The development of biofuels has been considered as an important countermeasure to abate anthropogenic CO2 emissions, suppress deteriorated atmospheric greenhouse effect, and mitigate global warming. ...To produce biofuels from biomass, thermochemical conversion processes are considered as the most efficient routes wherein torrefaction has the lowest global warming potential. Combustion is the easiest way to consume biomass, which can be burned alone or co-fired with coal to generate heat and power. However, solid biomass fuels are not commonly applied in the industry due to their characteristics of hygroscopic nature and high moisture content, low bulk density and calorific value, poor grindability, low compositional homogeneity, and lower resistance against biological degradation. In recently developing biomass conversion technologies, torrefaction has attracted much attention since it can effectively upgrade solid biomass and produce coal-like fuel. Torrefaction is categorized into dry and wet torrefaction; the former can further be split into non-oxidative and oxidative torrefaction. Despite numerous methods developed, non-oxidative torrefaction, normally termed torrefaction, has a higher potential for practical applications and commercialization when compared to other methods. To provide a comprehensive review of the progress in biomass torrefaction technologies, this study aims to perform an in-depth literature survey of torrefaction principles, processes, systems, and to identify a current trend in practical torrefaction development and environmental performance. Moreover, the encountered challenges and perspectives from torrefaction development are underlined. This state-of-the-art review is conducive to the production and applications of biochar for resource utilization and environmental sustainability. To date, several kinds of reactors have been developed, while there is still no obviously preferred one as they simultaneously have pros and cons. Integrating torrefaction with other processes such as co-firing, gasification, pyrolysis, and ironmaking, etc., makes it more efficient and economically feasible in contrast to using a single process. By virtue of capturing carbon dioxide during the growth stage of biomass, negative carbon emissions can even be achieved from torrefied biomass.
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•Systematic analysis of 650+ building LCA cases on life cycle greenhouse gas emissions.•Buildings life cycle GHG emissions are reducing due to energy efficiency ...improvements.•Meanwhile, embodied GHG emissions increased and are now dominating the life cycle.•New building upfront GHG investments dominate timeframe for climate change mitigation.•Improvements are needed to meet net-zero life cycle targets and avoid lock-in effects.
Buildings are major sources of greenhouse gas (GHG) emissions and contributors to the climate crisis. To meet climate-change mitigation needs, one must go beyond operational energy consumption and related GHG emissions of buildings and address their full life cycle. This study investigates the global trends of GHG emissions arising across the life cycle of buildings by systematically compiling and analysing more than 650 life cycle assessment (LCA) case studies. The results, presented for different energy performance classes based on a final sample of 238 cases, show a clear reduction trend in life cycle GHG emissions due to improved operational energy performance. However, the analysis reveals an increase in relative and absolute contributions of so‐called ‘embodied’ GHG emissions, i.e., emissions arising from manufacturing and processing of building materials. While the average share of embodied GHG emissions from buildings following current energy performance regulations is approximately 20–25% of life cycle GHG emissions, this figure escalates to 45–50% for highly energy-efficient buildings and surpasses 90% in extreme cases. Furthermore, this study analyses GHG emissions at time of occurrence, highlighting the ‘carbon spike’ from building production. Relating the results to existing benchmarks for buildings’ GHG emissions in the Swiss SIA energy efficiency path shows that most cases exceed the target of 11.0 kgCO2eq/m2a. Considering global GHG reduction targets, these results emphasize the urgent need to reduce GHG emissions of buildings by optimizing both operational and embodied impacts. The analysis further confirmed a need for improving transparency and comparability of LCA studies.
Green economic development has become a new strategy for large countries to contend with the energy crises and environmental pollution. Bamboo is a kind of sustainable resource with a fast growth ...rate and strong carbon fixation capacity which can be used to make various eco-friendly products. Bamboo fiber (BF) tableware is a product which is developed to replace non-degradable plastic food packaging products. The study takes the life cycle assessment (LCA) of green BF tableware production in Wanxian, Chongqing city, China, as an example and compares with the polypropylene (PP) tableware standard database to investigate the impact of production, transportation, waste and disposal methods on resources, the environment, and human health. The results showed that the environmental coordination of bamboo fiber tableware (BF) was better than PP tableware. The environmental impact of the 2 kinds of tableware mainly occurred in the raw material acquisition and product transportation stages, and the main impact was human health damage. A comparative study of different disposal options after waste showed that the benefits of both types of tableware were in the order of recycling > incineration > landfill. Independent of the disposal ratio, the benefits of BF tableware are positive. In contrast, PP tableware positively impacts the overall environment only when waste recycling reaches more than 30 %. On this basis, ecological design suggestions for 2 kinds of tableware are presented.
