to separate, they foul, and this renders the membrane useless.

"In our case, the superhydrophilic treatment results in an increased flux (flow) of water through the membrane and inhibits any hydrophobic material -- such as oil -- from passing through. The difference in solubility of the contaminants thus works to allow for separation of molecules that should in theory pass through the membrane."

Barron and his colleagues used cysteic acid to modify the surface of an alumina-based ceramic membrane, making it superhydrophilic, or extremely attracted to water. The superhydrophilic surface has a contact angle of 5 degrees. (A contact angle of 0 degrees would be a puddle.)

The acid covered not only the surface but also the inside of the pores, and that kept particulates from sticking to them and fouling the filter.

In tests with fracking flowback or produced water that contained guar gum, the alumna membrane showed a slow initial decrease in flux -- a measure of the flow of mass through a material -- but it stabilized for the duration of lab tests. Untreated membranes showed a dramatic decrease within 18 hours.

The researchers theorized the initial decrease in flow through the ceramics was due to purging of air from the pores, after which the superhydrophilic pores trapped the thin layer of water that prevented fouling.

"This membrane doesn't foul, so it lasts," Barron said. "It requires lower operating pressures, so you need a smaller pump that consumes less electricity. And that's all better for the environment."

Story Source:
Rice University. "Filter may be a match for fracking water: Superhydrophilic membrane cleans fluids for reuse." ScienceDaily. ScienceDaily, 25 September 2017. https://www.sciencedaily.com/releases/2017/09/170925104714.htm.

Fracking Wastewater is Mostly Brines, Not Human-Made Fracking Fluids

Date: October 17, 2016
Source: Duke University
Summary: Human-made chemical-laden fracking fluids make up less than 8 percent of wastewater being produced by fracked wells; more than 92% of it is naturally occurring brines, which carry their own risks but may have beneficial re-uses, say investigators.

Naturally occurring brines, not human-made fracking fluids, account for most of the wastewater coming from hydraulically fractured unconventional oil and gas wells, a new Duke University study finds.

"Much of the public fear about fracking has centered on the chemical-laden fracking fluids -- which are injected into wells at the start of production -- and the potential harm they could cause if they spill or are disposed of improperly into the environment," said Avner Vengosh, professor of geochemistry and water quality at Duke's Nicholas School of the Environment.

"Our new analysis, however, shows that these fluids only account for between 4 and 8 percent of wastewater being generated over the productive lifetime of fracked wells in the major U.S. unconventional oil and gas basins," Vengosh said. "Most of the fracking fluids injected into these wells do not return to the surface; they are retained in the shale deep underground.

"This means that the probability of having environmental impacts from the human-made chemicals in fracking fluids is low, unless a direct spill of the chemicals occurs before the actual fracking," he said.

More than 92 percent of the flowback and produced water -- or wastewater -- coming from the wells is derived from naturally occurring brines that are extracted along with the gas and oil.

These brines carry their own risks, Vengosh stressed. They contain varying levels of salts, heavy metals and naturally occurring radioactive elements, and their sheer volume makes disposing of them a challenge.

"But with proper treatment, they potentially could have beneficial reuses," he said, "especially out West, where our study shows most brines being produced by fracked wells are much less saline than those in the East. These Western brines, which are similar in salinity to sea water, could possibly be treated and re-used for agricultural irrigation or other useful purposes, especially in areas where freshwater is scarce and drought is persistent."

The Duke team published its findings Oct. 14 in the peer-reviewed journal Science of the Total Environment.

The researchers used three statistical techniques to quantify the volume of wastewater generated from unconventional oil and gas wells in six basins nationwide: the Bakken formation in North Dakota; the Marcellus formation in Pennsylvania; the Barnett and Eagle Ford formations in Texas; the Haynesville formation in Arkansas, Louisiana and East Texas; and the Niobrara field in Colorado and Wyoming.

Using multiple statistical techniques "helped us more accurately account for changes in each well's wastewater volume and salinity over time, and provide a more complete overview of the differences from region to region," said Andrew J. Kondash, a doctoral student in Vengosh's lab at Duke's Nicholas School, who led the study.

