Long-term storage of industrial ammonia in bulk quantities demands stringent pressure, temperature, and material compatibility requirements. Liquid ammonia boils at -33.34°C at atmospheric pressure and needs to be stored in special pressure ≥1.03 MPa or temperature ≤-33°C tanks. As prescribed in the API 620 standard, the double-walled ground storage tank (capacity 5000-50,000 cubic meters) is constructed with 304 stainless steel inner liner + carbon steel outer wall structure, the initial investment is 200-450 US dollars/cubic meter, the design period is 30 years, but the maintenance cost every year is 1.2% to 2.5% of the initial investment. In 2023, liquid ammonia leakage resulted from the corrosion of tank weld at Gujarat fertilizer plant in India, and the test revealed that the thickness of the tank wall was reduced from 12mm to 8.2mm (annual rate of corrosion 0.38mm), which forced the company to incur 1.2 million US dollars for emergency repair and loss of shutdown totaled 180,000 US dollars per day.
Cost-benefit analysis shows that when the storage cycle is more than 6 months, inventory holding cost must be balanced against market price volatility risk. For instance, taking the spot price of industrial ammonia in Southeast Asia in 2024, whose spot price annual volatility is up to 28% (standard deviation of US $54 / ton). If the purchased quantity of 10,000 tons is calculated using the six-month inventory cycle, the inventory carrying cost (insurance, energy consumption and depreciation) will be around US $12-15 / ton/month. For the same period of time, the difference between the peak and valley prices can be 140 US dollars/ton, and the income volatility coverage ratio is 3:1. But if evaporative gas (BOG) recovery systems are not sufficient in the storage facilities, then liquid ammonia evaporation loss on a yearly basis will be 0.8% to 1.2%, and that translates to 80 to 120 tons loss for each 10,000 tons of storage on a yearly basis, and that amounts to 34,000 to 51,000 US dollars (at US $425 / ton).
Control of security risk is the key to long-term storage. The explosion limit of ammonia vapor is 15%-28% (volume concentration), and leakage diffusion rate is significantly affected by air humidity – when relative humidity rises from 30% to 70%, the diffusion distance of ammonia falls by 42%. During an industrial ammonia leak from a storage tank at a Texas plant in 2021, 430 tons of industrial ammonia were released into the environment from a chemical production plant with a maximum concentration of 1,200 parts per million (more than four times the IDLH level of 300 parts per million) within a radius of 2.5 kilometers with a direct monetary loss of more than $230 million. Because of this, the EU SEVESO III directive requires storage capacity ≥500 tons to be fitted with infrared ammonia detection system (detection limit ≤5ppm), automatic spray dilution device (flow rate ≥50L/m²·min) and dual-circuit pressure release valve (response time < 0.5 seconds), and the transformation cost for compliance accounts for 8%-12% of the investment in storage tanks.
New technologies are changing the storage paradigm. The IHI Japan low-pressure atmospheric temperature storage tank (-33°[email protected]) utilizes vacuum insulated panel (VIP) technology to achieve a minimum of 0.05% daily evaporation rate and conserve 37% energy compared to traditional storage tanks, although at an increased construction cost of 25%. The intelligent corrosion monitoring system employed by BASF pilot in Germany is monitoring tank wall thickness in real time with distributed fiber optic sensor (accuracy ±0.01mm), lowering the detection cycle from 5 years to real time, and the likelihood of leakage to 0.003 times/year. The ammonia fuel cell energy storage project promoted by Yara in Norway transforms industrial ammonia into hydrogen power generation, the storage period can be 12-18 months, and the energy conversion efficiency can be 45% (15 percentage points higher than traditional coal-fired power generation), but the system’s initial investment can be as high as $2,800 /kW. Applicable to areas where the electricity price is ≥0.18 USD /kWh.
Regulation and market forces encourage the innovation of storage measures. China’s “Liquid ammonia Storage Safety Code” issued in 2024 requires population density within 500 meters of the storage facility to be less than 50 persons/km², forcing 23% of the East China small and medium-sized enterprises to shut down operation or move storage tanks, and market share of the large enterprises climbed to 68%. The EU Carbon Border duty (CBAM) has raised the implicit cost of carbon emissions for industrial ammonia to €85 / ton (2025), and stimulated green ammonia storage demand – the 200,000 ton liquid ammonia storage tank in Saudi Arabia’s Neom Green Hydrogen project has been made from carbon fiber reinforced composite (tensile strength ≥1800MPa). Despite the cost of $680 / m3, the life-cycle carbon footprint is reduced by 92%. Companies are recommended to opt for a dynamic storage model, incorporate the CME ammonia futures price curve (2025Q3 forward discount rate of 4.2%) and local safety requirements, introduce the inventory turnover rate of 8-10 times/year, and cap the overall cost of storage at 5%-7% of transaction value.