I’ve long argued on this blog that that fossil fuel replacement this century could, on technical grounds, be achieved via a mix of nuclear fission, renewables and perhaps also fossil fuels with carbon sequestration, with a high degree of electrification; nuclear would probably end up supplying over half of final energy.
A key component of this energy revolution would be to find feasible ways of converting clean electricity (or heat) into a usable liquid fuel, to replace oil. Although biomass will provide for some of this demand, it is unrealistic to expect vast areas of arable land to be turned over to ethanol production, and as such, various synfuels (e.g., hydrogen and hydrogen-nitrogen or hydrogen-carbon derivatives such as ammonia, hydrazine and methanol) will necessarily be required, manufactured using energy inputs to liberate free hydrogen from water, plus atmospheric or concentrated gas streams to provide the other constituent elements (C, N, O). (A useful recent overview of this topic is Forsberg 2009, Is hydrogen the future of nuclear energy?).
The hydrogen used in synfuel production will likely come from either electrolysis at ~30 % electricity-to-hydrogen conversion efficiency, or via direct nuclear (or solar) heat via high-temperature thermochemical water decomposition, catalysed using the hybrid S-I or Cu-Cl cycles, at a 60 % heat-to-hydrogen conversion efficiency (Orhan et al., 2010). The ratio of future (c2100) direct electricity use to the final energy used in synfuel manufacture (via electrolysis and nuclear heat) was estimated to be 0.4 by Eerkens (2006, pg 135), although this figure did not include battery electric vehicles or biofuels.
Okay, enough background from me. What I really want to highlight here is a recent presentation by Darryl Siemer (in collaboration with Kirk Sorenson and Bob Hargraves) at the 8TH Annual NH3 Fuel Conference 19-21Sep11, Portland OR. It’s entitled “Nuclear Ammonia – A Sustainable Nuclear Renaissance’s ‘Killer App‘”. Darryl notes that:
The case it makes for a US nuclear renaissance implemented with LFTRs would apply with equal force to one implemented with S-PRISMs [IFR]. There never will be a “second nuclear era” if we can’t/won’t convince people that it’s got some unique “killer apps”.
Above is an example slide. There were 50 slides presented in his main talk, plus another 64 kept in reserve for questions! You can view the lot here. It is well worth reading carefully through the whole deck — it is packed with useful information. (My only significant critique is the conflation of “uranium” with the once-through fuel cycle — the sustainability advantage of LFTRs/thorium are equally applied to uranium if the spent fuel is recycled in fast reactors).
After presenting at the conference, Darryl told me the the following:
My talk went great – 49 slides in 27 minutes (just two minutes over) followed up by ten minutes of question-answering during the subsequent break. During the 8 years that this conference has been going on, it was only the second talk given about how nuclear power could make it all actually come true… One thing that the audience seemed to appreciate was its explanation of how nuke-powered cement kilns could make the GHG-neutral “CHx”-type synfuels needed for applications (aviation, chainsaws, etc) that ammonia wouldn’t be much good for.
By the way, who is Darryl Siemer? Here is a brief bio: Darryl Siemer, Ph.D., is a retired Idaho National Laboratory “Consulting Scientist” and an expert in virtually all of the technical aspects of radioactive waste management. Dr. Siemer has 76 journal publications in subjects including electronic circuit design, “wet” analytical methods development, atomic spectrometry, chromatographic instrumentation, cement/concrete formulation, and chemical engineering/materials science related to nuclear fuel reprocessing and waste management. He earned his doctorate in chemistry from Montana State University in 1974 and was an assistant professor of chemistry at Marquette University from 1974-1978. Since then he has served as an affiliate/adjunct professor at the University of Umea (Sweden), Pennsylvania State University, the University of Idaho, and Idaho State University.