"This makes our findings much more useful, not just for scientists but for industry and regulatory agencies as well," he said.

Among other findings, the new study shows that the median volume of wastewater produced by an unconventional oil or gas well ranges from 1.7 to 14.3 million liters per year over the first five to 10 years of production. The volume of produced water coming from these wells declines over time, while its salinity increases.

"The salt levels rise much faster than the volume declines, resulting in a high volume of saline wastewater during the first six months of production," Vengosh said. After that, the volume of wastewater produced by a well typically drops, along with its hydrocarbon output.

Elizabeth Albright, assistant professor of the practice of environmental science and policy methods at the Nicholas School, co-authored the study with Kondash and Vengosh.

Story Source:

Materials provided by Duke University. Note: Content may be edited for style and length.

Duke University. "Fracking wastewater is mostly brines, not human-made fracking fluids." ScienceDaily. ScienceDaily, 17 October 2016. www.sciencedaily.com/releases/2016/10/161017150835.htm

Fracking and Pollution: Technology-Dependent Emissions of Gas Extraction in the US

Date: December 8, 2014
Source: Karlsruhe Institute of Technology. "Fracking and pollution: Technology-dependent emissions of gas extraction in the US." ScienceDaily. ScienceDaily, 8 December 2014. www.sciencedaily.com/releases/2014/12/141208074327.htm.

Summary: Not all boreholes are the same. Scientists used mobile measurement equipment to analyze gaseous compounds emitted by the extraction of oil and natural gas in the US. For the first time, organic pollutants emitted during a fracking process were measured at a high temporal resolution using a vapor capture system. The highest values measured by this process exceeded typical mean values in urban air by a factor of about one thousand.

The KIT measurement instrument on board of a minivan directly measures atmospheric emissions on site with a high temporal resolution.
Credit: Photo: F. Geiger/KIT.

Not all boreholes are the same. Scientists of the Karlsruhe Institute of Technology (KIT) used mobile measurement equipment to analyze gaseous compounds emitted by the extraction of oil and natural gas in the USA. For the first time, organic pollutants emitted during a fracking process were measured at a high temporal resolution using a vapor capture system. The highest values measured by this process exceeded typical mean values in urban air by a factor of about one thousand, as was reported in the ACP journal.

Emission of trace gases by oil and gas fields was studied by the KIT researchers in the USA (Utah and Colorado) together with US institutes. Background concentrations and the waste gas plumes of single extraction plants and fracking facilities were analyzed. The air quality measurements of several weeks duration took place under the "Uintah Basin Winter Ozone Study" coordinated by the National Oceanic and Atmospheric Administration (NOAA).

The KIT measurements focused on health-damaging aromatic hydrocarbons in air, such as carcinogenic benzene. Maximum concentrations were determined in the waste gas plumes of boreholes. Some extraction plants emitted up to about a hundred times more benzene than others. The highest values of some milligrams of benzene per cubic meter air were measured downstream of an open fracking facility, where returning drilling fluid is stored in open tanks and basins. Much better results were reached by oil and gas extraction plants and plants with closed production processes. In Germany, benzene concentration at the workplace is subject to strict limits: The Federal Emission Control Ordinance gives an annual benzene limit of five micrograms per cubic meter for the protection of human health, which is smaller than the values now measured at the open fracking facility in the US by a factor of about one thousand. The researchers published the results measured in the journal Atmospheric Chemistry and Physics ACP.

"Characteristic emissions of trace gases are encountered everywhere. These are symptomatic of gas and gas extraction. But the values measured for different technologies differ considerably," Felix Geiger of the Institute of Meteorology and Climate Research (IMK) of KIT explains. He is one of the first authors of the study. By means of closed collection tanks and so-called vapor capture systems, for instance, the gases released during operation can be collected and reduced significantly.

"The gas fields in the sparsely populated areas of North America are a good showcase for estimating the range of impacts of different extraction and fracking technologies," explains Professor Johannes Orphal, Head of IMK. "In the densely populated Germany, framework conditions are much stricter and much more attention is paid to reducing and monitoring emissions."

