Life Cycle Assessment Analysis Research Articles

Life cycle assessment of biochar and cattle manure application in sugar beet cultivation – Insights into root yields, white sugar quality, environmental aspects in field and factory phases

Sugar beet (Beta vulgaris L.) is a well-known sugar crop essential for supplying the global demand for sugar. Examining how different farming techniques affect the environment may help produce a high-quality crop with the least negative environmental effects. To this, the life cycle assessment (LCA) of biochar (B) and cattle manure (CM) applications at three different rates (5, 10, and 15 tons ha−1) compared with conventional chemical fertilization (CH) in the autumn and spring sugar beet crops has been studied. The system boundaries for LCA analysis were set from the cradle to the sugar factory gate. Based on the results, the highest amounts of root yield were obtained under CM10 and CM15 treatments with 24.5% and 23.2% increase in autumn cultivation and 34.8%, and 33.9% increase in spring cultivation, compared to CH. However, CM15 resulted in significantly lower sugar content (10.9%) than B5 (17%). Also, B utilization significantly reduced molasses content in sugar beet rather than CM in both cultivation periods. Further, biochar treatments (B5, B10, B15) significantly increased the white sugar yield in both cultivation times by 43.7%, 39.2%, and 36.1%, on average. Generally, the highest and the lowest global warming potential (GWP) were obtained from CM15 and B15 with 638.5 and 437.2 CO2-eq ton−1 root/sugar yields, respectively. These findings validate the hypothesis that using biochar in sugar beet production could reduce greenhouse gas emissions while increasing the amount of white sugar produced.

Social impact assessment of biofuel production for maritime and aviation sectors: a case study of a pilot biorefinery project

This work presents a comprehensive Social Life Cycle Assessment (S-LCA) and Social Cost-Benefit Analysis (S-CBA) conducted as part of a research project, studying biofuel production for the maritime and aviation sectors, from various types of non-food waste biomasses. The inclusion of social considerations complements and expands on the environmental and economic ones. The importance of social group criteria was determined through expert questionnaires, leading to the identification of social impacts groups and social criteria from stakeholders across participating countries. The results successfully identified and quantified social impacts, and align with those reported in similar cases in relevant literature. Social Cost-Benefits, monetarizing social factors, demonstrated several social benefits, including reduction in Greenhouse Gas Emissions. However, it also highlighted social costs, such as Economic Costs associated with the initial investment. The study revealed critical social hotspots within the impact categories, making significant strides in understanding the social impacts of biofuel production, providing valuable insights for decision-makers, and contributing to the broader goal of sustainable and socially responsible biofuel production.

From Transformation to Life Cycle Assessment of Biochar: A Case Study of Wheat Straw Biochar.

Biochar, as a carbon-rich material, exhibits significant potential for industrial applications. While numerous research endeavors have focused on its interactions within soil ecosystems, scant attention has been given to its behavior and potential impact on aquatic environments. In this study, we conducted an investigation to compare the environmental implications of pristine biochar with those of aged biochar. Initially, we assessed the interaction between biochar and key water quality indicators, revealing the release of endogenous ions (e.g., NH4+, NO3-, PO43-, Cu2+, and Cd2+) as well as organic substances (e.g., DOC) from both pristine and aged biochar samples. Aged biochar released higher amounts of ions and organic substances than pristine biochar due to the change in the structure and properties of aged biochar. Environmental risk and toxicity of pristine and aged biochar were subsequently evaluated using the potential ecological risk index (RI) and the impact on growth of Chlorella vulgaris, respectively. The values of RI for Cu indicated a very low degree of environmental risk, while those for Cd were dependent on water quality for surface water. Our study provided thorough analysis on the environmental assessment of biochar by combining experimental environmental transformation and life cycle assessment (LCA) analysis, suggesting biochar could have excellent environmental applications.

