Comprehensive Strategies for Reclamation of Soil Condition Affected by Coal Bed Methane Co-Produced Water

With the recent thrust on large scale extraction of coal-bed methane (CBM) at global levels, effective management of the CBM co-produced water (CBW) has emerged as an urgent environmental challenge in various CBM-producing countries. CBW typically contains high concentrations of Na⁺, Cl^-, HCO₃^- and CO₃^2-, which induce strong salinity and alkalinity and degrade the contaminated agricultural soils. We evaluated laboratory and field-based soil treatment strategies to mitigate CBW-driven soil degradation and restore soil conditions. Various grades of water with EC levels ranging between trace to 4 mS cm^-1 were prepared from CBW and incubated with unaffected soils for one month to simulate the contaminated soil conditions under laboratory. These CBW affected soils were then amended with graded combinations of gypsum (CaSO₄·2H₂O), vermicompost, and elemental sulfur using gypsum requirement of the soils as the basic criteria for different treatments and incubated for another 30 days. All these amendments substantially reduced various alkalinity indicating soil properties viz. SAR, RSC, and ESP of which gypsum + vermicompost mixtures, with or without sulfur, performed the best. Based on these results, three on-farm trials were carried out in CBW affected agricultural lands to assess the efficiency of gypsum+ vermicompost and vermicompost alone in reclaiming the CBW affected soils using rice as the test crop. Amended treatments produced marked improvements in soil quality with ~40% reduction in ESP and as well as crop performance showing ~186% increase in yield While this primary study offers practical, low-cost, and scalable options to reclaim CBW affected soils for undertaking agriculture, the long-term effects of these amendments will depend on the quantity, frequency and intensity of CBW contamination, occurrence of relevant soil factors, cropping patterns etc. For developing a recommendable technology, therefore, there is need for long term trials with these amendments under different soil conditions using the local as well as stress tolerant crops.