The energy and digital transition is transforming our economy at an unprecedented rate. Electric vehicles, renewable energy, energy storage, digitalisation, artificial intelligence and smart grids are all technologies set to play a key role in the coming decades. However, they all have one thing in common: they rely on a range of raw materials, the availability of which has become a strategic concern worldwide.
Lithium, cobalt, nickel, manganese, graphite, rare earths, gallium, germanium, antimony and phosphorus are some examples of so-called critical materials – resources that are essential for the manufacture of batteries, photovoltaic panels, wind turbines, semiconductors, fertilisers and numerous electronic devices. Their importance is such that the European Union regularly updates a list of Critical Raw Materials (CRM) to identify those resources whose scarcity or dependence on external sources could jeopardise the competitiveness and security of the European economy.
Europe is in a particularly vulnerable position. Although it consumes a significant proportion of these materials, it has limited capacity to produce and process them, relying heavily on imports from third countries. In some cases, virtually the entire supply is concentrated among a small number of international suppliers, giving rise to significant economic, industrial and geopolitical risks.
In Spain, we face the same situation. Although we have certain mineral resources and a long tradition of mining, we continue to rely heavily on imports to supply strategic sectors. This dependence is particularly significant in a context where demand for critical materials continues to grow, driven by the decarbonisation, electrification and digitalisation of the economy.
However, there is an opportunity that has remained in the background for decades. Beyond conventional geological resources, we have a vast quantity of valuable materials found in streams that we usually regard as waste or by-products. What has so far been seen as an environmental problem could become a strategic source of raw materials to strengthen our industrial autonomy.
When waste becomes a goldmine of opportunity
Traditionally, the extraction of raw materials has been associated with conventional mining. However, in recent years the concept of ‘urban mining’ has gained momentum; this approach views the waste generated by our society as genuine deposits of resources.
One of the most obvious examples is lithium-ion batteries. The exponential growth in electric vehicles and energy storage systems will mean that millions of batteries will reach the end of their useful life over the coming decades. This waste contains significant quantities of lithium, cobalt, nickel, manganese and graphite – materials whose primary extraction is often associated with high economic, environmental and social costs
Extraction of materials from a lithium-ion battery at the end of its service life
Recovering these materials using advanced recycling technologies allows them to be reintroduced into the value chain, reducing the need to import new raw materials and minimising the environmental impact associated with their extraction.
A similar phenomenon occurs with photovoltaic panels. Although most existing installations remain in operation, the number of modules reaching the end of their useful life will increase significantly in the coming years. In addition to glass and aluminium, these panels contain silver, high-purity silicon and other strategic materials, the recovery of which can help to close the production cycle for new renewable technologies.
The enormous potential of electronic waste
Waste electrical and electronic equipment is another of the most promising sources of critical materials. Computers, mobile phones, televisions, telecommunications equipment and a wide range of other devices contain valuable metals which, in many cases, occur in higher concentrations than those found in some currently mined ore deposits.
Rare earths, indium, gallium, copper, gold, silver and palladium are just a few examples of the elements found in this electronic waste. However, a significant proportion continues to be lost due to inadequate collection systems or recycling processes that fail to recover all the materials present.
Improvements in separation, sorting and recovery technologies can transform this waste into one of Europe’s main sources of strategic raw materials.
The hidden legacy of mining
Paradoxically, some of the future sources of critical materials could be found precisely in the waste generated by past mining operations. For decades, mining produced enormous quantities of waste rock, spoil heaps and tailings ponds, the composition of which was assessed solely on the basis of the resources that were economically viable at the time. Many elements that we now consider critical had no commercial value at the time and were left stored in these deposits.
We now know that many types of mining waste contain significant concentrations of rare earth elements, cobalt, scandium, germanium, antimony and other strategic materials. The application of new characterisation and recovery technologies is enabling us to reconsider these environmental liabilities as potential resources.
So-called ‘reminería’ also offers an additional advantage: it enables the recovery of valuable materials whilst contributing to the environmental restoration of degraded areas, thereby reducing the risks associated with soil and water pollution. In Spain, which has a long history of mining, these deposits represent an opportunity that has yet to be fully explored.
Industries also harbour valuable resources
Numerous industrial processes generate waste streams with significant potential for the recovery of critical materials. Steel slag, steelworks dust, industrial ash, metallurgical sludge and certain types of waste from the chemical industry contain strategic elements which, in many cases, end up being used in low-value applications or even sent for disposal.
Hydrometallurgical, electrochemical and biotechnological processes are demonstrating that it is possible to recover materials such as zinc, vanadium, manganese, chromium, gallium and rare earths from these streams. This approach not only reduces the need for primary extraction, but also fits perfectly with the principles of the circular economy, where waste from one activity becomes a resource for another.
The case of spent catalysts used in the chemical, petrochemical and energy industries also deserves special attention. These materials contain metals of high economic value, the recovery of which is becoming increasingly attractive from both a technical and strategic perspective.
Phosphorus: a critical material for food sovereignty
When people talk about critical materials, they usually think of batteries, semiconductors or renewable technologies. However, one of Europe’s most strategic resources is phosphorus, which we might call ‘the jewel in the crown’.
This element is essential for the production of fertilisers and, consequently, for agriculture and food security. Unlike other resources, there is no known substitute for its biological function, which makes its availability a matter of global concern.
Europe is heavily dependent on imports of phosphate rock and phosphate fertilisers, which are concentrated in a small number of countries. Consequently, the recovery of phosphorus from secondary sources has become an increasing priority.
Sewage sludge, ash from its incineration, digestate produced in biogas plants, livestock manure and certain agri-food waste contain significant amounts of phosphorus that can be recovered and reused in the production of fertilisers.
As well as strengthening industrial self-sufficiency, these strategies help to improve our food sovereignty and reduce the pressure on limited natural resources.
The unseen resources of rivers, reservoirs and seas
There are also potential sources that have only just begun to attract attention. Sediments accumulated in rivers, reservoirs, harbours and coastal areas contain materials that have been transported over decades by industrial, mining and urban activities. At certain sites, these sediments contain significant concentrations of metals that could be recovered using appropriate technologies.
A waterproof membrane used in water treatment processes.
Regular dredging operations generate large volumes of material that are usually managed as waste or used for purposes with little added value. However, a more detailed characterisation could reveal currently untapped opportunities for recovery. A similar situation applies to certain seabeds, where the presence of minerals rich in manganese, nickel, copper or cobalt has sparked growing international interest. Although the direct exploitation of these resources poses significant environmental challenges, their existence highlights that there are still numerous potential sources yet to be investigated.
A matter of industrial sovereignty
Recovering critical materials from secondary sources will not completely eliminate the need for imports, nor will it replace conventional mining. However, it can play a decisive role in strengthening European industrial resilience and reducing our exposure to increasingly uncertain international markets.
To achieve this, it will be necessary to develop more efficient recovery and separation technologies, improve waste collection and traceability systems, promote favourable regulatory frameworks, and encourage collaboration between public authorities, businesses and technology centres.
Ultimately, the transition to a more sustainable economy will depend not only on discovering new resources, but also on our ability to recognise the value of those we already have. Spent batteries, disused solar panels, mining waste, industrial slag, sewage sludge, river sediments and electronic waste constitute veritable reserves of critical materials scattered across our territory.
Perhaps the most important mines of the future are not those that have yet to be mined, but those we have been creating for years without being fully aware of their value. Making the most of them could become one of the keys to strengthening the industrial, technological and food sovereignty of Spain and Europe in the coming decades.
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.
