AGU#16 Redefining the Carbon Footprint of Coal

I found this item in the AGU newsroom today, I don’t quite know what to make of it.

Erosion clearly visible in the overburden left over from strip mining in Großräschen, Germany.


by Margaret Donelick

BiMBy Power Company, LLC will present a poster at the AGU Meeting on December 15 in San Francisco’s Moscone Center that describes an innovative device designed to provide grid-scale, renewable energy storage capacity and constructed using overburden from strip coal mines or waste rock from open-pit metal mines.

Called a Big Mass Battery or BiMBy, the device lowers the carbon footprint of burned coal by repurposing the overburden moved during mining to enable construction of an on-demand renewable energy power plant. A carbon footprint for coal similar to that of natural gas may be achieved by using the BiMBy to store compressed air. A carbon footprint for coal much lower than that for natural gas may be achieved by using the BiMBy to store compressed hydrogen, potentially making coal the go-to fossil fuel as fossil fuels are replaced by renewable energy sources.

Up to 30% of the volume of a typical pile of mine overburden/waste rock is pore space filled with air and/or water. Encapsulating the pore space deep within the pile to form a pressure vessel allows compressed gas to be stored within that pore space at a pressure determined by the load of mine overburden/waste rock overlying the encapsulated pore space. In the US, 3-4 giga-tonnes of mine overburden associated with coal mining and 1-2 giga-tonnes associated with metals mining are moved annually.

The worldwide totals are perhaps 5-10 times the US amounts. Widescale repurposing of mine overburden/waste rock for several decades in the US would provide enough energy storage capacity to replace a significant fraction of the fossil fuels currently burned to generate electricity; 10-20% replaced for BiMBys storing compressed air, and 100% replaced with capacity to spare for BiMBys storing hydrogen.

Using mine overburden/waste rock to build renewable energy storage creates the notions of ‘green coal’ and ‘clean gold’. The BiMBy concept offers skilled power plant jobs at active mine sites and a new strategy for converting inactive mine brown-field sites into on-grid or off-grid renewable energy power plants, as per EPA’s RE Powering America.

At a currently operating coal mine, a predictable BiMBy construction timeline can be the basis for a predictable longterm plan to operate and ultimately shutdown the mine. At an inactive and polluting metal mine, the BiMBy pressure vessel at such a polluting site is encapsulated and operated dry and with a positive air pressure, offering a potentially transformative way to satisfy environmental regulatory compliance at the site.

The 50 mega-tonnes of overburden moved annually as the Rosebud Mine near Colstrip, MT could be used to build compressed-air-based renewable energy storage capacity sufficient to convert 10,000 or more US homes to 100% renewable energy, or 200,000 or more homes over 20 years of mining. The 300 mega-tonnes of waste rock at the inactive Anaconda Mine near Yerington, NV could be used to convert 200,000 US homes to 100% renewable energy.


80 thoughts on “AGU#16 Redefining the Carbon Footprint of Coal

    • What a bunch of negative Nellies.
      Compressed air energy storage is a real thing. It is usually done in salt caverns. No technical reason why you could’t integrate the construction of this sort of thing into mining operations.
      From a permitting perspective, though, there are challenges. At least out West, the mining company usually doesn’t own the land. They only own the coal. And their permit says they have to restore the area to “like new” condition. Not sure if you could modify it to allow for a permanent energy storage installation.
      Also, most mines are nowhere near load or transmission lines. Most energy storage today derives its value from its location. The best locations are places like NYC, where building more transmission is hugely expensive. The odds of having a mine at a location where you need energy storage are vanishingly small.
      That said, in a case where we need a month of storage because we rely on wind and solar to power the entire economy, this could work.

      • Recognizing insanity when you see it makes you a negative Nelly?
        (Any grammarians out there, do you change a y to an ies when pluralizing a proper name? I honestly don’t remember.)
        How much energy does it take to build this storage chamber from the over burden. Remember that the over burden is just lose rubble. Seems to me you would have to build a concrete structure that is strong enough to hold up the weight of the rubble, seal it (concrete is porous remember), then move the rubble on top of the concrete structure you just built. Under such a scenario, the maximum pressure you can store in your structure is going to be twice the weight of the rubble on top of your structure.
        Now that you have spent hundreds of millions of dollars building your structure, you now get to pump it full of air. What is the efficiency of your pump? What is the efficiency of your generator when you release that air. Remember, while a pump can also be used as a generator, if you want maximum efficiency for both, you will need separate pumps and generators, which will of course add to your costs.
        How efficient is your sealing? Every bit of air loss is energy/money lost.
        Finally, if you want months of energy, forget about it, unless you are only planning on providing enough energy to power one or two small to mid sized homes.

