Putting the life back in science fiction

Next up, the ammonia economy?

This is another spun-off “strange attractor” from Antipope. It had nothing to do with the thread it was on, but the topic is interesting enough–if you’re into futuristic science fiction–that I wanted to summarize it here.

The basic idea is using ammonia as an alternate, carbon-free fuel. This isn’t as weird as it sounds, and there are a bunch of industrial efforts out there that might well project us into an ammonia age rather than a hydrogen one. Unfortunately, ammonia isn’t a panacea, so switching from fossil fuels to ammonia synthesized using solar or wind energy won’t be problem free. For those looking for dramatic conflict, ammonia has it.

Anyway, the fundamentals. Ammonia is NH3. If like me you’re lazy, you can go to Wikipedia’s article on energy densities, and find out that liquid ammonia has about 11.5 MJ/L of energy, slightly better than compressed natural gas (9 MJ/L) and liquid hydrogen (8.5 MJ/L), and less than propane (25.3 MJ/L) or gasoline (34.2 MJ/L), among many others.

As for making NH3, right now we make it in huge plants using the Haber-Bosch process, which makes ammonia using natural gas. Nitrogen is ubiquitous as N2 in the atmosphere, but N2 is a very stable molecule, and it takes a lot of energy to break it and turn it into NH3. Still, people are looking for better ways to do it. NH3 Canada is developing a miniature ammonia synthesizer that’s about four cubic meters in size and can produce 500 liters of ammonia per day, with each liter of ammonia taking 2 liters of water and 7.5 KWhrs of electricity to produce it. As a comparison, the average US home uses 909 kWhr per month or about 30 kWhr per day, which is about what it would take to make a gallon of ammonia using NH3 Canada’s technology. If it works.

To save you the math, that’s about 30% conversion efficiency, which isn’t bad. Ammonia synthesis could be used to store electricity from, say, wind turbines. The nice thing about NH3 Canada is that they want to use small units and stack them in banks, while the older technology uses huge furnaces to get efficiencies of scale.

What can you do with ammonia? You can actually mix it with gasoline and use it to run your car, if you get the mix right, and other researchers are working on creating engines that can run on pure ammonia. While there’s less energy in ammonia than there is in propane, it can be handled similarly. Pure (anhydrous) ammonia is fairly dangerous stuff, but then again, so is liquid hydrogen, and so are giant batteries if they’re fully charged. Energy density makes things dangerous.

Of course, ammonia has many other uses. We all know of it as a cleaner and fuel, and it used to be used in refrigerators before people switched to the much more efficient and dangerous CFCs [but see comments]. But it’s primary use is as a fertilizer and to make explosives, including gunpowder. Industrial nitrogen fixation underlies Big Ag all over the world, and it also underlies industrial warfare. Without huge amounts of gunpowder, things like machine guns don’t work, because there isn’t enough ammunition to make them fully functional killing machines.

Similarly, without huge amounts of nitrogen, the huge amounts of corn, wheat, and soy that are required to feed all seven billion of us wouldn’t exist. Some calculate that at least a third of us wouldn’t exist without fixed nitrogen in our food. The US has taken full advantage of this, and forcing huge supplies of cheap food on the world has been a major part of our foreign policy since the Eisenhower Administration. It was one way of beating communism, and protecting our high-yielding corn from things like being pirated by the Chinese is a matter of national security today.

I’m not a huge fan of Big Ag, even though I’d probably be dead without it. Still, if we want to switch from fossil fuels to renewables, adapting and expanding our existing fixed nitrogen infrastructure is a lot easier than trying to build the infrastructure needed to handle hydrogen.

That’s the good part. There are some downsides.

One is that when you burn ammonia in an engine, it produces NOx, which is a major source of air pollution. This can be fixed if there’s a catalytic converter on the exhaust pipe. I suppose, if you’re powering agricultural equipment, it might be possible to capture the NOx, convert it to nitrate or urea, and use it as fertilizer on the fields, thereby getting a second use from the fixed nitrogen.

One big problem with an ammonia economy is the same problem with renewables, which is that you’re capturing energy from the modern sun, and that’s all you get to play with. Fossil fuels use fossil sunlight from the last few hundred million years, and that’s a lot more energy. There’s no fossil ammonia, so we’d be stuck working in a lower energy environment. Currently, industrially fixed nitrogen takes about 1% of the global energy supply, but that’s a fixed 1%, and if it’s used for other purposes, people can starve. We’d have to ramp up NH3 production to store captured renewable energy, not depend on what’s already being made.

