How we want to change the world!

In a world in which the concepts of sustainability, reusability and environmental protection are becoming more and more important and where mechanisation determines our lives, everyone has to ask themselves how we want to face these hurdles of our time. The consequences of climate change as well as environmental pollution show us that action must be taken, that change is needed. Cleaning up pollution through remediation to restore a healthy environment aims to clean up the consequences of old mistakes. At the same time, investments in the expansion of renewable energy sources are meant to prevent new ones. Our team aimed to set a project in the context of these two key pillars which are meant to ensure the preservation of our planet. In developing the project, we looked for ways to combine these two aspects of remediation and expansion of renewable energy.

During research for our project, we came across the worldwide existing problem of heavy metal pollution. Increased anthropogenic activities such as years of coal and fossil-fuel usage and especially mining led to the hazardous release of substances such as cadmium, mercury and lead[1]. When toxic metals like cadmium get into soil and water, e.g. through the use of polluted fertilisers, these substances accumulate in crops and ultimately in animals and humans eating them. This bioaccumulation of cadmium becomes hazardous to health by causing chronic diseases of the renal, pulmonary, cardiovascular and musculoskeletal systems[2,3]. Even though efforts by the United Nations Economic Commission for Europe as described in the Aarhus Protocol[4] have been able to reduce pollution with cadmium, lead and mercury at the European level, it can be seen that cadmium pollution has increased in some countries such as Poland, Austria and Hungary compared to 2005[5]. This describes the situation in industrialised countries. However, it is thought to be of greater concern to rapidly industrializing, developing countries because of the increasing pace of industrial activities in these countries with increasing consumption and release into the environment[6]. Particularly countries like China[7] and India[8] face serious concerns with cadmium pollution. When dealing with potential pollution, monitoring the contamination through measurements is essential to prevent poisoning.

Confronted with this background, our project idea developed in form of a cost-effective chip-based detection of cadmium contamination using the chemotaxis system of Escherichia coli, to enable cheaper monitoring of cadmium pollution, for example in developing countries. In a second step, we thought of a system to recollect the cadmium from polluted water using these bacteria.

In terms of renewable energies, solar plants as well as wind and hydroelectric power plants are of particular importance. In the case of solar cells, we noticed that rare metals are needed for their production. In addition to the companies that use silicon for their panels, the world's largest manufacturer First Solar produces cadmium telluride modules. Thereby, one module contains 7 g of cadmium telluride. Since cadmium chloride is expensive at a cost of 30 cents per gram[9], the remediation of polluted water also offers the opportunity to recycle and sell the extracted salt to reduce the costs of the remediation and at the same time promote the production of new solar panels. In subsequent projects, a purification of our collected cadmium for the purpose of recycling would have been conceivable. However, in the course of our project we came across studies of the Stuttgart Institute for Photovoltaics on the subject of pollutant release from photovoltaic modules[10]. The final report shows that the hazardous cadmium salt can be washed out of the panels even by rainwater and thus enter the environment. Seven hundred thousand of these models are installed in the Germanys biggest solar power plant Lieberose in Brandenburg alone[11]. We discussed these results and decided that by recycling the cadmium for solar panels we could be contributing to a renewed cadmium pollution of the environment, which is contrary to our intention and ambition at its core. This study, as well as the continued use of cadmium modules, showed our team that cadmium will continue to pollute our environment in the future and thus remains a problem for which our project could provide a solution. Therefore, we focused our work on the chip-based detection of cadmium using a chemotaxis system and on the development of a remediation system for cadmium-polluted water.

After researching proteins for our project and developing biochemical pathways to realize our ambitions, we wanted to gain impressions of the conditions a model system has to withstand under real conditions. For this reason, we discussed our ideas and concepts with representatives of rECOmine. The alliance rECOmine consists of over 60 partners, including commercial and governmental institutions with the goal of utilising mining waste such as mine water, slag and ash with maximum economic efficiency to minimise environmental damage. In model regions such as the Erzgebirge innovative solutions for typical mining wastes are developed with the aim of finding worldwide applications. In discussions with the Alliance Coordinator, Phillip Büttner, we talk about rECOmines problems with cadmium contamination. Cadmium along with other heavy metals is washed out by the mining industry. It leaches from mining operations and can end up in soils, groundwater and rivers. These toxic contaminants have been detected in water as far as 450 km from their source. Regarding possible applications for our system, we talked about necessary conditions for such a system. When it comes to purifying wastewater, rECOmine works in alkaline medium which is why our E. coli system should also be stable at higher pH-values in order to fulfil its intended function of remediation. In addition, for a possible application it is especially important that the import of our E. coli system is specific for cadmium ions excluding comparable ions like Mn2+. We integrated the results from this exchange by testing our system for its stability in pH test series and aimed to adapt it to alkaline media by further modifications. In addition, we introduced concepts for screenings with different ions into our laboratory planning, which should enable us to estimate the specificity of our system. Overall, we were pleased to hear that rECOmine is interested in our system and can imagine an application in bioreactors that could be integrated into their purification chain of polluted water

rECOmine call

Figure 1: Screenshot of the online meeting with rECOmine from 08 August 2022. From top left to right: Phillip Büttner (rECOmine), Lucas Ban (iGEM Frankfurt), Dominik Pichert (Team Leader of iGEM Frankfurt).

REFERENCES
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  2. Genchi G, Sinicropi MS, Lauria G, Carocci A, Catalano A. (2020): The Effects of Cadmium Toxicity. Int J Environ Res Public Health. 26;17(11):3782. doi: 10.3390/ijerph17113782
  3. Rafati Rahimzadeh M, Rafati Rahimzadeh M, Kazemi S, Moghadamnia AA. (2017): Cadmium toxicity and treatment: An update. Caspian J Intern Med.;8(3):135-145. doi: 10.22088/cjim.8.3.135
  4. United Nations Economic Commission for Europe (2022): Protocol on Heavy Metals - The 1998 Aarhus Protocol on Heavy Metals. URL: https://unece.org/environment-policy/air/protocol-heavy-metals [03.10.2022]
  5. European Environment Agency (2021): Heavy metal emissions in Europe. URL: https://www.eea.europa.eu/ims/heavy-metal-emissions-in-europe [03.10.2022]
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  8. Govil, P.K, Sorille JE, Murthy MN, Sujutha D, Reddy GL, Rudolph-Lund K et al. (2007): Soil contamination of heavy metals in the Katedon Idustrial Development Area, Hyderabad, India. Environ Monit Assess 140: 313-323.
  9. Steiner, J. (2014): Tofu-Bestandteil ersetzt giftiges Cadmium-Salz. URL: https://www.deutschlandfunk.de/solarzellen-tofu-bestandteil-ersetzt-giftiges-cadmium-salz-100.html [03.10.2022]
  10. Nover, J. et al. (2017): Schadstoffreisetzung aus Photovoltaik-Modulen. URL: https://www.iswa.uni-stuttgart.de/ch/dokumente/Forschung_CH/2017_Projekt_Schadstoffe_Uni_Stuttgart_Abschlussbericht.pdf [03.10.2022]
  11. Wetzel, D. (2010): Streit um giftiges Cadmium spaltet Solarindustrie. URL: https://www.welt.de/wirtschaft/article7660982/Streit-um-giftiges-Cadmium-spaltet-Solarindustrie.html [03.10.2022]