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Producing food safely and sustainably in state-of-the-art aquaponics

In a two-year research project, Hof University of Applied Sciences is investigating sustainable food production in aquaponics without any microplastics. The researchers led by project manager Prof. Dr. Manuela Wimmer had received funding of EUR 220,000 for “BioBioCarrier” from the German Federal Ministry of Economics and Technology and as part of the Central Innovation Program for SMEs (ZIM)

Image: Hof University of Applied Sciences;

Plastics in the food chain are a frequently discussed and increasingly important topic: not least through the consumption of fish, consumers today are absorbing increasing amounts of microplastics into their own bodies. The main culprits here are the large quantities of plastic waste now found in the world’s oceans. There, they are broken down into tiny particles and ingested by marine animals. But the problem is not just the tiny particles. Toxins and other pollutants bind to the relatively large surfaces of the micro- and nanoparticles, accumulate there and can then be absorbed into the organism in large quantities. Microplastics have been detected in numerous environmental compartments and foods. Plastics can either enter the environment directly as microparticles or be converted from macroplastics into smaller fractions by environmental influences. In either case, this is a serious challenge

Avoiding microplastics

However, the problem of microplastics is not only found in the oceans, but also in freshwater – and this is precisely where the new research project comes in

In pond farming or in large aquacultures, microplastics can be eliminated much better due to the closed water systems. On the other hand, however, the human factor means that micro- or macroplastics can nevertheless enter the ponds or flow-through systems and from there find their way into the organisms of fish, useful plants or mussels. This risk is additionally increased by various functional plastic parts in the system itself

Prof. Dr. Manuela Wimmer, Head of the “BioBioCarrier” project
Prof. Dr. Manuela Wimmer heads the “BioBioCarrier” research project; photo: private;

Nevertheless, plastics are gaining acceptance for use as growth bodies because the material is stable, inexpensive, lightweight, and quite easy to shape into complex forms. A single growth body is considerably smaller than a curler, but looks very much like one and has a high surface area despite its small size. This surface serves as a settlement area for useful bacteria. However, its advantages also represent one of its greatest disadvantages: its durability. Conventional plastic takes about 100 years to decompose. So if microplastics are present in closed aquacultures, it will be a long-term problem. Closed aquacultures are characterized by repetitive recirculation of water. This is made possible by treating the water, i.e. purifying it. In these systems, only a maximum of 10% of the total water volume is added daily. This means that the evaporation of circulating water is mainly compensated for by surfaces in contact with the air.

Reason enough to find alternatives to ensure the benefits of closed aquaculture and integrated aquaculture – such as aquaponics – while excluding negative influences such as microplastics.

Integrated aquaculture represents the production of different organisms that mutually benefit from each other. A prominent example of this form of culture is aquaponics. A compound word of aquaculture and hydroponics. The combined production of aquatic animals and the culture of crops without the use of soil. The sustainable form of culture is forward-looking, because with the multiple use of water, a reduction in water demand of about 90% can be realized compared to conventional production. The scientists in the new project now want to develop an innovative solution for aquaponics.

Degradable bioplastics for aquacultures

Dr. Harvey Harbach, research associate in the project, explains the project approach

Our research focus is on the so-called aquaculture growth bodies. These serve as a settlement area for useful bacteria in a filter. These bacteria are used to treat the water of the aquacultures and clean it of harmful substances.”

Dr. Harvey Harbach, Research Associate
Dr. Harvey Harbach – shown here fishing a pond; photo: private;

These bacteria convert ammonium and nitrite into the more harmless nitrate, which acts as a plant fertilizer. This results in several advantages for the aquaponics operator. Nitrate naturally accumulates in the cycle as a metabolic product of fish. In conventional aquaculture systems, nitrate must be reduced by diluting the circuit water with fresh water. This results in costs for the fresh water, the temperature control of the water to the system values and the disposal of the contaminated wastewater. In the case of aquaponics, however, the nitrate and also other plant-available fertilizers are absorbed by the crops in the system and bound for biomass buildup. As a result, aquaponic production can save water, energy and fertilizers

Growing body in aquponics tank; Image: Hof University of Applied Sciences;

The problem so far, however, is that the necessary growth bodies are still made of conventional, i.e. petroleum-based plastics. The main goal of the “BioBioCarrier” project is therefore the production of biodegradable growth bodies made of biopolymers for biological water treatment without any microplastics.

