Treatment and purification of wastewater from different industries by electrochemical methods
The modern world is inconceivable without the various industries that shape it: the creation of value-added products from raw materials, although a concept as old as civilisation itself, would not have developed so rapidly without the Industrial Revolution, which made it possible to obtain products with little difference between them in less time and at a lower price.
Like everything else, this growth of the industry has brought with it a number of problems. Many of these have been solved over time or have been properly minimised to the point where they are no longer a problem. At the end of the day, the aim is to produce as little waste as possible in the transformation of raw materials into products, as this generation involves the treatment of waste in order to dispose of it properly.
Even so, there are some industries that are known to leave an indelible mark on the area in which they are located, such as the paper industry. It should be added that in the last 20 years the regulations implemented, as well as the work carried out by the pulp treatment companies themselves, has helped to reduce the industry’s carbon footprint (an environmental indicator that aims to reflect the total greenhouse gases emitted as a direct or indirect effect of, in this case, an organisation).
But, even with the work done so far, a system in which the waste generated is zero is impossible. An industry such as the paper industry will always generate wastewater that must be treated differently from that generated in households. Therefore, many companies in the industry are looking for ways to inert their waste flows so that they do not pose a problem for the environment.
Another industry that suffers from the same problem as the paper industry is the mining industry, where the extracted heavy metals are part of the gangue of the ore, which is of no economic interest to the company. The problem is when the concentration of heavy metals is too low to be trapped by physical methods such as coagulation or flocculation. Although the amount of metals in the waste streams is reduced, there is a certain amount of compounds harmful to the environment and humans that give the waste streams a concentration above the recommended levels.
To solve these problems, different techniques have been proposed to control the amount of harmful components that industries can discharge, but, in this blog entry, I want to talk mainly about different electrochemical techniques that exist to carry out this task. To do so, I think it is appropriate to make a brief summary of the branch that uses these techniques, which is electrochemistry.
Electrochemistry overview
Electrochemical reactions can be divided according to the potential needed to carry them out. When chemical reactions are induced by an external potential difference, i.e. a voltage needs to be applied to carry it out, the process is called electrolysis. On the other hand, if the electrical potential difference arises as a result of a chemical reaction, i.e. a voltage is generated as a consequence of the reaction, we are dealing with an ‘electrical energy accumulator’, commonly known as a battery or galvanic cell.
“Electrolysis. When chemical reactions are induced by an external potential difference”
Chemical reactions in which electrons are transferred between molecules are called redox reactions, which comes from the fact that, for a complete electrochemical reaction to take place, there must be a half-reaction in which one compound is reduced and another half-reaction in which another compound is oxidised, thus giving rise to this type of reaction. These reactions are essential in electrochemistry, as they enable the processes that generate or are induced by electricity.
In general terms, electrochemistry is concerned with investigating cases where oxidation and reduction reactions occur separately, either physically or at different times, within a system connected to an electrical circuit. This aspect is studied in analytical chemistry, specifically in potentiometric analysis.
The use of electrochemistry in industrial wastewater is based on the fact that metal ions often have different oxidation states (the theoretical electrical charge that an atom would have if all its bonds with other elements were completely ionic). By playing with these oxidation states and the presence of counterions that are capable of forming a low-solubility salt, a large part of the heavy metals can be removed, as well as other ions that are likely to be harmful.
Paper industry: capacitive deionisation
In the case of CARTIF, one of the electrochemical techniques used to treat effluent water from the paper industry is capacitive deionisation.
Capacitive deionisation (CDI) technology is based on the removal of anions and cations using an electric field and electrodes composed of carbon-derived materials with high porosity and good electrical conductivity. This method allows the localised accumulation of positive and negative charges around the electrodes in an alternating cell process, in which each cell functions as a supercapacitor that stores electrical energy while reducing the conductivity of the solution due to the removal of charges from the medium.
The inversion of polarity makes it possible to recover the accumulated energy at the same time as cleaning the electrodes on the surface of which the ions of opposite charge have been deposited. Thus, by circulating water against the current, a large part of the energy previously used in the desalination process is recovered, which can be reused to continue reducing the amount of dissolved salts. This process is repeated in cycles through several cells connected in parallel, alternating cells in operation and cells in cleaning. This makes it possible to obtain a continuous flow of desalinated water, a rejection flow (current with a high concentration of salts, which, as its concentration increases, is easier to dry and store in the future) and an energy recovery that is used in the active cells.