LCA analysis for assessing environmenstal sustainability of new biobased chemicals by valorising citrus waste

The global shift towards using biomass for biofuels and chemicals is accelerating due to increasing environmental concerns and geopolitical strategies. This study investigates a biorefinery model using citrus-processing-waste, specifically citrus pulp, to produce high-value products for various industries, including cosmetics, pharmaceuticals, flavours, fragrances, and food packaging. In Italy, particularly Sicily region, citrus processing generates significant amounts of waste, often improperly disposed of, contributing to environmental problems. Researchers have demonstrated that citrus waste can yield commercially valuable compounds. This study specifically focuses on orange peel waste (OPW), which constitutes about half of the fruit's weight, aiming to extract pectin and limonene through a combined process. The extraction process was carried out on a laboratory scale, and its sustainability was evaluated using a life cycle assessment (LCA) with SimaPro 8.1 software and the Impact 2002 + method. The functional unit adopted for this study is 300 g of OPW, obtained after the pre-treatment phase, from which 0.14 g of limonene and 8.22 g of pectin were extracted. The LCA results revealed that pectin extraction has a significantly higher environmental impact compared to limonene extraction, primarily due to the use of ethanol as a solvent, followed by electricity consumption. To mitigate this impact, the LCA assessed alternative, more sustainable solvents, resulting in a 73.4% reduction in the environmental footprint of the pectin extraction process. These findings underscore the critical role of LCA, even at the laboratory scale, in identifying environmental hotspots and providing insights for improving and optimizing processes for potential industrial-scale applications.

Hematite tailings to high-purity silica: Mechanistic studies and life cycle assessment analysis

This study aimed to recover high-purity silica from hematite tailings (HTs) using superconducting high-gradient magnetic separation (S-HGMS) technology. This process involved converting silica into a silicone-rich concentrate and subsequently employing a fluorine-free mixed acid to leach the silicon-rich concentrate to remove impurities and achieve refinement and purification. The optimization of the S-HGMS process was conducted using the "Box-Behnken Design" method, resulting in the following optimal conditions: a pulp concentration of 50 g/L, a magnetic velocity ratio of 0.076 T s/m, and a pulp velocity of 500 mL/min. These conditions yielded a silica grade range of 61.905% in the HTs to 91.818% in the silicon-rich concentrate, with corresponding recovery rates of 53.031%. Under the optimized leaching process, this resulted in an increase in the silica content from 91.818% in the silicon-rich concentrate to 99.938% in high-purity silica. Additionally, by analyzing the production process of 1 kg of high-purity silica from HTs using the process LCA method, environmental hotspots were identified, and corresponding solutions were proposed. This approach is vital for efficient utilization of HTs as a resource. This process has low energy consumption and is environmentally friendly, enabling the reduction of hematite tailings. It has a wide range of applications and offers substantial economic benefits, rendering it a promising candidate for industrial applications.

Towards sustainable fruit production: Identifying challenges and optimization strategies

CONTEXTThe transition to sustainable fruit production is vital for global sustainability and agricultural development. However, implementing these insights into practice faces significant challenges. OBJECTIVESPomelo (Citrus maxima), a prominent citrus species in tropical and subtropical regions, has been cultivated to enhance farmer profitability but increasing yields often comes at the cost of environmental degradation. This study uses pomelo as a case study to assess key factors influencing pomelo production and establish optimal practices that meet consumption-based food while co-benefits for environmental and economic sustainability. METHODSA comprehensive study was conducted by combining 1155 farm surveys (from 2010, 2018, and 2022) with 31 field experiments. Life cycle assessment (LCA), classification and regression tree (CART) analysis, and scenario analysis were employed to develop pathways for sustainable pomelo production in Pinghe County, Fujian Province, China. RESULTS AND CONCLUSIONSResults show no significant differences in pomelo yield across the three years; however, pomelo production in 2022 demonstrated a 60 %–67 % lower in environmental footprints and a 64 %–76 % higher benefit-cost ratio (BCR) compared to 2010 and 2018. Tree age was identified as a critical factor influencing pomelo yield, with optimal yields observed in trees older than 12.5 years. The rate of phosphorus fertilizer application was a key determinant of the phosphorus footprint (PF), which was positively correlated with phosphorus fertilizer rates. Similarly, nitrogen fertilizer application significantly impacted both carbon and nitrogen footprints (CF and NF) as well as the BCR. CF and NF increased with higher nitrogen fertilizer rates, while BCR exhibited a negative correlation with nitrogen fertilizer application. Implementing Science and Technology Backyards (STB) followed by farmer training of slightly more than pomelo nutrient requirements practice (SNRP) or coordinate management by farmers and researchers of matching pomelo nutrients requirement practice (MNRP) had 50 %–91 % lower environmental footprints per ton of pomelo produced and 15 %–44 % higher BCR compared to current farming practices (FP) via reducing 46 %–77 % N, 49 %–92 % P2O5, and 42 %–73 % K2O per hectare. Moreover, adopting 100 % MNRP in pomelo production, along with sustainable fertilizer practices and the implementation of innovative fertilizers, could reduce greenhouse gas (GHG) emissions (0.76 Tg), reactive nitrogen (Nr) emissions (8.76 Gg), phosphorus (P) losses (0.84 Gg), and augment net ecosystem economic benefits (NEEB) (0.94 billion CNY) at the county scale. SIGNIFICANCEOur study provides evidence-based strategies for achieving sustainable pomelo production through multi-stakeholder collaboration of STB, government, enterprises, and smallholders.

