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.
Both biomethane and biohydrogen are two gases that have been going strong in our current energy landscape. Both have a renewable origin and their formation can be associated with CO2 capture and storage processes, another of the great objectives of our society to fight against global warming.
Biomethane is nothing other than methane with a renewable origin, as opposed to natural gas where methane has a fossil origin. Biomethane is typically generated by purifying the biogas produced in anaerobic digesters that treat waste streams such as sewage sludge, manure or other biodegradable streams. It is the operation generally known as the upgrading process [1]. Biomethane has the added advantage that it is chemically identical to natural gas, so it can be substituted in any of its applications. For this reason, biomethane is expected to play a transcendental role in the decarbonization of the Spanish and European economy with a view to 2050 [2].
If we return form biogas, its other major component is CO2, but there is the possibility of reintroducing this CO2 to the anaerobic digester or treating it in another reactor and, through what is known as the methane process, generating more biomethane [3]. That is, we can use CO2 to generate methane, who gives more? But this process is not as mature as that of conventional anaerobic digestion and, although it has been shown to be technically feasible (more than 100 operating plants are known in Europe), the performance of the process needs to improve so that its economic viability is out of all doubt.
Once we have the biomethane, another option we have is to generate green hydrogen (named for its renewable origin) through a well-known reforming process. The reforming of natural gas to produce hydrogen is a common industrial practice, so reforming biomethane is an entirely plausible option. The usual reforming is carried out by reacting methanewith water vapor, but there is already work that has shown the possibility of replacing this water with CO2, so we return to using carbon dioxide as a raw material, removing it from the atmosphere and instead producing the desired hydrogen.
But hydrogen can also have a biological origin, which is what is known as biohydrogen. In nature there are algae and bacteria that generate hydrogen through their metabolic cycles. These organisms, grown in a controlled environment, can also become a biohydrogen factory. In this case, and as it happened in the methanation processes, it has been shown that the processes work and can be scalable, but the yields that are currently achieved remain a barrier to their implementation for industrial purposes.
But that’s what research is for, to keep working and make these processes (and others that we will talk about on another occasion) a reality in the short-medium term.
[1] Hidalgo, D., Sanz-Bedate, S., Martín-Marroquín, J. M., Castro, J., & Antolín, G. (2020). Selective separation of CH4 and CO2 using membrane contactors. Renewable Energy, 150, 935-942.
[2] Elguera, N. M., Salas, M. D. C., Hidalgo, D., Marroquín, J. M., & Antolín, G. (2020). Biometano, el gas verde que pide paso en España. IndustriAmbiente: gestión medioambiental y energética, (30), 50-56.
[3] Hidalgo, D. Martín-Marroquín, J.M. (2020). Power-to-methane, coupling CO2 capture with fuel production: An overview. Renewable and Sustainable Energy Reviews, Volume 132, 110057.
Anti-pollution measures, speed limits, parking restrictions, even the grey sky colour, and very, very alarming data. These are the consequences of the circulation of our cars in big cities. According to the European Environment Agency (EEA), more than 13% of the polluting particles in the 28 countries of European Union are produced by transport, which supposes almost 4.000 deaths per year. Only in cities, data ensure that traffic produces the 60% of emissions to the atmosphere. How long can we continue allowing this situation?
However, not all cars are so guilty of these emissions. Only 10% of the vehicles that circulate in our streets contribute 50% of the emissions, according to experts. They are what we call “high emitters” (HE). But, which are these cars? Diesel engines? The oldest ones? The worst maintained by theirs owners? Not necessarily. A high percentage of owners of highly polluting vehicles are not aware of it. Many of them have successfully passed the vehicle inspection and even 50% of these high emitters have less than two years.
How can we find out if our car is a “high emitter”?
LIFE GySTRA project, coordinated by CARTIF, purposes identifying this kind of highly polluting vehicles and monitor continuously the evolution of empiric emissions levels to quantify the savings of emission volumes. This process will be possible thanks to a new technological development, the RSD +. For the moment, the intention is to carry out tests and collect data in order to launch a new sustainable mobility policy.
The demonstration study will be carried out in Madrid (Spain) and Sofia (Bulgaria), where the intention is to control the vehicles that circulate in both cities thanks to three RSD + devices, adapted to the requirements of the EU in terms of NO2 emission control.
The public model in Madrid (Spain) is going to monitor 700,000 vehicles per year, with two RSD+ devices. The owners of the vehicles identified as HE will be notified to proceed with car reparation. With the repair of this kind of cars, it is expected to achieve emission savings of 14.8% (CO) and 22.7% (NOx, NO and NO2) of the total volume of emissions. If only the half of the total HE is repaired it would be possible to reduce CO2 emissions up to 16Mt per year.