Still, I can envision a world where giant farms host an overstory of huge wind turbines, all hooked up to ammonia synthesizers. The farmer uses the ammonia to run his equipment, then uses nitrates captured from the exhaust to fertilize his fields. Aside from the scale and all the problems with nitrogen runoff and pollution, this isn’t a bad setup.

There are some interesting follow-ons.
–One is politics. If most of the world switches to synthesizing ammonia from sunlight or wind, the countries that depend on petroleum exports are out of luck. The only parts of the Middle East that would continue to matter to the US (and possibly China and Russia) are Egypt and Israel, due to the Suez Canal. This means that the burgeoning crises in the region would have to be dealt with semi-regionally, if at all. And that’s bad for all those refugees. Russia is likely to be a hold-out in switching off fossil fuels, since they get so much power from oil and natural gas, but switching to ammonia would change international politics as much as did the switch to using oil in the early 20th Century.
–A second issue is fertilizer. It is feasible to synthesize huge amounts of ammonia, but other elements are essential for plant growth, and the world is starting to run short of minable phosphorus. We may well have phosphorus wars in the future, but the simpler solution is to recycle sewage and manure onto fields. This has all sorts of public health and disease vector implications, but it will keep people from starving And there are menu implications–you want to eat raw salad from a field that receives sewage? It’s a common practice in the developing world.
–A third issue is air pollution. I can easily see people using ammonia to power things like home generators in areas where the power grid is failing, but if these machines don’t have decent filters on their exhaust, they will put out a lot of air pollution. The resulting smog will degrade the performance of any local solar panels, but it might be simpler than investing in huge batteries and a smart grid to provide power when the sun doesn’t shine.

And who will control the ammonia? A nitrogen-based economy has less energy than does the current oil-based economy. Energy becomes power when it is scarcer, even more than it is currently. Right now, we’re seeing how Big Oil distorts politics all over the world. Small ammonia generators, like the NH3 Canada machine, change the current game that is dominated by a few huge producers, because they mean that small-scale producers can make small amounts of fuel, at least in the short term. Probably this means that the advantage shifts from those who produce ammonia to those who build ammonia synthesizers and can best ship the ammonia from producers to consumers. Over time, I suspect that a few big ammonia producers will dominate the industry in any one area. They will be, quite literally, power brokers.

Still, switching to ammonia could slow down global warming, because the great advantage of NH3 is there’s no carbon emission from using it. It beats things like bio-diesel and biomass cold. Unfortunately, we’re seeing increasing methane emissions from the Arctic, so even if we get civilization’s carbon emissions under control, we may be passing the tipping point as you read this. We’ll see.

If you want to write a SF-thriller set in the next few decades, you could do worse than to power the world with ammonia, and make the Politics of N a centerpiece of the story. After all ammonia isn’t just a fuel, it’s a cleaner, fertilizer, and a refrigerant. Who wouldn’t want to get rich off it? Something to think about.


10 Comments so far
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Good article. I think that in practice the toxicity of ammonia is the main issue. Poor handling, leaks and spills could be very unpleasant. The positive benefits, e.g. no carbon combustion, easily adapted infrastructure, probably outweigh the negatives, but who knows. A pilot program would be a good idea.
A key issue will be cost – how efficient is NH3 production from renewable, or even nuclear, power?

As regards recycling phosphorus, why not sterilize the sewage before using on the fields. Concentrated solar thermal systems might work well, I would even try to extract the organic nitrogen if it was economic, burning the rest for energy and using the phosphate rich ash directly.

Correction: “(…) before people switched to the much more efficient (and LESS dangerous) CFCs.”

Comment by Alex Tolley

I appreciate the comments, Alex. Thanks! So far as recycling sewage through incineration, there are a couple of problems. One is getting the incinerator contents homogeneous enough that it can be burned efficiently without blowing off a lot of smoke and exhaust gases. This is a bigger problem with trash, but sewage does vary over time too. It’s an endemic problem with incineration. The bigger problem is keeping metals, arsenic, etc. out of the resulting ashes. It only takes a few jerks dumping toxic waste down the drain (or down the manhole) rather than properly disposing of it to make a lot of sewage too toxic to reuse in any form. I’ve heard stories of sewer workers welding manhole covers shut near metal plating companies just to make illegal dumping harder. This is a common problem with all recycling programs, actually.