Fracking is increasingly discussed as a technology to extract fossil resources from unconventional deposits. Hydraulic breaking of suitable shale stone layers opens up the fossil fuels stored there and makes them accessible for economically efficient use. For this purpose, boreholes are drilled into these rock formations. Then, they are subjected to high pressure using large amounts of water and auxiliary materials, such as sand, cement, and chemicals. The oil or gas can flow to the surface through the opened microstructures in the rock. Typically, the return flow of the aqueous fracking liquid with the dissolved oil and gas constituents to the surface lasts several days until the production phase proper of purer oil or natural gas. This return flow is collected and then reused until it finally has to be disposed of. Air pollution mainly depends on the treatment of this return flow at the extraction plant. In this respect, currently practiced fracking technologies differ considerably. For the first time now, the resulting local atmospheric emissions were studied at a high temporary resolution. Based on the results, emissions can be assigned directly to the different plant sections of an extraction plant. For measurement, the newly developed, compact, and highly sensitive instrument, a so-called proton transfer reaction mass spectrometer (PTR-MS), of KIT was installed on board of a minivan and driven closer to the different extraction points, the distances being a few tens of meters. In this way, the waste gas plumes of individual extraction sources and fracking processes were studied in detail.

Major Class of Fracking Chemicals No More Toxic Than Common Household Substances, analysis finds

Date: November 12, 2014
Source: University of Colorado at Boulder

Summary: The 'surfactant' chemicals found in samples of fracking fluid collected in five states were no more toxic than substances commonly found in homes, according to a first-of-its-kind analysis.


Fracking fluid is largely composed of water and sand, but oil and gas companies also add a variety of other chemicals, including anti-bacterial agents, corrosion inhibitors and surfactants. Surfactants reduce the surface tension between water and oil, allowing for more oil to be extracted from porous rock underground.

In a new study published in the journal Analytical Chemistry, the research team identified the surfactants found in fracking fluid samples from Colorado, Louisiana, Nevada, Pennsylvania and Texas. The results showed that the chemicals found in the fluid samples were also commonly found in everyday products, from toothpaste to laxatives to detergent to ice cream.

"This is the first published paper that identifies some of the organic fracking chemicals going down the well that companies use," said Michael Thurman, lead author of the paper and a co-founder of the Laboratory for Environmental Mass Spectrometry in CU-Boulder's College of Engineering and Applied Science. "We found chemicals in the samples we were running that most of us are putting down our drains at home."

Imma Ferrer, chief scientist at the mass spectrometry laboratory and co-author of the paper said, "Our unique instrumentation with accurate mass and intimate knowledge of ion chemistry was used to identify these chemicals." The mass spectrometry laboratory is sponsored by Agilent Technologies, Inc., which provides state-of-the art instrumentation and support.

The fluid samples analyzed for the study were provided through partnerships with Colorado State University and colleagues at CU-Boulder.

Hydraulic fracturing, or "fracking," is a technique used to increase the amount of oil and gas that can be extracted from the ground by forcing fluid down the well. Fracking has allowed for an explosion of oil and gas operations across the country. In the U.S. the number of natural gas wells has increased by 200,000 in the last two decades, according to the U.S. Energy Information Administration.

Among the concerns raised by the fracking boom is that the chemicals used in the fracking fluid might contaminate ground and surface water supplies. But determining the risk of contamination--or proving that any contamination has occurred in the past--has been difficult because oil and gas companies have been reluctant to share exactly what's in their proprietary fluid mixtures, citing stiff competition within the industry.

Recent state and federal regulations require companies to disclose what is being used in their fracking fluids, but the resulting lists typically use broad chemical categories to describe the actual ingredients.

The results of the new study are important not only because they give a picture of the possible toxicity of the fluid but because a detailed list of the ingredients can be used as a "fingerprint" to trace whether suspected contamination of water supplies actually originated from a fracking operation.

