A comprehensive methodology for determining buffering capacity of landfill-mined-soil-like-fractions

Abstract

The utilization of landfill-mined-soil-like-fractions (LFMSF), which is a major fraction resulting from landfill mining (LFM) activity, is being debated owing to a lack of comprehensive understanding of its characteristics. In this context, based on the physicochemical properties of LFMSF, several of the earlier researchers have opposed its utilization as compost, feedstock in waste-to-energy, and fill material in civil engineering applications. However, it has been noticed that LFMSF consists of required amount of organic matter (OM) and inorganic carbon (IC) to make it suitable as a buffering material that would help to modify/treat geomaterials exhibiting extreme pH values. In this context, determination of its buffering capacity (BC), a parameter that quantifies the buffering potential, becomes essential. However, determination of BC by resorting to the existing protocols is not suggestible mainly due to (i) an extremely narrow range of the pH (3–8) employed, (ii) lack of incorporation of the optimal time required for reaction/pH stabilization (tpHS), (iii) concern for decomposition of OM during the addition of H+/OH− while experimentation and (iv) heterogeneity associated with the LFMSF unlike the geomaterials that are commonly tested (viz., agricultural soils and compost). Hence, to overcome these limitations, a comprehensive methodology that can be employed for determining the ultimate buffering capacity (BCu) by establishing appropriate tpHS (i.e., 200 h) and liquid to solid ratio (i.e., 20), which would eliminate the decomposition of OM over a broad range of pH (i.e., 2–12) has been proposed. Based on the testing of several LFMSF samples collected from unscientifically created landfills/dumpsites and engineered landfills in India, easy-to-use relationships between the (i) reaction time (t) and (ii) physicochemical properties of the samples that influence BC and BCu, directly or indirectly, have also been proposed.