The Problem
Phosphate is an essential element for all living organisms (Burut-Archanai et al. 2011). It is involved in diverse cellular functions, including structural function, energy and information transmission and information storage in almost all living organisms (Blank 2012). For plants, phosphate together with potassium and nitrogen, is a key limiting factor of plant growth and biological processes, and is therefore a major component of all common fertilizers to maintain high crop yields (de Boer et al. 2018).
It has been estimated that by the middle of this century, our world will be the home to over nine billion people, which will be constantly rising until the human population reaches eleven billion people at around 2100 stated by UN DESA (United Nations Department of Economic and Social Affairs), and thus implies a massive need for increased global food production by 70% to meet global demand by 2050 (Cordell et al. 2009). The most probable scenario estimates the demand of phosphate will have an annual rise by 2% until 2050 (Cordell et al. 2009). Especially developing countries like ones in Africa are predicted to experience a massive increase in the demand of phosphate (Heckenmüller et al. 2014).
Nowadays, the main source of phosphate is the phosphate rock which, like oil, is a non-renewable resource and takes approximately 10-15 million years to regenerate (White 2000). The current known phosphate rock reserves have been predicted to be depleted in the following 50-100 years (Cordell 2010), which will be not enough for the growing population. Moreover, the reserves are unevenly distributed on a global scale and the grade (i. e. actual phosphate content) of phosphate rock is slowly degrading and thus mining operations are only going to increase (Heckenmüller et al. 2014).
Phosphate rock deposits not only consist of phosphate rock, but also contain other minerals, heavy metals and radioactive materials, which leads to several risks. The mining of the phosphate rock for the production of fertilizers creates the risk for metals to accumulate in the soil and crops and enter the food chain. In addition, mining contributes to the redistribution of radionuclides into the environment, allowing those to be naturally introduced in products from the phosphate industry (de Boer et al. 2018).
Excessive use of fertilizers to maintain high crop yields has resulted in the accumulation of high amounts of phosphate in lakes, as the excess phosphate seeps into the groundwater (Kaur & Singh 2012). The studies conducted by Prasad & Prasad (Prasad and Prasad 2019) conclude that increasing concentration of phosphate in inland waters is the main cause for the formation of algal blooms and eutrophication. The rapid growth and accumulation of phytoplankton in waters results in anoxic bottom waters followed by the algae death, decomposition, and release of toxic compounds (Cordell 2010). Hypoxia and the release of toxic compounds result in the mortality of fish and other aquatic animals (Prasad and Prasad 2019).
In the summer of 2018, the Aasee lake in the German city of Münster went through eutrophication, leading to 20 tonnes of dead fish having to be removed from the lake. This event was due to high temperatures, but the conventional phosphate removal techniques were partly to blame, as they only precipitate the phosphate, instead of removing it (City Münster 2020). The impact on the local ecosystem was devastating, as the lake biome provides sustenance to many animals living in the surroundings (BLINKER 2020).
Due to a growing demand of phosphate for modern agriculture, but also growing environmental and economic concerns, there is a need to reassess the obtention of phosphate. In this project, we will analyse the phosphate problem in relation to the environmental impact and describe our sustainable approach using synthetic biology to close the phosphate cycle by modifying a mosses phosphate metabolism.
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