The authors caution that their results may not be applicable to all wells. Individual well operators use unique fracking fluid mixtures that may be modified depending on the underlying geology. Ferrer and Thurman are now working to analyze more water samples collected from other wells as part of a larger study at CU-Boulder exploring the impacts of natural gas development.

Thurman notes that there are other concerns about fracking--including air pollution, the antimicrobial biocides used in fracking fluids, wastewater disposal triggering earthquakes and the large amount of water used--that are important to investigate and ameliorate. But water pollution from surfactants in fracking fluid may not be as big a concern as previously thought.

"What we have learned in this piece of work is that the really toxic surfactants aren't being used in the wells we have tested," he said.

Electrodialysis Identified as Potential Way to Remove Salt from Fracking Waste Water

Fracking is a highly controversial and divisive issue. Proponents argue that it could be the biggest energy boom since the Arabian oil fields were opened almost 80 years ago, but this comes at a serious cost to the environment. Among the detrimental effects of the process is that the waste water it produces is over five times saltier than seawater, which is, to put it mildly, not good. A research team led by MIT that has found an economical way of removing salt from fracking waste water that promises to not only reduce pollution, but conserve water as well.

Hydraulic fracturing, or fracking uses water pressure to shatter oil shale formations, releasing oil and natural gas from deposits that would otherwise be uneconomical to exploit. One of the major problems with this process is that as the water is pumped through the oil shale, it picks up salt, and by the time it’s pumped back to the surface, it’s extremely salty – in the order of 192,000 parts per million (ppm). In contrast, seawater is only 35,000 ppm. This makes it not only too salty to be disposed of without reprocessing, but it’s also too salty to be reused in fracking.

The MIT research team sought to find the most cost effective means of desalinating fracking water. They found that electrodialysis is not only a promising way of cleaning up fracking waste water, but could also provide oil explorers with a closed-loop system that places less demand on local water supplies.

Diagram of the MIT desalinating process (Image: Jose-Luis Olivares/MIT)

Electrodialysis is not a new technology. It was developed half a century ago and is currently used to desalinate brackish water and seawater, for small-scale drinking water plants, in food processing, greenhouses, hydroponics, and desalinating various chemicals.

In electrodialysis, a series of membranes divide streams of water of different salinity into stacks. An electric current on either side of the stack draws the sodium and chlorine ions of the salt across the membranes, leaving the water behind. The end result is a very salty stream of water, and a relatively pure stream.

According to MIT, electrodialysis has been overlooked as a way of treating fracking waste water until now because the process was thought to only be effective on water that wasn't of such high salinity. However, the team’s research found that electrodialysis is not only practical, but economically viable – not the least because water conducts electricity better as it gets saltier, therefore the electrodialysis process works better.

The team found that the key was to desalinate the water in stages and rather than making the water potable, it only had to be cleaned up enough to be pumped back into a fracking well and used again. This not only has the potential to reduce the costs, but also alleviate pressure on local water supplies and minimize the need for disposal of contaminated water.

In addition, the process described by MIT is extremely flexible, allowing engineers to "dial" the saline output. This is important, because reusing the water will mean finding the most effective level of salinity for fracking, which is a question still to be answered.

According to the team, there’s still a lot of work to be done before the process is practical. In addition to tweaking the electrodialysis design, laboratory work needs to be done on removing oil, gas, and mineral contaminants that may clog the membranes, and new equipment needs to be designed, built, and tested to apply the new technology.

Green Fracking? 5 Technologies for Cleaner Shale Energy

Dusk falls at a hydraulic fracturing site in northeastern Pennsylvania. New technologies aim to reduce fracking's impact on land, water, and air.

It may seem strange to hear the words "fracking" and "environmentally friendly" in the same sentence.

After all, hydraulic fracturing, or fracking, in which high-pressure chemically treated water is used to crack rock formations and release trapped oil and gas, is a dirty term to many environmentalists. Critics decry the practice for consuming vast amounts of fresh water, creating toxic liquid waste, and adding to the atmosphere's greenhouse gas burden, mostly because of increased risk of leaks of the potent heat-trapping gas, methane. (See related quiz, "What You Don't Know About Natural Gas.")

