The reuse of waste in civil construction brings environmental and economic benefits. However, for these to be used in concrete, it is necessary a previous evaluation of their physical and chemical characteristics. Thus, this study aimed to characterize and analyze the waste foundry exhaust sand (WFES) for use in self-compacting concrete (SCC). Foundry exhaust sand originates from the manufacturing process of sand molds and during demolding of metal parts. It is a fine sand rich in silica in the form of quartz collected by baghouse filter. Characterization of WFES was conducted through laser granulometry, scanning electron microscopy (SEM) in the energy dispersive spectroscopy (EDS) mode, X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG) and derivative thermogravimetry (DTG) techniques. The waste was classified as non-hazardous and non-inert, with physical and chemical properties suitable for use in SCC composition, as fine aggregate or mineral addition. Five mixtures of SCC were developed, in order to determine the waste influence in both fresh and hardened concrete. The properties in the fresh state were reached. There was an increase in compressive strength and sulfate resistance, a decrease in water absorption of self-compacting concrete by incorporating WFES as 30% replacement.

The elevated presence of organic material in Brazilian urban solid waste, along with mismanagement of its disposal, can aggravate environmental problems from greenhouse gas emissions to water and soil pollution. In parallel, the paper and cellulose industries consume considerable resources and produce important solid wastes, including lime mud. These urban and industrial realities present common ground, from which a little-studied alternative arises in using biogas electrical energy from the co-digestion of the organic portion of urban solid waste using lime mud. This intersection can reduce the environmental impacts associated with inadequate management and disposal of solid waste, providing industry financial economy resources and contributing to Brazilian energy grid diversification. The current study used economic–financial indicators to evaluate the proposal’s economic feasibility. The obtained results presented a minimum population of 165,200 inhabitants, generating 39,295.77 m³/year of methane, in order to enable a co-digestion proposal. The sensitivity analysis indicated that a population of 185,500 inhabitants would provide a 10-year payback, an energy rate of USD 0.139, and 44,124.49 m³/year of methane to supply the population with power. The net present value was USD 23,336.94, with an internal return rate of 14.71% and a levelized energy cost of 0.103 USD/kWh.

This study evaluates the energy recovery from biogas generated through the anaerobic co-digestion of the Organic Fraction of Urban Solid Waste (OFUSW) with lime mud (LM). This approach aims to mitigate environmental impacts such as greenhouse gas emissions and pollution while promoting energy recovery for a diversified power matrix. Life cycle assessment (LCA) methodology, in accordance with the NBR ISO 14040 and 14044 standards, was used to compare five scenarios for the disposal of LM. The results highlight that the co-digestion scenario showed significant environmental benefits in 8 out of the 18 categories evaluated, such as reductions in eutrophication, acidification, and climate change. Additionally, the digestate produced helped avoid further environmental impacts. The integration of urban and industrial waste demonstrates the potential to enhance biogas productivity, generate savings for the pulp and paper industry, and promote sustainable practices. The innovation lies in the synergistic use of LM as a co-substrate, improving the efficiency of the anaerobic process and maximizing biogas production. This research provides a solid scientific foundation for decision-making in public policies and industrial practices, positioning itself as a viable and innovative proposal for the integrated management of solid waste and sustainable energy.

The article is well-written, and an extensive review was made. The subject of the paper is important and deserves attention. However, 1-The English needs to be revised properly. 2-Is it possible to classify the waste (hazardous, non-hazardous, i...

Dear authors!! A few changes were made to the article. More recent articles on the subject should be added to the review. It is necessary to compare your results with those of other authors in order to justify your results. Value what was done as...

The research topic is current and important; however, some facts were observed: The bibliographic review needs to be updated with more recent articles. The objective of the study was to analyze only the compressive strength of the concrete, but it co...