New Workflow Tracks Biodegradable Plastic in Soil with Unprecedented Accuracy

Developed by researchers at ETH Zurich and Agroscope, the analytical workflow combines Soxhlet extraction and proton nuclear magnetic resonance (¹H-NMR) spectroscopy to detect and measure the degradation of common biodegradable polymers in diverse soil environments. This marks a substantial step forward for manufacturers, regulators, and end-users aiming to ensure biodegradable materials function as advertised under real-world conditions.

Industries Dependent on Verified Biodegradability

Biodegradable polyesters such as PBAT (poly(butylene adipate-co-terephthalate)) and PLA (polylactic acid) are central to sustainability strategies across the agriculture, packaging, landscaping, and forestry sectors. In applications such as mulch films, seed coatings, slow-release fertilizer capsules, erosion control materials, and tree shelters, these plastics are intentionally deployed in open environments where full recovery is not feasible.

The new workflow is particularly relevant for:

• Agriculture: Validating biodegradable mulch films and soil-applied carriers.
• Packaging and Foodservice: Ensuring compostable packaging behaves as intended in soil or compost.
• Forestry and Landscaping: Monitoring degradation of protective tree wraps and geotextiles.
• Bioplastics Manufacturing: Supporting R&D and claims verification for new blends.
• Waste Management & Composting: Integrating materials into circular systems with proven degradation rates.

A Two-Part Methodology: Precision Meets Practicality

This method not only improves lab accuracy but also introduces a practical field component. The workflow includes:

• A standardized chemical analysis using Soxhlet extraction and ¹H-NMR to detect minute levels of residual polymers.
• A field-deployable system using polypropylene mesh bags, enabling mesocosm experiments in various soil types to mimic real agricultural conditions.

The method reliably measured the presence of eight biodegradable plastics and one conventional plastic (polystyrene) across six different soil types—including soils with high organic content that typically interfere with chemical testing—demonstrating its accuracy and versatility under real-world conditions.

Bioplastics Perform Differently Across Soil Types

After six months of incubation, PHBH (a polyhydroxyalkanoate) exhibited strong biodegradation across all soils, confirming its high environmental compatibility. In contrast, PBAT and PLA showed variable performance:

• PLA degraded poorly in acidic or biologically inactive soils.
• PBAT showed moderate, soil-dependent degradation.

These findings highlight the need for soil-specific verification of biodegradability claims—especially for products marketed as soil-degradable or compostable.

An Analytical Workflow to Quantify Biodegradable Polyesters in Soils and Its Application to Incubation Experiments

Toward Standardization and Environmental Accountability

With regulatory frameworks evolving and pressure mounting from consumers and investors, industries are increasingly expected to back sustainability claims with verifiable data. This new workflow offers:

• A scientific foundation for soil biodegradability certification (e.g., EN 17033).
• A field-applicable tool for monitoring real degradation rates.
• A way to differentiate bioplastics based on actual performance, not assumptions.

For companies in bioplastics manufacturing, environmental testing, and product development, this method bridges the gap between lab-based optimism and field-based reality.