No abstract

The shortage of water worldwide is increasingly worrying. Studies in the field suggest that sustainable water resource management via water recycling is fundamental to alleviate the issue. The use of rainwater is an important alternative source that must be considered, mainly, in the water crisis facing the planet. When integrated with the concept of green roofs, the capturing and treatment of rainwater in these structures becomes an even more ecological and sustainable practice. The water drained by the roof can be used for non-potable uses, such as flushing toilet bowls. One of the main concerns when using rainwater, even for non-potable uses, is the quality of the water available, so as not to put users' health at risk. In this way, the present work proposes to experimentally analyze the quality of rainwater drained in a green roof prototype for reuse purposes. The green roof prototype was installed on an experimental bench. After each rain event (four in total), two water samples were collected in the following situations: rainwater captured directly by a container next to the bench, and rainwater drained by the green roof prototype, captured by a container through existing drains at the base of the prototype. The analyzes of the collected samples were carried out at the Environmental Engineering Laboratory (LEMA / UFRJ) and performed according to the Standard Methods for the Examination of Water and Wastewater. Specifically, the experiments examine physicochemical and biological parameters following a rain event on a green roof prototype for sanitary use. Experimental results that were observed and analyzed include color, turbidity, pH, ammonia nitrogen, nitrite, nitrate, orthophosphate, total coliforms, and thermotolerant coliforms to indicate the rainwater quality from green roofs. The majority of parameters assessed were within the value thresholds indicated by the Brazilian standards, while the results of orthophosphate, fecal coliforms, color, and turbidity were not. The greatest divergence is in the concentration of orthophosphate, where a concentration of 10.88mg/L was obtained in this experimental study while other authors present values of 0.1 and 0.01mg/L. Total coliforms also presented high values, but within the expected range. Comparisons with technical documents and international references related to water quality to identify possibilities of the use of rainwater were also conducted. Results indicate that the water quality has the same order of quantity for turbidity, nitrite, and ammonia nitrogen parameters across the standards. Based on such observations, filtration and disinfection processes are therefore required in the green roof system for the use of rainwater for sanitary. Finally, the experimental study of rainwater quality on the green roof presented similar results comparing with international references. The use of green roofs combined with the use of rainwater demonstrates the potential and benefits as an alternative to face the water crisis.

In order to limit climate change by achieving goals of cutting emissions down to net-zero by 2050, stronger efforts are needed to reduce the whole life cycle emissions of buildings. Integrating residual bio-based and earth-based solutions to concrete seems to stand out in the sector since these solutions have the potential of lowering materials embodied emissions, and enhancing building thermal performance. However, it is still unclear how environmentally beneficial bio-based and earth-based materials are and how they behave mechanically when they are both integrated into concrete. In order to know their potential applications in the sector, this study aims to evaluate and compare the mechanical performance and environmental profile of Earth-based Bamboo Bio-Concretes (EBBCs) with different earth fractions as partial replacements of the cementitious matrix, by evaluating its Greenhouse Gas (GHG) emissions. For that, it was considered the use of only bio-based aggregates (bamboo waste) instead of mineral ones at a fixed volume fraction of 45%. The methodology involved the: processing and characterization of earth and bamboo; EBBCs dosage study and mechanical testing; consideration of fixed proportions of binders of 30:30:40 (cement: metakaolin: fly ash) which were replaced gradually by earth in the volume fractions of 10%, 15%, and 20%. The Life Cycle Assessment (LCA) was used for accounting GHG emissions. LCA scope was from cradle-to-gate considering biogenic carbon methodology and avoided impacts of incinerating bamboo waste. A sensitive analysis was performed to evaluate the impact of transport distances variation of bamboo waste. Mechanical results point to an increase in EBBCs compressive strength with the increase of earth content until 15% of cementitious matrix replacement. LCA results showed negative embodied GHG emissions in all mixtures with an average of -115,7 kgCO2-eq/m3 mainly due to the high biomass content in mixtures. The increase of earth content from 0% to 20% in the mixtures reduced emissions by 59,7 kgCO2-eq/m3 since the binder’s content was reduced. With that, EBBC seems to be a promising innovative material to help achieve net-zero carbon emission targets and a circular pathway in the building and construction sectors.

The shortage of water worldwide is increasingly worrying. Studies in the field suggest that sustainable water resource management via water recycling is fundamental to alleviate the issue. The use of rainwater is an important alternative source that must be considered, mainly, in the water crisis facing the planet. When integrated with the concept of green roofs, the capturing and treatment of rainwater in these structures becomes an even more ecological and sustainable practice. The water drained by the roof can be used for non-potable uses, such as flushing toilet bowls. One of the main concerns when using rainwater, even for non-potable uses, is the quality of the water available, so as not to put users' health at risk. In this way, the present work proposes to experimentally analyze the quality of rainwater drained in a green roof prototype for reuse purposes. The green roof prototype was installed on an experimental bench. After each rain event (four in total), two water samples were collected in the following situations: rainwater captured directly by a container next to the bench, and rainwater drained by the green roof prototype, captured by a container through existing drains at the base of the prototype. The analyzes of the collected samples were carried out at the Environmental Engineering Laboratory (LEMA / UFRJ) and performed according to the Standard Methods for the Examination of Water and Wastewater. Specifically, the experiments examine physicochemical and biological parameters following a rain event on a green roof prototype for sanitary use. Experimental results that were observed and analyzed include color, turbidity, pH, ammonia nitrogen, nitrite, nitrate, orthophosphate, total coliforms, and thermotolerant coliforms to indicate the rainwater quality from green roofs. The majority of parameters assessed were within the value thresholds indicated by the Brazilian standards, while the results of orthophosphate, fecal coliforms, color, and turbidity were not. The greatest divergence is in the concentration of orthophosphate, where a concentration of 10.88mg/L was obtained in this experimental study while other authors present values ​​of 0.1 and 0.01mg/L. Total coliforms also presented high values, but within the expected range. Comparisons with technical documents and international references related to water quality to identify possibilities of the use of rainwater were also conducted. Results indicate that the water quality has the same order of quantity for turbidity, nitrite, and ammonia nitrogen parameters across the standards. Based on such observations, filtration and disinfection processes are therefore required in the green roof system for the use of rainwater for sanitary. Finally, the experimental study of rainwater quality on the green roof presented similar results comparing with international references. The use of green roofs combined with the use of rainwater demonstrates the potential and benefits as an alternative to face the water crisis.