Technosol as an integrated management tool for turning urban and coal mining waste into a resource

Abstract

The present study aims to evaluate plant growth and chemical characteristics of technosols produced from fine coal waste and an organic compost from urban waste. This could be an alternative method for current disposal practices and a way to promote vegetation cover of mined lands. The experiment was conducted in 2 L containers filled with different substrates conditions: (I) exclusively coal waste, (II) coal waste + 2.5% organic matter, (III) coal waste + 5.0% organic matter, and (iv) agricultural soil as control. All substrates were performed in triplicate, with and without Alfalfa (Medicago sativa) planting. Plant growth was monitored for biomass production and plant tissue composition. Soils were evaluated in terms of fertility, acid generation potential, and sulfur speciation. The substrate composed exclusively of coal waste had almost no plant growth. However, the addition of compost allowed equivalent (with 2.5% organic matter) or even superior (with 5.0% organic matter) plant growth in terms of dry matter compared to the agricultural soil. At both levels of organic matter, soil fertility parameters were appropriate for Alfalfa growth. Regarding the plant tissue, the elemental composition of the shoots was considered adequate for cattle nutrition. Also, there was a reduction of both pyrite content and acid generation potential of the substrates after plant growth. In relation to urban waste, it is estimated that each hectare of technosol (condition III) could utilize around 550 t of organic compost. Thereby, this study addresses the possibility of improving waste management in both mining and urban contexts consistent with circular economy concepts.