“Inversion of polarity. Recover the accumulated energy at the same time as cleaning the electrodes on the surface of which the ions of opposite charge have been deposited.”
The main advantages of the CDI are:
Lower energy consumption compared to reverse osmosis (RO, which is based on applying pressure to the solution to push it through a semi-permeable osmosis membrane to filter it and remove the ions present) as it does not require high pressures to operate and allows recovery of much of the energy used in desalination, stored in the cells as in a capacitor.
Reduction in the use of chemicals, as no chelating agents are required to prevent clogging as in membrane-based technologies, as well as no need for acids and bases for resin regeneration in ion exchange systems.
Modularity and compactness. The possibility of using multiple cells in parallel facilitates compact assembly and progressive expansion of the treatment flow by adding modules, offering scalable growth and greater versatility, which is of great interest in the industry.
Mining industry: electrocoagulation
In the case of the mining industry, one technique that CARTIF has been considering is electrocoagulation (EC), which has a range of application that also covers suspended solids, emulsified oil, hydrocarbons and the like.
In its simplest form, an electrocoagulation reactor consists of an electrolytic cell with an anode and a cathode. When connected to an external power source, the anode material corrodes electrochemically due to oxidation, while the cathode undergoes passivation.
An electrocoagulation (EC) system essentially consists of pairs of conductive metal plates in parallel, which act as monopolar electrodes. In addition, it requires a DC current source, a resistance box to regulate the current density and a multimeter to read the current values. The conductive metal plates are commonly known as ‘sacrificial electrodes’. The sacrificial anode reduces the dissolution potential of the anode and minimises the passivation of the cathode. Sacrificial anodes and cathodes can be made of the same material or of different materials, depending on the composition of the solution to be treated.
The monopolar electrode arrangement with cells in series is electrically similar to a single cell with many electrodes and interconnections. In a series cell arrangement, a higher potential difference is required for a given current to flow, as cells connected in series have higher resistance. However, the same current will flow through all electrodes. In contrast, in a parallel or bipolar arrangement, the electric current is divided between all electrodes relative to the resistance of the individual cells, and each electrode face has a different polarity.
During electrolysis, the positive side undergoes anodic oxidation reactions, while the negative side undergoes cathodic reduction reactions. Consumable metal plates, such as iron or aluminium, are generally used as sacrificial electrodes to continuously produce ions in the water. The released ions neutralise the charges of the particles present in the solution and initiate coagulation. These ions remove undesirable contaminants, either by chemical reaction and precipitation, or by causing coalescence of colloidal materials, which can then be removed by removal of the organic layer that forms on the surface of the solution. In addition, as water containing colloidal particles, oils or other contaminants moves through the applied electric field, ionisation, electrolysis, hydrolysis and free radical formation can occur, which can alter the physical and chemical properties of the water and contaminants. As a result, the reactive and excited state causes the contaminants to be released from the water and destroyed or made less soluble.
Some of the advantages of this system, in comparison with the chemistry coagulation, are:
The flocs formed by EC are similar to flocs generated by chemical flocculation, except that EC flocs tend to be much larger, contain less bound water, are acid resistant and more stable, and can therefore be separated more quickly by filtration.
EC can produce an effluent with lower total dissolved solids (TDS) content compared to chemical treatments, particularly if metal ions can precipitate as insoluble hydroxides or carbonates.
The EC process has the advantage of removing smaller colloidal particles, as the applied electric field neutralises any residual charge, thus facilitating coagulation through the formation of larger micelles.
The CE process generally avoids the excessive use of chemicals, which reduces the need to neutralise excess products and reduces the possibility of secondary contamination caused by chemicals added in high concentration, as is the case when chemical coagulation is used in wastewater treatment.
The gas bubbles produced during the electrolysis of both the water in the solution and the components in the solution can conveniently transport the contaminating components to the surface of the solution, where they can be more easily concentrated, collected and removed.
In conclusion, we can state that industrial evolution has brought with it significant environmental challenges, especially in the management of waste and toxic pollutants. To mitigate these effects, electrochemistry has emerged as a key tool in wastewater purification, highlighting techniques such as capacitive deionisation (CDI) and electrocoagulation (EC). These technologies make it possible to reduce the concentration of heavy metals and other pollutants with less use of chemicals and lower energy consumption. Thus, electrochemistry offers sustainable solutions to minimise the ecological impact of industries by optimising the treatment of their waste and contributing to environmental protection.
