Recycling instead of phosphorus crisis  [02.04.20]

If it is not possible to use the resource phosphorus more sustainably, humanity is heading for a serious crisis: phosphorus is irreplaceable as a nutrient for plants, animals, and humans. If it returns to the soil via excretions or dead organic material, the cycle is complete. At present, however, agricultural production worldwide cannot do without mineral fertilizers with considerable amounts of additional phosphate, which has to be mined in natural deposits. However, these deposits are heading towards depletion and are also distributed extremely unevenly worldwide. On the other hand, environmental problems often occur in areas with high livestock density because too much phosphate is spread on the fields with liquid manure. A German-Chinese research training group is currently investigating approaches to solving this complex global problem using maize cultivation systems as an example. The goal: a sustainable recycling economy in the spirit of the bioeconomy. The joint doctoral program at the University of Hohenheim and the China Agricultural University (CAU) in Beijing has been funded by the DFG since October 2018.

 

 

If the current economic situation does not change, it is estimated that the natural phosphorus deposits will be exhausted in about 250-300 years. What sounds like a relatively long period of time is already being felt by farmers today in the rising prices of fertilizers.

And in the coming decades, inflation could go up dramatically. This is because increasingly, deposits of lower quality must also be exploited, which can be contaminated by heavy metals such as cadmium and uranium, for example. The rock phosphate extracted there must then be processed at high cost.

The unequal distribution of the resource is also problematic. Almost three quarters of the known deposits are located in only one country in the world: Morocco. Unstable political conditions there could have serious consequences for the entire world market in the future.

Phosphorus crisis: German-Chinese cooperation focuses on global problem

"If we do not start looking for alternative solutions today and set out on the path to a circular economy in the spirit of the bioeconomy, we are heading for a serious crisis," said Prof. Dr. Torsten Müller from the Department of Fertilization and Soil Matter Dynamics and spokesman of the German-Chinese Research Training Group on the German side.

A total of 35 doctoral students from the University of Hohenheim and the China Agricultural University in Beijing are researching precisely such approaches as part of the joint training program "Adaptation of maize-based food-feed-energy systems to limited phosphate resources (AMAIZE-P)". In mixed German-Chinese tandem teams, the young scientists are using maize cultivation systems as an example to investigate different approaches to using the scarce resource phosphorus as effectively as possible.

In fact, China, the most populous country in the world, will be particularly hard hit by the phosphorus shortage in the future: The People's Republic is still focusing on mining areas in its own country. But with constant consumption, these areas will probably be exhausted in about 35 years. If the current phosphorus requirements of Chinese agriculture have to be covered entirely by the world market in the future, this would also have consequences for the rest of the world: prices would make another big leap upwards.

"The paradox in the current situation is that there are regions in both Germany and China where phosphate is used almost wastefully: Where a lot of livestock farming and biogas production is practiced in Germany, environmental problems arise because too much phosphate ends up on the fields via liquid manure and fermentation residues. Similarly, in China, phosphate from organic sources is hardly taken into account when determining fertilizer requirements, while at the same time the use of mineral fertilizers is excessive. The soils cannot completely absorb the nutrient and it gets into streams, rivers, and lakes in considerable quantities. This leads to eutrophication, which can result in a pronounced algal bloom, among other things. In addition, phosphate is lost via wastewater and waste streams from agricultural cycles," explained Prof. Dr. Müller.

Example: Maize cultivation: Interdisciplinary approaches for diverse scenarios

Although at first glance the challenges in Germany and China appear to be similar, there are also major differences. The agricultural sector in both countries is structured differently: While larger farms dominate in Germany, Chinese agriculture is still largely characterized by small-scale farming. The climatic conditions of the two countries also differ greatly.

"It is precisely these differences that are so valuable for research cooperation. With parallel field experiments and economic analyses in Germany and China, we can cover a large part of the scenarios that arise worldwide. Especially with regard to our research subject, the maize crops, the conditions in Germany and China complement each other: "Together we can cover almost all production systems that play a role worldwide," said Dr. Marco Roelcke, coordinator of the German-Chinese research training group on the German side.

Corn, which is one of the most important staple foods worldwide, is particularly well suited for the broad research approach because of its diverse utilization possibilities: This is because corn is used as food for humans, as animal feed - in the form of grains or silage - for oil production, and as a biomass supplier for energy production or the production of basic chemicals through novel conversion processes in the spirit of the bioeconomy.

Compensating surplus and shortage

In twelve interdisciplinary research groups, the German and Chinese doctoral students pursue a variety of approaches.

