“Green hydrogen, blue hydrogen, gray hydrogen – do you know what they each represent?

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Hydrogen is the most abundant element in the universe. Depending on its source of production and the emissions generated during the production process, hydrogen energy is classified into gray hydrogen, blue hydrogen, and green hydrogen. Energy is the material foundation of human activities, and as addressing climate change and achieving carbon neutrality gradually become a global consensus, there have been new changes in humanity’s demand for energy and its methods of utilization. In December 2015, the Paris Climate Agreement was officially signed. Its main goal is to keep the global temperature rise below 2 degrees Celsius compared to pre-industrial levels, with efforts to keep it at 1.5 degrees Celsius or less. According to relevant statistics, 73% of global greenhouse gas emissions stem from energy consumption. To achieve the goals of the Paris Climate Agreement, the global energy system must undergo a profound transformation, shifting from an energy system based primarily on fossil fuels to an efficient, renewable, low-carbon energy system. Hydrogen energy is held in high regard for its zero carbon emissions during release, as well as its flexible and convenient storage and transportation methods, in terms of transforming the global energy system. Why is hydrogen energy favored? Hydrogen is the most abundant element in the universe, and hydrogen energy is the energy released by hydrogen during physical and chemical changes. As an energy source, hydrogen possesses highly competitive advantages: 1. It is environmentally friendly. Unlike traditional fossil fuels, hydrogen and oxygen can generate heat through combustion, or they can be converted into electrical energy using fuel cells. And in the process of converting hydrogen into electricity and heat, only water is produced, with no greenhouse gases or fine dust generated. 2. Utilizing efficient hydrogen: It is widely available, and boasts advantages such as good thermal conductivity, being clean and non-toxic, as well as high heat content per unit mass. Hydrogen contains about three times as much heat per unit mass as gasoline; it is an important raw material in the petrochemical industry as well as a fuel for rocket propulsion. 3. Flexible and convenient storage and transportation methods: Unlike fossil fuels, hydrogen is a secondary energy source that can be produced by splitting natural gas, oil, coal, and water. Besides its gaseous state, hydrogen can also exist as liquid or solid hydrides. When liquefied at -263°C, hydrogen’s volume is reduced to 1/800 of its original value; compression in high-pressure tanks facilitates its storage and transportation. Thanks to its numerous advantages, hydrogen energy has gained widespread favor. According to a report jointly published by the International Hydrogen Energy Commission and McKinsey, more than 30 countries and regions have already released hydrogen development roadmaps, and by 2030, global investment in hydrogen projects is expected to reach $300 billion. What is the difference between hydrogen in different colors? Although hydrogen is a clean renewable energy source that produces no carbon emissions during energy release, the current process of producing hydrogen is not 100% “carbon-free”. On Earth, hydrogen exists mainly in the form of compounds in water and fossil fuels. As a secondary energy source, hydrogen needs to be \"extracted\" through hydrogen production technologies. Currently, most existing hydrogen production technologies rely on fossil fuels, making it impossible to avoid carbon emissions. Based on the sources of hydrogen production and the emissions during the production process, hydrogen is classified into gray hydrogen, blue hydrogen, and green hydrogen. 1. Gray hydrogen: Gray hydrogen is hydrogen produced by burning fossil fuels such as oil, natural gas, and coal; emissions such as carbon dioxide are generated during its production process. At present, the vast majority of hydrogen available on the market is gray hydrogen, accounting for about 95% of global hydrogen production today. Gray hydrogen has a lower production cost; the hydrogen production technology is relatively simple, and it requires fewer devices and less space, resulting in a smaller scale of production. 2. Blue hydrogen: Blue hydrogen is produced by converting natural gas through steam methane reforming or autothermal steam reforming. Although natural gas is also a fossil fuel and greenhouse gases are generated during the production of blue hydrogen, advanced technologies such as carbon capture, utilization, and storage (CCUS) are used to capture these greenhouse gases, thereby reducing their impact on the environment and enabling low-emission production. 3. Green hydrogen: Green hydrogen is hydrogen produced using renewable energy sources such as solar energy, wind energy, and nuclear energy. For example, it is generated by electrolyzing water powered by renewable energy sources, and no carbon emissions are produced during its production. Green hydrogen represents the ideal form of hydrogen utilization, but due to current technological limitations and production costs, it will take some time before green hydrogen can be used on a large scale.