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 relevanceThis 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.
Life cycle assessment (LCA) and environmentally extended input–output analyses (EEIOA) are two techniques commonly used to assess environmental impacts of an activity/product. Their strengths and ...weaknesses are complementary, and they are thus regularly combined to obtain hybrid LCAs. A number of approaches in hybrid LCA exist, which leads to different results. One of the differences is the method used to ensure that mixed LCA and EEIOA data do not overlap, which is referred to as correction for double counting. This aspect of hybrid LCA is often ignored in reports of hybrid assessments and no comprehensive study has been carried out on it. This article strives to list, compare, and analyze the different existing methods for the correction of double counting. We first harmonize the definitions of the existing correction methods and express them in a common notation, before introducing a streamlined variant. We then compare their respective assumptions and limitations. We discuss the loss of specific information regarding the studied activity/product and the loss of coherent financial representation caused by some of the correction methods. This analysis clarifies which techniques are most applicable to different tasks, from hybridizing individual LCA processes to integrating complete databases. We finally conclude by giving recommendations for future hybrid analyses.
Abstract
This study presents a simple and agile yet holistic comparative assessment of the impact, in terms of non-renewable cumulative energy demand (nrCED) and global warming potential (GWP), of ...two envisioned scenarios for the future of an existing administrative building located in Fribourg, Switzerland: its demolition and reconstruction versus its in-depth renovation. Based on our set of hypotheses, results show that over all life-cycle phases (construction and operation) and the building’s lifetime, the renovation scenario’s GWP is 540 kgCO
2
-eq/m
2
lower than that of the reconstruction scenario, corresponding to a 50% savings. In terms of nrCED, the difference is of about 2 MWh/m
2
, a 45% savings in the renovation scenario. Both scenarios are found to comply with the SIA 2040 target values. These results, including findings on the most impactful elements, provide useful quantitative information for the decision-making and design team in their next steps toward defining the project.
•Operative parameters of HTL substantially influence the property and yield of bio-crude.•HTL produced a higher viscosity bio-crude than pyrolysis.•Apart from the temperature, pressure, biomass to ...solvent ratio altered the bio-crude yield.•Bio-crude generated by HTL scores over pyrolysis except for higher sulphur, yield, and viscosity.•TEA and LCA established variations in yield and properties of fuels with varying operating conditions.
An in-depth, comprehensive, and critical review of the hydrothermal liquefaction (HTL) technology for maximum yield of biocrude with enhanced properties has been undertaken. The feedstocks, process parameters, kinetic of HTL for bio-crude production have been systematically examined and collated from a board range of research. In the coverage of Techno-Economic Analysis (TEA) and Life Cycle Assessment (LCA) of HTL of feedstocks, this review overcomes the failure of existing literature to give due weightage to those crucial issues. HTL is introduced by the direct use of wet biomass that eliminates the drying unit, reduction in total expenditure, and conversion of materials into solid and liquid fuels at moderate temperatures (250–400 °C) and pressures (10–35 MPa). The introduction of hot pressurized water results in a lower yield of tar with higher energy proficiency. The biomass is delineated via elemental composition, renewable feedstock potential, and evaluation of dry versus wet biomass feedstocks. HTL is comprehensively reviewed through the process mechanisms, depolymerization reactions of biomass, hydrothermal liquefaction process of dry and wet lignocellulose feedstocks, and the effect of operating parameters. The product(s) description and evaluation, process advancements, energy efficiency, and kinetic investigation in relation to HTL form the final parts of this review. This review is aimed at optimization and commercialization of the HTL technology to meet the demands of the biofuel sector, the researcher working in the thermochemical conversion of feedstocks, and the development of new HTL reactors.
•Mortars sustainability was reviewed through a life cycle assessment (LCA) approach.•Results normalization improved the feasibility to compare diverse LCA studies.•Global warming potential category ...is strongly affected during mortars production.•Conventional binders’ replacement by secondary resources alleviates mortars impacts.
The in-depth research on efficient processes and alternative constituents for mortars production has a lack on the quantification of their environmental impacts. This work presents a critical review of life cycle assessment (LCA) studies performed in the construction sector, namely related to mortars. The gaps and barriers of these methods and final results are discussed through an overview of the main achievements on mortars’ environmental life cycle studies in Europe. Despite the future trends, LCA studies are more focused on cement-mortars and few researches on air lime, gypsum or earth mortar binders are reported in the literature.
