POTENTIAL OF MUNICIPAL SOLID WASTE (MSW) AS A SOURCE OF ENERGY IN SA Ä O PAULO: ITS IMPACT ON CO 2 BALANCE A. L. LEA Ä O and ING Hwie TAN UNESP-SaÄo Paulo State University, College of Agricultural Sciences, Department of Environmental Sciences, P.O. Box 237, Botucatu, SaÆo Paulo 18603-970, Brazil (Received 17 January 1994; revised 22 July 1997; accepted 25 July 1997) AbstractÐEnergy generation is needed in SaÄo Paulo and MSW represents a promising alternative, although it is more expensive than hydroelectric power. About 14 900 t/day of MSW is generated, of which 8433 t/day is domestic and commercial MSW. From this amount, 1800 t will be destined to gen- erate 30 MW of power. The eco-balance of CO 2 has been considered for incineration and recycling. The recycling program of plastics, metals, paper and glass would represent a signi®cant reduction in energy and CO 2 emission. The total CO 2 released is 3.34 Â 10 5 t/yr without recycling, and is 1.25 Â 10 5 t/yr with a recycling program. Most of the CO 2 comes from plastics and paper production. Economic aspects could probably favor incineration with energy production as the best option. # 1998 Published by Elsevier Science Ltd. All rights reserved KeywordsÐMSW; greenhouse eect; incineration; recycling; CO 2 emission. 1. INTRODUCTION The disposal of municipal solid waste (MSW) is becoming one of the biggest problems in SaÄo Paulo city. Although the MSW per capita is still low (0.7 kg/day), compared with other large cities around the world, it is expected to grow 2±3% per year (compared with 1% per year worldwide) (see Table 1). Disposal costs are increasing due to the larger volume of MSW generated and a reduction in available sites for land®lls. Limitations in space could be eased with a larger recycling program and incineration. MSW is a potential, large source of energy worldwide. Typical energetic values are 10.47 MJ/kg 1 in the U.S.A. and 12.48 MJ/kg in Europe. 2 In Brazil it is reported to be between 5.82 and 9.12 MJ/kg, 3 but is increas- ing due to the growth in utilization of plastics in packaging. 4 A waste-to-energy project for SaÄo Paulo was considered in the 1970s, but it became a more important option in the 1980s. Now, it is considered again. A thermal electric power plant using MSW and generating 30 MW of electrical power is being proposed, consuming 5 MW for its operation. 3 The cost is distributed as 70% for equipment, 20% for construction and 6% for projects. The total cost is estimated to be US$230 million, with operation costs of US$5 million/year over 30 years of operation. With a conversion e- ciency of 23% the cost would be US$80/ MWh, with 10% IRR, and no transmission costs. In comparison a waste-to-energy plant in Paris has a cost of US$10.73/MWh with an eciency of 50%. 2 Electric power supply tari in SaÄo Paulo is about US$40.00/MWh (mar- ginal expansion tari). To make waste incin- eration for energy production competitive, this would have to be the price charged. In this case, the price dierence (US$40.00/MWh), would have to be subsidized by the county government. The dierence would come from an incineration tax charged by the county gov- ernment. The alternatives for ®nal disposal are land®lls (US$9±24/t) and composting (US$8± 24/t). 3 The CO 2 released in Brazil was reported to be 45 million t in 1985. 5 Waste-to-energy is still a negligible portion of the energy supply of Brazil, but could become important in large populated areas such as SaÄo Paulo despite the consequent increase in CO 2 emissions. This work is a preliminary study of the importance of a recycling program in terms of CO 2 emis- sions in SaÄo Paulo city. The eco-balance of incineration from the CO 2 pollution point of view has been considered for the most import- Biomass and Bioenergy Vol. 14, No. 1, pp. 83±89, 1998 # 1998 Published by Elsevier Science Ltd. All rights reserved Printed in Great Britain 0961-9534/98 $19.00 + 0.00 PII: S0961-9534(97)00042-1 83