Controlling the optoelectronic properties of nitrogen-doped carbon quantum dots using biomass-derived precursors in a continuous flow system

The synthesis of carbon quantum dots (CQDs) from high molecular weight biomass-derived precursors poses a significant challenge due to the complex molecular structures and low conversion efficiency. This work demonstrates a green, rapid, and sustainable continuous hydrothermal flow synthesis (CHFS) approach for nitrogen-doped carbon quantum dots (NCQDs) from various biomass-derived precursors, including high molecular weight polymeric sources like chitosan, lignin, and humic acid. We find that the precursor structure significantly impacts the size of the fabricated NCQDs and their optical properties. Citric acid, a low molecular weight precursor, yields NCQDs with excitation-independent emission, higher quantum yields, and low non-radiative losses, while NCQDs derived from polymeric precursors exhibit excitation-dependent, red-shifted, and lower efficiency emission. Theoretical calculations, performed to understand the configuration and distribution of nitrogen dopants within the NCQD structure, show that pyridinic and graphitic nitrogen atoms exhibit a strong preference to aggregate near the centre of the edge of the NCQD and not in the vertices nor in the graphitic core, thus affecting the HOMO and LUMO, bandgap, and light absorption and emission wavelengths. The life cycle assessment (LCA) analysis highlights the green and scalable advantages of the CHFS process for producing NCQDs compared to batch methods, making it a sustainable and economically viable approach for large-scale NCQD synthesis from high molecular weight biomass-derived precursors. Hence, the combination of experimental data and theoretical calculations provides a comprehensive understanding of the structure-property relationships in these NCQDs.

Efficient arsenic removal from water using iron-impregnated low-temperature biochar derived from henequen fibers: performance, mechanism, and LCA analysis

The present study aims to investigate the low-energy consumption and high-efficiency removal of arsenic from aqueous solutions. The designed adsorbent Fe/TBC was synthesized by impregnating iron on torrefaction henequen fibers. Isothermal adsorption experiments indicated maximum adsorption capacities of 7.30 mg/g and 8.98 mg/g for arsenic(V) at 25.0 °C and 40.0 °C, respectively. The interference testing showed that elevated levels of pH, HCO3− concentration, and humic acid content in the solution could inhibit the adsorption of arsenic by Fe/TBC. Characterization of the adsorbent before and after adsorption using FTIR and SEM–EDS techniques confirmed arsenic adsorption mechanisms, including pore filling, electrostatic interaction, surface complexation, and H-bond adhesion. Column experiments were conducted to treat arsenic-spiked water and natural groundwater, with effective treatment volumes of 550 mL and 8792 mL, respectively. Lastly, the life cycle assessment (LCA) using OpenLCA 2.0.3 software was performed to treat 1 m3 of natural groundwater as the functional unit. The results indicated relatively significant environmental impacts during the Fe/TBC synthesis stage. The global warming potential resulting from the entire life cycle process was determined to be 0.8 kg CO2-eq. The results from batch and column experiments, regeneration studies, and LCA analysis indicate that Fe/TBC could be a promising adsorbent for arsenic(V).

