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Life-Cycle Energy Analysis

Life Cycle Assessment (LCA) is the systematic analysis of the environmental impact of products during their entire life cycle.

The life cycle of a product comprises its production, use and disposal. Environmental impacts are evaluated throughout, also including the upstream processes (e.g. production of raw, auxiliary and operating materials) and downstream processes (e.g. waste treatment) associated with the production and disposal of that product. Environmental impacts refer to all relevant extractions from the environment (e.g. ores and crude oil), as well as emissions into the same (e.g. wastes and carbon dioxide).

This tutorial describes the use of LCA as a tool that can give us some understanding of the environmental impact of specific commodities and services in the context of our overall environmental impact as individuals and as a society.

This lesson is based on and contains excerpts from Sandy Smith's Life Cycle Assessment - An Introduction, the UNEP's Towards a Life Cycle Sustainability Assessment: Making informed choices on products, and thinkstep's What is the Life Cycle Assessment (LCA) Methodology?, which you may want to consult for more details.

History

The concepts that later became (environmental) LCA first emerged in the 1960s (Baumann et al 2004). Until the early 1990s, studies that undertook an assessment of the material, energy and waste flows of a product's life cycle were conducted under a variety of names:

• Resource and environmental profile analysis (REPA)
• Eco-Balancing
• Integral environmental analyses
• Environmental profiles
• Cradle-to-Grave assessments

In 1990, the Society of Environmental Toxicology and Chemistry (SETAC) hosted workshops with the aim of developing a standardized method of (environmental) LCA. In 1995, the International Standards Organization (ISO) began to use that work as the basis for the ISO 14040 series of standards for conducting LCAs. Those standards underwent a significant revision in 2006.

The presence of international standards means that if an LCA is conducted in accordance with ISO 14040, you can have some understanding of how that LCA was conducted and whether it can be compared to other LCAs.

Objectives For Undertaking an LCA

Within a company, an LCA can be used to:

• Identify problem areas in production processes
• Compare products in the development stage
• Aid in short-term product/process design
• Aid in long-term product/process strategies
• Educate employes

Facing the general public, a company can use the results of an LCA for:

• Marketing
• Eco-labelling
• Certification
• Lobbying
• Information and education

Phases of an LCA

ISO-14040 (2006) defines four phases to an LCA:

Levi Strauss's LCA for a pair of jeans is used as an example in describing these phases.

Phase I: Goal and Scope Definition

• Define why this LCA is being conducted: Levi Strauss stated, The goal is that these findings will help LS&Co. and others in the apparel sector take more effective and holistic approaches to our industry's environmental impact. Another goal implied by the glossy presentation graphics is to market an image of an environmentally-responsible company
• Define who the audience(s) are going to be for the results: The writing is generally in plain, non-technical English, implying that the audience is the general public
• Define how the results will be communicated to that audience: An executive summary presentation PDF is prominantly linked on their sustainability web page. A technical document presumably exists internally
• Define the functional unit: The specific product (functional unit) being analyzed in the presentation is a pair of Levi's 501 (tm) jeans
• Define the system boundaries: How deep into the production process will the analysis probe?

  

• Define impact categories: What specific environmental effects will be assessed?

  

• Define other technical details: Assumptions and the (de)limitations of the study. Methods of allocating impacts when created by more than one product or function, etc

Phase II: Inventory of Resources and Emissions

All emissions released into the environment and resources extracted from the environment along the whole life cycle of a product are grouped in an inventory. This phase can be quite complicated and expensive, especially with products that have long supply chains and complex composition.

Phase III: Translate Results into Environmental Impacts

The inventory results or are translated, with the help of an impact assessment method, into environmental impacts. Impacts may be assessed at the midpoint or endpoint level.

Two standard impact assessment methods include Eco-indicator 95 and Eco-indicator 99. Eco-indicator 95 focuses on midpoint impact categories such as climate change or human toxicity, thereby organizing the information to allow for a further processing and meaningful interpretation. Eco-indicator 99 focuses on endpoint impact (damage) categories like human health, ecosystem quality, and resources.

Although it is not clear if Levi Strauss used EI 95, the impact categories listed above are midpoints rather than endpoints.

