A start-up backed by Amazon’s $2bn climate fund has unveiled the world’s first ammonia-powered truck.

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New York city-based Amogy, founded by four alumni from the Massachusetts Institute of Technology (MIT), has developed a novel process in which ammonia (NH3) is cracked on-board to make hydrogen, which is then put through a fuel cell to power the vehicle’s electric drivetrain — but the tank-to-wheel efficiency is lower than that of an equivalent electric or hydrogen fuel cell vehicle.

The company this week tested the technology, which it has retrofitted to the cab of a Class 8 heavy duty vehicle, by driving it around at the campus of Stony Brook university in New York state for “several hours”. The vehicle took eight minutes to fill.

Full-scale testing of the 300kW retrofitted truck is due later this month at a test track, and follows on from Amogy’s previous tests of the technology in a 5kW drone and a 100kW John Deere tractor.

Ammonia is being touted as a zero-emissions alternative to heavy fuels in some large transport applications — in particular shipping — due to its high volumetric energy density (3.5kWh per litre) compared to hydrogen (1.2kWh and 2.4kWh per litre for compressed and liquid respectively) and its relative ease of handling.

And, ammonia only needs temperatures of minus 33°C to retain its liquid state. Liquid hydrogen, by contrast, requires cryogenic temperatures of below minus 253°C.

But Amogy’s process will yield significant inefficiencies. At least half of the ammonia (NH3) tank’s 900kWh of “stored electrical energy” is likely to be lost during the process, based on best-case ammonia cracking efficiency of 76% and PEM fuel cell efficiency of 65% — and in a small-scale application such as this the efficiency is likely to be much lower.

Hydrogen-powered fuel cell vehicles (FCEVs) have a tank-to-wheel efficiency of around 50%, while battery-electric vehicles are up to 85% efficient.

The round-trip efficiency of an ammonia-powered fuel cell vehicle such as this is likely to be even more problematic, as the NH3 must first be made from hydrogen, which is in turn made from a power source or from fossil gas, losing energy at each stage of conversion.

By using ammonia in the tank rather than hydrogen, Amogy's technology has to add a total of two extra energy-gobbling conversions to the process.

And major questions remain of the risks to human health of using ammonia as a fuel. Shipping standards firm DNV is currently compiling a range of safety guidelines for NH3 use in the maritime industry that would require a level of procedure — such as the use of specialist equipment, air locks and personal protective clothing — as yet unheard of in road freight.

That hasn’t put off Amogy’s financial backers, which include online retail giant Amazon’s climate fund, as well as South Korean conglomerate SK, Saudi oil major Aramco and a range of private equity backers.

Last year the company announced it had raised $46m to develop its technology, with by far the most ($30m) coming from SK.

“Beyond its incredible energy-density and liquid phase at an ambient temperature, ammonia is an optimal fuel to achieve rapid decarbonisation of heavy transportations because it is available globally with existing infrastructure already in place,” said Seonghoon Woo, chief executive officer at Amogy.