      • PS: I forgot to mention that when you compress something, it heats up. When you put compressed air into such a structure, the hot air will lose heat to the structure, which will then radiate that heat to the rest of the environment. As the air cools, it will lose pressure. So a good portion of the energy you pumped into your storage structure is going to be lost as heat. Unless you spend money to super insulate your structure, which will of course multiply the cost of your structure dramatically.

  1. What a terrific idea.
    The 5 ton boulders which make up overburden will behave exactly as you want them to. AND they will be soft with smooth edges.
    So smooth that they will not ruffle any green feathers.
    What a doozy (or BiMBy) is Margy Donelick!!!!!

    • The key is, “Encapsulating the pore space deep within the pile to form a pressure vessel.” What is the encapsulating material? Can it prevent hydrogen from escaping as other have pointed out?
      But the major problem I see is how can storing the energy from coal as compressed air or hydrogen lower coal’s carbon footprint? You are just changing the time it is generated by storing it, the emissions remain the same. And we already have a way to deal with it, it is called “load following.” If we don’t need the generation, we cut back on it. Storing the coal generation can reduce the maximum power needed, called peak shaving, but not the emissions.

    • I’m always suspicious of something when a ghastly term like ‘repurpose’ is used! What happened to ‘use’ or ‘reuse’?

  2. With about 250 million household in the US….that will certainly make a dent (a dent so small no one could see it)

    • Yes, that was my first thought when I read hydrogen. H stands for Houdini : it can get out of anywhere.
      Even the compressed air sounded a bit fanciful.
      From what we have here it’s totally unclear what they are proposing. Energy storage by compressing air ?

  3. Hydrogen doesn’t stick around for long and will readily diffuse through steel. Wonder how long they are proposing to store it in porous slag heaps?

    • Amen to that. Whenever I read whimsical thinking of this bent my first question as an engineer was to ask the cost/energy question, “Do you get back a large enough portion of recovered losses to make the system viable?”
      This leave much to be questioned. This appears as just another method of storing potential energy like pumping water back uphill to be run through a hydro-turbine generator later. Seems the authors believe they have found a readily available pressure vessel in the overburden heaps. This seems rather ludicrous as there is no method to introduce the high pressure gases nor extract or recollect it. How is the compressed gas (hydrogen?) “infused” into porous rock….UNDER VERY HIGH PRESSURES REQUIRING QUITE SOME TIME. Doesn’t sound inexpensive. How do you get the high pressure gas back out without losing most of it? Gravel piles cant keep out rain water, and a tarp won’t be much good as a pressure collector.
      “A bad idea whose time has come.”

  4. Whats the bet the construction of these facilities would cost a bomb, and use more energy than they could store? And how do you seal a bubble that is deep underground without surrounding it in a skin first?

  5. Sounds like the Underpants Gnomes…
    Step 1: Collect Underpants
    Step 2: ?
    Step 3: Profit

    Doesn’t it take energy to inject the ? at pressure? Or do they just leak hydrogen there and then pour dirt on it (really quick)? =) And what is renewable about this process? I don’t get it. Should be interesting.

  6. Nowhere do its promoters prove that the BiMBy’ s EROEI (Energy Return on Energy Invested) or the ROI are positive.
    It’s another junk-science SC@M until they prove that.
    Who needs compressed air energy anyway??
    But for junk-science-based regulations about human CO2, the BiMBy brew would never have been concocted except by a drunken scientist. As things stand, a very cynical, enviroprofiteer, scientist is rubbing his her her hands together, cackling with misplaced green-eyed glee….
    Laugh now, Enviroprofiteer: Truth will have the last laugh.
    The models failed.
    Game over.

      • Just say “his.” Until very recently, in such a context “his” was understood to mean “his or her,” or even “his, her, or its” if corporations were involved. For example, “The seller can get full value for his land if it is in good condition and clear of encumbrances, such as liens.” The seller (antecedent of “his”) can be a man, a woman, a corporation, or a group. There’s no point in wasting space or ink. The substitution of “they” or “their” is simply an agreement error with the antecedent. Of course, there are times when “his or her” is necessary, and times when “her” is obviously correct (“Each student at Mary Baldwin College has her own mailbox”). (I think MBC has recently started admitting men as well as women, so that example is likely obsolete; the principle remains.)