•The environmental coordination of bamboo fiber tableware is better than PP.•Raw material and product transportation are the main sources of impact.•The maximum life cycle impact assessment for both tableware is the health impact.•The benefits of the 2 types of tableware were recycling > incineration > landfill.
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•Discussion of 3D to 4D transition and its associated processes for printing.•Decoded the world of shape memory effect in materials for 4D Printing.•Potential of stimuli in 4D ...printing have been reviewed.•Parametric evaluation of materials for 4D Printing and its influences on final properties.
The idea of 3D printing ever since 1980’s has agitated the research domains challenging the conventional techniques with its inordinate efficiency in the utility of material, superior surface resolution and single step production which are applied in biomedical, electronics, self-healing and most prominently in biomimetic applications. However, this additive technique could not be controlled to produce intricate structure, to suppress strain controlled dimensional change, and anisotropic behavior. This complexity and inflexible design that had barricaded their dimension were vanquished by 4D printing with its dynamic structures. The fourth dimension conferred vitality to the design using stimulus to drive the transformation in smart materials (Shape Memory Effect or SME). Smart materials are environmentally sensitive materials comprising of polymers, alloys, hydrogels, ceramics and composites, activated by heat (pre-strain), water (absorption), electromagnetic radiations (Infrared, IR), magnetic field, ohmic parameters (current and voltage), solvent and pH. 4D printing attempts to counterfeit natural processes (flower blooming, leaf cirrus (tendrils), and sunflower movement) in drug delivery, wearable electronics, fashion wares, self-transmuting origami structures, sensors and other engineering applications. This review engulfs the evolution, burgeoning advancements and life cycle prediction of 4D printing with focusing on the smart materials and associated features like stimuli response along with future scope and challenges.
The increasing pressure to reduce greenhouse gas emissions from buildings has motivated specialists to develop low-carbon products incorporating bio-based materials. The impact of these materials is ...often evaluated through life-cycle assessment (LCA), but there is no clear consensus on how to model the biogenic carbon released or absorbed during their life-cycle. This study investigates and compares existing methods used for biogenic carbon assessment. The most common approaches were identified through an extensive literature review. The possible discrepancies between the results obtained when adopting different methods are made evident through an LCA study of a timber building. Results identified that land-use and land-use-change (LULUC) impacts and carbon-storage credits are not included in most existing methods. In addition, when limiting the system boundary to certain life-cycle stages, methods using the –1/+1 criterion can lead to net negative results for the global warming (GW) score, failing to provide accurate data to inform decision-making. Deviation between the results obtained from different methods was 16% at the building scale and between 35% and 200% at the component scale. Of all the methods studied, the dynamic approach of evaluating biogenic carbon uptake is the most robust and transparent. 'Practice relevance' This critical review identified key methodological differences between the most commonly used methods and recommended standards for biogenic carbon accounting in buildings. This indicates a lack of consensus and guidance for conducting LCAs of bio-based construction products and buildings using bio-based materials. A case study applying four different LCA approaches on a timber building identified the inability to compare results and create proper benchmarks. Moreover, different methods lead designers to pursue different strategies to reduce a building’s carbon footprint. Regulators, the construction industry and the construction products industry are directly affected by this lack of comparability. This research highlights the flaws and benefits of commonly used methods. A clear and grounded recommendation is for practitioners to adopt dynamic biogenic carbon accounting for future assessments of bio-based materials and buildings.
Lignocellulosic biomass is a promising feedstock for sustainable biofuels and bioproducts. Among emerging bioproducts, lactic acid has attracted significant interest because of its growing ...application in many industries (e.g., packaging, medical, and pharmaceutical). In this study, BioSTEAMan open-source platformwas leveraged for the design, simulation, and evaluation (via techno-economic analysis, TEA, and life cycle assessment, LCA) of lignocellulosic lactic acid biorefineries. With a minimum product selling price (MPSP) between $1.38 and 1.91 kg–1 (5th–95th percentiles, baseline at $1.57 kg–1), the biorefinery was capable of producing market-competitive lactic acid (market price between $1.7 and 2.1 kg–1), and its performance could be further enhanced (e.g., MPSP down to $1.09 kg–1, global warming potential of 2.79 kg CO2-eq·kg–1, and fossil energy consumption of 31.7 MJ·kg–1) with advancements in key technological parameters (fermentation yield and separation process conversions) and optimization in process operation. Sensitivity analyses focused on the fermentation unit (across titer, yield, and productivity; neutral vs low-pH fermentation) and feedstock characteristics (carbohydrate content and price) were also included to quantify their impact on the sustainability of the biorefinery. Overall, this research highlights the ability of agile TEA/LCA to screen promising biorefinery designs, prioritize research needs, and establish a road map for the continued development of bioproducts and biofuels.
•The paper provides a detailed inventory for a PEM water electrolyser system.•An energy model was built to analyse the future energy mixes required by the system.•LCIA results prove the relevance of ...the electricity mix for most impact categories.•By 2050, the analysed system has less impact compared to the reference system.
