Critical Factors in Lab-Scale Compostability Testing

Composting offers a solid waste management alternative to landfilling resulting in soil amendment products with fertilization and moisture retention benefits and collateral methane reduction by diverting organic wastes from anaerobic landfill environments. An increasing array of materials and products are marketed as compostable, though only a limited range of these are covered by certification schemes. Greater accessibility and deeper understanding of compostability testing is needed to promote meaningful evaluation of the viability and optimal conditions for composting wider ranges of materials. This article describes various critical aspects of laboratory-scale methodology that can be optimized for more consistent, accurate, and efficient testing. While most of the reviewed studies are based on standardized international test methods, modifications to vessel design, medium, control systems, and evaluation show promise. Learnings are also drawn from biodegradation tests using soil and aqueous media. Particular consideration is given to evaluating compostability of textiles, including nonwovens, which today are primarily disposed of in landfills yet have the potential to supplement organic carbon in compost mixtures with nitrogen rich food waste. Furthermore, biodegradation properties of both natural and man-made textile fibers have received growing attention in recent years. Fiber fragments found in oceans and the surge of disposable face coverings used during the COVID-19 pandemic have been widely covered in the mainstream media, highlighting the importance of understanding biodegradation properties for textiles. This review consolidates and organizes diverse and essential procedural details reported in various standards and studies with the goal of encouraging and guiding successful implementation of compostability testing more broadly in laboratories. Certain gaps in test methodologies are identified to help focus future research. Reliable, accessible testing is crucial to expand the beneficial impacts of composting in waste management.