A preliminary investigation of anaerobically digested municipal sludge cake and contaminated soil for recycling by pyrolysis

Abstract

This work has investigated the potential of pyrolysis as a recycling solution for two largely uncharacterised waste streams, anaerobically digested (AD) municipal sludge cake and brownfield soil (contaminated with oily sludge). Characterisation of emitted organic compounds from pyrolysis were captured in a solvent (acetone) scrubber and analysed by GC-MS. Both AD sludge cake and brownfield soil showed considerable promise for 'green-er' fuels, as a source of syngas (with CO supplementation) and volatile aromatics essential for fuel quality. However, these waste streams also generated significant amounts of additional highly toxic pollutants of varying chemistries, further emphasising the importance of using a trapping approach applicable to a broader range of chemicals. Pleasingly the acetone trap showed very good efficacy in capturing this breadth of chemistries, supporting its use as an alternative capture and preparative method, for monitoring volatile and semi-volatile organic tars Keywords Scrubber Pyrolysis/gasification contaminants Tar analysis Gas chromatography-thermal conductivity detection (GC-TCD) Gas chromatography-mass spectrometry (GC-MS)