Nitrogen mineralisation and greenhouse gas emission from the soil application of sludge from reed bed mineralisation systems

Abstract

A sludge treatment reed bed system (STRB) is a technology used for dewatering and stabilising sewage sludge via assisted biological mineralisation, which creates a sludge residue suitable for use as fertiliser on agricultural land. We evaluated the effect of sludge residue storage time (stabilisation time) for three STRBs on soil N mineralisation and CO₂ and N₂O emissions in soil. The experiment revealed that the N mineralisation rate and emissions of CO₂ and N₂O decreased as a function of treatment time in the STRBs. Mixed sludge residue (sludge residue subjected to different treatment times) for the three STRBs resulted in N mineralisation rates similar to the sludge residue subjected to a shorter treatment time but lower N₂O emissions similar to the values of the older sludge residue. This finding reveals that combining fresh and more stabilised sludge residue ensures high N availability and reduces N₂O emissions when applied to land.

Keywords: C mineralisation; Mineralisation systems; N mineralisation; N(2)O and CO(2) emissions; Recycling of organic waste; Sewage sludge treatment.