This study discusses the potential of H2 production by proton exchange membrane water electrolysis as an effective option to reduce greenhouse gas emissions in the hydrogen sector. To address this topic, a life cycle assessment is conducted to compare proton exchange membrane water electrolysis versus the reference process - steam methane reforming. As a relevant result we show that hydrogen production via proton exchange membrane water electrolysis is a promising technology to reduce CO2 emissions of the hydrogen sector by up to 75%, if the electrolysis system runs exclusively on electricity generated from renewable energy sources. In a future (2050) base-load operation mode emissions are comparable to the reference system. The results for the global warming potential show a strong reduction of greenhouse gas emissions by 2050. The thoroughly and in-depth modeled components of the electrolyser have negligible influence on impact categories; thus, emissions are mainly determined by the electricity mix. With 2017 electricity mix of Germany, the global warming potential corresponds to 29.5 kg CO2 eq. for each kg of produced hydrogen. Referring to the electricity mix we received from an energy model emissions can be reduced to 11.5 kg CO2 eq. in base-load operation by the year 2050. Using only the 3000 h of excess power from renewables in a year will allow for the reduction of the global warming potential to 3.3 kg CO2 eq. From this result we see that an environmentally friendly electricity mix is crucial for reducing the global warming impact of electrolytic hydrogen.
The sustainable utilization of biochar produced from biomass waste could substantially promote the development of carbon neutrality and a circular economy. Due to their cost-effectiveness, multiple ...functionalities, tailorable porous structure, and thermal stability, biochar-based catalysts play a vital role in sustainable biorefineries and environmental protection, contributing to a positive, planet-level impact. This review provides an overview of emerging synthesis routes for multifunctional biochar-based catalysts. It discusses recent advances in biorefinery and pollutant degradation in air, soil, and water, providing deeper and more comprehensive information of the catalysts, such as physicochemical properties and surface chemistry. The catalytic performance and deactivation mechanisms under different catalytic systems were critically reviewed, providing new insights into developing efficient and practical biochar-based catalysts for large-scale use in various applications. Machine learning (ML)-based predictions and inverse design have addressed the innovation of biochar-based catalysts with high-performance applications, as ML efficiently predicts the properties and performance of biochar, interprets the underlying mechanisms and complicated relationships, and guides biochar synthesis. Finally, environmental benefit and economic feasibility assessments are proposed for science-based guidelines for industries and policymakers. With concerted effort, upgrading biomass waste into high-performance catalysts for biorefinery and environmental protection could reduce environmental pollution, increase energy safety, and achieve sustainable biomass management, all of which are beneficial for attaining several of the United Nations Sustainable Development Goals (UN SDGs) and Environmental, Social and Governance (ESG).
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•Synthesis strategies and unique properties of biochar-based catalysts are reviewed.•Recent advances and challenges in catalytic applications of biochar are addressed.•Machine-learning approaches accelerate practical catalytic applications of biochar.•Environmental impacts and economic feasibility of biochar-based catalytic applications are emphasized.•Biochar-based catalytic applications support several UN Sustainable Development Goals.
•Recent updates in recycling carbon fibre reinforced composites are reviewed.•Mechanical, thermal and chemical methods along with influential parameters are discussed.•The methods of manufacturing ...yarns and nonwovens from dry carbon fibre scraps are reviewed.•The environmental impacts of processing CFRC wastes are discussed.
Carbon fibre reinforced composites (CFRC) continue to play a key role in the growth and development of many weight sensitive industries. However, their proliferation has raised increasing concerns regarding the required practices and strategies to deal with these expensive engineered structures at the end of their life cycle. This has brought into focus the need to develop more sustainable and efficient recycling solutions for these products. Similarly, the necessity of managing dry carbon fibre scraps generated during the manufacturing process of CFRC has attracted more attention in recent years. This review article provides an overview on recent advances in recycling CFRC as well as processing dry carbon fibre scraps. Influential parameters, advantages, drawbacks, and possible environmental impacts of the main technologies of processing CFRC waste including mechanical, thermal (pyrolysis and fluidised bed), and chemical (solvolysis and low temperature chemical processing) will be evaluated. Their potential effects on mechanical characteristics and surface chemistry of fibres are assessed. Moreover, recent processing methods of dry and semi-finished carbon fibre scrap are also reviewed. Specific attention is paid to the recent developments in producing hybrid yarns and nonwovens made of waste carbon fibre. The methodologies developed in this area, their processing conditions, as well as other important findings are discussed. This review paper provides a valuable platform for researchers and decision makers working in the field of carbon fibre by providing a clearer picture on the options available to recycle CFRC, and the methods of developing value-added products using waste carbon fibre.
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