Limestone (calcite, CaCO₃) is an abundant and cost-effective source of calcium oxide (CaO) for cement and lime production. However, the thermochemical decomposition of limestone (∼800 °C, 1 bar) to produce lime (CaO) results in substantial carbon dioxide (CO_2(g)) emissions and energy use, i.e., ∼1 tonne [t] of CO₂ and ∼1.4 MWh per t of CaO produced. Here, we describe a new pathway to use CaCO₃ as a Ca source to make hydrated lime (portlandite, Ca(OH)₂) at ambient conditions (p, T)-while nearly eliminating process CO_2(g) emissions (as low as 1.5 mol. % of the CO₂ in the precursor CaCO₃, equivalent to 9 kg of CO_2(g) per t of Ca(OH)₂)-within an aqueous flow-electrolysis/pH-swing process that coproduces hydrogen (H_2(g)) and oxygen (O_2(g)). Because Ca(OH)₂ is a zero-carbon precursor for cement and lime production, this approach represents a significant advancement in the production of zero-carbon cement. The Zero CArbon Lime (ZeroCAL) process includes dissolution, separation/recovery, and electrolysis stages according to the following steps: (Step 1) chelator (e.g., ethylenediaminetetraacetic acid, EDTA)-promoted dissolution of CaCO₃ and complexation of Ca²⁺ under basic (>pH 9) conditions, (Step 2a) Ca enrichment and separation using nanofiltration (NF), which allows separation of the Ca-EDTA complex from the accompanying bicarbonate (HCO₃ ^-) species, (Step 2b) acidity-promoted decomplexation of Ca from EDTA, which allows near-complete chelator recovery and the formation of a Ca-enriched stream, and (Step 3) rapid precipitation of Ca(OH)₂ from the Ca-enriched stream using electrolytically produced alkalinity. These reactions can be conducted in a seawater matrix yielding coproducts including hydrochloric acid (HCl) and sodium bicarbonate (NaHCO₃), resulting from electrolysis and limestone dissolution, respectively. Careful analysis of the reaction stoichiometries and energy balances indicates that approximately 1.35 t of CaCO₃, 1.09 t of water, 0.79 t of sodium chloride (NaCl), and ∼2 MWh of electrical energy are required to produce 1 t of Ca(OH)₂, with significant opportunity for process intensification. This approach has major implications for decarbonizing cement production within a paradigm that emphasizes the use of existing cement plants and electrification of industrial operations, while also creating approaches for alkalinity production that enable cost-effective and scalable CO₂ mineralization via Ca(OH)₂ carbonation.

Rainwater Harvesting System (RWHS) can play a multipurpose role, contributing to the management of rainwater runoff, in addition to the water supply. This article assessed the potential reduction in stormwater runoff by adopting small-scale RWHS in the Brazilian semiarid region based on the Curve-Number (CN). RWHS could minimize runoff in frequency and volume, leading the built environment to perform closer to the land’s natural conditions. Before urbanization, the region had a CN of 76. In post urbanization, a case study of multiple houses showed that the adoption of RWHS could reduce the CN from 86 to 80. A reasonable design (0.5 demand fraction and 2000 L tank capacity) could minimize runoff volume by 34% and frequency of occurrence by 66%. Even RWHS with a minimal design, i.e. small tank capacity and low demand, might contribute to the safety of people, resilience, and sustainability of the city’s infrastructure.

The present study evaluated the microbiological risk for roof-harvested rainwater (RHRW), with Campylobacter as the pathogenic microorganism of reference, using a Quantitative Microbial Risk Assessment (QMRA). QMRA has been widely used as an alternative method for epidemiological assessment of human exposure to microorganisms that can cause diseases, through a four-step process: hazard identification, exposure assessment, dose–response assessment, and risk characterization. The results presented drinking as the water use with the highest median value for microbiological risk, with 3.4 × 10⁻⁴ disability-adjusted life years (DALYs) per person per year (pppy), and bathing, food washing, hose irrigation and toilet flushing with median values of 6.5 × 10⁻⁷, 4.0 × 10⁻⁷, 2.1 × 10⁻⁷ and 1.4 × 10⁻⁷ DALYs pppy, respectively. Therefore, drinking would be the only water use that would require preliminary treatment for its safe use, considering the acceptable risk standards set by the World Health Organization for drinking water. However, with the adoption of a sanitary barrier and a simple point-of-use treatment system, it was observed that drinking rainwater would have a median microbiological risk of 2 × 10⁻⁶ DALYs pppy, enough to meet the safety criteria considering developing countries.

