Chemicals
The chemical industry (including fertilisers) is the largest consumer of energy within the industrial sector. This prominence is largely due to the fact that approximately half of the energy input in the chemical subsector is used as feedstock, i.e., fuels serving as raw material inputs rather than as energy sources (IEA).
In 2023, hydrogen production was responsible for emitting 920 million tonnes of CO₂ (IEA).
Hydrogen can be produced from various feedstocks including plastic wastes, but currently it is derived mostly from fossil fuels. The feed of the hydrogen plant consists of hydrocarbons in the range from natural gas to heavy residue oils and coke. Hydrogen production using a hydrocarbon-rich feedstock requires, as a first step, the conversion of the feedstock into a carbon oxides- and hydrogen-rich synthesis gas. The synthesis gas generation can be conducted by different techniques, such as steam reforming and partial oxidation.
Hydrogen is often categorized by color labels that indicate its production method and associated environmental impact. Here are the commonly referred colors of hydrogen:
- Gray Hydrogen: Produced from natural gas or methane through steam methane reforming (SMR) without capturing the greenhouse gases generated in the process.
- Blue Hydrogen: Similar to gray hydrogen, but incorporates carbon capture and storage (CCS) to trap and store the carbon dioxide emissions produced during the process, resulting in lower greenhouse gas emissions.
- Green Hydrogen: Generated through the electrolysis of water powered by renewable energy sources such as wind, solar, or hydroelectric power.
Hydrogen production units are typically integrated into larger industrial processes, e.g., as for an installation producing ammonia.
EU CBAM Reminder: Not covered is the production of synthesis gas or hydrogen within refineries or organic chemical installations where the hydrogen is used exclusively within those plants and not for the production of goods under the CBAM Regulation.
This is the most commonly used method for hydrogen production on an industrial scale. This process involves reacting hydrocarbons, primarily methane from natural gas, with steam to generate hydrogen and carbon monoxide. Although natural gas is the most common feedstock, refinery gas, liquefied petroleum gas (LPG), and light naphtha might also be used. The overall reaction is endothermic (i.e., it absorbs heat), requiring high temperatures between 700°C and 1,000°C.
The heat required for the endothermic steam reforming reaction is typically supplied by burning a portion of the natural gas feedstock or other fuels in an external furnace. The process often includes heat recovery systems that utilize waste heat from the reformer furnace to produce the steam required for the reactions.
In its simplest form, the steam methane reforming process for pure hydrogen production consists of four stages:
- Desulphurisation: The feedstock undergoes desulphurisation since sulphur compounds present in the hydrocarbon feedstock can poison catalysts used in subsequent reactions.
- Steam Methane Reforming: The desulfurized methane reacts with high-temperature steam over a nickel-based catalyst within a reformer furnace. This reaction produces a synthesis gas (syngas) composed mainly of hydrogen (H₂), carbon monoxide (CO), and a small amount of carbon dioxide (CO₂).
- Water-Gas Shift Reaction: The syngas is then subjected to the water-gas shift reaction, where carbon monoxide reacts with additional steam to produce more hydrogen and CO₂.
- Gas Cooling and Purification: After the shift reaction, the gas mixture is cooled, and impurities such as CO₂ are removed. One common method for hydrogen purification is Pressure Swing Adsorption (PSA).
The stream of CO₂ produced by the steam reforming process is very pure and is separated and captured for further use, e.g., for urea production.
The EU CBAM covers the following production steps for hydrogen via steam reforming:
- Raw material pre-treatment - natural gas desulphurisation;
- Steam reformation - primary and secondary, H2/CO generation;
- Shift conversion - carbon monoxide to carbon dioxide and hydrogen;
- Separation & purification - CO2 removal, separation processes as present including cryogenic, adsorption, absorption, membrane, hydrogenation (methanation);
- Emissions control - for treating releases to air, water or ground.
The diagram below shows the example of an installation producing 50,000 tonnes of hydrogen via the steam reforming route.
Please note that these values are purely for explanatory and illustrative purposes, as each factory will have its unique design
Inputs
Fuels:
- Natural gas: 218,750,000 m3 --> 471,240 tCO2e
Electricity:
- Grid: 35,000 MWh → 20,426 tCO2e (indirect emissions)
Resulting in the following direct and indirect specific embedded emissions (SEE):
- Direct: 9.4248 tCO2e/tonne
- Indirect: 0.4085 tCO2e/tonne
A variation of the steam reforming process is steam reforming with carbon capture and sequestration (CCS), often referred to as 'blue hydrogen' production. This approach involves capturing the CO₂ generated during the reforming process and permanently sequestering it in geological formations, thereby preventing its release into the atmosphere.
