Altered chemical evolution in landfill leachate post implementation of biodegradable waste diversion.

Within the UK implementation of the European Union Landfill Directive (1999) has led to the diversion of biodegradable waste (BW) from municipal solid wastes away from landfills. It has been widely anticipated, but thus far not verified, that the diversion of BW and consequent reduction in BW reaching landfill would lead to a change in the degradation processes occurring within landfills and that this would be reflected in an altered evolution in leachate chemistry compared to pre-Directive landfills. This paper provides evidence based on leachate chemistry from two operational landfills together with calculations of the reduced BW content, that demonstrate the acetogenic phase that characterised pre-Directive landfill leachates is missing and is now more typical of methanogenic phase leachate. The paper demonstrates how data from national datasets and detailed landfill records can be used to constrain likely and upper estimates of the amount of BW going into post-Directive landfills, and the observed change in the evolution of leachate chemistry which has resulted from a decrease in BW content from typical values of BW (pre-Landfill Directive) of 22% to an inferred 12% in the case-study landfills. Data provided here add to the growing literature that estimates the amount of BW in recent post-Directive landfills which importantly allow the quantitative linkage between a decrease in landfilled BW and observed changes in leachate chemistry to be established such that future landfill operators can increase confidence in the effect of Directive implementation on landfill operational parameters.