Challenges to reducing post-consumer plastic rejects from the MSW selective collection at two MRFs in São Paulo city, Brazil

Journal of Material Cycles and Waste Management https://doi.org/10.1007/s10163-022-01387-9 ORIGINAL ARTICLE Challenges to reducing post‑consumer plastic rejects from the MSW selective collection at two MRFs in São Paulo city, Brazil Carlos Alberto Correa1 · Marcio Adilson De Oliveira2 · Christiane Jacinto2 · Giulliana Mondelli2 Received: 3 November 2021 / Accepted: 2 March 2022 © Springer Japan KK, part of Springer Nature 2022 Abstract The present study is concerned with an overview of the main aspects of the selective collection from the municipal solid waste in São Paulo City and the limitations of its two automated Material Recovery Facilities (MRFs) to tackle the problem of reducing recyclable plastic waste sent to landfills as rejects. The research aimed to characterize the composition of screened mass flows of as-received mixes from the selective collection at the two MRFs through in situ random collection campaigns. The results of the gravimetric analysis have shown that both MRFs provided higher recovery yields (> 40%) for paper, cardboard, Tetrapack®, ferrous and non-ferrous metals (aluminium), akin to some post-consumer plastics (PET, HDPE/LDPE and PP) that ranged from 38% for PP up to 89% for HDPE, Losses in recovery yields of recyclable plastics after the screening process resulted from lack of clear resin label identification, inefficient materials sortation by households and poor recognition capabilities of the MRFs screening devices to target and segregate specific types of plastics such as PS and vinylic. Packaging design complexity, multi-layered material diversity, and food contaminated post-consumer packaging pose further challenges to improve the plastics recovery capabilities of the two MRFs. Keywords Municipal solid waste (MSW) · Material recovery facility (MRF) · Post-consumer plastics (PCPs) · Selective collection · MSW gravimetry Introduction The global capacity of plastics production has been growing exponentially since the 50’s and reached 368 million metric tons in 2019, followed by 367 million metric tons in 2020 [1]. A total amount of 8.3 billion tons of plastics were produced between 1950 and 2015 [2]. Plastics global production itself represents 6% of the oil consumption or about 6% of the oil consumption by the aviation sector. At current growth rates, the plastic sector will represent 20% of the global oil consumption and 15% of the C O2 emissions in 2050. In 2005, a total of 6.3 billion tons of solid plastic waste was generated, with 79% landfilled or discarded in the environment, 12% incinerated and only 9% was recycled. At the present pace, a global capacity of 1 million metric * Carlos Alberto Correa 1 Strategic Nucleus for Waste Revaluation-Federal University at ABC, Santo André, SP, Brazil 2 Engineering, Modelling and Applied Social Sciences Centre, Federal University at ABC, Santo André, SP, Brazil tons per year might be reached within the next decades with unpredictable environmental impacts if rates of recovery and recycling of waste and discard remain at present levels. The Ellen MacArthur Foundation estimates that 78 million tons of plastics are produced annually from virgin feedstock for packaging applications [3, 4]. Only 14% of this amount is collect for recycling, with 10% recycled into lower value products (cascaded recycling), 4% process losses and only 2% reprocessed as Post-Consumer Resins (PCR). The larger volume of plastic packaging waste is destined to landfills (40%), incineration and/or energy recovery (14%) and leaked into the environment as litter (32%). The growing impact of plastic waste on Municipal Solid Waste (MSW) streams has also been highlighted by Tsiamis et al. [5], whilst The United Nations has declared waste management policies as a top priority to curb plastic littering spread around the world [6]. Reuse and recycling represent the only alternative to divert plastic waste from landfilling, incineration or littering. In terms of waste management, recycling provides the technical means to return raw materials to market by screening and sorting reusable products from the bulk of the MSW 13 Vol.:(0123456789) Journal of Material Cycles and Waste Management stream. Early studies on recycling rates of plastic waste realized in the USA have shown that depending on the material collected, plastics would comprise 4–14% by weight of the recyclables in a recycling program [7]. Most importantly, in countries strongly reliant on landfill dumping, recycling can help diversion of MSW from overstressed public landfills extending their operation life span and also improve the efficiency and ash quality of incinerators and composting facilities by removing non-combustible materials, such as metals and glasses from waste-to-energy streams. Plastic materials that have been contaminated by food or organic matter usually have a residual unpleasant odor from leachates which devaluates Post-Consumer Resins (PCR). Further issues which are faced by recyclers of such kind of waste are the effluents with high concentrations of organic matter and microplastics which demand water treatment and solid waste removal for environmental controlled disposal. Other problems faced by mechanical recycling are the multilayer packaging, since multilayer films manufactured with different types of resins and adhesives make them impossible to be separated by conventional recycling methods. Blisters used for medicaments are examples of multilayer packaging made of plastic and aluminum which are very hard to be recycled, regardless the huge volume of waste they generate. All these shortcomings hampering mechanical recycling have raised interest over new platforms such as waste-to-energy and chemical recycling to reducing plastic waste [8]. In such cases, the plastic material is modified chemically to breakdown its molecular structure into its original building blocks that could be used in the production of fuels or monomers as raw materials for new products [9, 10]. As a consequence of the complexities of PCP recycling, the global amount of plastics ending in landfills by 2015 was nearly half of the produced amount, or about 150 million tons annually, not to mention the amounts that escape the MSW collection schemes and are leaked into the environment. In Brazil, wide availability of virgin resins at low prices, lack of tax incentives for recyclers, contaminated waste streams and a waste collection system strongly focused in the final disposal in landfills, make the plastic recycling sector low competitive, adding to the very low recycling rates of PCRs, as shown in [11]. A big challenge is being posed over Materials Recovery Facilities (MRFs) worldwide in regard to the characterization of the post-consumer waste in terms of its diverse typology. To improve the yield performance and reduce the amount of rejects at MRFs, primary data about the composition of the MSW selective collection are essential to achieve recycling goals. (...truncated)