In life cycle assessment (LCA), the same characterization factors are conventionally applied irrespective of when the emissions occur (the same importance is given to emissions in the past, present, ...and future). When the assessment is constrained by fixed timeframes, the appropriateness of this paradigm is questioned and the temporal distribution of emissions becomes of relevance. One typical example is the accounting for biogenic CO2 emissions and removals. This article proposes a methodology for assessing the climate impact of time‐distributed CO2 fluxes using probability distributions. Three selected wood applications, such as fuel, nonstructural panels, and housing construction materials are assessed. In all the cases, CO2 sequestration in growing trees is modeled with an appropriate forest growth function, whereas CO2 emissions from wood oxidation are modeled with different probability distributions, such as the delta function, the uniform distribution, the exponential distribution, and the chi‐square distribution. The combination of these CO2 fluxes with the global carbon cycle provides the respective changes caused in CO2 atmospheric concentration and hence in the radiative forcing. The latter is then used as basis for climate impact metrics. Results demonstrate the utility of using emission and removal functions rather than single pulses, which generally overestimate the climate impact of CO2 emissions, especially in presence of short time horizons. Characterization factors for biogenic CO2 are provided for selected combinations of biomass species, rotation periods, and probability distributions. The time discrepancy between biogenic CO2 emissions and capture through regrowth results in a certain climate impact, even for a system that is carbon neutral over time. For the oxidation rate of wooden products, the use of a chi‐square distribution appears the most reliable and appropriate option under a methodological perspective. The feasibility of its adoption in LCA and emission accounting from harvested wood products deserves further scientific considerations.
Summary
Norway, like many countries, has realized the need to extensively plan its renewable energy future sooner rather than later. Combined heat and power (CHP) through gasification of forest ...residues is one technology that is expected to aid Norway in achieving a desired doubling of bioenergy production by 2020. To assess the environmental impacts to determine the most suitable CHP size, we performed a unit process‐based attributional life cycle assessment (LCA), in which we compared three scales of CHP over ten environmental impact categories—micro (0.1 megawatts electricity MWe), small (1 MWe), and medium (50 MWe) scale. The functional units used were 1 megajoule (MJ) of electricity and 1 MJ of district heating delivered to the end user (two functional units), and therefore, the environmental impacts from distribution of electricity and hot water to the consumer were also considered. This study focuses on a regional perspective situated in middle‐Norway's Nord‐ and Sør‐Trøndelag counties. Overall, the unit‐based environmental impacts between the scales of CHP were quite mixed and within the same magnitude. The results indicated that energy distribution from CHP plant to end user creates from less than 1% to nearly 90% of the total system impacts, depending on impact category and energy product. Also, an optimal small‐scale CHP plant may be the best environmental option. The CHP systems had a global warming potential ranging from 2.4 to 2.8 grams of carbon dioxide equivalent per megajoule of thermal (g CO2‐eq/MJth) district heating and from 8.8 to 10.5 grams carbon dioxide equivalent per megajoule of electricity (g CO2‐eq/MJel) to the end user.
•A water budget model for Canadian agricultural conditions was developed.•The model has minimum input requirements, which are easily available.•It can estimate evapotranspiration, runoff, deep ...percolation, and soil moisture.•Its overall performance was found comparable with other agri-hydrological models.
This study used data collected from three cropland sites (two in Manitoba and one in Prince Edward Island) in Canada.
In efforts to accurately describe the water dynamics in agricultural soils, most of the agri-hydrological models developed are highly complex, such that they require detailed input data, of which most of them are not always measured or otherwise readily available. However, the comprehensive and complex representations of the processes may not be justified when data is scarce. Thus, this study developed a soil water budget model that could describe the movement of water through Canadian agricultural soils using a few parameters only. The model was developed by selecting algorithms from various existing models, whose data requirements are readily available in literature and public Canadian databases.
The model developed in this study can simulate evapotranspiration, runoff, deep percolation, and soil moisture content for various seasons (i.e., growing, non-growing/dormant, and pre-planting/post-harvest) with minimum data requirement, which addresses the limited availability of data in the country for crop and hydrological modeling. Moreover, the model is simple and easy to use, and can work without calibration. It was tested using three site-specific datasets, and results show that despite its simplicity, its overall performance was comparable with those of other agricultural models that use cascade flow framework for hydrology.
