Biodegradable Mulching Films in Agriculture: A Sustainable Future

Agri-plastics

The use of plastic in agriculture, known as ‘agri-plastics’, began in 1948 in the USA, significantly improving crop yields and replacing traditional materials like glass and paper. Agri-plastics offer benefits such as efficient water and nutrient use, weed control, and earlier harvests. While current usage is estimated at 6.6 million tons per year, it’s projected to increase by 64% by 2030 to meet growing food demands.

Agri-plastics materials offer benefits like increased yields and resource efficiency, but their low biodegradability poses significant environmental challenges, as they must be removed and disposed of after use, often ending up in landfills or incinerated.

Paving the way to more sustainable alternatives bio-based plastic materials are promising solutions. Bio-based plastics are derived from plant-based resources but are not inherently biodegradable. While the term ‘bioplastic’ often implies both bio-based and biodegradable, this is not always the case. Therefore, one of the promising solutions for sustainable agriculture is the use of biodegradable plastic. These eco-friendly alternatives are designed to decompose in the soil, reducing the environmental impact associated with traditional polyethylene (PE) films.

The Rise of Biodegradable Plastics

Biodegradable plastics are designed to break down faster than traditional plastics, reducing their environmental footprint. In agriculture, these materials are primarily used as mulching films, in the construction of greenhouses, and to package agricultural products, reducing the reliance on conventional plastic packaging.

Biodegradable polymers, which are used to make biodegradable plastics, can be categorized based on various factors, including their origin, synthesis method, and chemical composition. A primary classification divides them into three main groups:

  • Natural or Biobased Biopolymers: derived from renewable biological sources such as plants (e.g., starch, cellulose), animals (e.g., chitin, collagen), or marine organisms. They include polysaccharides (such as starch, cellulose, carrageenan, chitosan), lipids (waxes, glycerides), and proteins (collagen, gelatin, albumin).
  • Microbial Biopolymers: derived from microorganisms, and include bacterial cellulose, polyhydroxyalkanoates (PHA), polyhydroxybutyrate (PHB), poly(3-hydroxybutyrate-co-3- hydroxyvalerate) (PHBV).
  • Synthetic Biopolymers: synthesized chemically from renewable or fossil-based resources. Polylactic acid (PLA), most commonly used, is produced by fermentation processed from biomass, whereas polylcaprolactone (PCL), polyvinyl alcohol (PVA), and poly(glycolic acid) (PGA) are derived from synthetic petrochemical by-products.

These biodegradable plastics are designed to break down by microorganisms into carbon dioxide, water, and biomass under natural conditions after crop harvest, reducing their environmental impact and contributing to more sustainable agricultural practices.

Future for Agriculture: Biodegradable mulching films (BDMs)

Biodegradable mulching films (BDM) are agricultural films made from biodegradable plastics designed to cover the soil surface around plants. They are mostly produced as blends of bio-based polymers designed to serve as a common substitute for conventional plastic mulching films. These films serve several purposes, such as moisture retention, weed suppression, soil temperature regulation, prevention of soil erosion, and maintenance of soil structure.

Various studies have confirmed the advantages of using BPMs. It was reported that the degradation performance of BPMs depends on the nature of biodegradable materials, soil type, and climate. Years ago, it was reported that BPMs are not only involved in replacing traditional plastic films but also increase crop yields, such as tomatoes, and reduce the need for fertilization. In 2022, it was reported that BPM improved maize yields compared to traditional methods. Moreover, BPM demonstrated a greater yield advantage, particularly in regions with moderate rainfall. This research highlights the potential of mulching techniques, specifically BPM, in enhancing agricultural productivity and water use efficiency.

Benefits of Biodegradable Mulching Films

  1. Environmental Sustainability: Unlike conventional polyethylene (PE) mulching films, which can persist in the environment for decades, biodegradable mulching films are designed to decompose into natural non-harmful elements. ​ This reduces the accumulation of plastic waste in agricultural fields and minimizes the risk of soil and water contamination.
  2. Labor and Cost Efficiency: Biodegradable mulching films can be tilled into the soil after use, eliminating the need for labor-intensive removal and disposal processes. ​ This not only saves time and money but also reduces the environmental impact associated with plastic waste management.
  3. Enhanced Soil Health: The incorporation of biodegradable mulching films into the soil can stimulate microbial activity, potentially improving soil organic matter dynamics. This can lead to healthier soil ecosystems and better crop yields over time. ​

Current Research and Future Directions

adoption of BDMs. Incomplete biodegradation of BDMs can lead to the release of residual micro-bioplastics, nano-bioparticles, and additives into the soil, potentially impacting soil health. The current purchase cost of BDMs is significantly higher than traditional polyethylene (PE) films, which may discourage farmers from adopting this sustainable alternative. In addition, the long-term effects of BDMs on soil functions, processes, and microbial communities are still poorly understood and require further investigation.

Highlighting the need for long-term studies in natural environmental conditions to evaluate their actual impact on soil health and agroecosystem sustainability, key areas of focus include:

  1. Biodegradation Standards: Establishing clear standards for the conditions under which BDMs biodegrade to ensure safe end-of-life.
  2. Field Experiments: Conducting field experiments to assess the real-world performance and environmental impact of BDMs.
  3. Additives and Residues: Investigating the effects of additives used in BDMs and the potential risks associated with their release into the soil.

InPlasTwin: Tackling Microplastics from Biodegradable Mulching Films

The InPlasTwin project, a collaboration of six research institutions, is dedicated to investigating the release of micro and nanoplastics (MNPs) from biodegradable mulching films used in agriculture. Progress will be achieved by studying the generation of microplastics from biodegradable mulching films under environmentally relevant degradation conditions. This will include developing a list of characterization requirements, focusing on parameters established through project tasks. The project aims to raise awareness about sustainable alternatives to biodegradable mulching films and their environmental benefits.

Conclusion

Biodegradable plastic mulching films hold great promise as a sustainable alternative to conventional PE films in agriculture. While they offer numerous environmental and economic benefits, challenges related to incomplete biodegradation, soil ecosystem impact, and cost must be addressed. Continued research and field studies are essential to fully understand the long-term effects of BDMs and to develop standards that ensure their safe and effective use.​ As the agricultural sector moves towards more sustainable practices, BDMs could play a crucial role in reducing plastic waste and promoting soil health.

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Project Coordination
Asst. Prof. Janja Vidmar
Research Associate
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Jožef Stefan Institute,
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Olivera Stojilović Trivunić
Head of Ecosystem Development
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Gordana Racić
Scientific Project Manager, PhD
gordana@foodscalehub.com

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