Skip to content

Sewage Set To Become Car Fuel Of Tomorrow!

May 9, 2021

By Paul Homewood


h/t Ian Magness

 Olivia’s latest pile of ……!




I would like to crowdsource this.

There seem to be some pretty obvious issues, for instance:


  • How much energy does a gram of hydrogen contain, in petrol equivalent?
  • Converting ammonia to hydrogen involves cracking at high temperatures; how much energy would this entail?
  • What would be the likely cost of all of this?
  • How would the hydrogen be stored and transported?

I have no doubt that we have the technology to do this, but is it practical?

  1. Tim Leeney permalink
    May 9, 2021 7:02 pm

    2 grams of hydrogen per tonne of sewage! Sell your oil shares now.

    • bill permalink
      May 9, 2021 7:40 pm

      sounds more like brown hydrogen rather than green !

  2. Jack Broughton permalink
    May 9, 2021 7:05 pm

    Dozens of hair-brained schemes to make hydrogen from wastes are being pushed by the fund-troughers. Of course it is technically possible to make hydrogen from many streams, but the practicalities and economics are invariably and inevitably useless. In simple terms, if hydrogen cannot be made economically from the simple feedstocks, it certainly cannot be made from these difficult feedstocks.

    • Stephen Bazlinton permalink
      May 10, 2021 10:17 am

      Indeed, the easiest way to generate hydrogen is by splitting the most abundant molecule in the planet…H20, why go through sewage, ammonia, surely a long way round!!

  3. Joe Public permalink
    May 9, 2021 7:08 pm

    Hi Paul

    1kg H2 = 33.33 kWh

    2gm = 0.06666kWh

    • Joe Public permalink
      May 9, 2021 7:12 pm

      (Bugger – hit ‘Post reply’ too early.)

      The late Prof Sir David Mackay informs petrol has a calorific value of ~10kWh per litre.

    • John Cullen permalink
      May 9, 2021 10:45 pm

      Hello Paul and Joe,

      Ref. 1 gives hydrogen’s calorific value as 39.0 kWh/kg and that for petrol as 13.0 kWh/kg. However, once allowance has been made for their containers then, according to Ref. 2, these values fall to approximately 2 kWh/kg for hydrogen and 12 kWh/kg for petrol.

      Thus hydrogen as a naked material has the higher calorific value in gravimetric terms. But once the containment system is included then petrol is by far the superior fuel. Ref. 2 also suggests that the same conclusion is reached on volumetric terms.

      1. David JC MacKay, “Sustainable Energy – without the hot air”, UIT Cambridge, 2009, page 199.
      2. John Andrews & Nick Jelley, “Energy Science”, 3rd ed., OUP, 2017, page 409.


      • Joe Public permalink
        May 9, 2021 11:38 pm

        39.41 kWh/kg is the higher heating value (HHV or Gross cv)

        33.33 kWh/kg is the lower heating value (LHV or Net cv), the useable energy.

        Prof David MacKay:

        “The gross calorific value is the actual chemical energy released when the fuel is burned. One of the products of combustion is water, and in most engines and power stations, part of the energy goes into vaporizing this water. The net calorific value measures how much energy is left over assuming this energy of vaporization is discarded and wasted.

        When we ask “how much energy does my lifestyle consume?” the gross
        calorific value is the right quantity to use. The net calorific value, on the
        other hand, is of interest to a power station engineer, who needs to decide
        which fuel to burn in his power station. Throughout this book I’ve tried to
        use gross calorific values.”

        Motor vehicles cannot make use of the energy of vaporization,

  4. Lorde Late permalink
    May 9, 2021 7:10 pm

    That wont even start my engine!

  5. Lorde Late permalink
    May 9, 2021 7:13 pm

    I might start a trial to see if I can power my car off our muck heap. wher would I apply for a

  6. Joe Public permalink
    May 9, 2021 7:17 pm

    “How would the hydrogen be stored and transported?”

    Energy intensively.

    For vehicles, low volumetric energy-density hydrogen would be compressed to 700bar / 10,000psi. Approx 4kWh of energy would be needed to compress 1 kg (33.3kWh) of H2 to 700bar.

    Click to access 9013_energy_requirements_for_hydrogen_gas_compression.pdf

  7. Is it just me? permalink
    May 9, 2021 7:32 pm

    In answer to the question: Is it practical? No. If hydrogen fuel cells are a “silly idea” (according to Elon Musk – who calls them hydrogen ‘fool’ cells) – then this is a silly idea (cubed)..

