BACKGROUND AND OBJECTIVES: Jakarta's municipal solid waste generation is reaching landfill capacity due to rapid urbanization, metropolitan lifestyles, and industrial growth. Landfill mining increases capacity and reuses materials when landfill expansion is not feasible. At Bantargebang's integrated municipal solid waste treatment facility, the landfill mining plant produces materials akin to soil and refuse-derived fuel. This study assesses the suitability of soil-like material’s physical and chemical properties as a growing medium.METHODS: For seven consecutive working days, fine fractions less than 50 millimeters obtained from trommel screening of landfill materials were sampled using the quartering technique. Samples were analyzed for moisture, ash, texture, cation exchange capacity, pH, total organic carbon, total Kjeldahl nitrogen, carbon-to-nitrogen ratio, phosphorus, potassium, and heavy metals. Soil-like material composition and physical properties followed American Society for Testing and Materials and International Soil Reference and Information Centre standards, chemical properties followed Natural Resources Conservation Service and United States Department of Agriculture guidelines, and heavy metals followed Environmental Protection Agency methods. In a greenhouse experiment, soil-like material and compost were mixed in proportions ranging from 100 to 60 percent soil-like material by weight, in 10 percent steps, to assess their effectiveness as a growing medium for Calliandra calothyrsus.FINDINGS: Composition analysis showed that 40.61 percent of the landfill-mined fine fraction consisted of soil-like material particles smaller than 4.75 millimeters with high organic matter, sufficient inorganic materials, and elevated heavy metals, particularly iron, manganese, and cadmium. The organic matter was primarily undecomposed and unstable, characterized by a total organic carbon level of 57.08 percent, significant volatile solids at 78.60 percent, and a carbon-to-nitrogen ratio of 27.9, potentially resulting in microbial nitrogen immobilization. With a cation exchange capacity of only 16.39 centimoles per kilogram, moisture levels at 32.78 percent, a texture primarily consisting of coarse sand, and low levels of potassium at 598.33 milligrams per kilogram and phosphorus at 140.20 milligrams per kilogram, significantly restricted the performance of the growing medium. A greenhouse experiment showed that an 80 percent soil-like material–20 percent compost mix performed best, yielding an average final plant height of 51.67 centimeters over 127 days, exceeding other ratios (39.33–49.61 centimeters).CONCLUSION: Plant growth initially relied on seedling nutrients, then on compost, with soil-like material gradually supplying nitrogen. Enhancing nutrient availability and minimizing metal toxicity can be achieved through stabilization via co-composting or blending with nutrient-rich amendments.
Sudiana et al. (Thu,) studied this question.