In the transition to a more sustainable world, green hydrogen has emerged as an essential resource to decarbonise key sectors such as industry and transport. In 2024, the European Union and other countries have redoubled their efforts with historic investments to build infrastructure and promote the production of renewable hydrogen, which will be crucial to meeting climate targets. This investment underlines the key role of green hydrogen in combating climate change and creating a carbon-free economy.
Green hydrogen, unlike conventional hydrogen, is generated from renewable energy-based technologies (e.g. from electrolytic cells combined with renewable energies such as wind or solar) without emitting polluting gases. This process makes it a clean and safe option for reducing global emissions. However, its mass adoption depends on successful transport and storage challenges, and this is where hydrogen carrier molecules play an essential role.
Hydrogen carrier molecules or ‘green molecules’: the key to the development of the green H2 sector.
Hydrogen in its pure state is difficult to store and transport because of its low energy density and because it requires special pressure and temperature conditions. Carrier molecules, such as methanol, ammonia and formic acid, allow hydrogen to be stored safely and stably, making it easier to handle and transport. These molecules act as ‘packaging’ for the hydrogen, which can be released at the point of consumption without logistical complications.
Methanol, a versatile carrier, is obtained by combining green hydrogen with captured CO₂, and can be practically reconverted to hydrogen at the point of use. Ammonia is another promising carrier, with a high hydrogen density and an existing transport infrastructure, making it ideal for large-scale industrial applications. The lesser-known formic acid is easy to handle and an excellent choice for smaller applications, such as fuel cells in light-duty vehicles.
Applications of H2 and its derivatives in transport and industry
The flexibility of these carrier molecules opens up a wide range of applications. In the transport sector, they can be used in trucks, trains and buses, enabling carbon-free mobility. This year we have seen the first hydrogen buses operating in Germany, and Japan has launched hydrogen trains, showing the potential of hydrogen in sustainable public transport. Carrier molecules make storing and refuelling green hydrogen more practical, helping to reduce dependence on fossil fuels over long distances.
Fuente: Freepik.es
In industry, green hydrogen and its carriers are viable alternatives to replace coal in high-temperature processes, such as steel production, and as a feedstock in the chemical industry, where green hydrogen replaces grey hydrogen in the production of ammonia and methanol, essential chemicals in the manufacture of fertilisers and plastics.
In addition, green hydrogen is also key to energy storage. With the growth of renewable energies such as solar and wind, efficient methods are needed to store excess energy and release it when needed. Surplus renewable energy can be converted into green hydrogen and stored in carriers such as methanol or ammonia, which can then be converted back into energy when demand is high or renewable generation is low. This helps to make the electricity grid more stable and sustainable, and reduces the intermittency of renewable sources.
The challenges and opportunities that the immediate future of green H2 and its derived ‘molecules’ brings us
Despite its potential, green hydrogen still faces significant challenges. One of these is the cost of production, which remains high compared to fossil fuels. However, technological progress and government support are reducing these costs, with expectations that green hydrogen will become more accessible in the coming years. In addition, investments in distribution infrastructure and refuelling stations are needed to bring green hydrogen to scale, enabling its use in industrial and transport applications around the world.
CARTIF’s Biotechnology and Sustainable Chemistry Area is also developing technologies to make the production of green hydrogen more efficient and economical, reducing the costs of electrolysis and improving materials for the safe storage of hydrogen in carrier molecules. These advances bring these technologies closer to commercial scale, making green hydrogen competitive and accessible in an energy market that increasingly demands sustainability. Through projects such as CATCO2NVERSand H2METAMO, we are working on capturing CO₂ for conversion into green methanol, a high value-added hydrogen carrier. These projects not only investigate how methanol and ammonia can facilitate hydrogen storage and transport, but also explore the potential of these carriers for direct use in industrial and energy applications.
“At CARTIF, we are pioneers in green hydrogen and its chemical storage in the form of green molecules and are committed to the advancement of green hydrogen and its carriers as a solution for a low carbon economy.”
In short, green hydrogen and its derivatives are beginning to transform the way we think about energy. This resource represents a unique opportunity to reduce carbon emissions and provide clean energy in a variety of industries and applications. At CARTIF, we believe that green hydrogen is the path to a sustainable future and we are committed to developing technologies that enable its mass adoption to have a positive impact on the planet.