As for the dangers of CFCs, you’re absolutely right, locally to users, they’re much less dangerous. In the atmosphere, they’re more dangerous in terms of ozone depletion and greenhouse gas activity. It’s one of those conditional statements that makes for great arguments in the comments…

Comment by Heteromeles

Does anyone have any good pointers to sources of useful information about the difficulties of sewage processing and recycling? My first thought in response to the contaminant problems for sewage recycling was a combination of filtration, fractional distillation and/or centrifuging/settling for sorting out everything. I’m sure that idea has already been studied–maybe even tried–and found wanting because it’s so simple and could be done with technology as much as a century old. (Probably takes too much energy or is otherwise cost prohibitive.) I don’t know these things however, and sources to read up about the issues and what hasn’t worked would help map out where old ideas end and new ideas start.

Comment by anonymous coward

I do, but unfortunately, my source won’t work for anyone else: I’ve got a close relative who’s on a waste committee for a major metropolitan area in the US and has been for decades. I’ve heard a lot from the perspective of someone who gets stuck trying to sort out the mess (quite literally). Every meeting they get proposals from businesses that want to divert some stream of waste and recycle it. Almost always, the problem is that there’s no way to get the waste stream homogeneous enough for the proposed method to work. It’s really a problem of a few idiots messing everything up. For example, when I used mulch from a city on a landscaping project, it also contained used diapers and other trash, because people had been too lazy to find the right bin to throw their trash in. Household cleaners, antibiotics, even wet wipes make it harder to recycle sewage, and so forth. They have taken measures like welding down the manhole covers near a metal plating shop to keep that shop from dumping its excess metal waste down the sewer, but getting every last idiot to stop being idiotic is impossible. This is a general issue with environmental problems: all too often, the system is vulnerable to the actions of a few idiots, so even if almost everyone is doing the right thing, a few idiots can still make it unworkable.

What did work a century ago was people buying household waste, and you can read about that in King’s Farmers of Forty Centuries, where Asian merchants bought night soil and sold it to farmers as fertilizer. The downside of that system is that you had to cook all food, and even then, GI diseases spread fairly regularly through the food supply. In the developing world today it’s not uncommon for farmers to use urban sewage, from sewers, with the metal contamination and everything, then to sell the resulting vegetables back to the urbanites. Supposedly the farmers figure that if the urbanites cared about having healthy vegetables they’d do more to clean up their sewage, and it’s one reason I’m not interested in eating raw veggies in most parts of the world.

Comment by Heteromeles

“…but getting every last idiot to stop being idiotic is impossible.”
This squares with my expectation that people will be stupid, no matter how much you educate or incentivize them not to be, or punish them for it. On a less theoretical level, preventing all damage caused by stupidity is impossible in the real world as long as Upper Class Twit of the Year-type corrupt idiot children of the affluent continue to grasp the levers of power: At best education and idiot-limiting moves are a supplemental approach since economic and technological development is putting ever-increasing power into the hands of those idiots.
This requires a systematic solution that would clean up any imaginable pollution problem that doesn’t exterminate the human race outright. That realization got me focused on sewage, since it does get adulterated with every other kind of liquid and mixed-phase pollution that it can be.

Comment by anonymous coward

I agree with what you said, AC, but it’s important to realize that it’s idiots of every level of society. Janitors using toxic cleaners can cause as much trouble as a high class twits. They’re different kinds of problems, but any solution to waste disposal has to be idiot proof, and that’s been the biggest technical barrier so far.

Comment by Heteromeles

It’s hard to run an internal combustion engine on pure ammonia. If you partially pre-dissociate ammonia to about 10% hydrogen the mix will burn reliably in an ICE. You could also pre-dissociate nearly 100% of it to hydrogen and then the ammonia just becomes a storage intermediate for hydrogen. Last year researchers published a catalyst system based on cheap, abundant elements for this ammonia-to-hydrogen back transformation: http://pubs.acs.org/doi/pdf/10.1021/ja5042836

The X-15 space plane used anhydrous ammonia as fuel; it worked there because combustion in pure oxygen is more vigorous: https://en.wikipedia.org/wiki/North_American_X-15

