Plants can help us decontaminate the environment, since they are capable of metabolizing or accumulating different types of compounds. Phytoremediation technologies are widely used throughout the world: aquatic and terrestrial species can be used to treat urban or industrial wastewater. In addition, certain species make it possible to treat sludge and soils with the presence of toxins.
These tools are very sustainable, since they require a low energy input to function. However, they have an Achilles heel: what do we do with the contaminants accumulated in the structure of the plant? This is where the circular economy comes into play, which makes it possible to valorize contaminated plant waste to produce materials with high added value.
Circular economy and environmental restoration
Recognizing, measuring and expressing the value of water, and incorporating it into decision-making, is essential to achieve sustainable and equitable management of water resources. This is what the report says valuing water (the value of water) of the United Nations, which also reviews water valuation methodologies, advocating a circular economy approach.
In a global context dominated by climate change, we need to approach environmental recovery processes from the perspective of the circular economy. In fact, in its circular economy strategy, the European Union literally indicates that “a circular economy means using processes that restore, renew or revitalize their own sources of energy and materials and waste as little as possible”.
A clear example of the European Union’s decision to promote research projects in this line is the Recovery and Resilience Mechanism, endowed with 672.5 billion euros, to generate employment in various areas. Among them stands out the clean production of energy and the restoration of the environment.
The value of vegetable waste
If we look for examples of the application of the circular economy, the concept of bioeconomy automatically appears. It is based on the use of resources of biological origin to provide goods and services in a sustainable way.
According to the FAO, the bioeconomy “offers a unique opportunity to comprehensively address interconnected societal challenges, such as food and nutrition security, dependence on fossil resources, scarcity of natural resources and climate change.”
Within the concept of “bioeconomy” not all biological resources have the same value. Thus, the use of agricultural crops (first generation biomass) is not interesting because it can compete with food. However, using non-food organic materials (second generation biomass), such as forestry or agricultural residues, makes it possible to convert waste into a useful and sustainable material resource.
Having said that, is it possible to combine bioeconomy, water conservation and circular economy? And take advantage of the synergies of all these disciplines?
Two projects of the Integrated Environmental Recovery Technologies Laboratory (EARTH laboratory) of the University of Castilla-La Mancha were born around this concept: the ALMA MATER and CENIT projects, financed respectively by the Junta de Comunidades de Castilla-La Mancha and by the Ministry of Science and Innovation in its call for projects for the ecological and digital transition.
Obtaining catalysts and metals
Within the framework of these initiatives, we have carried out research in order to take advantage of the contaminated biomass obtained from phytoremediation to produce catalysts with which to carry out reactions of great interest (disinfection, production of hydrogen peroxide, obtaining hydrogen, etc.). Thus we reduce the need for fossil fuels, the usual raw material for these catalysts.
We have applied these techniques to recover plants contaminated with metals from the old abandoned mining district of San Quintín, in the Valle de Alcudia and Sierra Madrona Natural Park (Castilla-La Mancha). And we are also applying it to remove pharmaceutical and personal hygiene products from water.
So far, we have used the red arenaria (Spergularia rubra) to remove heavy metals and mass (cladium mariscus), the reed (Phragmites australis) and the bulrush (Typha latifolia) for the removal of organic compounds.
In mining districts, the extraction of the metals contained in the plants also allows the recovery of increasingly scarce resources. Among these metals are rare earths, so named because of their low surface concentration and the difficulty in isolating them.
A few years ago, due to social pressure, a project for its extraction in the open air in Campo de Montiel was cancelled. Currently, more than 95% of its production is in China, which is why most European countries depend on international trade for these products.
For this reason, with processes based on circular economy we not only want to give a new life to potential waste. The design of the processes also seeks to obtain the maximum value of the raw materials from the environmental, economic and strategic point of view.
In other words, we work to triangulate water treatment through circular economy and bioeconomy, to achieve increasingly strategic and sustainable processes demanded by society.