Summary
The challenge of assessing emerging technologies with life cycle assessment (LCA) has been increasingly discussed in the LCA field. In this article, we propose a definition of prospective ...LCA: An LCA is prospective when the (emerging) technology studied is in an early phase of development (e.g., small‐scale production), but the technology is modeled at a future, more‐developed phase (e.g., large‐scale production). Methodological choices in prospective LCA must be adapted to reflect this goal of assessing environmental impacts of emerging technologies, which deviates from the typical goals of conventional LCA studies. The aim of the article is to provide a number of recommendations for how to conduct such prospective assessments in a relevant manner. The recommendations are based on a detailed review of selected prospective LCA case studies, mainly from the areas of nanomaterials, biomaterials, and energy technologies. We find that it is important to include technology alternatives that are relevant for the future in prospective LCA studies. Predictive scenarios and scenario ranges are two general approaches to prospective inventory modeling of both foreground and background systems. Many different data sources are available for prospective modeling of the foreground system: scientific articles; patents; expert interviews; unpublished experimental data; and process modeling. However, we caution against temporal mismatches between foreground and background systems, and recommend that foreground and background system impacts be reported separately in order to increase the usefulness of the results in other prospective studies.
•Environmental externalities are crucial to sustainability assessments.•Economical plus monetised LCA impacts provides an estimate of true cost of hydrogen.•Ten hydrogen production technologies were ...assessed and compared on monetary basis.•At present, steam methane reforming with CCS emerged as the most promising option.
Hydrogen has been identified as a potential energy vector to decarbonise the transport and chemical sectors and achieve global greenhouse gas reduction targets. Despite ongoing efforts, hydrogen technologies are often assessed focusing on their global warming potential while overlooking other impacts, or at most including additional metrics that are not easily interpretable. Herein, a wide range of alternative technologies have been assessed to determine the total cost of hydrogen production by coupling life-cycle assessments with an economic evaluation of the environmental externalities of production. By including monetised values of environmental impacts on human health, ecosystem quality, and resources on top of the levelised cost of hydrogen production, an estimation of the “real” total cost of hydrogen was obtained to transparently rank the alternative technologies. The study herein covers steam methane reforming (SMR), coal and biomass gasification, methane pyrolysis, and electrolysis from renewable and nuclear technologies. Monetised externalities are found to represent a significant percentage of the total cost, ultimately altering the standard ranking of technologies. SMR coupled with carbon capture and storage emerges as the cheapest option, followed by methane pyrolysis, and water electrolysis from wind and nuclear. The obtained results identify the “real” ranges for the cost of hydrogen compared to SMR (business as usual) by including environmental externalities, thereby helping to pinpoint critical barriers for emerging and competing technologies to SMR.
Debates remain on the influencing factor and long-term performance of C-S-H-seeded paste. In this study, phase-pure seeds were prepared from diluted Ca3SiO5 hydration. The seed structures were ...determined using synchrotron-based X-ray diffraction, X-ray absorption spectroscopy, and transmission electron microscopy. Nano-foils and similar Ca and O environments were present in seeds of different Ca/Si; nanofibers were present in high-Ca seeds only which showed lower silicate polymerization. Calorimetry and setting results showed a greater hydration acceleration with high-Ca seeds; seed shape dominated the acceleration. 0.5 wt% high-Ca seeds increased 1- and 28-days paste strength by 300% and 20%, respectively. Life-cycle assessment showed negligible (<1%) influence of seeds on energy demand and CO2 emissions of the paste production. The CO2-intensity normalized by strength of seeded pastes decreases by ~25% at 28 days. This study sheds light on the use of C-S-H seeds from waste concrete and wash water, as a means of lowering cement demand.
This paper reports the composition and properties of highly flowable self-consolidating concrete (SCC) mixtures made of high proportions of cement replacement materials such as fly ash and pulverized ...limestone instead of high dosage of a plasticizing agent or viscosity-modifying chemical admixtures. Self-consolidating concrete mixtures are being increasingly used for the construction of highly reinforced complex concrete elements and for massive concrete structures such as dams and thick foundation. In this study, by varying the proportion of portland cement (OPC), Class F-fly ash (F), and limestone powder (L), SCC mixtures with different strength values were produced, and the properties of both fresh and hardened concrete were determined. For a comprehensive analysis and quantification of emissions and global warming potential (GWP) from concrete production, life-cycle assessment (LCA) was employed. We find that high volume, up to 55% by weight replacement of OPC with F, or F and L produces highly workable concrete that has high 28-day and 365-day strength, and extremely high to very high resistance to chloride penetration along with low GWP for concrete production.
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