Resumo:
The generation of urban solid waste and its management still represent a problem of
relevant dimensions in Brazil. The high presence of organic matter in these wastes can
aggravate environmental problems, either by the emission of greenhouse gases, water or soil
pollution. At the same time, the pulp and paper industry consumes large amounts of resources
and produces important solid waste, including lime mud. By uniting urban and industrial reality,
an alternative that has not yet been studied emerges, with which electrical energy is used from
biogas from the co-digestion of the organic fraction of urban solid waste with lime mud. This
intersection can reduce the environmental impacts associated with the inadequate management
and impacts inherent to each of these wastes, providing savings in financial resources for the
industry and also contributing to the diversification of the Brazilian energy matrix. To assess
the environmental sustainability and economic viability of this alternative, the present work
used economic-financial indicators and the life cycle assessment methodology. The results
obtained showed a minimum population of 165,200 inhabitants to make a co-digestion proposal
feasible. The sensitivity analysis showed that the energy tariff at R$ 0.75, with a payback of 10
years, would provide a population of 185,500 inhabitants for economic viability and
attractiveness, with a net present value of R$ 125,552.74, the internal rate of return at 14.71%
and a levelized energy cost of 0.55 R$/kWh. Meanwhile, the lime mud life cycle assessment
showed that, among the 5 proposed scenarios, co-digestion is significantly advantageous,
avoiding environmental impacts especially in 8 of the 18 assessed impact categories, namely
freshwater eutrophication, ecotoxicity marine, terrestrial acidification, fossil fuel depletion,
freshwater ecotoxicity, climate change, particulate matter formation and marine eutrophication.
In addition, digestate contributed significantly to avoided impacts. Thus, the study made it
possible to combine economic viability and environmental benefits, in such a way as to
structure adequate foundations for a deepening of the proposal and for a rational, sustainable
and economically viable use of biogas from the co-digestion of the organic fraction of urban
solid waste with lime mud.