Partial oxidation (POX) is a process where hydrocarbon feedstocks react with a limited supply of oxygen at high temperatures to produce a synthesis gas (syngas) composed mainly of hydrogen (H₂) and carbon monoxide (CO). This method is particularly suitable for heavy feedstocks such as residual heavy oils, coke, coal, and even waste plastics. However, natural gas can also be used.
Hydrogen processing in this system depends on how much of the gas is to be recovered as hydrogen, and how much is to be used as fuel. Where hydrogen production is a relatively small part of the total gas stream, a membrane is normally used to withdraw a hydrogen-rich stream. That stream is then refined in a purification unit.
The stream of carbon dioxide produced from the process is of high purity and may be separated and captured for further use.
The EU CBAM covers the following production steps for hydrogen via partial oxidation:
- Air separation unit - to produce oxygen for the partial oxidation step
- Gasification - H2/CO generation
- Synthesis gas clean up - soot and sulphur removal
- Shift conversion - carbon monoxide to carbon dioxide
- Separation & purification - CO2 removal, separation processes including cryogenic separation (liquid nitrogen)
- Emissions control - for treating releases to air, water or ground
The diagram below shows the example of an installation producing 78,840 tonnes of hydrogen via the partial oxidation route.
Please note that these values are purely for explanatory and illustrative purposes, as each factory will have its unique design
Inputs
Fuels:
- Heavy Fuel Oil (HFO): 235,000 tonnes --> 734,835.60 tCO2e
Electricity:
- Grid: 47,304 MWh → 27,606.61 tCO2e (indirect emissions)
Resulting in the following direct and indirect specific embedded emissions (SEE):
- Direct: 9.3206 tCO2e/tonne
- Indirect: 0.3502 tCO2e/tonne
EU CBAM Reminder: Where the produced hydrogen has been certified to comply with Commission Delegated Regulations (EU) 2023/1184, an emission factor of zero for the electricity may be used.
Hydrogen is produced as a by-product during the electrolysis of brine in the chlor-alkali process, which also yields chlorine and sodium hydroxide (caustic soda). The hydrogen generated is of high purity and is formed at the cathode in the electrolytic cells. There are three primary cell technologies used in this process:
- Mercury Cell: In this process, a mercury cathode is used to form a sodium amalgam, which is later reacted with water to produce sodium hydroxide and hydrogen gas.
- Diaphragm cell: This method uses a porous diaphragm to separate the anode and cathode compartments. Chlorine gas is produced at the anode, while hydrogen and sodium hydroxide form at the cathode.
- Membrane cell: The most modern and environmentally friendly method, this process uses an ion-exchange membrane to separate the anode and cathode compartments. It produces high-purity chlorine, hydrogen, and sodium hydroxide with greater energy efficiency.
In all three processes, the hydrogen gas produced at the cathode is typically of very high purity. After production, the hydrogen is cooled, dried, and purified to remove water vapor and other impurities, which may include traces of oxygen. When renewable energy sources are used for electrolysis, hydrogen with a low carbon footprint can be produced.
EU CBAM Reminder: Where the produced hydrogen has been certified to comply with Commission Delegated Regulations (EU) 2023/1184, an emission factor of zero for the electricity may be used.
Hydrogen production via water electrolysis involves splitting water molecules into hydrogen and oxygen using electricity. This method yields a high-purity hydrogen stream with minimal direct emissions, primarily limited to oxygen and water vapor. However, the overall environmental impact depends significantly on the electricity source:
- Non-Renewable Energy Sources: If the electricity originates from fossil fuels, indirect emissions will be associated with the hydrogen production process.
- Renewable Energy Sources: Utilizing electricity from renewable sources like wind, solar, or hydro power results in green hydrogen, characterized by negligible greenhouse gas emissions.
The diagram below shows the example of an installation producing 10,000 tonnes of hydrogen via water electrolysis using conventional electricity from the grid.
Please note that these values are purely for explanatory and illustrative purposes, as each factory will have its unique design
Inputs
Electricity:
- Grid: 550,000 MWh → 125,565 tCO2e
Resulting in the following direct and indirect specific embedded emissions (SEE):
- Direct: 0 tCO2e/tonne
- Indirect: 12.5565 tCO2e/tonne
The diagram below shows the example of an installation producing 10,000 tonnes of hydrogen via water electrolysis using self-generated clean electricity.
Please note that these values are purely for explanatory and illustrative purposes, as each factory will have its unique design
Inputs
Electricity:
- Grid: 550,000 MWh → no GHG emissions
Resulting in the following direct and indirect specific embedded emissions (SEE):
- Direct: 0 tCO2e/tonne
- Indirect: 0 tCO2e/tonne
