Sustainable valorization of municipal solid waste into nutrient rich biochar and compost for agricultural use

Abstract

In many developing countries, repeated cropping removes soil nutrients and organic matter, leading to a gradual decline in soil fertility. This study converted the biodegradable fraction of MSW collected from the Mehmood Booti Dumping Site (Lahore, Pakistan) into biochar (pyrolysis at > 550 °C) and compost (pit composting, 60–70 days) and evaluated their individual and combined use as soil amendments for okra (Abelmoschus esculentus L.) in a pot experiment (RCBD, four replicates). Biochar production achieved a 33.3 ± 0.7% yield and was alkaline (pH 8.0 ± 0.2) with high ash content and cation exchange capacity, indicating strong potential for nutrient retention. Compost matured to a stable product with C/N 9.84 ± 0.1, confirming suitability as a nutrient-rich organic fertilizer. Compared with the unamended control, all amendments improved post-harvest soil properties, with the combined treatment (CB-5%) showing the strongest overall effect: CEC increased to 33.31 ± 1.11 cmolc kg⁻¹, bulk density decreased to 0.84 ± 0.11 g cm⁻³, water-holding capacity increased to 72.01 ± 1.10%, and soil organic matter rose to 5.84 ± 0.07%; macronutrients also peaked under CB-5% (N 1.85 ± 0.01%, P 1.93 ± 0.02%, K 2.23 ± 0.01%). These soil improvements translated into superior crop performance: CB-5% produced the greatest plant height (33.25 ± 0.25 cm), dry biomass (32.51 ± 0.57 g), chlorophyll content (68.33 ± 0.29 SPAD), and fruit yield (38.37 ± 0.29 g), outperforming chemical fertilizer (29.46 ± 0.44 g) and single-amendment treatments. These findings highlight the potential of MSW-derived biochar and compost as sustainable soil amendments, supporting integrated waste valorization and environmentally friendly agricultural practices.