  8. MrGrimNasty permalink
    May 9, 2021 7:34 pm

    Eh? Why not just use the ammonia as fuel for cars etc, or sell it on and save some of the energy that is normally expended making ammonia industrially?

    • MikeHig permalink
      May 10, 2021 9:54 am

      Exactly! Why spend energy and money breaking down ammonia which is a commecially-viable material?
      One of the greatest developments in science was the synthesis of ammonia: the Haber-Bosch process. It enabled the production of synthetic fertilisers just when the world was running out of natural sources. (Sadly it also allowed the manufacture of explosives; without it the First World War would have ground to a halt after a few months).
      While we’re looking at such nonsense, waste water treatment can generate a lot of methane, often used onsite for heat and power or even exported to the grid. Instead of those productive uses, they could spend loads of dosh putting in a steam reformer to generate hydrogen……

  9. May 9, 2021 7:37 pm

    Flatus would surely be more direct, cheap and, needing little processing, simpler as fuel.

  10. Harry Passfield permalink
    May 9, 2021 7:47 pm

    This really takes me back to my youth when we just didn’t know how perceptive we were when we claimed our cars ‘went like sh*t!’
    And all this time I thought it was my passenger…

  11. Harry Passfield permalink
    May 9, 2021 7:51 pm

    Hang on…I just caught the last line: they extract TWO GRAMS of hydrogen per TONNE of sewage!!!!
    Words fail me!!

    • 1saveenergy permalink
      May 9, 2021 7:57 pm

      Yup, a really ‘dense’ energy source !

    • Mack permalink
      May 9, 2021 8:06 pm

      They claim a 0.02 % return. I wonder what the margin of error is?

    • Robert Christopher permalink
      May 9, 2021 10:53 pm

      To put it into perspective, mining ore with two grams of Gold per tonne of ore is just about viable, depending on where its found.

      And it ‘would be’, not ‘could be’ ! 🙂

      • Brian Jackson permalink
        May 10, 2021 9:02 am

        2 grams per tonne?
        We’d have given our best clogs for 2gpt.
        The big open cut mines around the world operate at fractions of that.
        Bj in UK.

  12. Ray Sanders permalink
    May 9, 2021 8:01 pm

    “nitrogen which can be safely released into the atmosphere” FFS does Olivia actually know what the majority of the atmosphere actually is? And does she moronically think that most people don’t know? Who is this effing idiot?

  13. MrGrimNasty permalink
    May 9, 2021 8:06 pm

    Remember this story that was doing the rounds a few years back? Where there’s muck there’s….. gold!

    In the middle is the blindingly obvious sensible cost effective use of sewage waste; burn it for energy, that’s got to be more CO2 neutral than wood pellets; and the waste heat could be used to dry/sterilize more for compost/soil conditioning etc.

  14. Andrew Harding permalink
    May 9, 2021 8:22 pm

    Petrol is flammable enough, but hydrogen! Pumping hydrogen into fuel tanks of vehicles, what could possibly go wrong?

    To compound this stupidity, I assume that the H2 is created by the electrolysis of water. Where does the electricity come from to do this? We have already established that there is insufficient energy available in renewables to power our homes, factories, transport, hospitals etc

    We seem to be moving towards an energy policy, that has its origins in a Lewis Carroll children’s story!

    • 1saveenergy permalink
      May 9, 2021 8:28 pm

      Most hydrogen produced today is made via steam-methane reforming, of natural gas.

    • Stuart Brown permalink
      May 9, 2021 9:15 pm

      From the article: “The process works by first stripping the ammonia out from the sewage stream and then “cracking” the ammonia at high temperatures.”

      The Telegraph don’t give a link, but a bit of delving leads me to these people, via a news link to the award of £225K free cash from the ‘Innovation in Water Challenge’ They say:

      “Ammonia in raw domestic sewage is found in concentrations of about 30 mg/litre.”

      So if a thousand litres of ‘water’ is a tonne, then that’s 30g of ammonia (NH3) containing 5g of H2 by my reckoning, so the figures are about right! Then they also say:

      “The single important input is waste-heat with which to drive the chemical reactions. If waste-heat is not available, the fuel-cost can be as prohibitive as that of chemical additions or carbon source requirements. Where waste-heat is available, from an engine-exhaust or unwanted biogas, the long-term operating cost can be confined to plant Operation and Maintenance, as well as electricity costs.

      The preferred option within the Organics process is to use the ammonia-laden air as combustion air in the heat-raising process. By this means ammonia gas is destroyed as a part of the process of thermally powering the system.”