Co-author
David Díez Rodríguez. Researcher at the Biotechnology and Sustainable Chemistry area.
One of the main challenges facing the Spanish Mediterranean basin is the scarcity of water resources, a critical factor for agricultural production in the region. Agriculture is a vital economic sector, dominated by irrigated crops such as vegetables and, currently, olive groves. The latter, traditionally rainfed, have been converted to irrigated crops due to the decrease in rainfall observed in recent decades. Both vegetables and olive groves require a constant and adequate water supply during their most demanding production phases, which intensifies the pressure on the limited water resources available in the area.
These irrigated crops are essential not only for food production but also for the local and national economy. For example, olive oil production in Andalusia is a fundamental pillar of the Mediterranean diet and represents a significant portion of Spain’s agri-food exports. In 2023, Spain exported 684,500 tons of olive oil, demonstrating the importance of this sector in international trade. The olive tree, although drought-resistant, has specific water requirements that are crucial for its development and production. Generally, olive trees require between 0.4 and 0.8 litres of water annually, depending on factors such as soil type, tree age, and climatic conditions. During critical periods, such as flowering and greening, water needs increase considerably, making adequate irrigation vital to ensure a quality harvest.
Water balance of Andalusia, Spain (2021-2050) (mm/day)
Furthermore, the quality of water used for irrigation is crucial. Water with high salinity or contaminants can negatively affect olive tree growth and the quality of the oil produced. Inadequate irrigation can lead to problems such as reduced yield and concentration of phenolic compounds, which are essential for the organoleptic properties of olive oil. Therefore, the use of quality water is not only vital for the health of the olive tree but also directly influences the quality of the final product, impacting the profitability of the crop.
However, the dependence of these crops on irrigation water poses various challenges for long-term sustainability, especially in the context of climate change that is exacerbating water scarcity. Efficient management of water resources thus becomes a priority to ensure the viability of olive oil production and other crops in the region.
The PRIMA NATMed project, coordinated by CARTIF, addresses water scarcity in the Mediterranean region through the implementation of Nature-based Solutions (NbS) in existing water infrastructures. Its innovative approach, based on the development and implementation of “Full-Water Cycle-NbS”, aims to optimize water management and improve related ecosystem services, while providing environmental, social, and economic benefits to Mediterranean communities.
One of NATMed´s key initiatives is the implementation and improvement of reclaimed wastewater treatment and storage systems for reuse in agriculture. This strategy provides an alternative water source that not only helps conserve natural water sources by reducing the overexploitation of ecosystems and water resources, but also provides farmers with a reliable source of irrigation, especially in water-scarce regions. Furthermore, the use of reclaimed water supplies nutrients to crops such as phosphorus and nitrogen, which reduces the need for chemical fertilizers and, consequently, decreases production costs, thus contributing to the economic and environmental sustainability of agriculture in the Mediterranean region.
An example of this strategy is the Spanish case study of the project located at the Center for New Water Technologies (CENTA) in Carrión de los Céspedes, Seville, where the combination of various artificial wetlands is being optimized with the aim of providing reclaimed water for irrigation of crops such as olive groves. These wetlands can be of different types, including:
Hybrid configuration: Vertical Subsurface Flow + Free Water Surface.
Floating helophyte wetland.
Aerated treatment wetland.
French vertical flow wetland
Center for New Water Technologies (CENTA) in Carrión de los Céspedes, Seville
Artificial wetlands are human-created ecosystems that emulate the natural water purification processes found in natural wetlands. These NbS leverage an intricate network of interactions between substrate, plants, and microorganisms to effectively purify wastewater. As water flows through the wetland, contaminants are removed through a series of complementary processes: suspended solids are trapped in the maze formed by the substrate and plant roots; organic matter is decomposed by a diverse community of microorganisms thriving in both aerobic and anaerobic conditions; nitrogen is absorbed by plants or transformed by specialized bacteria; phosphorus is captured by the substrate; and pathogens are neutralized by a combination of factors, including toxic substances produced by plant roots and the action of predatory microorganisms. This synergy of physical, chemical, and biological processes makes artificial wetlands an effective and sustainable solution for wastewater treatment.
