Life Cycle Analysis and Temporal Distributions of Emissions: Limitations of Product-Centered Emission Analyses

Abstract Although the product-centered focus of life cycle analysis has been one of its strengths, this analytical perspective embeds assumptions that may conflict with the realities of the problems to which it is applied. This paper demonstrates, through a series of mathematical derivations, that all the products in use, rather than a single product, frequently should be the appropriate unit of analysis. Such a "fleet-centered" approach supplies a richer perspective on the comparative emissions burdens generated by alternative products, as well as eliminating certain simplifying assumptions imposed upon the analyst by a product-centered approach. A sample numerical case, examining the comparative emissions of steel-intensive and aluminum intensive automobiles, is presented to contrast the results of the two approaches. The fleet-centered analysis shows that the "crossover time" (i.e., the time required before the fuel economy benefits of the lighter aluminum vehicle offset the energy-intensity of the processes used to manufacture the aluminum in the first place) can be dramatically longer than that predicted by conventional life cycle analyses. The fleet-centered perspective explicitly introduces the notion of time as a critical element of comparative life cycle analyses and raises important questions about the role of the analyst in selecting the appropriate time horizon for analysis. Moreover, with the introduction of time as an appropriate dimension to life cycle analysis, the influences of effects distributed over time can be more naturally and consistently treated

The impact of surface albedo on climate and building energy consumption: review and comparative analysis

This paper presents a state-of-the-art review of the existing research on the climate impacts of albedo. Different analytical approaches and modeling works are synthesized and discussed.This research was carried out by CSHub@MIT with sponsorship provided by the Portland Cement Association and the Ready Mixed Concrete Research & Education Foundation. CSHub@MIT is solely responsible for content

Air leakage has strong influence on building life cycle impacts

Making informed decisions at the earliest stages of the design process can lead to improved building performance. There are many aspects of a building’s design that can influence overall energy consumption. This research identifies air leakage as influential in determining the life cycle impacts of a residential building. This brief presents results from an analysis using the CSHub’s streamlined building life cycle assessment (LCA) tool, the Building Attribute to Impact Algorithm (BAIA).This research was carried out by the CSHub@MIT with sponsorship provided by the Portland Cement Association and the Ready Mixed Concrete Research & Education Foundation. CSHub@MIT is solely responsible for content

 Evaluation of the Albedo-induced Radiative Forcing and CO2 Equivalence Savings: A Case Study on Reflective Pavements in Four Selected U.S. Urban Areas

There is a growing interest in developing cool pavement strategies to mitigate pavement’s impact on the global warming in recent years. One of the mitigation strategies is by increasing the solar reflectance (or albedo) of the pavement surface, which directly contributes to global cooling by adjusting radiative forcing and potentially reduces the energy demand in the urban areas. In this paper, the radiative energy budgets in four urban areas are investigated based on the data derived from NASA satellite measurements. The radiative forcing (RF) due to the change of urban surface albedo as a result of reflective pavements is estimated using a simplified engineering model. The carbon dioxide (CO2) equivalence savings are also calculated with reference to the 100-year global warming potential of CO2. Results show that the implementation of reflective pavement has a great potential to reduce global warming. The CO2 reduction is significant in the urban areas but also affects the surrounding regions to some extent. In the end, we recommend using a climate model incorporating site-specific information that enables the visualization of the outputs through spatial maps. The results from this work would be useful for guiding the implementation of the cool pavement strategies.CSHub@MIT is conducted with sponsorship provided by the Portland Cement Association and the Ready Mixed Concrete Research & Education Foundation

Fleet-Based LCA: Comparative CO2 Emission Burden of Aluminum and Steel Fleets

No Abstract Provide

How to Improve Pavement Life Cycle Cost Analysis: A Case Study of Minnesota

Life cycle cost analysis (LCCA) frameworks are used by some transportation agencies for economic assessment, but there have been challenges implementing the approach, particularly in the characterization of initial and future costs of materials, as well as their associated uncertainties. This research brief presents a case study which focused on characterizing initial and future pay item costs as a function of project size for a probabilistic LCCA of the entire life cycle including user cost impacts.This research was carried out by the CSHub@MIT with sponsorship provided by the Portland Cement Association and the Ready Mixed Concrete Research & Education Foundation. CSHub@MIT is solely responsible for content

Materials Availability and the Supply Chain: Risks, Effects, and Responses

Supply chain stakeholders should be aware of the stresses that supply chains place on materials use and the vulnerability of the supply base for that material to change. The question of materials availability is an issue that has been addressed many times over the past 200 years by scientists, engineers and economists, and it is an issue with many levels of complexity. This document examines the question of materials vulnerability, or conversely materials availability, from the perspective of a supply chain decision-maker. Specifically, it addresses four elements of this question: (1) Outcomes: What types of changes can be observed in supply chains as a result of limited materials availability? (2) Mechanisms: What can cause supply chains to face limited raw materials availability? (3) Metrics: How can supply chain decision-makers screen for materials availability vulnerability? (4) Strategies: How can supply chains adapt to become more resilient to potential limited materials availability? This paper, through the use of detailed case analyses, suggests that there are specific outcomes – technological, operational, and geographic – which can be expected within supply chains when limitations on materials emerge and that at least two mechanisms can drive limited access to materials. These results are complemented with an examination of metrics to diagnose vulnerability and a preliminary discussion of preventative prescriptions for the supply chain

Accounting for Rehabilitation Activity Uncertainty in a Pavement Life Cycle Assessment using Probability and Decision Tree Analysis

In any life cycle assessment (LCA) for pavements, the designer must decide on which rehabilitation activities will be used to maintain the pavement over the analysis period. While this sounds simple, the fact is that there are many different rehabilitation scenarios that could be performed when the pavement requires rehabilitation, and which one is used will impact the LCA results. This creates inherent uncertainty and variability in the LCA results solely due to the selection of the rehabilitation scenario used in the analysis. Currently, most LCA’s apply a single standard rehabilitation scenario to all pavements. The problem with this approach is that because each project is unique, the activities may or may not be representative of the actual set of activities done on that particular pavement. The only way to get meaningful indication of a project’s pavement environmental impact is to look at the impact of all (or at least most) of the potential rehabilitation activities that could be used to maintain the pavement over the analysis period. This paper shows how State Highway Agencies (SHAs) can use probability and decision tree analysis to evaluate many rehabilitation scenarios in order to determine a range of LCA results, as well as a probability adjusted, expected value LCA result. This process quantifies the underlying uncertainty that different the rehabilitation selection can have on the LCA results so that a more informed decision can be made when comparing the alternate pavement designs. A case study based on alternative designs and rehabilitation scenarios used by a SHA demonstrates the decision tree analysis process and shows how the risk profiles for the two alternatives considered are not equivalent. For this case, this results in the probability-adjusted LCA results being different than the single standard rehabilitation scenario results.CSHub@MIT research is carried out with sponsorship provided by the Portland Cement Association and the Ready Mixed Concrete Research & Education Foundation