      In other words, the most sensible way of dealing with the trivially small, but still troublesome, amount of ammonia in sewage is to separate it out and burn it to fuel the extraction process!

      Unless someone is giving out free cash…

      • Dan permalink
        May 10, 2021 11:23 am

        So from my reading, post below, ammonia removal in an air stream (stripping) seems to be used for high ammonia areas. The generation of anhydrous ammonia from the resulting air stream doesn’t seem to be that onerous.

  15. Ellen Jenkins permalink
    May 9, 2021 8:37 pm


  16. Laurie Marlow permalink
    May 9, 2021 8:43 pm

    Hydrogen has a greater energy density than petrol and is a “better” fuel source. From 2g of petrol, you could get about 70,000J. From 2g of hydrogen, you could get 240,000J. Hydrogen oxidation simply produces water, whereas petrol can produce NOx, CO2, SOx and other greenhouse gases. One of the biggest problems with hydrogen fuel is storing it. Not only does H2 leak from the tiniest gaps, but when mixed with oxygen in the air (in a great enough quantity), makes rocket fuel, which is highly explosive.
    Hydrogen tanks require expensive gas separation membranes so this is a large cost of storing hydrogen.
    Hydrogen fuel is slow to take off as the internal combustion engine is now a very efficient model and widely accepted machine that is used in most cars and buses. Hydrogen fuel is still in its early stages of development for domestic use.
    Cracking ammonia is performed at around 450 degrees Celsius and requires a steel catalyst. It can be very efficient as N2 is a thermodynamically and entropically favourable product. Ammonia cracking produces 75% Hydrogen gas and 25% nitrogen gas, so the yield is not bad either. It can be a cheap process (~$3/kg H2) and there is a lot of research going on to make ammonia splitting (and water splitting) a viable process for domestic hydrogen fuels. Not only with sewage, but with photovoltaic cells, quantum dot technology and even transforming CO2.

    • Ray Sanders permalink
      May 9, 2021 9:42 pm

      Water splitting (by means of electrolysis) is most certainly not “viable”. 1kg of hydrogen has an energy density of around 33.5kWh but it takes a minimum of 50kWh to produce it from water, compress and store it usefully. To release that energy in a fuel cell runs at about 40% efficiency. So you have an energy carrier that throws away a minimum of two thirds of the original input from the most expensive form of energy i.e. electricity. There is a very good reason why hydrogen is not used as a mainstream energy carrier and is not going to be anytime soon if ever. There is an outside chance of hydrogen being produced from nuclear power either by High Temperature Electrolysis or even Thermolysis but only for feedstock to produce synthetic hydrocarbons probably as aviation fuel.

    • Graeme No.3 permalink
      May 9, 2021 11:56 pm

      Laurie Marlow
      I would dispute your optimistic claim; hydrogen is being touted by the Greenies as having “3 times the energy of petrol” and they are not known for underestimating any supposed benefit.
      Further, hydrogen oxidation giving only water occurs only with an oxygen feed, burning it in air produces NOx.
      And what little chemistry I can recall say that ammonia is NH3 i.e. 14 parts by weight of nitrogen or 82%.

      • martinbrumby permalink
        May 10, 2021 2:39 am

        Cut out the crap.
        Make hydrogen directly from Greenies.
        Expensive, but it’s a concept I could get behind.

    • AC Osborn permalink
      May 10, 2021 9:31 am

      Laurie, please remind us of the energy density of Natural Gas, as in Fracked Gas?
      Why not power ICE vehicles directly with Gas?

    • tomo permalink
      May 10, 2021 7:01 pm

      The Upp fuel cell charger

  17. Shoki Kaneda permalink
    May 9, 2021 9:15 pm

    What a shitty idea.

    • 1saveenergy permalink
      May 9, 2021 9:34 pm

      Olivia’s sitting on a stool, flushed with pride over this crap, so none of your septic deposits !

  18. Ray Sanders permalink
    May 9, 2021 9:26 pm

    To put the whole concept of “energy density” into context, if you take 1 litre of water at the top of a 100 metre high dam and allow it to fall through a turbine the energy density is Zero point zero ,zero one Megajoules per kilogram) which is why the lakes behind hydro electric dams are so incredibly large to produce worthwhile amounts of power.
    Conversely diesel comes in at about 46MJ/kg which is a mere 46,000 times more energy by mass which is why we mostly use fossil fuels.
    Then just think that the energy density of Uranium in a breeder reactor is 80,620,000MJ/kg
    (that is Eighty Million, Eight Hundred and Sixty Thousand Mega Joules per kilogram) which is why we should be using more nuclear reactors and the waste is somewhat more trivial than sewage by a long, very long, incredibly long way.