Masonry wall is a key construction subsystem, but it embodies significant environmental and energy burdens within the life cycle of buildings. Soil-cement bricks and blocks stand as an alternative low-cost masonry material, but despite the widespread claim to be environmentally friendly, more systematic investigation is lacking. This study aimed to assess the life cycle environmental and energy performance of 1.0 m² of a soil-cement brick masonry wall from cradle-to-construction in terms of carbon, energy, and water footprints, and fossil and mineral resource use, as well as compare it with conventional technologies such as ceramic and concrete block masonries in Brazil. Results showed that raw materials are a major contribution to soil cement masonry walls, followed by the joints and links with columns, in which cement stands out among other inputs. Hydraulic pressing in brick production had a negligible burden increase compared with manual pressing. The PVA mortar joint outperformed the PVA glue one, whereas resin coating performed better than cement mortar. In comparison with ceramic and concrete masonry walls, the soil cement masonry presented overall better environmental and energy performance and was the least affected by the inclusion of finishing coating layers and transport of materials in the sensitivity analysis scenarios, although improved scenarios of conventional options could be competitive, e.g., ceramic masonry with blocks produced by firing reforested wood for the carbon footprint. Scale-up analysis revealed that widespread deployment of soil cement masonry in the built environment would substantially avoid environmental and energy burdens compared with conventional technologies.

A siderurgia de ferro e aço tem sofrido pressões e transformações determinantes nos últimos anos em função dos impactos ambientais gerados pelo setor. O ferro gusa, principal matéria-prima do aço, é produzido majoritariamente por meio de alto-fornos, uma tecnologia intensiva em consumo de energia, de recursos primários e, também, em emissão de gases de efeito estufa (GEE). Ao passo que o setor se vê pressionado com a escassez de matérias-primas e as repercussões da mudança climática, rotas tecnológicas em processo de desenvolvimento têm indicado um potencial melhoria no desempenho ambiental do ciclo de vida do ferro gusa. A Avaliação de Ciclo de Vida (ACV) é um método que visa estimar os impactos ambientais de produtos, serviços e processos, considerando desde a cadeia de suprimentos até a obtenção do produto final, bem como uso, e descarte final. Neste estudo, realizou-se uma revisão sistemática da literatura, análise bibliométrica e de patentes com o objetivo de levantar evidências e investigar as lacunas acerca dos aspectos ambientais da produção de ferro gusa, dos impactos do seu ciclo de vida e das reivindicações de inovação na siderurgia associadas às tecnologias "verdes". Verificou-se uma tendência de crescimento tanto em contribuições científicas quanto em registros de patente na última década, acentuada a partir de 2013. Os tópicos em destaque na discussão acadêmica abrangem desde inventários de fluxos no início da década, até o desempenho ambiental do processo produtivo, nos estudos mais recentes. O domínio tecnológico esteve focado na viabilização do reaproveitamento de resíduos, desenvolvimento de materiais alternativos e otimização de processo. Geograficamente, os países asiáticos, sobretudo a China, destacaram-se com a maior quantidade de contribuições acadêmicas e tecnológicas, embora países da Europa, das Américas e a Austrália também tenham se mobilizado ativamente. A convergência observada nesses resultados evidenciou a ocorrência de fenômenos análogos em diferentes perspectivas de produção de conhecimento: academia e indústria. Por fim, o tema revela ainda possuir potencial de aprofundamento, especialmente com respeito aos fornos em desenvolvimento.