  7. Unless the porous over-burden has adsorptive characteristics that permit low pressure storage and recovery, why not just build a large pressure vessel and be done with it? The over-burden will have to be encapsulated some how in order to work.

    • Not only that, but they’re talking about preparing and storing compressed air. Compressing air takes energy. From where does that energy come? Is the energy provided by the coal-burning plant? If that’s the case, from where comes the CO2 benefit?
      Or are they saying that the air within the nether regions of the mine tailings heap is compressed by the overburden, and that this natively compressed air can provide energy? If so, how is that renewable?
      They call it a “battery,” which implies a charge/discharge cycle. What is that cycle? It all seems very nebulous to me, at least the way it’s presented in the press release.

      • It is all sensible when you remember how senseless it is to generate electricity directly from wind power. Power that can’t be scheduled or dispatched is more trouble on the grid than its worth. If you use wind power to compress air you could generate electricity on demand and with the stored energy you could schedule the power. The cost of ‘vesseling’ the compressed air makes the technology look unaffordable – here is an idea that drives down that cost and offsets the carbon dioxide released in coal’s combustion by increasing the amount of carbon-free electricity produced as a direct result of mining.
        I am not worried about CO2 emissions. But I do think directly generating electricity from turbines as the wind blows is folly. Expensive, useless, folly. Using wind power to compress air to use as the motive force is much more sensible.

      • But, willy, wind power is perfectly predictable, so in the UK we just turn down the gas power as the predicted wind comes on stream, then back up as wind drops off.
        Using grid storage makes it even more efficient – we use the grid storage during time wind ramps down to allow time to fire up the gas, meaning less spinning reserve needed (it doesn’t need much anyway)

        • “But, willy, wind power is perfectly predictable,”
          No it isn’t, not even close.
          Why do you keep telling porkies?

      • “Griff December 13, 2016 at 1:10 am
        You really have no idea what you are talking about.

      • willy, you are taking something that is already way to expensive, and making it even more expensive by adding a very inefficient storage mechanism to it.

      • In Griff’s world, the fact that meterologists can tell you that tomorrow will be windier than today, means that wind is perfectly predictable.
        Then again, Griff’s an idiot.
        When it comes to energy generation, perfectly predictable means that you are able to predict, minute by minute, the exact wind speed down to fractions of a mile per hour for any given point within the turbine array several hours in advance.
        That’s not possible, and will never be possible, but Griff will continue to spread his lies.

  8. ooooh oooooh better yet, use this rock for those “green” chain lights that there was a post about a couple weeks ago. 300 Mega-tonnes of rock would make for a lot of those “gravity lights”
    hmmm just gotta figure out who is going to lift the 300 Mega-tonnes of rock every 30-40 minutes.. DOH!!

    • easy! send the pre-lifted rocks to africa along with the gravity lights.
      that will give them unlimited free energy.

  9. What? Clean energy from… dirt?
    I mean that’s all “overburden” is. Rocks and dirt. This is the saddest thing I’ve ever read.
    Or maybe the most brilliant. I mean fleecing well-heeled greens by telling them they can power their homes with dirt is the kind of brazen thing that surely requires lots of planning and off-shore bank accounts.

  10. How exactly do they propose to seal that puppy? If waste heaps are broken rock, it would seem more than a bit porous, so something like hydrogen would tend to leak a bit, wouldn’t it?

  11. If they are proposing compressed air as a means of storing unreliable renewable energy, that’s NOT anything new. Way back when some windfarmers used an abandoned mine to store compressed air. Problem was that when the compressed air was released to drive turbines, it did what every expanding gas will do – it got colder and lost a lot of its PSI. Get this : what they did was to turn on natural gas heaters to heat up the air being released. I have not heard further about this strategy
    so I assume it is dead as a door nail.

  12. You have to put the overburden back when the mine closes. I guess that’s why they are saying it will work for a few decades. I have to wonder if this messes with all the regulations about how to store and deal with overburden and waste rock—there’s a long list.

  13. So people are looking for ways to store CO2. How about this: We have a very large unused under ground storage facility out in Utah We could pack that facility full of those people, tie rope around their ankles and as they pass out we could drag them outside through a trap door. We could even set it up were we could get CO2 credits.

