You know how fracking is so controversial, because applying high pressure to deep formations might cause hydrocarbons to migrate upwards and contaminate shallow drinking water aquifers? Texas has got the next best thing. This article calls it “fracking for uranium” which is just plain wrong. Fracking relies on high pressure to break apart rocks holding oil and gas. Uranium harvesting relies upon geochemistry to leach uranium out of rocks – no high pressure needed – and it has relatively low water requirements. Unfortunately, it does have one other difference that makes it way more controversial: uranium harvesting is occurring within drinking water aquifers.
Here’s how it works. Uranium is naturally present at trace levels in certain rock formations. A company in Texas is injecting oxygenated water into underground aquifers that are normally anoxic. This exposes the rock formations to different geochemistry and induces the uranium to dissolve into solution. Extraction wells recover the uranium-laced groundwater and precipitate out the uranium.
I’m sure the process works, but at what cost? Injection typically acts like a “bubble” that expands outward, with some mixing at the fringes. In other settings, like aquifer storage and recovery, it has already been shown that it’s virtually impossible to completely recover the injected “bubble” due to the mixing at the fringes. If you’re just talking about water storage, as in aquifer storage and recovery, that’s one thing. But we’re talking about intentionally mobilizing a contaminant in a drinking water aquifer. The mixing at the fringes means that uranium is going to stay in the groundwater, and potentially be pulled into someone else’s well eventually.
Maybe it doesn’t seem like a big deal now, especially if the aquifer in question isn’t heavily used. But Texas is really running out of water. The drought hit Texas hard this year, and their response has largely been to push for further conservation, rather than to expand long-term plans for water recycling or desalination (the only two realistic long-term options). So even if energy is at stake, I’d be awfully hesitant to sign away aquifers for uranium leaching, given that there are many sources of energy, but Texas is running short of water sources.
An interesting article has recently been published in an open-access journal called “Environmental Research Letters.” I’m torn on open-access journals: people should have access to research results, but the quality of publication suffers without higher quality reviewers. That said, this article seems pretty informative. The authors attempted to quantify the energy used in the US in 2010 for treating and delivering water, and they found a whopping 12.6% of energy consumption in the US is due to water.
I found this figure instructive, showing the difference in energy requirements for various types of water sources and treatment levels. Note the difference between desalted water and normally treated water is large, but the difference between desalted water and the California State Water Project water (which is pumped from the Bay-Delta to southern California) is small. No wonder southern Californians are getting more excited about seawater desalination and water recycling, assuming that cost scales with the energy intensity of the water source.
With some pretty complicated flow diagrams, the authors come to one very striking conclusion:
We estimate that 5.4 quads of this primary energy (611 billion kWh delivered) were used to generate electricity for pumping, treating, heating, cooling and pressurizing water in the US, which is approximately 25% more energy than is used for lighting in the Residential and Commercial sectors . (Despite this equivalency, much more policy attention has been invested in energy-efficiency for lighting, rather than reducing hot water consumption or investing in energy-efficient water heating methods, even though the latter might have just as much impact.)
In other words, reducing hot water consumption or investing in energy-efficient water heating methods could have a similar impact to switching our personal lightbulbs to compact fluorescents, yet there has been no policy push to educate people on this aspect.
Results like these are fascinating and instructive. Once we know where the energy is going and how much our water really “costs”, we can make adjustments that make sense without revamping the whole system. You and I can be more energy efficient by taking shorter showers and turning water off while lathering up with soap and shampoo. California can promote water recycling in southern California instead of desalination and increasing imported water, which would save on energy without cutting off the State Water Project. I’m sure many more examples of efficiency improvements are available — we just have to think a little outside the box.
Last one of these, I promise: Sacramento is also expanding its wastewater biogas facilities. Construction is underway on a co-digestion plant for fats, oils, and grease, and they’ve even agreed to accept material shipped from outside Sacramento, which was previously off-limits. Seems only fair if they mention EBMUD, but again, the media makes them sound like trendsetters…
Today’s news includes a tidbit from Humboldt, California. The Humboldt Waste Management Authority is embarking on a food-waste-to-methane project, with a pilot project starting this week and full scale requests for proposals to begin in May. Besides removing food wastes from landfills, the project will cut fuel costs associated with shipping to the landfills in Redding and Medford, and it even has potential to generate enough energy to be sold back to the grid. Sound eerily familiar? That’s because EBMUD just announced its net energy generation from an identical project last week. It is a good sign that other waste management utilities in the state are following EBMUD’s lead. Plus, if the economics of the energy generation work out, these waste utilities might have to start answering to their customers as to why they have not implemented this kind of energy- and cost-saving project.
The local water utility here in the East Bay has achieved a remarkable feat: they are producing enough energy from their main wastewater treatment plant to sell power to the grid. I had hoped to report on this after viewing the plant myself, but I was turned away from the Grand Opening Dedication Ceremony of their new gas turbine on Tuesday. Turns out that I needed media credentials. Oh well.
Wastewater treatment is notoriously energy intense, if for no other reason than that water is heavy to move around. According to the East Bay Municipal Utility District (EBMUD), the average California power cost to deliver one million gallons of water is approximately 7000 kW-hrs. So a common move towards energy efficiency is to cap all tanks for water and sludge, then recover the methane (a.k.a. natural gas) to be burned for energy. This also alleviates a lot of odor issues with wastewater treatment plants — trust me, I used to work at one in East St. Louis. Well, EBMUD had already done that. They had 3 gas turbines running about 6.3 MW, which was nearly enough (90%) to power the wastewater treatment plant, and they had excess methane. So they just bought and installed a big, efficient gas turbine, 4.5 MW, to use the excess methane and generate energy in excess of their needs. That’s right, a wastewater treatment plant is producing enough power to sell some to the grid.
Now, the East Bay utility in general will still need to purchase energy from the grid occasionally for water treatment and delivery and maybe office building use. Their 2010 energy purchase amounts to 9.3 MW, more than the roughly 3.8 MW excess capacity that they just added. So they’re not exactly going to get rich. Yet.
The real secret behind the EBMUD strategy is the food wastes that they accept (for a fee) from regional restaurants, wineries, cheese producers, and chicken farms. They feed all this disgusting junk to a tank full of microbes, and end up with way more methane than standard sewage would provide. This stuff is too complex to toss in a standard wastewater treatment plant or even to travel through sewer pipes, but a bunch of trucks deliver it every day to the specialized bioreactors EBMUD has had since 1991. Considering that this junk would otherwise end up in a landfill, emitting methane (a greenhouse gas far more potent than carbon dioxide) unchecked, this economical decision also makes sense from an environmental perspective. It’s nice when we can all agree on something.