"An important focus is on sustainable fertilizer strategies and the question of how excess phosphate from regions with high livestock density can be transferred to agricultural regions with phosphate deficiency in a resource-friendly manner," explained Prof. Dr. Müller. "In retrospect, it was a political mistake to promote structural change with spatial differentiation of these two economic forms. However, in the foreseeable future there is no way back to the traditional mixed farms. We must therefore seek technological solutions to deal with the existing situation."

In principle, plants can only efficiently utilize phosphorus if all other nutrients, such as nitrogen, are also available to them in sufficient quantities. One problem with fertilizing with liquid manure and fermentation residues is that nitrogen and phosphorus are not present in an optimal ratio to each other. The excess phosphate cannot be absorbed by the plants and is therefore lost unused.

In order to solve this problem, research groups in the research training group are working on practicable ways of further processing liquid manure and fermentation residues in order to separate the nitrogen and phosphorus streams again and make optimum use of these two nutrients. In a win-win situation, energy and basic chemicals should also be produced.

New corn varieties, optimized crop rotations, nutrient recovery

In addition, the German-Chinese working groups are also working on completely different approaches: For example, the breeding of new maize varieties that better absorb the nutrient via their roots, or the optimization of crop rotations, since the phosphate in the soil can be made more readily available by alternating maize and pulses. Further subprojects are dealing with the utilization of phosphate in the digestive tract of humans and livestock.

"Human excretions are also a source of phosphate that can be fed back into the cycle. Due to the current legal situation in Germany, however, sewage sludge cannot be applied directly to fields. We think: Sewage sludge is better than its reputation - and are therefore also looking for ways to recover the phosphate it contains in large sewage treatment plants," said Prof. Dr. Müller.

Think Tank: Interdisciplinary exchange in block seminar

"Twice a year, a block seminar, which takes place alternately in Germany and China, ensures that all teams can exchange ideas on an interdisciplinary basis: A think tank that is enriched by external experts from all over the world. The doctoral program is accompanied by intercultural training, career workshops, and numerous other formats," said Dr. Roelcke.

The fourth block seminar took place from 9 to 16 March 2020 at the University of Hohenheim and the Untere Lindenhof in Eningen unter Achalm and dealt with the overall topic "P-Nutrition and Recovery".

"Since, due to the Corona crisis, only those Chinese doctoral candidates who had previously been in Germany could be present in person, their colleagues who remained in China delivered PowerPoint presentations or video files set to music, which were then shown in the seminar. Conversely, all lectures and discussions of the block seminar were also recorded. We will certainly benefit from the newly tested forms of digital cooperation in the future," Dr. Roelcke stated.

The Research Training Group is also closely networked with the CHIKOH - China Competence Hohenheim program: Since October 2017, the program has been strengthening the China expertise of scientists and students with a wide range of offers. With excursions and workshops, the University of Hohenheim aims to actively contribute to the mutual transfer between business and science. An important item on the agenda is the "Hohenheim China Dialogue" as an exchange platform for representatives from science, business, and society from the region.

BACKGROUND: China Agricultural University (CAU), Beijing

The China Agricultural University (CAU) in Beijing is the leading university in Asia in the field of agricultural sciences and always among the top performers in worldwide rankings. CAU scientists research and teach in the fields of agriculture, life sciences, resources, environment, electronic data processing, computer science, agricultural engineering, management, and social sciences. The University of Hohenheim and CAU maintain one of the oldest existing German-Chinese university partnerships (since 1979). In November 2019, the 40th anniversary of this unique friendship was celebrated in Beijing.

BACKGROUND: Science Year 2020 Bioeconomy

In 2020, the Science Year organized by the Federal Ministry of Education and Research (BMBF) will be dominated by the bioeconomy - and thus a sustainable, biobased economy. The aim is to produce and use natural substances and resources in a sustainable and innovative way, thus replacing fossil and mineral raw materials, manufacturing products in a more environmentally friendly way, and conserving biological resources. This is more necessary than ever in times of climate change, a growing world population and a drastic decline in species. The Science Year Bioeconomy puts the spotlight on this topic.

The bioeconomy is the central theme of research and teaching at the University of Hohenheim. It combines the faculties of agricultural sciences, natural sciences, economics, and social sciences. In the Science Year Bioeconomy, the University of Hohenheim will inform experts and the public about the topic in numerous events. In March, the monthly focus is on: Conserving resources - recycling management and economic development

Text: Leonhardmair / Translation: Neudorfer