James Hill, chief executive of the Calgary, Alberta-based energy services firm GasFrac, is one of a handful of technology pioneers determined to change that. Hill's company has introduced a new fracking method that uses no water at all. Instead, GasFrac uses a gel made from propane—a hydrocarbon that's already naturally present underground—and a combination of what it says are relatively benign chemicals, such as magnesium oxide and ferric sulfate, a chemical used in water treatment plants. Over the past few years, GasFrac has used the process 2,500 times at 700 wells in Canada and the United States.

"We're actually using hydrocarbons to produce hydrocarbons," Hill said. "It's a cycle that's more sustainable."

GasFrac is one of a growing number of companies, including giant GE and the oil services firm Halliburton, that are pioneering technological improvements to mitigate some of the environmental downsides to the process that has spurred a North American energy boom. (See Interactive, "Breaking Fuel From Rock.") Besides GasFrac's water-free method, other companies are working on ways to use recycled frack water or non-potable brine in fracking. Some are working on replacing harsh chemicals used in the process with more benign mixtures, or to cleanse water that's been used in fracking. Other innovators are looking to replace diesel-powered drilling equipment with engines or motors powered by natural gas or solar energy, and to find ways to find and seal leaks that allow methane, a potent greenhouse gas, to escape.

Such efforts have even won cautious support from some environmental activists, who've decided that it may be more realistic to mitigate the consequences of fracking than to fight its use.

"Natural gas is a potential energy bounty for the country, and development is probably inevitable," said Ben Ratner, a project manager for the nonprofit Environmental Defense Fund. (See related "Interactive: Breaking Fuel From Rock" and "The Great Shale Gas Rush.") "That's why we're investing our energy into doing everything, from science to policy to working with companies, to maximize the potential climate advantage that gas has over coal, and minimize the risk to public health and the environment. We think natural gas can be an exit ramp from coal, but we have to do it right." (See related, "U.S. Energy-Related Carbon Emissions Fall to an 18-Year Low," and Natural Gas Nation: EIA Sees U.S. Future Shaped by Fracking.")

Here are a few of the efforts to make fracking greener:

Water-Free Fracking: GasFrac's fracking system, which uses a gelled fluid containing propane, has other advantages besides eliminating the need for water, according to Hill. Because the gel retains sand better than water, it's possible to get the same results with one-eighth the liquid and to pump at a slower rate. Because GasFrac says the amount of hydrocarbon in the gel is comparable to what's in the ground, the fluid can simply merge into the flow being extracted from the ground, eliminating the need to drain contaminated wastewater and haul it away in trucks for disposal, usually at deep-well injection sites. "We present a much smaller footprint," he said. (See related, "Fracking Waste Wells Linked to Ohio Earthquakes.")

Using Recycled Water or Brine: While fracking typically uses freshwater, industry researchers have worked to perfect friction-reducing additives that would allow operators to use recycled "gray" water or brine pumped from underground. Halliburton's UniStim, which went on the market about a year ago, can create a highly viscous fluid from any quality of water, according to Stephen Ingram, the company's technology manager for North America. In northeastern Canada, one producer has tapped into a deep subsurface saline water aquifer for a portion of its supplies for hydraulic fracturing.

Eliminating Diesel Fumes: The diesel-powered equipment used in drilling and pumping wells can be a worrisome source of harmful pollutants such as particulates, as well as carbon emissions that contribute to global warming. And diesel fuel is expensive. Last year, Apache, a Houston-based oil and gas operator, announced it would become the first company to power an entire fracking job with engines using natural gas. In addition to reducing emissions, the company cut its fuel costs by 40 percent. Halliburton has introduced another innovation, the SandCastle vertical storage silo for the sand used in fracking, which is powered by solar panels. The company also has developed natural-gas-powered pump trucks, which Ingram said can reduce diesel consumption on a site by 60 to 70 percent, resulting in "a sizable reduction in both emissions and cost."