Finally, the optimization of artificial wetlands developed in the NATMed project seeks to address the challenge of water scarcity in irrigated agriculture by providing alternative irrigation sources, which also reduce the need for chemical fertilizers, thus contributing to the environmental and economic sustainability of the region. As part of this approach, irrigation water quality parameters will be measured to ensure compliance with current regulations, in addition to analysing the nutrients provided to the soil, such as phosphorus and nitrogen, and their impact on crop production. A key aspect of the project is its potential for replicability in other locations to address the challenge of water scarcity in the Mediterranean region, which is being facilitated through engagement and training activities with relevant stakeholders in the area. These initiatives are fundamental to ensuring the long-term viability of agriculture in the region in the face of climate change and increasing water demand.
Spain is well known for its Mediterranean climate, characterized by high temperatures and low precipitation, particularly during summer. These features attract many tourists every year that choose Spain as holiday destination to enjoy its sunny beaches, vibrant cultural experiences and outdoor activities. Unfortunately, this climate is not only perfect for tourism but also fosters conditions that can lead to the outbreak of wildfires. And guess what? The increasing heatwaves and prolonged dry spells, caused by climate change, aggravate the work of the firefighters who need more resources to extinguish the fires.
Spain’s Fiery Stats: Where do we stand?
In 2023, the European Forest Fire Information System (EFFIS) ) estimated that around 91,000 ha of forest area were burnt. That’s like burning through the size of nearly 130,000 soccer fields! By using EFFIS data, it was possible to compare the surface of burnt area in several EU countries. The outcomes of this comparison are that, in 2023, Spain was the third country with most burnt area just after Greece (174,773 ha) and Italy (97984 ha). It is relevant to notice that Greece, Italy and Spain present similar climatic conditions, characterized by high temperatures and low precipitation.
Statistics from burned Spanish areas. Source: EFFIS
And here’s the kicker: in 2024, the flames have already gobbled up 37,000 hectares, putting Spain ahead of other Mediterranean countries. The recent Andújar wildfire in Jaén (Andalusia) alone scorched 835 ha of area that usually hosts an extensive variety of flora and fauna.
Hot zones: Where wildfires hit the hardest in Spain
Not all of Spain is equally flammable, but some regions are definitely more fire-prone. Andalusia frequently experiences wildfires, particularly in areas with dense forests and shrubland. Remember the Sierra Bermeja fire in 2021? It was one of the worst wildfires in years. Cataluña, especially near the Pyrenees, also faces frequent wildfires, like the intense blazes during the scorching summer of 2022. And let’s not forget Galicia in the northwest, where wildfires regularly sweep through rural and forested areas.
Source: Elordenmundial.com
What’s fuelling the flames?
Humans, of course! Whether it’s a careless camper, an arsonist, or a farmer burning fields, we’re often the ones lighting the match. But climate change effects are also major catalysts for wildfires. Rising temperatures, causing increased heat and dryness that make the vegetation more susceptible to ignition by reducing their moisture. Shifting precipitation patterns, which mean more drought frequency, making vegetation more prone to catch fire.
And don’t forget extreme weather events such as wild storms, that can produce lightings and thereby increasing the likelihood of natural ignition, while strong winds fan the flames, compromising the control of the fires, and making them spread.
The aftermath: What’s at stake?
When wildfires rage, the damage is not just environmental, it is economic and social, too. Forests and natural habitats are destroyed with the related loss of biodiversity, soil degradation, and increased carbon emissions is a direct consequence of wildfires on the environment. Economically, the destruction of homes, infrastructure, and agricultural lands hits communities hard. Tourism, a lifeline for many regions, can also be severely affected. And let’s not overlook the health risks. Wildfire smoke can affect vulnerable populations like the elderly and those with respiratory conditions, leading to respiratory illnesses and other health issues after a prolonged exposure.
Fighting fire with strategy and innovation
Battling wildfires is not just about putting out flames; it is about being smart before they even start. That means investing in research to understand fire behavior and the impacts of climate change, developing new firefighting technologies, and educating the civilians to increase public awareness on this matter.
The Spanish government is also stepping up with strategies and solutions to mitigate the risks of wildfires and adapt to the challenges posed by a changing climate that can worsen these risks like better land management practices (e.g. clearing vegetation and creation of firebreaks), reforestation with fire-resistant species, and enhancement of early warning systems. Moreover, the implementation of a well-organized firefighting system including brigades, aerial units and military units is essential to quickly control wildfires. Additionally, the European Union supports Spain through the European Civil Protection Pool, providing further resources to fight extensive wildfire.