Long-lasting fertilization effect

But it is not only the plastic particles, which are harmful to the organism, that are to be avoided in the future. The slow decomposition of the biodegradable growth bodies is accompanied by another positive effect

When the growth bodies decompose, essential plant nutrients are continuously released into the water as part of the decomposition process, which are required by the cultivated crops for growth. This therefore results in automatic fertilization. As a result, no or much less fertilizer would have to be added manually.”

Prof. Dr. Manuela Wimmer

To date, one problem with aquaponics is that an operator must have expert knowledge of aquaculture and crop production in order to oversee both crops and intervene when problems arise. Typically, entrepreneurs have expertise in either aquaculture or hydroponics. Experts in both subjects are rare. In the case of aquaponics, this also means that nutrient concentrations of the water have to be determined manually and then re-dosed if necessary – an increased workload for the operator. With an automated fertilizer supply, the project actually aims to reduce the working time previously required for this. In this way, costs can be saved and at the same time the nutrient supply to the plants can be optimally guaranteed in the long term. Basically, in this way the operation and also the conversion to aquaponics becomes more attractive for a broad target group of aquaculture and also hydroponics enterprises.

Institutes of the Hof University of Applied Sciences work together

The project combines the expertise of no less than two institutes at Hof University of Applied Sciences and is thus the first ever inter-institutional project at the Hof teaching and research institution: “In this project, the Institute for Applied Biopolymer Research (ibp) and the Institute for Water and Energy Management (iwe) will further develop a forward-looking technology in an interdisciplinary and cross-disciplinary manner. The replacement of petroleum-based plastics with bioplastics fits ideally into sustainable and resource-saving food production through aquaponics. Hof University of Applied Sciences is thus strengthening its profile as a green tech university,” said University President Prof. Dr. Dr. h.c. Jürgen Lehmann. The BioBioCarrier project is being implemented in cooperation with the company Christian Stöhr GmbH & Co. Elektro- u. Kunststoffwaren KG from Marktrodach and is led by the Institute for Water and Energy Management.

Institute for Water and Energy Management

The Institute for Water and Energy Management (iwe) works on scientific topics with a special focus on making existing systems and processes more sustainable and at the same time more economical with the help of innovative technologies. In the field of integrated aquaculture, the iwe conducts research especially in the area of applied sustainability, which includes the topic of aquaponics. Dr. Harvey Harbach is the contact person in this research focus and works on the questions in this field. This has also led to the question of a growth body made of bioplastics. Negative influencing factors are to be excluded and positive ones used profitably. Beside this research project the close exchange and the problem definitions of regional enterprises in addition, national and international enterprises form the basis for the research projects of the research emphasis “integrated aquaculture” at the Green Tech university yard.

The topics of economic sustainability can also be found in the other research topics in the field of aquaculture. The project “Innovative Adaptation of Integrated Aquaculture in Existing Fish Farms”, InnoFisch for short, as part of the Green Technology Workshop Hof project, which is co-financed by the European Regional Development Fund with 1.47 million euros at 50%, also pursues the goal of implementing research results in an application-oriented manner. In 2021, the iwe will again be involved in the area of environmental education. In two educational projects, Dr. Harvey Harbach is in charge of the technical elaboration and knowledge transfer on the advantages of aquaponics.

Institute for Applied Biopolymer Research

The core competencies of the Institute for Applied Biopolymer Research (ibp) are the handling of bioplastics, their processing, application qualification in the context of innovative products, their recycling as well as surface functionalization. These are mainly in-depth application-related studies on biobased and/or biodegradable products. The challenge and tasks within the BioBioCarrier project consist in the production of a defined stable bioplastic with controllable degradation behavior for the release of the necessary additives in the aquaponics system.

Note: This article first appeared in the trade magazine “Der Lebensmittelbrief 5/21”.

Dr. Harvey Harbach
Prof. Dr. Manuela Wimmer
Rainer Krauß

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