Over the past decades, hydrogen has been identified as a potential clean fuel, although its mass adoption has been hampered by the abundance of oil and low relative prices of fossil fuels, as well as, in recent years, by the advance of the battery electric vehicle. Today, while technological advances have brought down the costs of hydrogen production and use, it is essential to scale up these technologies and define a roadmap to optimise the necessary investments. The current energy transition points to an era of sustainable energy gases, and the consumption of renewable hydrogen and methane is expected to surpass that of coal and oil in the 21st century. In this context, renewable hydrogen, or hydrogen produced with low CO2 emissions, emerges as a key player in the decarbonisation of the global economy.
Biohydrogen is a specific type of renewable hydrogen defined as hydrogen produced by biological processes or from biomass as feedstock. Biomass, one of the most abundant renewable resources on all continents, is the subject of increasing research into its alternative uses and valorisation. This interest is also focused on the conversation of waste streams into energy, because of the potential to transform large quantities of agricultural, forestry, industrial and municipal waste into biohydrogen and other renewable gases, thus benefiting sustainable development. The efficient use of renewable feedstocks derived from biomass and waste as a fuel source clearly presents a significant opportunity for a more sustainable planet.
“Biohydrogen. Specific type of renewable hydrogen defined as hydrogen produced by biological processes or from biomass as feedstock”
Biohydrogen has characteristics that make it a renewable element capable of providing safe, economically competitive and 100% carbone dioxide-free energy in its production and use. Despite this, the penetration of this low-carbon hydrogen remains limited. It is crucial to understand the reasons for this situation, the emerging trends and the technological route that will enable its consolidation as an energy vector.
Biohydrogen production
Biohydrogen production has gained worldwide attention due to its potential to become an inexhaustible, low-cost, renewable source of clean energy. Feedstocks for its production include lignocellulosic products, agricultural residues, food processing residues, aquatic plants and algae, and human effluents such as sewage sludge. Under proper control, these resources will become a major source of energy in the future. Biomass has the potential to be an important source of renewable hydrogen, complementing other processes that produce biomaterials.
The main methode of obtaining biohydrogen is from biomethane generated in anaerobic digestion, through a process known as reforming. Gasification, on the other hand, converts organic matter into hydrogen-rich synthesis gas. Alongside these thermochemical technologies, biological hydrogen production, such as dark fermentation and the use of microalgae, offer additional promising methods. Dark fermentation uses anaerobic bacteria to break down organic matter and produce hydrogen. Microalgae, on the other hand, can generate hydrogen through biophotolysis, a process that converts sunlight and water into hydrogen and oxygen. This set of technologies presents a wide range of possibilities for biohydrogen production.
Storage and distribution
The storage and distribution of hydrogen in general, and biohydrogen in particular, represent crucial aspects of its large-scale adoption. Storage in high-pressure tanks is currently the preferred option, although other methods exist, such as injection into existing gas infrastructure of storage in chemical materials. Hydrogen can be stored in a gaseous or liquid state, either on the surface or in solids, or in hydrogen-bearing chemical compounds. These storage options aim to overcome current limitations and facilitate the uptake of hydrogen as an energy carrier.
Applications and uses
The current interest in the hydrogen economy is due to its enormous opportunities for penetration in the energy sector, especially in mobility and chemicalstorage of renewable energy. In the case of biohydrogen, it is also an efficient method of managing organic waste streams. The production of renewable hydrogen has increased in recent years, mainly used in the manufactureof ammonia. Renewable ammonia can also be used as an energy storage medium, energy carrier or fuel. Hydrogen production therefore not only has industrial applications, but also offers innovative energy solutions.
In metallurgy, hydrogen is used in the direct reduction of iron for steel production, and in transport, it can generate clean energy in vehicles. These diversified applications demonstrate the potential of biohydrogen to transform key sectors of the economy. However, its large-scale adoption requires overcoming technological, logistical and market barriers, as well as establishing appropriate policies for its regulation and development.
Biohydrogen perspectives
Biohydrogen, like other energy carriers, has advantages and disadvantages. While other forms of energy already have an established position, hydrogen, and in particular biohydrogen, is progressively advancing in trying to replace options such as coal or natural gas in sectors such as energy, industry and transport. The main driver for this is the need to reduce pollutant emissions, which has generated considerable interest in this energy vector. However, low energy density, infrastructure and installation costs, and factors associated with security are the main barriers slowing down its implementation. While some of these barriers can be removed by cost reductions resulting from research breakthroughs, others, such as energy density, cannot be changed. Here, the use of derivatives mainly from the chemical industry can play a key role in the energy system or in the transport sector.
Barriers can be addressed or adapted, but this will not be achieved without a joint effort by both the private and public sectors. There must be joint objectives and policies on aspects such as the homogenisation of standards that affect, above all, storage limits. Currently, there is no robust global market due to low demand, which is partly a consequence of low generation and direct consumption at generation sites. As biohydrogen progressively breaks through, demand will increase and generation will have to be done on a large scale. This increase in generation and demand will make material transport routes, which are cost-effective especially over long distances, viable. Hydrogen-specific pipelines, trucks and shipping routes will emerge to meet this demand. With this opening and development of adapted means for hydrogen and biohydrogen, a progressive increase in the areas of potential use will be observed, where transport, especially by heavy vehicles and ships, and energy storage in liquid ammonia tanks will play a key role.
Biohydrogen has the potential to solve today’s pollution problems, but its widespread use is not immediate. The change starts now and the willingness to change must be evident. The next steps include research into all biohydrogen production processes to increase their efficiency and thus their competitiveness; integration of distribution and demand interfaces; management of global policies and technologies; coordination in the face of multilateral sectoral initiatives; and the creation of a knowledge base to serve as a model for the establishment of initiatives.
More information about this theme:
Hidalgo, D., Martín-Marroquín, J. M., & Díez, D. (2022). Biohydrogen: future energy source for the society. In Organic Waste to Biohydrogen (pp. 271-288). Singapore: Springer Nature Singapore.
Ph. D. in Chemical Engineering. Her research lines are focused on the valorization of organic waste, bioprocesses and bioproducts.
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