Optimized Chemical Bath Deposition for Low Cost, Scalable, and Environmentally Sustainable Synthesis of Star-Like ZnO Nanostructures.

This paper highlights an affordable and straightforward method called chemical bath deposition (CBD) for generating different morphologies of ZnO-based nanostructures. In particular, a specific protocol was found to drive the growth versus a high-yield in-plane symmetric six-arm nanostructure, named a nanostar (NS). Each arm of the star consists of a cluster of parallel wires, creating a subnanostructure with a huge surface-to-volume ratio. As-grown NSs present a mixed phase of ZnOHF and ZnO, which converts to ZnO under thermal annealing at 300 °C. The NSs have a highly exposed surface area (13.2702 m2·g-1) and exhibit an energy gap of 3.25 eV. A cradle-to-gate life cycle assessment (LCA) analysis has shown the high ecofriendly potential of this synthesis route and identified hotspots that need to be addressed to minimize the environmental impact of NS synthesis on an industrial scale.

Treatment of brominated epoxy resin waste in subcritical dimethylformamide wastewater: Upcycling of brominated epoxy resin and dimethylformamide degradation

The debromination and upcycling of brominated epoxy resin (BER) waste is important for the e-waste treatment, while the degradation and removal of N, N-dimethylformamide (DMF) is the critical step for the DMF wastewater treatment. In this study, a co-treatment strategy was proposed for the BER waste and DMF wastewater by the subcritical water process. The co-treatment was carried out using subcritical DMF wastewater (SDW) as the reaction medium. The results showed a significantly synergistic effect between the BER conversion and DMF degradation in the SDW process. The optimal reaction conditions were as follows: reaction temperature of 300 °C, solid-to-liquid ratio of 1:15 g/mL, DMF wastewater of 30000 mg/L and reaction time of 60 min. Under the optimal reaction conditions, the debromination ratio of the BER was 98.57 %, the degradation ratio of the DMF reached 99.59 %, and phenolic substances with a purity of 86.61 % were recovered. The formation of HBr from the debromination of the BER was the most significant factor affecting the pH of the system, which had a noticeable impact on the degradation of the DMF. The main degradation products of the DMF were dimethylamine (DMA), methylamine (MA), NH3, NH4+, and CO2. The products degraded from the DMF could significantly promote the debromination and conversion of the BER. Life cycle assessment (LCA) analysis showed that the SDW process had low CO2 emissions. It is believed that the SDW process proposed in this study is an efficient technology for the synergistic treatment of the BER waste and DMF wastewater.

An Entrained Flow Biomass Gasification Technology with the Fluidized Bed Concept for Low-carbon Fuel Production

For accomplishing the vision of building of a net-emission zero society, low-carbon fuels such as e-fuel, Sustainable Aviation Fuel (SAF), and chemical products generation, plays a significant role. Especially, among the low carbon fuels, SAF is the most crucial. Ammonia and electric aircraft are under way as alternatives to fossil-derived jet fuel (kerosene). However, none of these have yet found their way to commercialization. Among the SAF production technology, biomass gasification and Fischer-Tropsch (FT) synthesis technology are one of the lowest CO2 emission processes, according to Life Cycle Assessment (LCA) analysis. However, at present there are some issues about biomass grinding, tar, ash treatment, gas purification and wastewater. We, at Mitsubishi Heavy Industries (MHI) R&D laboratory have developed entrained bed gasification, adopting the fluidized bed concept in which biomass particles are recirculated in the gasifier without fluidizer. Principally desired outcomes of this development was to reduce the grinding power, simplify the structure by using atmospheric pressure process, and lower tar concentration while maintain suitable temperature to prevent ash from melting inside gasifier. Empirical and actual results showed that the developed gasifier can obtain high carbon conversion ratio and low tar as compared to the traditional gasification processes for low-carbon fuel production and produce reliably stable syngas for low-carbon fuel synthesis with single gasifier. Based on the pilot plant operation results, effectiveness of moderate (1223 – 1323 K) temperature gasification with this concept has been demonstrated too. As a conclusion, development needs and expectation of gasification technology for contributing to carbon neutral society are mentioned.