CARTIF’s contributions to address fire risks in Spanish regions
RethinkAction, project led by CARTIF comprises the Almería province in Andalusia as one of its case studies. The project collects information on the area (e.g. historical and future values of climate variables), assesses the potential climate-related risks and creates risk maps. These maps provide useful insights on the risk of drought, heatwaves and storm in each municipality of the province and each vulnerable sector that can be exposed to these risks such as agriculture, tourism, water management and biodiversity.
Furthermore, CARTIF participates to the NEVERMORE project. This project includes the Region Murcia as case study. A climate-related risk assessment is performed also for this region and a map highlighting the most affected municipalities is produced. Such as the RethinkAction project, the NEVERMORE project provides relevant information not only on the most affected municipalities but also on the most vulnerable sectors involved. Knowing the municipalities with high probability to be affected by climate change is incredibly relevant for the prevention of fires, to identifying the missing resources that are necessary to contain possible outbreaks.
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.
Fermentation is perhaps one of the oldest technologies that has accompanied humanity for thousand of years. Throughout history, numerous evidences and traces have been found that demonstrate the use of fermentation by several cultures and civilisations, as a common and fundamental practice in the production of food and beverages, or even for medicinal and ceremonial purposes.
For example, archaeological remains have been found in China (7000-6600 BC ) of a fermented drink made from rice, honey and fruit in ceramic vessels, or in Iran (5000 BC) ceramic jars with wine residues, or Egyptian hieroglyphs and papyri (2500 BC) describing the production of beer and wine, as well as their consumption in religious ceremonies everyday life.
In addition, the analysis of botanical remains (seeds, plant fragments) has provided evidence of the use of fermented plants, or more recently the analysis and study of the DNA of yeasts and other microorganisms has provided genetic evidence of the use of fermentation since ancient times. These ancient methodes laid the foundations for the use and evolution of a practice that has evolved significantly over time.
The application of biotechnological techniques for the manufacture of pharmaceutical, biofuels, fertilisers and nutritional supplements has proven to be an age-old tool that has been adapted and sophisticated to suit today´s needs.
Global challenges such as environmental sustainability, food security, food scarcity, waste reduction and recovery find in fermentation a powerful tool to address these problems.
In this way, the use of different microorganisms can be the key to the revalorisation of different by-products and waste from industry, transforming them into high-value products such as biofuels (biodiesel, biogas), biodegradable compounds (bioplastics), or molecules of interest (lipids, organic acids, dyes, etc.) that can be incorporated back into the value chain thus contributing to a circular economy.
Fermentation can transform some agri-food by-products, which would otherwise be wasted, into products with an improved organoleptic profile by reducing or transforming undesirable compounds that negatively affect taste and texture. In this way, fermentation processes can improve the organoleptic profile and, thus the acceptability of certain by-products, which can then be incorporated back into the value chain.
Another future challenges is the increase in the world´s population, which brings with it an increase in demand for protein and poses challenges to the sustainability of traditional protein sources such as meat and dairy products. This is where the use of microorganisms, in this case fungi fermentation, emerges as an alternative to traditional protein sources. Fungi fermentation is key to obtaining microproteins that allow the development of flavours and textures that mimic meat and are sensorially appealing to the consumer. These types of proteins are rich in high quality nutrients, and are also presented as an alternative that requires fewer natural resources (water and land) and produces fewer greenhouse gases.
Fermentation also has the potential to mitigate pollution, playing an important role in waste management and pollutant reduction. Thus, certain organic wastes (waste oils, industrial waste, polluted waters) can be fermented to produce biogas, fertilisers and bioplastics, or it can be used to treat wastewater by reducing organic compounds before they are released into the environment. These processes can also be used in biorremediation processes, soil and contaminated area treatments.
According to the latest research, certain bacteria and fungi could be used to ferment and degradeplastics, such as polyethylene and polyester, or even use them as a source of carbon to obtain compounds of interest.
Therefore, fermentation today isn´t restricted to its use in the food industry for the production of fermented foods. Society must recognise and explore the alternatives offered by biotechnology, and in particular fermentative processes, to face present and future challenges.
Harnessing the abilities of bacteria, yeasts and fungi to transform waste materials into useful products, reduce waste and pollution will allow us to move towards a cleaner and sustainable future, thanks to micro-organisms, felow travellers that have served mankind for thousand of years, and may now be the solution to many of our future challenges.
