Low-cost, low-risk pathways

Nitrogen fertilizer production must meet the needs of people and the planet. That means cost-effective carbon dioxide (CO₂) intensity reduction. GW scale greenfield site green ammonia facilities may be the long-term goal, but getting to that level of investment and CO₂ intensity reduction is a huge leap from the ammonia eco-system of today. Smart use of existing production assets can reduce cost and risk. Phased implementation of new technologies will also support cost-effective scale-up. This article discusses actionable pathways to enable a fair and just energy transition for all.

Greenhouse gas (GHG) emissions are the issue

European and US debt is at an all-time high. Developing nations are struggling to feed their people and bring them basic healthcare provisions. The costs of war in Europe and the Middle East are eating into national budgets.

The notion that governments will borrow huge additional sums of money to pay for a net zero future is unrealistic. It is necessary to accelerate progress with limited budgets which means achieving the best ‘bang for our buck’ with nitrogen fertilizer decarbonisation.

It is not the ‘greenest’ projects that will proceed and receive infrastructure scale investment: only the ‘best’ projects will be bankable. What does ‘best’ mean? To banks it means a clear business case with an acceptably low level of risk.

As companies review CO₂ management and hydrogen decarbonisation mid-decade, it is abundantly clear that responsible use of fossil fuels is a reality that businesses must work with, not against, for many years to come.

The use of fossil fuels with appropriate GHG emissions mitigation is compatible with a net zero vision. Fossil CO₂ and methane emissions going into the atmosphere are the issue, not the use of fossil fuels per-se. Addressing the real problem will be the most cost-effective solution.

Sequester captured CO₂ from natural gas and coal

When ammonia is made from steam methane reforming (SMR) of natural gas, C_O2 leaving the reformer must be removed to enable the catalytic Haber-Bosch ammonia synthesis reaction to take place.

Every natural gas-fed ammonia plant already has a CO₂ capture facility. The capital expenditure (CAPEX) is spent and the energy costs for CO₂ capture are committed. Some of the CO₂ is reacted with ammonia to make urea. The remainder of the captured CO₂ can be sequestered to reduce the CO₂ intensity of nitrogen fertilizer production.

Coal-fed ammonia production is also low-hanging fruit. Immediately after coal gasification, the raw syngas is fed to a Rectisol unit where CO₂ and sulfurous gases are removed. At present, this CO₂ is generally blown into the atmosphere, unless a portion of it is required for urea production.

This captured CO₂ from coal gasifiers must also be a priority for sequestration, since the CAPEX and operational expenditure (OPEX) costs of the Rectisol plant are absorbed into the overall costs of fertilizer production. To reduce the CO₂ intensity of coal to ammonia, the only incremental costs are CO₂ transmission and sequestration.

Meaningful CO₂ reductions are being held back by ‘tight’ regulations

The ‘blue’ hydrogen CO₂ intensity levels are relevant for new-build ammonia and nitrogen fertilizer projects based on autothermal reformers (ATRs) or gas heated reformers (GHRs). This technology yields all of the CO₂ as a high-pressure stream with a high concentration of CO₂, enabling low unit costs of CO₂ capture.

However, the ‘blue’ hydrogen CO₂ intensity levels are not relevant for ammonia plant SMRs. This is the technology operating today in almost all gas-fed ammonia fertilizer plants. For an SMR to achieve the ‘blue’ certification, CO₂ must be captured from the low-pressure post-combustion flue gas in addition to the high-pressure syngas.

Post-combustion CO₂ capture is expensive since the stream pressure and CO₂ concentration are both low. On the other hand, capturing CO₂ from the high-pressure syngas stream of a SMR is cost effective, but results in only a 70% CO₂ capture rate – lower than the threshold required to hit ‘blue’.

In essence, new blue ammonia ATR/GHR plants are too CAPEX intensive in a market where asset utilisations are not running at more than 90%. And, cost-effective decarbonisation retrofits to existing SMR plants will not meet the blue requirements. The tight definition of ‘blue’ ammonia has resulted in a stalemate.

In almost all parts of the world there has been significantly less progress to meet net zero targets than ambitions have declared. ‘More of the same’ is not the answer. The world needs high-impact action now. Ideas that can rapidly and cost-effectively be deployed.

Making rapid impact means the industry must accept that the next 30 years will be about rapid, retrofit decarbonisation of existing infrastructure in addition to progressive deployment of ultra-clean technology. To enable this, there must support for GHG emissions reduction in all forms rather than CO₂ intensity thresholds which indirectly promote certain technologies above others.

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