Imagine, if you will, a sack of fertilizer and a flask of wood alcohol, sitting at a bar. Through the entrance comes a streamlined ship of the sea, a proud and beautiful cargo cruiser of the waterways of the world. She’s come to drink away her sorrows at her long-standing relationship with the bad boy of energy, residual bunker fuel, known by his friends and enemies simply as resid.
Both the sack and the flask immediately set out to woo the vessel. And so they tell her their stories of how much better they would treat her and her sisters than resid would, how responsible they are, how long their own histories are. They tell her that while they are traditionally do not consort with beautiful marine vessels like her, instead having long-standing, non-monogamous relationships with fields and industrial plants, they would like to welcome her and her sisters into their non-traditional relationship.
Now, both fertilizer and flask have dirty secrets of their own. Both spring from the samewomb as resid. Every ton of them is made from crude oil’s brother natural gas today, who had a much better image, but has since been found to be almost as coarse as resid beneath the dapper attire.
But they both promise that they are working on being better, that they will clean up their ways, that they have big plans to improve themselves, and besides, compared to resid they are practically altar boys. They both tell her that they are working on parting ways with gas, and instead turning to water, specifically the squeakiest clean part of water, the saintly hydrogen. Apply a little tingle of electricity, and the saint is released to be turned into the contents of the flask and sack.
It’s working, too. The ship is leaning toward them, hoping to be able to get free of the cruel grip of resid and the abuse he wreaks everywhere he goes. She’s willing to believe their stories, but somewhere in the back of her mind, a little voice is asking, “Is this too good to be true?”
Of course it is
When I was in Glasgow at Stena Sphere’s technical summit this week, methanol as a shipping fuel was central to the discussions of maritime decarbonization. Ammonia was smelling up the wings but not present, as an ammonia organization had declined to send a representative. Stena has already ruled out ammonia in any event, but does have a joint venture with Proman for methanol, which means that stakeholders in the group are already somewhat committed to the pathway. That’s going to be challenge for them, but Maersk is much more committed.
Let’s start with the basics. Methanol is an alcohol that is manufactured from natural gas right now. My sources suggest 170 million tons of annual market, but the Proman representative Peter Schild used 120 million tons as the figure. Regardless, between 100 and 200 million tons of methanol is already manufactured around the world. The 800-pound gorilla, Methanex, buys old chemical processing plants, rejigs them for methanol manufacturing relatively lose to markets and ships short distances to customers. The methanol industry loves the idea that its product will become the clean fuel for maritime shipping, as even with my 170 million tons and massive electrification and efficiency programs cutting burnable fuel demands by two-thirds, what’s left over is a tripling of their annual market. That’s not a new market, that’s a multiplication of their market. If the methanol industry can make their case, they’ll be ramping up plants globally and all the current major players will be giving their shareholders dividends hard to dream of before the transition.
Ammonia isn’t an alcohol. It’s a nitrogen molecule and three oxygen molecules. We manufacture about 150 million tons of it as well, almost entirely for fertilizer, and also manufacture it mostly from natural gas. It’s not as good at burning as methanol, it has the advantage that it doesn’t have carbon, so no CO2, and the disadvantage that it has lots of nitrogen and so is more likel to create N2O with its global warming potential of 265 times that of CO2. Oh, and when it interacts with water it turns from a liquid whose fumes will screw a sailor up for life to a corrosive gas that will just kill them before turning into a third chemical that goes back to being really bad for human health.
Neither ammonia or methanol can share tanks with other fuels. They are other. They are separate. So in ports, if we wanted to use them as marine fuels, we’d need new tanks and new pumps and new hoses, not an insurmountable requirement. We ship both of them around the world, as both are essential industrial and agricultural feedstocks. Most ports aren’t equipped to deal with either of them. While the Proman representative’s slides talked about 122 ports with methanol storage, there are about 800 ports worthy of the name and the ports with methanol storage aren’t focused on putting the methanol in fuel tanks, but distribution storage tanks.
As both ammonia and methanol are made rom natural gas, they are both climate change problems. Methanol is made from a process that turns the natural gas into an intermediate synthetic gas which it then distills into the alcohol. While the industry makes the claim that its manufacturing carbon footprint is 0.2 tons of CO2e per ton of methanol, peer-reviewed independent assessments put it at 1.4 tons of CO2e per ton of methanol. I find the independent assessments more reliable. And, of course, when you burn it, the carbon in the alcohol binds with oxygen.
Every ton of fossil-derived methanol burnt produces over three tons of CO2. Oops. That means using methanol today results in about 4.5 tons of CO2e for every ton of methanol burned. That’s worse than burning resid or diesel by a lot, as they have emissions of about 2.7 tons of CO2 per ton of fuel.
And then there’s the kicker. Methanol has about 45% the energy density by mass as resid or diesel. That 4.5 tons becomes 10 tons. Yeah, burning methanol instead of more directlyburning fossil fuels results in 3.7 time the CO2 emissions for the same distances traveled. In its current form, methanol isn’t remotely a solution, it’s an amplification of the problem by a factor of four.
Ammonia represents demand for about 30 million tons of hydrogen a year, and each ton of hydrogen drags 8-10 tons of CO2e behind it between upstream emissions and CO2 from steam reformation with natural gas. That’s about 7 tons of CO2e per ton of ammonia. When ammonia is put on fields, part of it turns into N2O, one of the oxides of nitrogen, with its high GWP of 265 times that of CO2. That means the lowest emissions form of ammonia’s dominant use results in about 10 tons of CO2e per ton of fertilizer. It’s a big climate change problem, in the same magnitude range as global aviation and marine shipping, and requires fixing.
Oh, but wait. This begs the question. If putting it on fields produces lots of nitrous oxides, what does burning it do? After all, any combustion in our nitroge-rich atmosphere tends to bind oxygen and nitrogen into N2o. Of course, this has been studied. The range of combustion in maritime engines is from 0.06 grams of N2O per kWh to 1.95 grams of N2O per kWh. What does that do to the already high tons of CO2e per ton of ammonia? (I really didn’t want to do energy and mass unit conversions after 20 hours of travel across eight timezones yesterday, so I’m going to go make another Americano before starting this. Hopefully I’ll get it right the first time.)
Ammonia has an energy density of 15.6 MJ/L. That 15.6 MJ is 4.3 kWh. Burning it in a high-efficiency marine engine means that we would get about 50% of that energy as useful forward motion, or 2.16 kWh to be generous. Heading up to metric tons, that means about 2,160 kWh. At 0.06 grams of N2O per kWh, that’s about 0.000132 tons of N2O. At a GWP of 265, that’s the equivalent of only 0.03 tons of CO2e per ton of ammonia. That’s not bad.
But the increments of emissions go up fast. The next on is 0.47 grams N2o per kWh. Plugging that in gets 0.26 tons of CO2e per ton of ammonia on top of the existing CO2e debt. The top end of ammonia emissions is 1.95 grams of N2O per kWh and plugging that in results in 1.1 tons CO2e per ton of ammonia.
Achieving the best case scenario requires engines carefully designed to create those levels, careful maintenance, and no contaminants in the ammonia. For this workup, we’ll assume that on average the second lowest is most likely, and add 0.26 tons of CO2e to emissions.
And it has a lower energy density than methanol, about 42% that of resid or diesel. That means that while it doesn’t produce CO2 when burned (no carbon in the NH3 molecule), its actual carbon footprint per nautical mile is over six times that of resid or diesel today.