Life Cycle Assessment Analysis Based on Material Selection in Sustainable Airport Buildings

Sustainable airport buildings aim to minimize environmental impacts through energy efficiency, water conservation, and waste management. This is achieved by employing green building materials and utilizing renewable energy sources to reduce their carbon footprint. In this study, life cycle assessment (LCA) was conducted to assess the environmental impacts of three main construction materials—concrete, steel, and wood—used in sustainable airport buildings. These materials were selected for their widespread use in eight different airport terminal buildings with sustainability certifications. The environmental impacts of these materials were calculated and compared using OpenLCA 1.9.0 software and the ECOinvent database, adhering to the standards set forth by the Environmental Product Declaration (EPD) initiative. The findings indicate that wood, as a construction material, has a significantly lower impact on global warming compared to steel and concrete, with a global warming potential (GWP) ratio of less than 60%. Steel, with a GWP of approximately 90% of that of concrete, also showed a lower impact than concrete. Additionally, other environmental impacts, such as stratospheric ozone depletion potential (ODP) and acidification potential (AP), were also examined, highlighting the trade-offs associated with each material.

CO2 treatment of recycled concrete aggregates with high mortar contents: From finding optimal treatment condition, quality enhancement, to life cycle assessment

With increasing construction and demolition waste, the demand for recycled concrete aggregates (RCA) has risen, yet their inherent poor-quality limits usage. In response, CO2 treatment has been developed to enhance RCA quality while contributing to CO2 reduction efforts. This study investigates the effect of CO2 treatment on RCA with high mortar contents for sustainable construction applications. Treatment conditions were optimized by evaluating the CO2 consumption ratio and reaction kinetics under various temperatures (10–50°C), pressures (250–1000 kPa), relative humidity (30–70 %), and initial saturation (30–100 %). X-ray imaging confirms carbonation within the mortar, evidenced by increased greyvalues. Environmental assessment of leachate reveals a significant reduction in chromium concentration from 0.18 mg/L to 0.11 mg/L and a decrease in pH from 10.1 to 7.8 after CO2 treatment, suggesting the potential of CO2 conditioning to mitigate the environmental impacts. Mechanical tests, the aggregate crushing value (ACV) test, and the freeze-thaw (FT) resistance test, demonstrate the improved resistance and durability, with a decrease in ACV from 35.5 % to 33.2 % and FT mass loss from 25.1 % to 20.0 %. The life cycle assessment analysis shows that a simplified CO2 treatment achieved a significant reduction of 138.257 kg CO2 eq per ton of RCA compared to the conventional RCA process. These findings highlight the dual benefits of CO2 treatment: enhanced mechanical performance and reduced environmental impact, promoting the use of recycled aggregates in sustainable construction practices.

Life cycle assessment of Al-Cu-Ag-Si recycling process from photovoltaic waste

As raw materials become increasingly scarce, it is important to efficiently recycle PV panels to recover the highest quantity and quality of secondary raw materials. This study evaluates the environmental impact and the related benefits of an innovative process for c-Si PV panels recycling, which permits to recover most of the raw materials contained in them. Life Cycle Assessment analysis was carried out with “grave-to-cradle” perspective. Inventory was supported by data from a pilot plant located in Venice (Italy). ReCiPe 2016 method was used for the impact assessment. The results showed that environmental benefits are due to the recovery of aluminium, copper, silicon, silver and glass. Normalization of impact assessment results demonstrates main relevant impact categories of this process, and gravity analysis underlines what steps in the recycling process mainly contribute to the environmental benefits. Sensitivity analysis showed that quality of recovered materials influences the environmental profile of recycling process.

