Potential of municipal solid waste (MSW) as a source of energy in São Paulo: its impact on CO2 balance

doi:10.1016/S0961-9534(97)00042-1

Biomass and Bioenergy

Volume 14, Issue 1, 10 March 1998, Pages 83-89

https://doi.org/10.1016/S0961-9534(97)00042-1 Get rights and content

Abstract

Energy generation is needed in São 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 generate 30 MW of power. The eco-balance of CO₂ has been considered for incineration and recycling. The recycling program of plastics, metals, paper and glass would represent a significant reduction in energy and CO₂ emission. The total CO₂ released is 3.34×10⁵ t/yr without recycling, and is 1.25×10⁵ t/yr with a recycling program. Most of the CO₂ comes from plastics and paper production. Economic aspects could probably favor incineration with energy production as the best option.

Introduction

The disposal of municipal solid waste (MSW) is becoming one of the biggest problems in São 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 landfills. 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 increasing due to the growth in utilization of plastics in packaging.[4] A waste-to-energy project for São 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 efficiency 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 efficiency of 50%.[2] Electric power supply tariff in São Paulo is about US$40.00/MWh (marginal expansion tariff). To make waste incineration for energy production competitive, this would have to be the price charged. In this case, the price difference (US$40.00/MWh), would have to be subsidized by the county government. The difference would come from an incineration tax charged by the county government. The alternatives for final disposal are landfills (US$9–24/t) and composting (US$8–24/t).[3]

The CO₂ 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 São Paulo despite the consequent increase in CO₂ emissions. This work is a preliminary study of the importance of a recycling program in terms of CO₂ emissions in São Paulo city. The eco-balance of incineration from the CO₂ pollution point of view has been considered for the most important materials: glass, paper, plastics and metals (mainly steel).

Section snippets

Material and methods

The comparison between the different alternatives considered was based on the carbon content released to the atmosphere of the different fuels used in fabrication process. It should be noted that some American data were used, and in Brazil electricity use by industry is much more common than in the U.S.A., where most energy comes from fossil fuels. Nevertheless, the hydropower potential in Brazil is completely exhausted, and new power plants to solve the energy supply crisis will come from

Results and discussion

Table 3 shows the final results of CO₂ emission for each material. The first total represents the case of no recycling (incineration or landfill), and second total is the case where the material is recycled. Each material is discussed in detail.

Glass represents 2.3% of the MSW mainstream. The average consumption of energy for glass production is about 10.89 MJ/kg in São Paulo city.[10] There were no significant differences among the companies and industrial processes. Glass companies in São

Conclusions

In São Paulo, due to the low rate of voluntary separation and the high cost of curbside recycling collection programs (recovering bottles, cans, newspaper, cardboards and other clean papers), incineration appears to be more feasible. Additionally, incineration would reduce the requirements for landfills by 90–95%. This alternative could change if the population is educated to separate plastics and clean paper for recycling at higher rates than can be expected today. The summary of our

Acknowledgements

We are grateful to Roberto Pessine, from CESP-São Paulo Electric Co., for help with information and scientific discussions.

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The potential energy that could be produced from solid wastes in Brazil tops 50 TWh. Equivalent to some 17% of the nation's total power consumption at costs that are competitive with more traditional options, this would also reduce greenhouse gases emissions. Moreover, managing wastes for energy generation purposes could well open up thousands of jobs for unskilled workers. Related to power generation and conservation, energy use requires discussions on the feasibility of each energy supply option, and comparison between alternatives available on the market. Power conservation is compared to projects implemented by the Federal Government, while power generation is rated against thermo-power plants fired by natural gas running on a combined cycle system. Although the operating costs of selective garbage collection for energy generation are higher than current levels, the net operating revenues of this scheme reach some US$ 4 billion/year. This underpins the feasibility of garbage management being underwritten by energy uses and avoided environmental costs. The suggested optimization of the technical, economic, social and environmental sustainability of the expansion of Brazil's power sector consists of compatibilizing the use of fossil and renewable fuels, which is particularly relevant for hybrid thermo-power plants with null account on greenhouse gases emissions.
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Potential of municipal solid waste (MSW) as a source of energy in São Paulo: its impact on CO2 balance

Abstract

Introduction

Section snippets

Material and methods

Results and discussion

Conclusions

Acknowledgements

Res. & Energy

Applied Energy

Managing solid waste

Sci. Am.

CO2 better understanding the role of energy in the long term

Energy J.

Potential of municipal solid waste (MSW) as a source of energy in São Paulo: its impact on CO₂ balance

CO₂ better understanding the role of energy in the long term