Treating Wastewater: At hydraulic fracturing sites, the amount of wastewater typically far exceeds the amount of oil produced. The fluid that returns to the surface through the well bore is not only the chemically treated frack water, but water from the rock formation that can contains brines, metals, and radionuclides. (See related, "Forcing Gas Out of Rock With Water.") That wastewater must be captured and stored on site, and then often is shipped long distances to deep well injection underground storage facilities. There have been few treatment options. But Halliburton has developed the CleanWave treatment system, which uses positively charged ions and bubbles to remove particles from the water at the fracking site. Last September, GE and its partner Memsys also tested a new on-site treatment system that allows the water to be reused without being diluted with freshwater, by employing a desalination process called membrane distillation. (See related Quiz: What You Don't Know About Water and Energy.

Plugging Methane Leaks: A major fracking concern has been whether companies are allowing a significant amount of natural gas to escape, because methane—the main component of natural gas—is a potent greenhouse gas, 34 times stronger than carbon dioxide (CO2). A recent study concluded U.S. methane emissions are likely 50 percent higher than official government estimates. (See related, "Methane Emissions Far Worse Than U.S. Estimates.") New U.S. Environmental Protection Agency regulations that go into effect next year will require that all U.S. oil and gas sites have equipment designed to cut a wide range of pollutants, a step that the agency expects will cut methane. (See related, "Air Pollution From Fracked Wells Will Be Regulated Under New U.S. Rules.")

Methane emissions from onshore oil and natural gas production could be reduced by 40 percent by 2018, at a cost that's the equivalent of just one cent per thousand cubic feet of natural gas produced, concludes a just-released study, conducted by Fairfax, Va.-based consulting firm ICF International for the Environmental Defense Fund. EDF's Ratner said that inspectors equipped with infrared cameras can spot leaks at fracking sites, which can then be plugged. "The cameras cost about $80,000 to $100,000 apiece," he noted. "But that can pay for itself, because the more leaks you fix, the more gas you have to sell." (See related blog post: "Simple Fixes Could Plug Methane Leaks From Energy Industry, Study Finds.")

Another improvement that can reduce methane emissions: Replacing conventional pressure-monitoring pneumatic controllers, which are driven by gas pressure and vent gas when they operate. A U.S.-wide move to lower-bleed designs could reduce emissions by 35 billion cubic feet annually. And switching out conventional chemical injection pumps used in the fracking process, which are powered by gas pressure from the wells, and replacing them with solar-powered pumps, operators could eliminate an 5.9 billion cubic feet of methane emissions annually, the EDF report concludes.

The Cost-Benefit Equation

Some solutions do not require advanced technology. A study released Wednesday by the Boston-based Clean Air Task Force suggests that almost all of the methane leaks from the oil and gas infrastructure could be reduced at relatively little expense, often by simply tightening bolts or replacing worn seals.

A number of greener fracking technologies already are being implemented, according to industry officials. But one obstacle is economic. The newer, more environmentally friendly technologies generally cost more than the legacy equipment they would replace. Extracting natural gas with water-free fracking, for example, could cost 25 percent more than conventional fracking, according to David Burnett, a professor of petroleum engineering at Texas A&M University who heads that school's Environmentally Friendly Drilling Systems Program. He said that switching fracking equipment from diesel to natural gas is the innovation that's catching on most rapidly, because it provides a clear economic benefit as well as helping to lower carbon emissions. With the rising cost of renting fracking rigs, companies are eager to find improvements that will reduce their costs, he said.

Green fracking is "the same as with any industry—if you come out with a game-changing technology, you can get in the market first and ride that," Burnett said. (See related, "Can Natural Gas Bring Back U.S. Factory Jobs?")

But Halliburton's Ingram said that innovations such as chemical treatments to make brine usable will drop in price as the technology is perfected. "Eventually it will become the lower-cost chemistry," he said.

A more difficult hurdle might be overcoming what Ingram calls "sociopolitical constraints" around the country. One major issue that reduces incentives to invest in green fracking innovations: the generally low price of freshwater. (See related, "Water Demand for Energy to Double by 2035.")

Source: This story is part of a special series that explores energy issues. For more, visit The Great Energy Challenge