    • May 10, 2021 9:43 am


      You are being disturbingly logical. We need you advising the govt but you need to disguise your knowledge. So can you reinterpret your comments above in a much greener manner so Boris and Carrie believe you actually are on their side and not the side of common sense?

  19. May 10, 2021 1:37 am

    Sewage treatment plants already burn their waste products to generate power. Just about enough is produced to run the treatment plant. The more modern type of treatment plant – i.e. the activated sludge process, needs powerful blowers in order to aerate the sewage. And as I’ve just said, the in-house sludge burning power station provides just about enough power for the blowers. If there is any surplus, it isn’t very much.

  20. Stephen Lord permalink
    May 10, 2021 4:14 am

    The US DLOD Defense dis lots of resaearch on using Ammonia as a fuel as part of a plan yto have fuelfror vehicles after a nuclear attack. They foundthat burning ammonia cause massive clouds of nitrogen dioxide so that is a major issue. Cracking ammonia to nitrogen and hydrogen is feasible but it is not possible to convert all the ammonia so there has to be purification to remove the ammonia and the nitrogen.
    If you can make ammonia cheaply a better use is as fertilizer.

  21. Graeme No.3 permalink
    May 10, 2021 6:20 am

    It might be easier to anaerobically digest the manure to produce methane. This could then be burnt to CO2 which could be piped into greenhouses to boost food production.
    I know – CO2 is evil and destroys the planet although there is no proof of that at all.

  22. alexei permalink
    May 10, 2021 6:22 am

    The DT today raising the alarm for tea drinkers –

  23. Julian Flood permalink
    May 10, 2021 9:18 am

    I see that Joe Public is giving us the figures for hydrogen vs petrol. Perhaps he would like to comment on my scheme for getting to Net Zero in a gradual way by using a combination of carbon and hydrogen, This compound would have the huge advantage of not needing to be held in the chemical equivalent of Alcatraz — hydrogen is a notoriously leaky molecule — and would have greater energy density. It can be made by fermenting sewage and even makes itself spontaneously in the right circumstances, combining four hydrogen atoms to one carbon. As fuel for internal combustion engines it has very low NOX and negligible particulates, could be passed along pipes to homes where it makes an ideal space heating fuel and if only we could make enough of it we could cut CO2 emissions by half in very short order.
    If only we could find a lot of it somewhere it would keep the Green fascists happy for decades.


    • John Cullen permalink
      May 10, 2021 10:19 am

      Hello Julian,

      I’m not sure you are entirely correct in being able to keep the Greens happy with your unEarthly idea since, as prof. Dieter Helm points out [Ref. 1], “Greens are very good at telling us what they are against. The trouble is there is not much left. They are against nuclear of course, they don’t like coal and oil, and they really hate shale gas, since ”

      1. Dieter Helm, “The Carbon Crunch”, Yale, revised & updated 2015, page 244.

      • John Cullen permalink
        May 10, 2021 10:24 am

        [Oh! The joys of computer editing. Aaaagh.]

        “… since they rightly realize that it is a direct threat to the economics of their preferred wind farms.”

        In other words it is politics and ideology rather than economics and science. And that is a tough nut to crack.


  24. Colin MacDonald permalink
    May 10, 2021 10:57 am

    We have a good number of Hydrogen fuelled buses here in Aberdeen, I actually like them, they are far quieter than their diesel equivalents. And no pm10’s etc. Given that the H2 is derived from Methane I’m uncertain as to how they help achieve our “emissions” targets.
    Indeed, given that they don’t use compression ignition one has to assume they’re even less efficient, I mean, there’s a reason all commercial vehicles run on diesel.

    • MikeHig permalink
      May 10, 2021 11:54 am

      Does that mean they use spark-ignition engines or do they have a fuel cell driving an electric motor?
      I’m no expert but I’m guessing that the very wide flammability/explosive range of hydrogen would cause difficulties with compression-ignition.
      Either way they will still produce NOx.

  25. Dan permalink
    May 10, 2021 11:13 am

    Anaerobic digester a for sewage will generate a gas typically 60% methane. Typically these units provide enough gas to power for the waste water treatment plant (electricity and gas) and for some electricity export.

