Case study on plastic footprint in organic horticulture and alternatives

Congratulations to our coworker Victoria Eckerle who successfully defended her master thesis today at the University of Oldenburg

Title: Plastic in Agriculture - A Case Study

Abstract of Chapter 1

Modern agriculture has become heavily dependent on agricultural plastic products, from the seedling trays over greenhouse tunnel films to the harvesting crates. Such applications have improved crop production, especially in organic horticulture, in terms of crop yield and food security, as well as regarding environmental aspects such as water consumption. On the other hand, the leakage of plastic items or fragments thereof into the environment during usage and disposal at the end-of-life are bearing high risks for the entire environmental system. To capture the status quo of plastic use in organic horticulture, a plastic footprint assessment was developed and applied in a case study at one specific organic horticultural farm in Southwest Germany. The plastic footprint was therefore defined as the total weight of plastic, which is used in any form from cultivation to ready-to-sell fruits and vegetables, considering of plastic leakage during the production process and the resulting plastic waste at its end-of-life. Therefore, a database structure was evolved and filled during interviews with the farmers. On this database, the plastic demand of the entire company was computed on 10.5 tons in 2023, while the 25 crops were computed to demand from 5 g/kg plastic for Chinese cabbage to 69 g/kg plastic for blackberries. The plastic material flow was traced in a conceptual model and showed the potential for plastic leakage and the actual end-of-life. Based on this, recommendations for action were developed, following the waste hierarchy concept. The focus was put on plastic reduction and where unavoidable, designing for reuse and recycling or, in case of potential leakage into the environment, biodegradation.

Abstract of Chapter 2

Mulch films are among the most used plastic products in agriculture worldwide. Due to their use in the open environment, there is a high potential for leakage, which is why biodegradable alternatives were developed. These films begin to biodegrade over time, so temporarily formed microplastic fractions continue to decompose until completely mineralized and thus have less of an impact on soil functions and organisms through accumulation. For the successful application of those films in the field, however, a better understanding of the behavior in the open environment is wanted. Therefore, this study tested three as OK biodegradable soil certified mulch films in the open field and in mesocosm tanks, simulating scenarios during and after service-life. Film samples were exposed to the soil surface and buried in the soil to study the service-life and end- of-life, as well as the influence of water and additional nutrients and microorganisms on biodegradation. Samples were regularly monitored via photo documentation. The evaluation of the images allowed to determine the disintegration behavior, which showed clear differences related to the material composition. Soil moisture was the decisive factor for the rate of disintegration, proving to be useful for controlling disintegration of the mulch film during and after its service-life. In addition, film that was incorporated to a minimum of 3 cm into the soil was found to disintegrate faster than laying on top of the soil surface. However, to support biodegradation of pieces that remained on top of the soil, compost tea (microbes and nutrients) indicated an acceleration of biodegradation, which seemed particularly effective for film pieces that remained on the soil surface.

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