Engines running on hydrocarbon fuels form nitrogen oxides also, particularly when they are burning lean. That’s why catalytic converters made since the early 1980s are designed to break down nitrogen-oxygen compounds. Lean ammonia combustion produces more nitrogen oxides than hydrocarbon combustion, but so far I haven’t been able to find quantitative data on the final emissions levels after exhaust goes through a catalytic converter. If the tailpipe emissions limits can’t be met with conventional catalytic converters, you could instead use a urea based selective catalytic reduction system like newer diesel trucks are equipped with: http://news.pickuptrucks.com/2014/04/top-10-facts-about-diesel-exhaust-fluid.html

The round trip conversion efficiency of electricity + water + nitrogen -> ammonia -> mechanical motive power is low. I don’t think it is significantly more efficient than electricity + water + CO2 -> hydrocarbons -> mechanical motive power, and the hydrocarbons are significantly more energy dense. Applications where energy density is critical like air travel and satellite launches will probably still use synthetic hydrocarbons even after the fossils run out, assuming there’s not a total complexity collapse. Applications where efficiency is more important are better off with batteries. I think there is a niche for agricultural use, though, since if an agricultural region already has a system for making ammonia fertilizer the excess production potential is “free” or very cheap fuel. Maybe there’s a niche for powering large ships too, where you need more energy density than batteries provide but much less than aircraft need.

Comment by Matt

Good points, Matt. I’m throwing it out as an interesting alternative that gets us away from carbon-based fuels altogether, but as you correctly point out, carbon-based fuels are generally more energy dense, and that’s always going to be part of their appeal.

Switching from fossil fuels to nitrogen fuels is somewhat like switching from assault rifles to air guns. The air guns may or may not be better than the muzzleloaders which are the other alternative (Google girandoni air rifle if you want to see what I’m hinting at), but the last guy to abandon his assault rifle retains a huge advantage until he runs out of ammo, no matter how much destruction he causes in the process.

This gets to the whole other topic, of what the differences are between transforming society to be sustainable and society collapsing to a sustainable level. The problem with continuing to use carbon, even if it’s synthetic fuels, is that you’re not getting carbon out of the air, with all the problems this causes with exacerbating climate change. With a nitrogen economy, one can theoretically use nitrogen and batteries as major energy storage media, and limit carbon to the carbon sequestration industries, where the goal is to get carbon into the soil and plants and keep it there as long as possible. There might be some political advantage to doing this, or not. At this point, I’m simply playing with the idea and throwing it out for others to play with.

Comment by Heteromeles

Synthetic hydrocarbon production works against atmospheric CO2 reduction goals if dead plant matter that would otherwise lock up carbon is being converted to fuel. That’s one of the ways that biofuels fail at carbon neutrality, even if (especially if?) they are made out of “waste” materials that normally wouldn’t be used by humans at all. Accelerating the breakdown of waste biomass to make fuels means that each carbon atom spends a larger portion of time in the atmosphere, where we don’t want it, even if you’re not compounding the damage by using fossil inputs to grow/harvest biomass.

I don’t think that the same problem applies to synthetic hydrocarbons made from CO2. Making nitrogen based fuels is not reducing the equilibrium CO2 concentration of the air either. Both synfuel approaches are orthogonal to reducing atmospheric CO2. Now if you’re positing underground injection Carbon Capture and Storage projects that start diverting part of their CO2 to make synthetic hydrocarbons, ok, that makes things a bit worse… But I think CCS is a pipe dream anyhow.

Both synthetic ammonia and synthetic hydrocarbons could make global warming worse via indirect effects depending on how they are used. Leakage losses of synthetic methane could increase global warming just like leakage losses of fossil methane, since methane has a significantly higher global warming potential than CO2 in the medium term. Depending on the combustion conditions and post-combustion treatment, ammonia can form some of the even more potent GHG nitrous oxide.

Comment by Matt

Another comment about ammonia: I adore electrochemical solid state ammonia synthesis. It operates at low pressure and is much simpler than Haber-Bosch. Scale-up would be done by replicating small reactors in blocks, similar to how a big solar PV plant is just small PV plants tiled over a larger area. One of the major SSAS developers is located in my town and has done proof-of-concept work with the national laboratory I used to work at. A few years ago I thought it was going to be the next big thing in ammonia.

Unfortunately for this promising technology, first the great recession drove ammonia demand and prices way down from where they were in 2008. Then fracking drove American natural gas prices down so that instead of Haber-Bosch ammonia plants closing in the US, as was the trend a decade ago, they’re building more of them. Back in 2008 it looked like SSAS driven by wind power could turn a tidy profit on ammonia, competing with natural gas based Haber-Bosch plants. That scenario is now on hold indefinitely.

Comment by Matt

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