Assessing pretreated municipal solid waste degradation by BMP and fibre analysis

Abstract

Landfill continues to be the major method of Municipal solid waste (MSW) disposal in the UK and many othercountries despite considerable efforts to limit its use. The EU Landfill Directive requires, amongst other things, thatwaste is treated to reduce its biodegradability prior to disposal to landfill. This pre-treatment is often achievedthrough what is generically termed mechanical-biological treatment. Predicting the biodegradability or degradationpotential of these pre-treated wastes is important for the long term management and aftercare of landfill sites. Toaddress this, a series of biochemical methane potential (BMP) tests have been undertaken to characterize theanaerobic biodegradation potential of two mechanically biologically treated (MBT) waste samples in terms of biogasyield, solids composition (loss on ignition, total carbon, cellulose, hemicellulose and lignin contents), and assessmentof leachate characteristics during the biodegradation process. Experimental results from a long term study of MBTwastes treated to different standards are analyzed and compared. The relationship between biogas potential andsolids composition was investigated, and carbon and nitrogen mass balances are discussed. The biogas potential wasshown to correlate well with the ratio of cellulose plus hemicellulose to lignin, loss on ignition and total carboncontent of the waste indicating a clear link between these parameters. The results indicate that solids composition ofMBT wastes may provide a useful indication of the biodegradation potential. The mass balance indicates that a largeproportion of carbon and nitrogen remain locked up in the waste material and is not released.