Lab ‘Dissolution Testing’ on Waste—Does it Work?
Biomass by Energy Content, Biomass by CV, the 'Selective Dissolution Method (SDM)' are all differing terminologies for the same test, which seems to have become the default test for many operators to determine the level of biogenic material in residual waste... But does it?
Monksleigh's recent analysis of the 51 operational EFW plants reporting their biogenic carbon emissions in their Annual Operator Performance Reports, via their feedstock input (see diagram below), shows that some of the widest measurements are linked to those EFW facilities that employ the SDM test to determine the amount of biogenic material in their waste.
In parallel, Monksleigh have been working with some of our LA and industry clients to determine the level of biogenic content in their input waste stream and we also requested that the UKAS accredited laboratories we work with undertake the SDM test on the residual waste (both ' loose black bag' residual waste and RDF).
However the scale and the variance in results have surprised us.
From the results returned from the laboratories it has become increasingly clear that this type of analysis for black bag waste is both highly variable between laboratories and indeed between samples. The heterogeneous nature of the material and the potential for 'false positives' (materials containing high levels of fossil carbon such as oil, rubber, viscose, nylon, polyurethane and silicon rubber throwing out the result) are such that the measurements can (and are) varying significantly - although to a lesser degree for RDF. We are also witnessing these excessive biogenic results in RDF that has arisen from the processing of C&D waste streams.
It would seem however that our findings are not new and a scientific paper published in 2014 found the same issues with SDM. Indeed the report by Ricardo that accompanies the recent UK ETS consultation notes the limitations of the test for waste that contains more than 10% natural and/or synthetic rubber and waste containing inorganic carbonates. Why then is the use of SDM still the analytical method of choice by many operators to determine the content of biogenic material in mixed residual waste?
For any help with understanding your waste analysis requirements and the implications for the measurement of your biogenic content and its ramifications for the future UK ETS (whether an LA, waste company or an EFW) — Contact Monksleigh.
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