The new nitrogen

Urea is the volume; nitrate is the value. Nitrate carries a premium because the plant takes it up immediately, it is what greenhouses and fertigation systems buy, and a fifth of it goes into explosives, where the buyer is a mine and the alternative is a truck from the coast. Starting where the value density is highest is the point, not a limitation — and 30 bn EUR of nitrate is not a small pond. The share the technology can reach is much larger than that, because urea is not a preference, it is a compromise. Urea is shipped because it travels well, not because it grows more: on the field it loses nitrogen to ammonia volatilisation, and its efficiency depends on rain and incorporation that the farmer does not control. Nitrate is taken up directly, and making it locally at a price set by a power contract removes the reason urea won in the first place. Nitrogen-enriched organic fertiliser goes further still: the acid is fed straight into the farm’s own slurry or digestate, which fixes the ammonia that would otherwise be lost, keeps the carbon and the potassium and phosphorus already in it, and returns a complete fertiliser made on the farm that spreads it. That product competes with urea on delivered cost per kilo of nitrogen taken up by the crop — and it is where the volume of the nitrogen market is.

Birkeland–Eyde lost on energy — it ran at roughly 60 kWh/kgN on hydropower, against a Haber–Bosch process that had cheap gas, a century of optimisation and enormous scale. What has changed since: power electronics that did not exist (solid-state supplies, fast switching), electricity that is now periodically free or negative in the very grids that have too much wind and solar, a carbon cost on the fossil route, and a freight bill that has become the second cost of the industry.

Take the chain in three parts. Making it: ammonia is one of the most carbon-intensive commodities there is, at roughly 2.4 tonnes of CO₂ per tonne of ammonia and about 450 Mt of direct CO₂ a year, because the natural gas is the hydrogen as well as the fuel. The Ostwald step then adds nitrous oxide, which is some 273 times as potent as CO₂: an unabated nitric acid plant emits around 8 kg of N₂O per tonne of acid, and even in industrialised countries nitric acid still accounts for about three quarters of the chemical industry's process N₂O. Moving it: a couple of per cent, on a chain that ships the molecule from a wellhead to a farm. Spreading it: the largest block of all — nitrous oxide out of the soil. Across the whole synthetic-nitrogen supply chain, Menegat and colleagues put 2018 emissions at 1.13 GtCO₂e, 2.1% of global emissions, averaging 10.5 tonnes of CO₂e per tonne of nitrogen consumed, split 38.8% production, 58.6% field, 2.6% transport.

What the plasma route removes is the production block and most of the transport block — about 4 tonnes of CO₂e per tonne of nitrogen — and it removes it structurally rather than by abatement. There is no reformer, so no process CO₂: the only carbon is whatever the electricity carries, which is zero on a renewable contract and falling everywhere else. There is no ammonia oxidation over platinum, which is where the N₂O is formed, so that stream does not exist to be abated. And the unit sits where the nitrogen is used, so the freight goes too. Field emissions are not a production question and we do not claim them — though nitrogen-enriched organic fertiliser changes what is applied, fixing ammonia in slurry that would otherwise be lost. On today's European carbon price the production block alone is a real number in the delivered cost, and CBAM puts it on imports too.

Operational low-emission ammonia capacity is about 0.9 Mt against 182 Mt of world production — half a per cent, after a decade of subsidy and announcement. Green ammonia also inherits every structural feature of the incumbent: large plants, remote siting, shipping, and a second plant to get to nitrate. Moreover, it increases the energy consumption of the existing process, increases the capex, and cannot run economically on intermittent renewable energy, as it depends on a stable electricity supply.