    • Mills has been at it for 25 years and still no energy device has been sold to the public.
      Therefore a scam.
      Climate Heretic

    • That explains why such an old idea is not the current energy paradigm. This is only new packaging and a green marketing scheme to make unreliable sources of grid power look practical somehow.

  14. To Engineer is Human! The Role of Failure in Successful Design.
    Quantify to avoid failures. Plan safety for when failures happen.
    The consequence of providing 300 deg C steam to mobilize “Oil” sands (aka bitumen) using Steam Assisted Gas Drainage (SAGD) is that “blowouts” can happen. And HAVE happened. e.g. launching volkswagon sized boulders. For images see:
    SAGD Blowout

    On May 18, 2006, a major blowout occurred at Total’s Joslyn SAGD project. The incident near the heel of a SAGD pair created a huge 125m x 75m crater with rock debris flying up to 300m away. On the aftermath of the incident, that was decribed as “catastrophic” by the regulator, Total abandoned its Joslyn SAGD project

    300 C Steam has a pressure of 1,246 psi or 85 bar!

  15. Bad overburden storage resulted in pictured erosion. When the open pit closes, the (US) plan is always to restore uneroded overburden and replant/reforest. So an intermediate improperly managed ‘mining scar’ is just deceptiive BS. The first years after a section of my Wisconsin farm forest is selectively logged is equally ugly–until we get in to harvest the crown wood as firewood, and Nature takes back over. After Five years, heck we even lose the opportunistic wild black rasberries.

  16. Compressed air energy storage looks so attractive. For years people have been trying to produce a viable compressed air powered automobile. We still don’t have a practical vehicle. link
    Even if the overburden was capable of efficiently storing compressed air, there seem to be other issues that prevent it from being useful.

  17. I suspect that the primary mining activity in this case is subsidy mining. Maybe if they get enough they can hire a competent engineer to explain to them why this won’t work.

  18. So perhaps they could come back and tell us about it once they have a working, cost effective pilot plant of reasonable scale?

  19. I get so annoyed by those people blithely talking about carbon sequestration. The carbon was already sequestered in the form of coal. Once you burn it, it stops being carbon and becomes CO2. In other words two atoms of oxygen for every atom of coal. If it was a product in a grocery store, you would have to name it after the largest ingredient.
    In other words, they are proposing oxygen sequestration. Which creates a problem for me, since I breathe oxygen.

  20. I do not know what drugs these guys use to come up with these hare-brained schemes, but I sure would like to get my hands on some for the coming festive season.

  21. Assuming no increase in power demand, with the overburden producing power, less coal would need to be mined to produce power, meaning less overburden??
    I don’t know if this makes sense other than as a small offset to continued mining: it isn’t a world wide/large scale solution.
    Might as well put solar panels on the waste tips?
    I note Queensland is using two old open cast mines for pumped storage (don’t recall if coal mines or other)

  22. A possible use for mine over burden. Yawn.
    Wait! If we can say it could be used for the latest pop science craze, we might generate some interest. How ’bout we say it is a “device designed to provide grid-scale, renewable energy storage capacity?”
    A technology looking for an application. Desperately seeking an application.

  23. Batteries, batteries, batteries….Our Tesla wannabes sure always fall back on bloody batteries.
    I like it better when these Californian subsidy hogs talk about going to Mars. It’s more fun, plus there’s the eco-tourism angle.
    Hey, maybe they could use mine overburden to practise their Mars walking. That’d count as a green job, right?

  24. So, the plan is to pump hydrogen at very high compression ratios into porous rocks with non-negligible organic matter (coal dust) with no built in cooling. So if there is a single hot spot what happens? Or if when taking a gas and compressing it a hot spot develops what is going to happen?

  25. This is embarrassing. Is this the kind of stuff that they are presenting? Did they get grant money for this? Much better off pumping water uphill to a lake with hydro capabilities.
    If you want to take advantage of temp differences to enhance pressure…, probably short storage times. Any long term storage is wortheless because of leakage . Actually this is lke a water tank for air but with the warm fuzzy of beautifying ugly coal waste/overburden. Energy in = e. out. this is only about 50% efficient and that is with a piston / flywheel/ and awesome transmission gearing. I know!

  26. Oh, My. Sorry Anthony, you should have seen these comments coming.
    From all I read, solutions to cut energy consumption is a multi-tiered problem. I’d proposition that social-media cuts CO2 emissions. After all, those teenagers are sitting on their couches, instead of driving cars and hanging at the mall.
    I do have a question, where are we with Superconductivity power lines? Not heard anything for a decade or so.

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