Ammonia synthesis from natural gas is responsible for ~2% of all CO2 emissions. We can make CO2-free ammonia and also use it for fuel, It’s NH3, more energy dense than liquid H2.
Ammonia synthesis may come from electricity, water, and air, using emerging technology. It may also be made using the intermediate hydrogen vector.
Besides its use for fertilizer for almost half of world food production, it has a new role in replacing residual fuel oil burned in shipping. It may also find a use in fueling heavy trucks.
Sulfur is the air pollutant that the UN’s International Maritime Organization is trying to reduce. Over 39,000 large ships ply the ocean water.
Burning fuel containing sulfur produces sulfur dioxide, SO2. It is sewed into the atmosphere where it combines with H2O to make H2SO3, sulfuric acid. This is the cause of acid rain. It also nucleates small particles that can cause respiratory distress.
Most nations eschew fission power for ship propulsion. The advantage of cheap fuel-ups that last for years has been dismissed by politics, not science.
This graphic of (mostly) CO2 emissions illustrates that they were expected to rise from 1 Gt/year to 2 Gt/year by 2050, even if the industry used energy efficiency measures such a slowing the speed of ocean transit vessels.
Most of IMO motivation for reducing ship emissions comes from SO2 emissions. Today’s fuel could be expensively reprocessed to reduce sulfur from 3.5% to 0.5% at refineries, or alternative propulsion power sources can be used, such as nuclear power or ammonia fuel.
Today ammonia is made from natural gas methane (CH4), emitting CO2 in the process. With a cheap hydrogen source, we can manufacture ammonia, which emits no greenhouse gasses when burned.
A difficulty with ammonia fuel is that it is has only 1/3 the energy per unit volume, compared to petroleum fuels. Either storage tanks must be 3X larger or range must be reduced. Hydrocarbon fuels are comparatively excellent in energy density compared to alternatives.
You can literally “burn” air, combining oxygen and nitrogen to make NO2 and NO3 if the temperature is hot enough, as in high compression piston engines. NOx is a noxious greenhouse gas that can cause haze and acid rain. Volkswagengate was about bypassing NOx removal systems to increase mileage.
The US DOE published a nice, readable technical introduction to ammonia fuel.
Ammonia NH3 fuel is difficult to burn well, because the ignited flame spreads more slowly in the engine cylinder than, say, methane CH4 fuel or other hydrocarbons.
Some ammonia carriers have been fueled with CNG (compressed natural gas). NYK will use some of its cargo fuel (ammonia) likely mixed with CNG methane CH4 to accelerate combustion.
Here’s an introduction to engineering combustors for pure ammonia fuel.
Ship engines can be really big, powerful, and slow. Making them cost-effective with ammonia fuel is emerging technology.
With tens of thousands of expensive cargo ships in operation, retrofitting existing engines is an large, important business opportunity for MAN.
Fritz Haber and Carl Bosch founded the industry to produce ammonia at global scale over a century ago. With out ammonia fertilizer we’d only feed 2/3 of the world’s population. Each received a Nobel Prize for this.
Haber later developed chlorine gas used in World War I. His wife became distraught and committed suicide.
Ammonia can be a feedstock for solid fertilizer manufacturing, or may be directly injected into the soil.
Diesel fuel was in short supply during World War II, and Belgium public transportation relied on ammonia mixed with coal gas (CO and H2) for public transportation.
The X-15 fuel was ammonia and liquid oxygen.
The max speed of 7,274 km/h (2 km/sec) at 31 km altitude was the highest ever recorded by a crewed, powered aircraft.
This truck crossed America on a fuel mixture of ammonia and gasoline.
To make the car more eco-friendly, it has been equipped with a Bigas International NH3 engine system that uses ammonia to enable the model to have zero emissions at low speeds. When more performance is required, the 2.0-liter four-cylinder petrol engine takes over.
Ammonia can be toxic. The industry is experienced in the safe production, transport, and use of ammonia.
The 3000 miles of pipelines transfer ammonia to farming regions.
Since ammonia is toxic, many people dismiss it out of hand, without further analysis. [Like fission power?]
Studies concluded the risks of using ammonia is similar, if not lower, than for gasoline, LPG (liquified petroleum gas), LNG (liquified natural gas), CNG (compressed natural gas), methanol, and hydrogen in internal combustion engines or fuel cells.
Ammonia fuel handling might well be limited to professionally trained ship crews and truck drivers. This may be important because the shipping and heavy transport sectors use 2000 GW of power. Power consumed by individuals’ EVs will amount to about 300 GW.
I’d initially considered that hydrogen (H2) from electrolysis would be a feedstock for ammonia (NH3) synthesis, just as in the Haber-Bosch process. Additionally, a solid oxide fuel cell can make ammonia directly from water and air.
Agricultural Iowa understandably studies such ammonia synthesis.
Recently this process has been advanced by Haldor Topsoe, a Danish company with a reputation for catalysts.
Reduces energy costs by combining both exothermic and endothermic chemical processes in the same solid oxide electrolysis cell (SOEC).
Item 3 implies that the reversible SOEC/SOFC might act as an energy storage device.
Item 4 says we won’t run out of materials for catalysts.
Item 5 emphasizes the risk of relying on supplies of lithium for Li-ion batteries, and platinum catalysts for hydrogen electrolyzers.
Darryl Siemer estimated 6800 kWh per tonne of ammonia produced. Haldor Topsoe predicts 7200 kWh/t! With cheap electricity the world can have cheap ammonia fuel.
Confession: no cost estimate for plant capex depreciation.
Ammonia energy is competitive with gasoline energy.
Ammonia fuel in a combustion engine will be cost competitive with gasoline in a combustion engine.
However, we don’t have to burn ammonia. An ammonia solid oxide fuel cell generating electricity for an EV will be twice as efficient in energy use and in $ per 100 km. Fuel cell EVs running on hydrogen pay the penalty of needing 700 bar compressed hydrogen in reinforced onboard tanks. Ammonia is more energy dense, at only 10 bar pressure.
The world would use 700 GW of ammonia-carried power in this model of a fully electrified world, with 400 GW to replace residual fuel oil for shipping cargo, and 300 GW for fertilizer for food production.
Ammonia may have an even bigger role supplanting some of the 1600 GW consumed by heavy transport. Ammonia toxicity requires safe handling, so it is a potential fuel for trained professional truck drivers and ship crews.
Ammonia production from methane by Haber-Bosch process is responsible for 2% of world CO2 emissions.
Ammonia fertilizers are responsible for over 1/3 of world food production.
39,000 tanker ships and cargo ships are propelled by diesel engines burning residual fuel oil with 3.5% sulfur content. Their CO2 emissions amount to 2% of world CO2.
The International Maritime Organization is requiring ships to reduce check sulfur emissions from burning residual fuel oil. Ammonia combustion emits no CO2 and no sulfur oxides making sulfuric acid which creates harmful particulates < 2.5 micron in diameter.
MAN is developing ammonia internal combustion ship engines and designing plans to retrofit ships.
The reverse of a solid oxide ammonia fuel cell is a solid oxide electrolysis, SOEC. Haldor Topsoe has designed efficient fuel cell stacks that can produce ammonia at 7 kWh/kg-NH3. At ThorCon owners’ cost of $0.03/kWh electricity costs are ony 20 cents/kWh. The synthesis factor capex and opex costs also must be included.
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