There are numerous strategies that can be used to reduce the embodied carbon footprint of real property investments, many of which can be accomplished for no additional cost and with minimal ...performance impacts. This study aims to propose the incorporation of the life cycle carbon quantification into the government procurement of real property process in order to reach out to low-carbon durable and sustainable structures as a theoretical contribution. As a practical contribution, an integrated embodied carbon measurement application is developed in a building information model (BIM) environment to act as a decision making tool in a government office building as a case study. It supports updating procurement policies and procedures to request construction materials with lower embodied carbon in construction. Analysis of concrete assembly groups in the case study along with determination of volume of concrete in each assembly is conducted to devise a reasonable list of elements to be considered for low-carbon concrete compliancy based on an industry average benchmarking approach. Considering the numerous concrete vendors that supply concrete products to a given region, a novel concrete embodied carbon measurement approach is proposed where cradle-to-construction impacts were accounted for. The outcome of the proposed integrated tool showed the procurement of concrete mix design from one specific nearby facility resulted in more efficient GHG reductions and the results showed especially the significance of considering transportation impacts of delivering ready-mixed concrete elements to the project site.
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•A material-specific embodied carbon framework into procurement is proposed.•Two low-carbon material compliancy pathways are recommended.•A BIM-based embodied carbon concrete calculator is developed.•Procurement of concrete mix from nearby facility resulted in more efficient carbon reductions.•Results showed the significance of transportation impacts to the project site.
Summary
Use of biomass‐based electricity and hydrogen in alternative transport could provide environmentally sustainable transport options with possible improvements in greenhouse gas balance. We ...perform a life cycle assessment of electric vehicle (EV) and fuel cell vehicle (FCV) powered by bioelectricity and biohydrogen, respectively, derived from Norwegian boreal forest biomass, considering the nonclimate neutrality of biological carbon dioxide (CO2) emissions and alteration in surface albedo resulting from biomass harvesting—both with and without CO2 capture and storage (CCS)—while benchmarking these options against EVs powered by the average European electricity mix. Results show that with due consideration of the countering effects from global warming potential (GWP) factors for biogenic CO2 emissions and change in radiative forcing of the surface for the studied region, bioenergy‐based EVs and FCVs provide reductions of approximately 30%, as compared to the reference EV powered by the average European electricity mix. With CCS coupled to bioenergy production, the biomass‐based vehicle transport results in a net global warming impact reduction of approximately 110% to 120% (giving negative GWP and creating a climate‐cooling benefit from biomass use). Other environmental impacts vary from −60% to +60%, with freshwater eutrophication showing maximum reductions (40% for the EV case and 60% for the FCV case) and photochemical oxidation showing a maximum increase (60% in the FCV value chain).
The comparability of environmental product declarations (EPDs) and the heterogeneity of their life cycle assessment (LCA) methods are considered the main challenges facing the credibility of results. ...In this study, a probabilistic tool was proposed and developed to gain insight into what is necessary to achieve the unrealized vision of comparable EPDs. The developed framework incorporated several uncertainty sources, such as life cycle inventory and allocation rule choices, and data quality and variability of the input parameters in a consistent way. Then, the framework was applied to a case study of concrete mix designs. The comparative results of the industry benchmarks and the mix design population show that for a given compressive strength level, all the ternary blended cement mixtures have a statistically significant lower GWP than that of the industry-average benchmark. However, a 40 kg CO2eq difference in the comparative GWP results of portland cement and binary mixtures (with an average impact of 345 kg CO2eq) may not result in a statistically significant difference. The major source of variation in the stand-alone LCA results comes from the methodological choice of database selection with portland cement inventory data. However, the impact of methodological choices on the variance of the comparative results is trivial and the variability of portland cement content dominated the variance. Therefore, as long as the LCI database is representative of the context, the methodological choices may be a minor concern in the comparative analysis.
•The inconsistencies among LCA methods for EPD development avoids a fair comparison.•A probabilistic method is proposed to develop EPDs and to compare them consistently.•Methodological choices have the least contribution to the variance in comparative analyses.•Ternary blended mixtures result in a significantly lower impact than benchmarks.
Buildings are responsible for a considerable portion of the embodied and operational CO2 emitted by human activities. Some building attributes have taken on the mantle of “environmentally ...preferable”. Through a systematic literature review, this paper investigates if the literature on whole building Life Cycle Assessments (LCA) confirms some environmental assumptions that are perceived as always truthful, e.g. (i) “wood is better than concrete and steel”, (ii) ”renovation is preferable to demolishing and building anew”, and (iii)“operational loads are more intensive than embodied loads”. The search also allowed to trace if advanced methodological modelling in LCA brings new insights into the mentioned perceptions. The assessment of over 250 case studies pointed that LCAs applied to complex systems, such as a building, embed crucial issues to be modeled, and rules of thumb lose veracity. Furthermore, as LCA incorporates deepened mathematical models, outcomes become less predictable, and paradigms should be interpreted with care.