Development and characterization of polylactic acid/starch biocomposites – From melt blending to preliminary life cycle assessment

This study presents a comprehensive analysis encompassing melt blending, characterization, life cycle assessment (LCA), and 3D printing of a range of polylactic acid (PLA)/starch biocomposites, with starch content varying from 0 to 50 wt%. To enhance compatibility between the starch particles and the PLA matrix, we utilized a solvent-free method to graft N-octadecyl isocyanate (ODI) molecules onto the surface of the starch particles, resulting in ODI-g-starch, which yielded several improved properties. Notably, toughness and elongation at break improved by approximately 170 % and 300 %, respectively. Moreover, the crystallinity increased from 11.6 % in plain PLA to 30.1 %, suggesting that the uniform dispersion of ODI-g-starch particles acted as nucleating sites for the crystallization of PLA chains. Additionally, viscosity decreased significantly with the introduction of ODI-g-starch particles, indicating their plasticizing effect, thereby enhancing the processability and ease of fabrication of the biocomposite. Crucially, our LCA analysis revealed a significant reduction in the carbon footprint of these biocomposites, up to 18 % and 63 %, compared to plain PLA and selected fossil-based plastics, respectively, upon the incorporation of ODI-g-starch. In summary, our research introduces the newly developed PLA/starch biocomposites as a sustainable and eco-friendly alternative to commercially available plain PLA and specific fossil-based plastics.

Life cycle environmental impacts of urban water systems in China

Urban water systems in China are facing multiple challenges, including rapid urbanisation, climate change and infrastructure ageing. It is crucial to evaluate their environmental performance from a holistic perspective in planning and management processes. To the best of our knowledge, there is a lack of nationwide life cycle assessment (LCA) studies on China's urban water systems that cover all system stages. Therefore, this study aims to present a comprehensive and nationwide LCA analysis that pinpoints the environmental hotspots and their major sources across China. This study was conducted based on water utility databases at the province level, covering water abstraction and treatment, waterwork sludge treatment, water distribution, sewage collection, stormwater drainage, wastewater treatment and sewage sludge treatment. Nine environmental impact categories were calculated and analysed. The results reveal the inequity of environmental impacts across provinces, with overall impacts geographically higher in the east and south, lower in the west and north. However, at the functional unit level, the impacts in the northern and northeastern provinces are higher than other regions. Most environmental categories are dominated by multiple water system stages. The analyses of underlying drivers found that purchased electricity is the primary source of several environmental impacts. This study provides a holistic understanding of the environmental performance of China's urban water systems, offers some insights for comprehensive decision-making support on sustainable water system management, and can also serve as a benchmark for future scenario analysis to explore options for reducing environmental impact.

Life cycle-based multi-objective model for optimal gaseous fuel generation and portfolio allocation in gas grids: A strategic decarbonization

Biomethane and hydrogen are acknowledged as transformative opportunities for decarbonizing the conventional gas grid. Essential to this transformation is the modeling of the gaseous fuel supply chain, particularly with hydrogen and biomethane, offering crucial insights for decision-makers. This study introduces a life cycle thinking-based multi-objective optimization model for the integrated design of biomethane and hydrogen gaseous fuel supply chain networks. The model determines optimal resource allocation for the production of the two fuels, integrating them into the conventional gas network. Moreover, it allocates conventional natural gas, biomethane, and hydrogen optimally across building, industry, and transport sectors, considering the life cycle environmental and economic performance of fuel integration paths. Objective functions include minimization of life cycle emissions and levelized cost of energy while maximizing revenue from fuel sales. Integrating life cycle assessment and cost analysis tools, the optimization model quantifies emissions and life cycle costs for biomethane and hydrogen paths. Results identify Pareto-optimal fuel production paths and portfolios, revealing that integrating the alternative fuels into the current gas grid can significantly reduce emissions (up to 250 tonCO2eq/year) and generate substantial carbon tax savings (up to $16,250/year). This model is useful for gaseous fuel industry stakeholders, offering a comprehensive view of supply chain costs and detailed insights into emission benefits when integrating alternative fuels into existing gas networks.

