Waste Manage Res 2003: 21: 309–x?x Printed in UK – all rights reserved Waste Management & Research Copyright © ISWA 2002 Waste Management & Research ISSN 0734–242X 309 Waste Manage Res 2003: 21: 309–317 Printed in UK – all rights reserved Copyright © ISWA 2003 Waste Management & Research ISSN 0734–242X Introduction Baling is a technique through which compaction is achieved for easier handling and better transportation and storage of materials. Baling has long been used by farmers for man- aging hay and cotton. An application of the baling tech- nique has been used in Sweden as a method for the storage of fuel waste for incineration (Hogland & Marques 1999, Hogland 1998, Ansbjer et al. 1995, Hogland & Tamaddon 1995). Previous studies (Martinez & Gourdon 2000, 1999, Hogland 1998, Ansbjer et al. 1995, Hogland & Tamaddon 1995, Tamaddon et al. 1995a,b,c) looked into the gaseous emission from the baled waste to enable the characterisa- tion of the processes occurring within the waste. It has been found that baling is, so far, the most promising technique for storage of waste for either incineration or recovery of raw material (Andreottola & Lagazzi 2000, Grover et al. 1999, Hogland & Marques 1999, Hogland 1998, Ansbjer et al. 1995, Hogland & Tamaddon 1995, Tamaddon et al. 1995a,c). The baling technique applied to waste has many advantages, for instance low risk for self ignition, stabil- ity during storage, almost no energy loss, clean and tidy handling and transport, volume reduction up to 1/3 and water tightness. Problems not solved yet regarding baling of waste are related to odour, bird picking and ageing of plastic during long term storage. This paper focuses on the physical and chemical proc- ess occurring inside the baled waste, with emphasis on the gaseous emissions. Decomposition of waste In landfills, the biological degradable fraction is described in terms of polymers, lignocelluloses and polysaccharides, as well as fats and proteins. Depending on the environ- mental conditions, the final products can be carbon diox- Diauddin R. Nammari William Hogland Viatcheslav Moutavtchi Department of Technology, University of Kalmar, Kalmar, SE-391 82, Sweden. Marcia Marques Department of Environmental Engineering, Rio de Janeiro State University UERJ, Rua São Francisco Xavier 524, Bl E, Sl 5024, Maracanã, CEP 20559-900 Rio de Janeiro, RJ, Brazil. Sven Nimmermark Department of Agricultural Biosystems and Technology, University of Agricultural Sciences, P.O. Box 43, SE -230 53, Alnarp, Sweden. Keywords: Baling, waste fuels, emissions, leachate, waste decom- position, oxygen consumption, CO 2 emission, wmr 536–4. Corresponding author: Diauddin R Nammari Department of Technology, University of Kalmar, Kalmar, SE-391 82, Sweden. E-mail: diauddin.nammari@hik.se, Fax: ++46 48 044 6330 Received 28 September 2001, accepted in revised form 24 March 2003. Over a period of seven months, the temperature and the emissions from six cylindrical and two rectangular stored bales containing waste for later use as fuel were measured. The bales were kept at two different ranges of tempera- tures: 30-35˚C and 20-25˚C respectively. It was found that only the rectangular bales showed significant produc- tion of CO 2 . The increase of emission for one of the rec- tangular bales kept at 30-35˚C, was 0.246% vol. CO 2 per day for a 2-week period, after which there was a decrease of CO 2 concentrations at a rate of 0.0224% vol. during a 32-week period. The other rectangular bale kept at 20- 25˚C, exhibited a similar trend. However, the increase of CO 2 concentrations was less at a rate of 0.0259% vol. per day during a 8-week period, after which the CO 2 emission decreased at a rate of 0.0224% vol. per day during a 25- week period. All the bales exhibited aerobic decomposi- tion in the sampling point. However on measuring the leachate concentrations, it was evident that the bales were actually in the equivalent acid-generating phase of a young landfill. The temperature inside the bales did not increase higher than the ambient air temperature. Physical and chemical processes in baled waste fuel, with emphasis on gaseous emissions