This is also interesting — a video of a car that runs on ammonia:
It’s not just about ammonia, of course. As another potential vehicle fuel, you can read about the boron car concept in the online chapter on that topic from Prescription for the Planet (by Tom Blees). And for further details on boron, see these articles by Graham R.L. Cowan at the SCGI site. In short, there are some really exciting possibilities for decarbonising the transport sector in addition to stationary electricity, once we have in place the clean electricity and heat sources such as nuclear fission. I hope that these slides and articles help you better grasp that important holistic view.
123 replies on “Nuclear Ammonia – a sustainable nuclear renaissance’s ‘Killer App’?”
I think for various reasons synthetic methane, rather than ammonia will be the fuel of choice. Sunk costs, the possibility of blending it with natural gas and its nontoxicitiy all speak in favour of methane. In addition to using it in CNG/LNG vehicles, it can be converted further into more complex liquid hydrocarbon fuels, like kerosene.
The CO2 necessary to produce methane will most probably not be drawn directly from the air but come from digested biomass. Biomass digestion produces mostly CH4 and CO2. The CH4 would be fed directly into the gas grid, while the CO2 would be combined with hydrogen to produce yet more CH4.
I think George Olah, Nobel prize winner in chemistry, would agree with you. Read his book on The Methanol Economy.
As an experiment I’ve tried burning charcoal in pure O2 from water electrolysis. Needs more work. If at all possible N2 and H2S should be excluded which is why flue gas and air injected underground coal gasification UCG are not good primary sources of CO2. Clean air at .04% w/w is too dilute.
The thing that gets me about gas enthusiasts (NG and CSG) they seem to think it is forever. Somehow we can export most of our offshore gas resources as LNG, replace coal fired baseload power stations, make urea fertiliser for an ever growing population, balance wind and solar and use it to replace diesel. It all sounds good. What do we do in the second half of the century when the cheap gas is gone? Gas seems to be regarded as an inorganic magic pudding. Inorganic because it doesn’t make much CO2 when burned and a magic pudding because no matter how much we use there’ll always be more. Wrong on both counts.
Regarding using biomass plus nuclear hydrogen to make methane or other fuels:
The aviation industry will have priority access to this type of fuel (hydrocarbon synthetics), because everything else is much worse for jets. I don’t see aviation disappearing, because jets really are faster and in some cases cheaper than high speed trains.
We’ll have enough trouble growing enough biomass just for the jets (even with a 2x? improvement from the nuclear contribution). Any extra land we put to this use reduces the area that we can devote to food production and wildlife.
On top of that, it is not clear that synthetic methane can beat the price of ammonia. That’s the deal breaker.
Yeah, with the addition of nuclear hydrogen to convert the CO2 produced in anaerobic digesters to methane, the yield doubles.
I did a back of the envelope calculation (too bad I lost the excel file when my notebook crashed) that Germany could supply all of its transport energy requirements that way, using only 10%-20% of the availible agricultural land, which the environment ministry says is sustainable and doesn’t impact food prices.
Anyway, it would be unrealistic to think that all transportation would be powered by synthetic methane. Whatever can be electrified will be electrified and in addition to that there will be a substantial shift from non-electric to electric transportation, so the actual methane demand would be far lower than gasoline demand today.
Biogas seems to be far superior in energy yield per hectare compared to liquid biofuels. It gets even better when combined with hydrogen.
In addition to that hydrocarbon compounds are used in countless products without which life as we know it would be unthinkable. Hence we’ll need to produce carbon-based synthetic liquids even if we don’t use them for transportation.
Realistically, what are the applications for which liquid (or energy dense) fuels are indispensable? The only ones that come to mind are:
– Long-distance trucking
– Small boats (cargo ships could probably work quite nicely with NPPs)
– Cars that do 200km+ trips on a semi-regular basis
How can we solve these specific applications? Well, Aviation will probably have to survive on synfuels – nuclear-sourced process heat and electrolysed hydrogen would be a good way of making that less GHG-intensive. Heck, you could source some of the syngas feedstock from plasma arc gasification.