Benefit-Loss Analysis of Electricity Generation in Indonesia: Life Cycle Assessment and Economic Input-Output Analysis Application

This paper presents a benefit-loss analysis of Indonesia's electricity generation from 2014 to 2018. The loss and benefits are expressed as Disability-Adjusted Life Years (DALY) per capita. In this paper, the benefit is the contribution of value-added triggered by electricity demand to GDP per capita. The value-added is calculated using the economic input-output model. The relationship between GDP per capita with DALY per capita is derived to estimate the reduction in the value of DALY per capita. The loss is the health damage of pollutants produced by electricity generation and is calculated using Life Cycle Assessment. The rise in DALY caused by the pollutants is quantified using Eco-Indicator 99. The results show that the average benefit-loss ratio is 1.257. In Indonesia, the average rate of change of the benefit with respect to electricity consumption per capita is lower than the rate of change of the loss. The analysis also shows a positive relationship between the rate of change of the benefit with the rate of change of electricity price. Promoting renewable energy and improving efficiency are ways to increase the benefit-loss ratio. The results also suggest that increasing the price is a lucrative alternative to increasing the benefit-loss ratio.

Unraveling the Potentials of Extremophiles in Bioextraction of Valuable Metals from Industrial Solid Wastes: An Overview

The continuous dumping of industrial solid wastes into the immediate environment is incommodious since these waste materials cause pollution and serious hazards to human health. In addition, these solid wastes are complex and consist of toxic chemical substances, heavy metals, and valuable metals, hence warranting treatment before disposal. Bioleaching is a green and sustainable technology for the solubilization and mobilization of metals from solid matrices. The leaching efficacy is contingent on the types and physiology of the organisms, the elemental content of the solid wastes, and the presence of appropriate bioprocess parameters at optimum conditions. Extremophilic microbes, including thermophiles, acidophiles, alkaliphiles, and halophiles, are recognized as excellent biological agents for the efficient bioextraction of metals from industrial solid wastes due to their aptitude for survival under harsh bioleaching conditions. Therefore, this review provides insights into the employability of extremophilic microorganisms as a biofactory for the recovery of valuable metals from various industrial solid wastes. More so, it discusses the sustainability of the bioleaching technique in terms of its life cycle assessment (LCA) and techno-economic analysis.

Conceptual design and life-cycle environmental and economic assessment of low-carbon cement manufacturing processes

Cement manufacturing, a fundamental process industry characterized by high CO2 emissions, sees over 58% of its emissions stemming from the limestone calcination process. However, this significant source of CO2 has not yet been adequately addressed by most existing cement decarbonization processes. As such, systematic environmental and economic comparisons between different cement processes are essential. This paper proposes a new cement process (NCP) that uses natural gas to react with limestone to reduce CO2 emissions and simultaneously produce high-value-added chemical products (methanol). To explore strategies for further improving the performance of the CO2 emission reduction, two processes are developed, integrating the organic Rankine cycle (ORC) and carbon capture and storage (CCS) units with the traditional cement process (TCP) and the NCP, namely TCP-ORC-CCS and NCP-ORC-CCS respectively. Life cycle assessment (LCA) and economic analysis were performed on the TCP, NCP, TCP-ORC-CCS, and NCP-ORC-CCS processes, revealing their advantages and limitations in different scenarios. LCA adopts the "cradle to gate" system boundary, which includes the whole cement process from ore mining to clinker generation and other processes used for carbon reduction. The LCA results show that four cement processes exhibit different environmental performances when choosing different allocation methods. Under economic allocation, the global warming potential (GWP) of TCP, NCP, TCP-ORC-CCS, and NCP-ORC-CCS are 933, 300, 432, and 194 kgCO2eq/ton·clinker, respectively. The comprehensive analysis indicates that NCP has the best comprehensive economic and environmental performance when natural gas and methanol prices are 332 and 319 $/ton, respectively. The price fluctuation of natural gas and methanol is found to greatly impact the levelized cost of clinker (LCOC) of NCP through sensitivity analysis. NCP is economically preferred over TCP when the price of methanol (MeOH) is at least $76 above approximately two-thirds of the price of methane (CH4). Similarly, NCP-ORC-CCS is more advantageous than TCP-ORC-CCS when the price of MeOH is at least $87 above nearly two-thirds of the price of CH4. This study provides a comprehensive analysis for low-carbon cement process design to achieve CO2 emissions reduction.