Ammonia (NH3) is emerging as a potential marine fuel due to its zero carbon dioxide emissions when combusted. “Green Ammonia”, the environmentally friendly version, which is produced using renewable energy sources, is the sustainable alternative to conventional ammonia. This provides ship owners with a fuel option that could have no well-to-wake CO2 emissions, which will assist in meeting IMO’s 2050 emissions reduction targets, according to Marine Insight.
Ammonia as a Maritime Fuel
Traditionally known for its use in agriculture and industrial sectors, Ammonia has emerged as a promising alternative marine fuel due to its potential to reduce greenhouse gas emissions and promote sustainability in shipping. Advances in ammonia combustion technology and fuel cells are being developed to address issues of toxicity and low energy density, aiming to improve safety and efficiency. As the shipping industry seeks greener solutions, ammonia’s role as a sustainable fuel is increasingly being recognized.
Properties
Technical Specification/Details
Boiling point: With a boiling point of -33 °C, it is a gas at room temperature and requires to be compressed and cryogenically stored.
Density: It has a density as a liquid fuel of approximately 0.68 g/cm³ at -33 °C. In its gaseous form at standard temperature and pressure, it is 0.77 Kg/m³
Solubility: Ammonia is highly miscible meaning it will readily dissolve in seawater in case of a spill. However, it is harmful to aquatic life and its effects vary depending on its concentration, the water temperature, and the pH levels.
Flammability: It is not inherently flammable but its flammability range in air is 15% to 28% by volume, meaning it can form explosive mixtures with air within this range.
Toxicity: It is highly toxic and Corrosive and requires specialized handling.
Energy Density: Ammonia has a lower energy density (approx. 3.5 kWh/kg) compared to Heavy fuel oil (HFO) (approx. 12.6 kWh/kg). This means we need to burn almost three times as much quantity of Ammonia compared to HFO to achieve the same energy output.
Types of Ammonia
The several types of Ammonia based on its production methods and use cases are:
Conventional Ammonia: Produced through the Haber-Bosch process, which combines nitrogen and hydrogen derived primarily from natural gas. This type of ammonia is typically used in fertilizers and industrial applications and can be adapted for use as a marine fuel.
Green Ammonia: Produced using renewable energy sources. The process involves generating hydrogen through the electrolysis of water using renewable electricity and then synthesizing ammonia from this hydrogen and atmospheric nitrogen. Green ammonia aims to minimize the carbon footprint associated with its production and is considered a more sustainable option.
Blue Ammonia: Produced from natural gas, like conventional ammonia but with carbon capture and storage (CCS) technologies employed to reduce CO₂ emissions during production. Blue ammonia represents a transitional approach, aiming to lower the carbon intensity of ammonia production while transitioning to greener alternatives.
Technology Readiness
While there are currently no ships in service using Ammonia as a fuel since ammonia-fueled engines are not yet commercially viable, there are 2-stroke and 4-stroke Engines under development.
Existing marine engines and fuel systems need significant modifications or replacements to handle ammonia’s unique properties. While ammonia doesn’t produce CO₂, it can create nitrogen oxides (NOₓ) during combustion. Advanced technologies or after-treatment systems, such as selective catalytic reduction (SCR), are required to manage NOₓ emissions effectively.
The Fortescue Green Pioneer started its journey towards becoming the world’s first ocean-going ammonia-powered vessel in 2022 when Fortescue successfully converted a four-stroke engine to run on ammonia, in combination with diesel, at its land-based testing facility in Perth, Western Australia.
Operational Considerations
Storage and Handling
Ammonia is stored in specialized pressurized tanks at a temperature lower than its boiling point of -33 °C. A double-walled, insulated tank design is required to maintain the required temperatures and prevent leaks.
Adequate ventilation and Gas absorption systems are crucial to disperse any accidental releases of ammonia gas, preventing the accumulation of toxic vapors.
Ammonia gas detectors and alarms should be installed onboard to provide early warning of leaks and to monitor air quality continuously.
General safety
Ammonia is a colorless gas with a characteristically pungent smell. It poses health risks if inhaled, ingested, or absorbed through the skin.
It is highly toxic, and exposure can cause severe respiratory issues, skin irritation, and burns. Handling requires personal protective equipment (PPE) to protect workers from ammonia exposure, including gloves, goggles, and gas masks. The use of high-efficiency respirators with ammonia-specific filters protects against inhalation of ammonia vapors.
Availability and Costing
The global production of ammonia was 170 million tonnes in 2018, up from 126 million tonnes in 2000. Global production capacity has increased by 6% in 2023.
97% of the planned capacity increase is based on natural gas as the feedstock, and mainly in countries with cheap natural gas. 31% of global ammonia was produced in China, 10% in Russia, 8.9% in the US and 7.9% in India.
For comparison, the fuel consumption of all ships was estimated to be 200 million tonnes in 2020, which corresponds to roughly 500 million tonnes of ammonia on an energy basis. Since shipping fuel demand is also expected to increase further, the current production of ammonia can only cover a moderate fraction of the demand for marine fuels.
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Source: MarineInsight
