What you need to know about Green Hydrogen

The use of hydrogen as an alternative to decarbonize the energy matrix has been increasingly discussed and its use is already part of the strategic planning of many countries.

But what do you know about this element? What is green hydrogen?

These and some other recurring questions on the subject were the subject of Mitsidi's Expandir program, available on YouTube, and whose answers are summarized below.

What are the characteristics of Hydrogen?

Hydrogen, which is being thought of so much when the subject of energy transition is addressed, is a molecule formed by two hydrogen atoms. The hydrogen atom is the smallest atom in existence, generally formed by only one proton and one electron (although there are radioactive variations that contain neutrons in the nucleus). The hydrogen molecule is also extremely small, being formed by two of these hydrogen atoms covalently bonded.

In its molecular form, hydrogen is gaseous, not very dense, odorless, tasteless, colorless and non-irritating. However, it is a flammable gas and has a boiling point below -200°C, as can be seen on the website PubChem.

The hydrogen atom is the most abundant element in the universe, as we can see in the article by Walter J. Maciel. On our planet, it is the third most abundant, as stated on the website H2Brasil, however it makes up only 0.00005% of the atmosphere according to the article, this leads to the conclusion that this element is, for the most part, associated with other atoms, in the composition of molecules. The production of molecular hydrogen consists of these interactions and providing conditions for the bond between hydrogen atoms to occur predominantly. In this palette of nuclei used to classify hydrogen, there are also other nuclei that vary according to the production process. For example, gray hydrogen is produced from natural gas without carbon capture (CCUS – Carbon Capture Utilization and Storage) and blue hydrogen, which is produced from the reforming of natural gas, but with carbon capture (CCUS). Thus, green hydrogen is considered less polluting than gray hydrogen, for example.

What are the advantages and disadvantages of hydrogen in relation to other fuels (natural gas, gasoline, diesel, etc.)?

Hydrogen is a very interesting element from an energy point of view because it has a high energy density per weight, 2.8 to 3 times greater than gasoline. However, one of the main specifications is the low energy density per volume, around 4 times lower than gasoline, which makes it difficult to store and transport the gas.

What is the clarity with hydrogen fuel cells?

Fuel cells transform the chemical energy of a fuel, in this case hydrogen, into electrical energy and heat, similar to what happens with batteries, and can have several applications for energy storage, use in electric vehicles and in isolated systems. It is a process that is the opposite of electrolysis, in which oxygen and oxygen react and release energy and water. Since the transportation sector is one of the largest emitters of CO2, the use of vehicles powered by hydrogen fuel cells has the potential to contribute to decarbonizing the energy matrix of countries.

It is worth noting, however, that Brazil has a major advantage compared to other European countries because it also uses ethanol, produced from sugar cane (a clean and renewable source), as fuel in the transportation sector. Even so, it is still advantageous to have a vehicle powered by a fuel cell with H2, instead of ethanol, because the performance is better, in addition to being more efficient than a combustion engine. Each one has advantages and disadvantages and leads to one of the “colors” of hydrogen.

Reforming processes are the most widely used today and are based on reactions between methane and carbon monoxide and water, producing hydrogen and carbon dioxide. This process can have an additional stage of capturing carbon dioxide, reducing its impacts on the climate. It is a process with a moderate energy requirement, but which, in general, has high impacts, both due to energy use, carbon dioxide release, and intensive water use.

Electrolysis processes are the most reported and the biggest bet on the market at the moment. It basically consists of using electrical energy to create a difference in electrical potential between a positive and negative pole, inside a piece of equipment called an “electrolytic cell”, causing water molecules to break down and form hydrogen and oxygen molecules. If the electrical energy used comes from sources such as wind or solar energy, the hydrogen produced will be considered green hydrogen. It can be a process that is practically emission-free in its operation, but it requires large amounts of energy and water.