Phase 4: Interpretation

Interpretation should generate a set of conclusions and recommendations. It should also (according to ISO 14040) raise significant environmental issues, including an evaluation of the study considering completeness, sensitivity and consistency checks; and limitations.

The Levi Strauss report describes the LCA results both in quantitative terms and in relatively plain English. Numbers are given context - such as describing the CO₂ emissions for each pair of jeans as equivalent to 69 miles driven by the average US car. They also note that one third of the CO₂ associated with jeans over their lifetime comes from care by the owner, with the suggestion that this can be reduced by washing the jeans less frequently.

ISO 14040 mandates critical review by a panel of experts for results that are made public. On page 7 of the Levi Strauss presentation, there is a note that, STUDY CONDUCTED BY: Industrial Ecology Consultants and LS&Co. PANEL REVIEWED: Conforms with ISO 14040 and 14044 standards

Energy Interpretation

This class focuses on energy and, unfortunately, the Levi Strauss LCA does not report energy directly. However, it does report that each pair of jeans represents 33.4 kg CO₂-e (CO₂ equivalent), which can be used to estimate energy.

Conversion factors:

• Carbon Dioxide Emissions Coefficient of 71 kg CO₂ per million BTU
• Per-capita annual energy use in the US in 2014 was around 300 million BTU
• US consumers buy around 450 million pairs of jeans a year
• American total energy use in 2014 was around 98 quads
• Each American is responsible for around 19,800 kg CO₂ per year

33.4 kg/CO2 / 71 kg CO2 per million BTU
= 0.47 million BTU per pair of jeans

0.47 million BTU / 300 million BTU per American
= 0.15% of an average American's annual energy footprint


0.47 million BTU * 450 million pairs of jeans 
= 211 trillion BTU

211 trillion BTU / 98 quadrillion BTU US per year 
= 0.2% of total US energy use


33.4 kg/CO2 / 19,800 kg CO2 per American
= 0.17% of average American's annual carbon footprint

So, jeans by themselves do not represent a significant contributor to your energy or carbon footprints. And since you should probably wear something on your legs in the winter, they're probably as good as anything else, although you may consider to wearing them longer and washing them less frequently.

If you see a report that does list energy in megajoules (the metric/scientific unit), one megajoule (MJ) is 948 BTU. For example, a lawnmower engine over its lifetime requires 5,500 MJ:

5500 MJ * 948 BTU/MJ = 5.2 million BTU

5.2 million BTU / 300 million BTU per American
= 1.7% avg. American's annual energy use

That is a bit more significant than a pair of jeans, but you should probably still mow your grass.

Other LCA Examples

• Apple Computer Products
• Lawn Mower Engines
• National Geographic Print Magazine

Limitations of LCA

Smith points out some limitations and critiques of LCA:

• LCA is not a triple bottom line approach: the focus is primarily on environmental effects and does not consider economic or social issues
• Time: A LCA takes a long time to execute. Accordingly, it is just a snapshot and any changes in production processes or conditions during the preparation of the LCA will not be part of the findings
• Subjectivity: Despite the rigorous quantification implied by the numbers, there are numerous points in the analysis (notably in choosing the boundaries of what will be analyzed or apportioning effects across multiple products) where subjective value judgements must be made by the researchers. These can be benign or intentional (if a company wants to make their results look better than they are)
• Nonlocality: Contemporary products often have global supply chains, so significant local environmental impacts can be diluted by the implicit distribution of those effects as small when considered in a global context
• Difficult to Communicate: The results of environmental (midpoint) LCA are in units and substances that most laymen do not understand (how many people really know what a Joule is?) As with climate change research, translating that esoteric data into meaningful public information is problematic and fraught with opportunities for misunderstanding.
• Data Quality: Data from the supply chain may require significant additional labor from mangers, with opportunities for neglectful or intentional misreporting.

Arnold (1993) provides a lengthy and detailed critique of LCA.

Strengths of LCA

• Provides a holistic, big-picture view
• Adds some level of rigor that can manage subjective judgements and provide clear rationale when difficult decisions need to be made
• Offers specific information that can guide producers and consumers in making rational choices
• Each LCA helps advance the state of the art