•In complex systems - such as buildings – environmental paradigms lose veracity.•As sophisticated models are incorporated in LCA, outcomes become less predictable.•Practitioners should add mathematical depth to LCA studies to bring new insights.•Transparency in methodological choices is consistently missing.
Climate change is expected to impact both the operational and structural performance of infrastructures such as roads, bridges, and buildings. However, most past life cycle assessment (LCA) studies ...do not consider how the operational/structural performance of infrastructure will be affected by a changing climate. The goal of this research was to develop a framework for integrating climate change impacts into LCA of infrastructure systems. To illustrate this framework, a flexible pavement case study was considered where life‐cycle environmental impacts were compared across a climate change scenario and several time horizons. The Mechanistic‐Empirical Pavement Design Guide (MEPDG) was utilized to capture the structural performance of each pavement performance scenario and performance distresses were used as inputs into a pavement LCA model that considered construction and maintenance/rehabilitation materials and activities, change in relative surface albedo, and impacts due to traffic. The results from the case study suggest that climate change will likely call for adaptive design requirements in the latter half of this century but in the near‐to‐mid term, the international roughness index (IRI) and total rutting degradation profile was very close to the historical climate run. While the inclusion of mechanistic performance models with climate change data as input introduces new uncertainties to infrastructure‐based LCA, sensitivity analyses runs were performed to better understand a comprehensive range of result outcomes. Through further infrastructure cases the framework could be streamlined to better suit specific infrastructures where only the infrastructure components with the greatest sensitivity to climate change are explicitly modeled using mechanistic‐empirical modeling routines.
AbstractClimate change is expected to impact both the operational and structural performance of infrastructure such as buildings, roads, and bridges. However, infrastructure design guides widely rely ...on historical climate data, if any, for informing design requirements. The goal of this research was to explore a methodology for modeling bridge deck design against corrosion attack in a changing climate. Three deterioration stages were simulated to understand the time to deck failure. Corrosion initiation of reinforcing steel was considered by utilizing a deterministic diffusion-based model predicting the time to reinforcement corrosion initiation. Crack initiation and crack growth were also simulated using mechanistic approaches to illustrate the sensitivity of bridge deck deterioration and design service life to changes in bridge deck design and a changing climate across major cities in Canada. The findings indicate that a changing climate has the potential to significantly alter the service life of a bridge deck, but the effect is strongly dependent on the durability design of the bridge deck. It is recommended that bridge designers strive to utilize mechanistic-empirical models that incorporate high-resolution climate data as inputs for better understanding changes in deterioration as a consequence of a nonstationary climate.
All costs within the life cycle of a building are known as its life cycle cost (LCC). In the design process of a building, the use of a lower initial cost index to select an option among others with ...similar performance may not lead to an economically optimal alternative during the life cycle. Hence, today, building designers and investors require a tool to estimate life cycle cost at the conceptual design stage to select an economically efficient option. Resilient solutions generally lead to a higher level of complexity and upfront costs and carry additional embodied environmental impact as well. This study aims to support the design of resilient buildings using a sound LCC methodology in the preliminary design stage. The research aims to integrate LCC capabilities directly into a Building Information Model (BIM) and increase the economical relevance and scientific robustness of LCC indicators towards better LCC cost optimization. The plugin, which is developed in the BIM tool is represented to use cost and resiliency factors to predict the whole process cost of building projects to assist designers in selecting a cost-efficient and resilient design option. The LCC of a building includes its initial cost, repair and maintenance cost, operating cost and salvage value at the end of the building's useful life, and all of which were considered in the estimation. The earthquake expected failure and human fatality cost are calculated to consider the resiliency index in building design. The application of the proposed framework to design a residential building is developed and validated on two design options. The application of the actual building project illustrates that by increasing the initial cost in the second alternative by 4.6%, its annual expected failure cost is decreased by 35.4%, and its total life-cycle cost is reduced by almost 10.4% within the first 45 years of operation. The reduction in the cost of the building and human fatality due to failure during an earthquake means the building's resilience would be improved. Using the developed plugin, designers could estimate LCC of the buildings at the early design stages and design more resilient buildings with better economic performance in its life cycle according to the proposed indices.
•The research integrates LCC capabilities directly into a BIM.•Resiliency factors are integrated in predicting the whole cost process.•The earthquake expected failure and human fatality cost are calculated for resiliency index.•By increasing the initial cost by 4.6%, its expected failure cost is decreased by 35.4%.•The proposed BIM-LCC approach results in reduction on cost and resilience improvement.
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