Boron (As proposed by G.R.L Cowan and promoted by Tom Blees in Prescription) might be a good application for trucking and maybe even small boats, although there might be issues with oxygen generators and marine environments.
DME synfuel would make a lot of sense as a ‘drop-in’ solution for personal transport and possibly as an interim one for marine and long-distance trucking.
The biggest question of all however, is how do you get the current industries and end-users to switch over to our cleaner alternatives that have been proposed in the comments here?
How to get industry to change?
Make it insanely profitable.
Heat from coal is 8 times cheaper than heat from oil. Make vehicle fuels from carbon-neutral blends of coal + cellulosic biomass.
Has about 10% more energy than oil, can be distributed in today’s distribution chain and consumed in today’s vehicles.
The downside would be powering the plasma torches and dealing with what the carbon-capture system captured.
Long-distance trucking will not have a bright future unless cheap, light, very high capacity batteries are developed or synfuels cost about the same as gasoline / diesel today, which I doubt will be the case.
Aviation will continue to need hydrocarbon fuels. Our entire mature aircraft technology and aviation infrastructure is built around that type of fuel. Hydrogen is not really a viable alternative right now. It is too bulky and too difficult to handle. The result of the aviation sector’s reliance on liquid fuels will probably be that people fly less than they do today. Short-haul flights will lose out to high speed rail and even some transcontinental long-distance services may lose market share to high-speed sleeper trains (the Chinese plan a high-speed connection from Beijing to Moscow and Berlin, on entirely new tracks designed for speeds of up to 350 km/h).
Small boats could be electrified. I’m skeptical about nuclear freighters. Safety and proliferation concerns will probably preclude the widespread adoption of nuclear propulsion in shipping outside of special niches. Imagine the public outcry if a nuclear freighter were taken over by Somali pirates!
Large cargo vessels will probably use synthetic methane (LNG)/ammonia or any other suitable synfuel. Computer-controlled kites and sails will see widespread use because the use of such systems reduces fuel consumption. If synfuels are very expensive, we may even witness the return of pure sailing vessels for “slow cargo” and the construction of a large transcontinental railway network in Eurasia.
LNG tanker ships (bubble boats) already use vapour from the cryogenic tanks as fuel. Mine trucks are starting to use LNG
The tanks appear to be shielded from falling rocks. Allegedly the expansion of the Olympic Dam mine will take 19 billion litres of diesel so LNG is an alternative.
I think CNG could power farm machinery even if the region has no gas lines. Mother cylinders could be used to refill vehicle sized cylinders. There are going to be accidents and methane leakage but that’s the price for squandering oil.
On the price point for synfuel it seems possible that petroleum based fuels may not increase in price that much even as they run out. Note how a barrel of oil stays under $120 or so despite a decline in exportable crude since 2005. The lack of a price signal to make the switch is arguably a form of market failure.
The price signal is causing switching on the supply side, as natural gas to diesel (Shell, Qatar), and tar sand mining (Canada) become reliably proffitable and enter the market. Coal-to-liquids, and perhaps some newer coal + gas to liquids processes would also be proffitable at current prices, but the risk associated with building a plant that then might not opperate if oil prices decline is preventing implementation for the moment. Demand side switching requires much higher prices. European fuel costs of ~$2/L ~ $7.50/US gal have not yet provoked a big switch to electric or even plug-in hybrids, just smaller and incrementally more efficient conventional vehicles. Battery cost/performance is still not good enough, even here. The oil price on its own is never going to push this transition.
I think for transformation of biomass into methane, partly direct and partly via CO2, you could use plancton from seawater instead of corn or grass grown on agricultural land. This is what actually happens in nature so you would win two times,
getting usable methane and reduce the input of carbon dioxide and methane into the atmosphere/raising the pH of the oceans.
Don´t forget you can re-concentrate nitrogen and phosphorus as well.
