Mass balance to assess the eﬃciency of a mechanical–biological treatment J. de Arau ´jo Morais, G. Ducom * , F. Achour, M. Rouez, R. Bayard Laboratoire de Ge ´nie Civil et d’Inge ´ nierie Environnementale, INSA-Lyon, LGCIE, F-69621, France Accepted 11 September 2007 Available online 29 October 2007 Abstract Using mechanical–biological treatment of residual municipal solid waste, it is possible to signiﬁcantly lower landﬁll volume and gas and leachate emissions. Moreover, the landﬁll characteristics are improved. The performance of the Mende (France) mechanical–biological treatment plant is assessed via mass balances coupled with manual sorting according to the MODECOMä methodology and biochemical methane potential after 90 days of incubation. The site includes mechanical sorting operations, a rotary sequential bioreactor, controlled aerobic stabilisation corridors, maturation platforms, and a sanitary landﬁll site for waste disposal in separated cells. Results showed that several steps could be improved: after a ﬁrst sieving step, about 12% of the potentially biodegradable matter is landﬁlled directly without any treatment; mechanical disintegration of papers and cardboards in the rotary sequential bioreactor is insuf- ﬁcient and leads to a high proportion of papers and cardboards being landﬁlled without further treatment. Two ﬁne fractions go through stabilisation and maturation steps. At the end of the maturation step, about 54% of the potentially biodegradable matter is degraded. The biochemical methane potential after 90 days of incubation is reduced by 81% for one of the two ﬁne fractions and reduced by 88% for the other one. Considering the whole plant, there is a reduction of nearly 20% DM of the entering residual municipal solid waste. Ó 2007 Elsevier Ltd. All rights reserved. 1. Introduction With its waste reduction targets, the introduction of the EU Council Directive 99/31/EC resulted in the develop- ment of new waste management strategies in Europe. The objective of the Directive is to prevent or reduce as far as possible negative eﬀects on the environment from the land- ﬁlling of waste by introducing stringent technical require- ments for waste and landﬁlls. The Directive is also intended to prevent or reduce the adverse eﬀects of the landﬁll of waste on the environment, speciﬁcally on surface water, groundwater, soil, air and human health. In partic- ular, ‘‘Member States shall set up a national strategy for the implementation of the reduction of biodegradable waste going to landﬁlls’’. Reducing biodegradable waste that goes to landﬁlls will reduce the need for landﬁll space and signiﬁcantly diminish gas and leachate production and settlements. The mechanical–biological treatment (MBT) of residual municipal solid waste (MSW) is a management technology to achieve this target. MBT can be developed to improve the sorting of recyclable materials and/or to reduce the environmental impact of landﬁlling associated with anaer- obic biological activity. MBT of residual MSW prior to landﬁlling consists of mechanical pre-processing stages, fol- lowed by biological stages that reduce and stabilise the bio- degradable matter under controlled anaerobic and/or aerobic conditions. The goals of MBT have already been expressed (Heer- enklage and Stegmann, 1995; Scheelhaase and Bidlingma- ier, 1997). The mechanical pre-processing stages are designed to treat the input with two major objectives: 0956-053X/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.wasman.2007.09.002 * Corresponding author. Tel.: +33 4 72 43 81 94; fax: +33 4 72 43 87 17. E-mail address: gaelle.ducom@insa-lyon.fr (G. Ducom). www.elsevier.com/locate/wasman Available online at www.sciencedirect.com Waste Management 28 (2008) 1791–1800