    Ammonia is also generated during this process. There are several methods to deal with ammonia eichbis a poison at “high” concentrations to the digestion process, and not desired in the combustion gas. Many involve chemical/biological treatment options meaning the ammonia essentially gets broken down.

    There is a method where the ammonia could be contained is thermal stripping. This process is used but the resulting ammonia/air stream is typically combusted in a thermal oxidizer.

    Suez have built several plants in Hong Kong (1997) and elsewhere. Some energy is needed but it doesn’t appear to be a major concern for the overall balance.

    I presume that this process would be modified, possibly by stripping the ammonia from air using water. This produces anhydrous ammonia.

    Whatever the final use for the ammonia, the process seems mature.

  26. Gerry, England permalink
    May 10, 2021 12:06 pm

    Back when the Royal Institution’s Christmas lecture series could be watched without vomiting, the presenter was demonstrating fuel density by how many turns of the London Eye the same weight of each would achieve. It was to demonstrate a problem with batteries which in the new woke lectures would not be permitted, as the battery could not even achieve one revolution managing about a quarter. The best result was hydrogen but while petrol was included diesel wasn’t.

  27. Horse permalink
    May 10, 2021 12:38 pm

    To introduce a historical note, in the late 50’s I was apprenticed at a company that made industrial gas turbines. We had an contract to supply 8 1000hp turbines to the London Northern Outfall Sewage Works (Beckton Sewage Treatment Works?). Two of these were to drive centrifugal compressors and six generators. The scheme was to blow air from the compressors through sewage effluent in a tank or tanks, and use the resultant gas to power the gas turbines. The compressor turbines would be started on oil and then switched to the “sewage” gas once sufficient was available. I assume the scheme was viable but I have never seen confirmation, although I understand there were initial problems in preventing the sewage entering the air pipes when the compressors were not running!

  28. David Cox permalink
    May 10, 2021 2:14 pm

    Decomposition of ammonia into hydrogen and nitrogen is an endothermic reaction (see
    2NH3  N2 + 3H2 Enthalpy of reaction is -45.72kJ/mole.
    i.e the reaction requires an energy input of 45.72 kJ/mole of ammonia.
    This is equivalent to
    45.6 x 0.0012/4.184 = 0.1308 kWh/mole of ammonia
    Decomposition of 34 g of ammonia (2 moles) results in the production of 6g (3 moles) of hydrogen gas. On a kilogram scale, 34kg of ammonia would produce 6 kg hydrogen with an input of 261.6 kWh.
    The article suggests a yield of 2 g/tonne of sewage. On this basis 3000 tonnes of sewage needed to produce 6 kg of hydrogen. Manipulation of 3000 tonnes of sewage in the process is likely to require a lot more energy input! Similarly, compression of 6kg of hydrogen up to say 700bar (suggested by Joe Public, upthread) would require significant energy input, yielding a little over than 1 cubic metre of compressed gas.

  29. Dave Cowdell permalink
    May 10, 2021 2:22 pm

    Two things that I can not understand, first why has the Daily Telegraph even considered this worthy of publication unless the date was April 1st? Second, who is funding the trials for this, clearly there is grant funding involved probably a 3 year project, for such a nonsense concept?

    • tom permalink
      May 10, 2021 9:00 pm

      Dave Cowdell

      if you want to see what sort of stuff gets handed Innovation grants …..

      Look no further than the 16MB Excel spreadsheet at Innovate UK’ s .gov presence.

      I’d add that many of the larger items have parallel funding streams via other organs of gubbermint.

      • Dave Cowdell permalink
        May 11, 2021 9:34 am

        I have done a couple of NERC projects as an SME and after 3 years the project just misses commercialisation. Not to worry, up pops another grant application with the same project but with a different title. Keeps the heads of department comfortably employed. EU projects are a different matter however, you just need creative accountants.

    • Stuart Brown permalink
      May 10, 2021 10:06 pm

      Who’s funding it? Ofwat.

      This particular piece of nonsense is Organics Ammonia Recovery, who say themselves that the best way of dealing with the ammonia is to burn it to help drive the separation process from the sewage. See my comment above. But y’know, quarter of a million quid for free was worth a punt!

    • Stuart Brown permalink
      May 10, 2021 10:17 pm

      I’ve just looked at the other winners, lord help me. Some are sensible but:

      ‘Enabling Whole Life Carbon Design will deliver the tools and processes required to support the cultural and behavioural changes necessary to deliver low whole life carbon and cost solutions and ultimately ‘zero carbon emissions’ as a water industry.’

      They got quarter of a million too.

Comments are closed.

%d bloggers like this: