In this study, a biofiltration system was designed using mature composts of municipal solid waste (MSW) or MSW mixed with pruning residues (MSW-P) as packing materials to treat vapours of alpha-pinene (a dominant volatile organic compounds (VOC) emitted during the MSW-P co-composting). Monitoring the efficiency of the biofiltration system was carried out using a photoionization analyser, a commercial electronic nose (e-nose) and gas chromatography - mass spectrometry (GC/MS). Using an EBRT of 66 s, removal efficiencies for both kinds of biofilters were greater than 90% removal at different stages of the experiment. The acclimatisation periods were 10 and 25 days for the MSW biofilter and MSW-P biofilter, respectively. Removal efficiency of the system was strongly dependent upon the moisture content of the packing materials. As moisture content in the biofilters fell to below 66% for the MSW and 51% (dry basis) for MSW-P, the removal efficiency decreased to less than 90%. E-nose and GC/MS data indicate a complete degradation of the alpha-pinene. The e-nose detected a characteristical background emission (odour fingerprint) of each type of biofilter. Results suggest that e-nose's will become a more powerful tool for monitoring VOCs in biofiltration and composting processes in the future. (C) 2013 Elsevier B.V. All rights reserved.