A recent review of solid-state ammonia synthesis suggests this still has a very long way to go
paywalled, unfortunately, but the public abstract contains the useful information
10^-8 is a lot of zeros in the wrong place. Converting to more sensible units, 1.13E-08 mol/cm2/s is 1.13E-04 mol/m2/s or 0.113 mmol/m2/s
Ammonia energy content is 317 kJ/mol or 317 J/mmol (Reference in Roger clifton’s post, above), so the power supplied as ammonia is 317 * 0.113 = 36 W/m^2.
The electrodes used are porous with lots of internal surface area, but it’s still a few watts/g. You would need hundreds of tonnes of expensive rare-earth catalysts to build powerplant-scale facilities. Of course, if a company were working to develop this and made a major improvement, it wouldn’t get published in the open literature and get picked up in the review, but Haber-Bosch isn’t looking too threatened just yet, and ammonia produced by Haber-Bosch and burned in engines is not a great energy carrier, the losses are too high. If you can replace that with solid state synthesis to do electricity + steam + nitrogen –> ammonia + oxygen, and then use the related technology of ammonia fuel cells to reverse the process in the vehicle, the round-trip efficiency will beat anything except batteries, and without range limitations. That realy would be a ‘killer app’, but we’re not there yet.
Hydrazine fuel cells make sense because the two nitrogens are already together. What evidence is there of the existence of ammonia fuel cells?
References for direct ammonia fuel cells:-
Lots of talk, some lab demos, nothing scaled up.
For the production of synthetic methane, the source of the CO2 will most likely be biological. Growing plants is the most cost-effective way to bind large amounts of atmospheric CO2. Since liquid fuel demand will be much reduced by the time we need synfuels (which is after we have completely decarbonised the electricity sector, land use competition between energy crops, food crops and undeveloped land shouldn’t be a major issue. The best thing would be, however, to tap into oceanic biomass (algae) to get that CO2.
Renewables may be quite useful for the production of synfuels, since intermittency is not so much an issue here. In some regions, the marginal cost of a kWh wind power (although intermittent) is lower than the marginal cost of a kWh (new) nuclear power.
I agree that bio-carbon is already ‘in the loop’ above ground. This gives rise to arguments whether building timber is a more sequestered form of carbon than say paper pulp which will soon be burned or rot. I tried a Filipino method for making charcoal from grass but it made a smelly mess. The advantage of perennial grasses is that they don’t need trucks and chainsaws to harvest or any replanting. Roadside weeds, food processing waste and gasified garbage are other sources of biocarbon. I’m not confident that commercial algae farming will succeed.
The converse is of course that coal, oil, gas, kerogen, bitumen and limestone are pre-sequestered carbon that we are returning to the atmosphere after millions of years safely underground. Leaving it all there doesn’t appear to be an option.
Using excess windpower may have problems we don’t know about yet. I was surprised to learn offshore wind turbines may need diesel generators for black starts after being idled.
In my opinion we should encourage the use of natural gas instead of oil in transportation wherever possible. This would make the switch to synfuel CH4 easier after the electricity sector has been decarbonised. To totally eliminate emissions we’ll have to eventually use carbon which is recycled above ground.
I’m not talking about using excess wind power. The most economical option would be to use the wind turbines solely to supply power to the electrolyzers. Energy crops such as corn or perennial grasses could be grown on the land between the turbines.
How much methane/CO2 could we produce from the bio waste produced every year in the US or some other country using anaerobic digestion?
Charles Forsberg has published several papers on using nuclear heat and hydrogen to enhance the energy available from biomass. He thinks you could get enough diesel / kerosene this way for most of US transport demand – 1.3 billion tonnes / year of biomass at 45% carbon giving ~680 million tonnes of diesel, about 12 million barrels/day. Methane would have higher energy content for the same carbon.
Conference paper http://wp.ornl.gov/sci/scale/pubs/ldoc8011_aiche07_nuc_biomass_liq_fuel_paper_clearancer.pdf