Assessment of UFMSW as a Soil Amendment: Effects on Plant Development

Abstract

Municipal solid waste management faces challenges in handling the undersized fine fraction, which is typically landfilled due to its heterogeneous composition. Unlike source-separated organic waste, undersized fraction of municipal solid waste (UFMSW) from mixed household waste streams contains both organic and inorganic material, limiting its suitability for conventional composting. Increasing restrictions on landfilling demand alternative valorization routes. Owing to its high organic content, the incorporation of UFMSW into soil or planting media is promising, yet its complex composition necessitates the evaluation of its effects on plant growth and contaminant uptake. This study assessed soil properties, plant performance and heavy metal accumulation using UFMSW-treated (20–100% w/w) potting soil. UFMSW was pre-stabilized over 4 weeks beforehand and consisted of particle sizes <4.5 mm in diameter. Garden cress (Lepidium sativum) was used for germination tests and marigold (Tagetes erecta) for growth as well as uptake studies. Higher UFMSW contents (B60–B100) caused sharp increases in COD, BOD, conductivity and TDS, indicating high organic loads and salinity stress. L. sativum germination declined as the concentration increased, showing complete inhibition at ≥B60. In contrast, T. erecta at B20 exhibited enhanced growth in terms of its leaves, branches, reproductive structures and the diameter of its stem without notable metal accumulation. No plants survived when treated with B40–B100 due to severe dehydration. These findings highlight that while high UFMSW levels are phytotoxic, low-level amendments (20%) can enhance growth without increasing metal uptake, supporting targeted waste valorization strategies.