Pyrolysis is a process in which an organic material is exposed to high temperatures without the presence of oxygen, preventing it from combusting, and as the temperature increases, the chemical bonds of the molecules of this material break. If a simple hydrocarbon is used as the organic material (methane, for example), the products of this process will be only hydrogen and carbon. If there are other atoms in the hydrocarbon molecule (sulfur or nitrogen, for example), more complex reactions and other molecules can be released, but there are parameter optimizations that can help generate the maximum possible hydrogen and the minimum contaminants. It is one of the purely physical-chemical processes with the lowest energy requirement and without the need to use water, or the release of carbon dioxide, but a high level of optimization is required to ensure that there are no harmful substances at the end of the process.

In the figure below, taken from an article in Forbes, we see the comparison of the typical use of resources of these three production paths for the production of one ton of hydrogen.

Hydrogen production bioprocesses are further subdivided into types of biological action, as we can see in the image below taken from the ScienceDirect website, but, in general, they are processes in which a biological element (fungi, algae or bacteria) is used as the main production element. In general, these are processes that deactivate less energy, but tend to have a lower production and the optimization of parameters, to ensure that the organisms produce as much hydrogen as possible, can be highly complex.

Source: Sciencedirect

What is the potential for production and use of green hydrogen in the current market, both nationally and internationally?

First, it is important to understand how the hydrogen chain works in order to understand all its possibilities. The figure below represents this chain, from production to final use:

Source: IRENA

Source: IRENAConsidering this chain, in Brazil, the production of green hydrogen from renewable energy sources, such as wind and solar, through the electrolysis process, has a high potential due to the growing participation of these electrical (84.8%) and energy (48.3%) sources in the country (2020 Data, EPE). Compared to the global scenario, the electrical and energy matrices have 27% and 14%, respectively, according to IEA data from 2019. It is worth noting that there is still untapped potential for offshore wind generation, which could also be a source of energy for the production of green H2.

Considering the use of biofuels (ethanol/biodiesel, biogas and bio-waste (agroforestry and agro-industrial) which, through reforming, pyrolysis or gasification processes, can produce green H2, it is worth highlighting the great potential linked to the use of ethanol to produce green H2 due to the industry already consolidated in the country.

The most promising regions for the production of Green H2, linked to each source due to the distribution of existing generation (SIGA, ANEEL), are below:

• Wind → Electrolysis → Northeast region with emphasis on Rio Grande do Norte, Bahia and Piauí.
• Solar → Electrolysis → North and Northeast regions, with emphasis on Pará, Ceará, Paraíba, Alagoas, Piauí and the extreme north of Bahia.
• Ethanol → Reform → Central-West, Southeast and Northeast regions
• Biogas → Pyrolysis or gasification → South, Southeast and Central-West regions
• Biodiesel → Reform → South, Southeast and Central-West regions
• Bio-waste → Gasification → All regions due to the different agricultural crops.

Source: ABH2

In addition, studies indicate that Brazil has reserves of hydrogen in its natural form (Source: Engie Research in conjunction with Geo4u) demonstrating presence in the soil and deep wells of the São Francisco Basin, in Minas Gerais. In addition to Minas Gerais, areas in the states of Ceará, Goiás, Tocantins, Roraima and Bahia were studied. However, this list could be even longer since some regions were not even studied. In Brazil, the main centers of green hydrogen production are concentrated in the Port of Pecém in Ceará, the Port of Açu in Rio de Janeiro and the Port of Suape in Pernambuco and are motivated by the export of Green H2 abroad.

Internationally, according to data published on the BBC website, Australia, China, Germany, the Netherlands, Saudi Arabia and Chile are the countries with the largest Green H2 production projects in the world. Regarding the consumption of green hydrogen, Brazil has the following sectors as potential buyers of the input: Fertilizers, Cement, Energy, Mining, Chemicals, Steel, Transportation, Flat Glass, Food. It is worth noting that fertilizer was the most imported product by Brazil in 2021, originating mainly from Russia and China. This dependence on consumption can be minimized by the domestic production of the product using green H2 to replace natural gas for the production of nitrogen fertilizers such as ammonia. In addition, due to the construction of Hydrogen Hubs close to the country's important ports, there is a declared intention to export this input, mainly to Europe.