On the other hand, the fleet model of Sofia(Bulgaria) is going to control a fleet integrated by 150 buses continuously measured. A recent study on buses concluded that identifying 6.6% of HE and repairing them their emissions were reduced by up to 84%. This monitoring program will allow higher emission savings, and fuel savings are expected to be 3-5% for the HE.
The repair of these vehicles does not only mean environmental advantages, but it will mean economic savings and the improvement of vehicle conditions.
If the project team achieves these objectives, it will greatly reduce pollution in our cities, even reaching to avoid episodes of high pollution and the restrictions, which mean headache for citizens and administrations.
The project is designing too an emission reduction policy that includes information campaigns aimed at population, some more general and others specific to the owners of the most polluting vehicles.
The project consortium is integrated by five partners, three of them technological and two from the administration. Firstly, CARTIF coordinates the proposal; OPUS RSE is the company that will develop RSD+ technology for remote contamination monitoring; and CIEMAT, the research centre that will calibrate the equipment and perform the characterization and evaluation of emissions. On the other hand, the Spanish Traffic General Direction and the City Council of Sofia (Bulgaria) will lend their support for the demonstration study in the cities of Madrid and Sofia, respectively.
Food security of two-thirds of the world s’ population depends on the availability and use of fertilizers. In the transition from a fossil reserve-based to a bio-based economy, it has become a critical challenge to close nutrient cycles and move to a more effective and sustainable resource management, both from an economical and an environmental perspective.
Mineral fertilizers production require significant amounts of fossil energy. Hence, the dependency of agriculture on fossil reserve-based mineral fertilizers (especially nitrogen, phosphorus, and potassium) must be regarded as a very serious threat to future human food security. On the other hand, estimates of phosphorus reserves expect that depletion will occur within 100 to 300 year, taking into account the current trends on population growth and demand for nutrients. But impacts on the economy are expected to occur much sooner than the time of depletion, because resource scarcity will drive in advance to higher product prices.
At the same time, the agricultural demand for mineral fertilizers is continuously growing, due to a variety of factors, such as the increasing world population, the rising meat consumption, and the cultivation of energy crops. In this sense, the FAO has reported a five-fold increase in fertilizer consumption between 1960 and 2015 and this organization projects a continued increase in the coming years. The tension between offer and demand will continue pushing up the prices for nutrient resources.
Despite these circumstances, large amounts of nutrients are dispersed in the environment every day, in a controlled or uncontrolled way, through the disposal of waste streams. In addition, the intensification of animal production and the resulting manure excesses, combined with a limited availability of arable land for the disposal of waste (manure, sludge, etc.) and the excessive use of chemical mineral fertilizers, has led to surplus fertilization and nutrient accumulation in many soils worldwide. These facts have frequently caused environmental pollution.
As a consequence, it is clear that a new global effort is needed to draw a new scenario where improved nutrient use efficiency and, at the same time, reduced nutrient losses provide the bases for a greener economy to produce more food and energy while reducing environmental impact.
Four are the key points when dealing with nutrients recycling according the scientific community:
– The sustainability of our world depends fundamentally on nutrients. In order to feed 7 billion people, humans have more than doubled global land-based cycling of N and P. – The world’s N and P cycles are now out of balance, causing major environmental, health and economic problems that have received far too little attention. – Insufficient access to nutrients still limits food production and contributes to land degradation in some parts of the world, while finite P reserves represent a potential risk for future global food security, pointing to the need for their prudent use. – Unless action is taken, increases in population and per capita consumption of energy and animal products will exacerbate nutrient losses, pollution levels and land degradation, further threatening the quality of our water, air and soils, affecting climate and biodiversity.
Recycling energy and materials through re-connecting crop and livestock production becomes indispensable for attaining agricultural sustainability in all the senses, not only in the environmental sense. It is time to reconnect nutrient flows between crops production and livestock sectors. To do so, it is needed to invest in agro-industrial processes, which can contribute in the upcycling of mineral nutrients from organic flows towards mineral fertilizer. This approach calls for the further development of a third (after crop and animal production) agro-industrial pillar to be developed in addition to and support of the two existing main pillars of agricultural activity, namely agro-residue processing and upcycling.
Note: this text is part of a contribution of the author to the book “Science, Technology and Innovation for Meeting Sustainable Development Goals” to be published in 2017 by the Colorado State University.
