Five Percent: Conserve Energy

Climate Change Is Important: Energy Conservation is the First Step


April 19, 2009

Life Cycle Assesment: Use Carefully

Category: Climate Change,Sustainability – Tom Harrison – 2:29 pm

Life Cycle Assessment (LCA) is a method of evaluating the entire cost of a given product, from cradle to grave. It’s a very, very important aspect of understanding our consumer society and it’s impact on the earth. It’s also a very highly technical process and one that is susceptible to error; it’s quite easy to miss some subtleties and get the whole thing wrong. The New York Times printed an article about life cycle assessment today, and I think the authors may have done more harm than good.

To be fair, the article appears to be accurate. Its authors discuss the trade-off between a reusable stainless steel water bottle and a single-use plastic bottle. They explain, in a large graphic, how the process of making stainless steel impacts the environment and incurs costs in energy, transportation, toxins, and so on. One could read the article and conclude that a reusable cup is a bad choice, especially after reading statements like

One stainless steel bottle is obviously much worse than one plastic bottle.

This is a true statement, and is only qualified in a sort of vague way, namely that while there are costs, they are mitigated over time as the mug is re-used. They present this data as:

…if your stainless steel bottle takes the place of 50 plastic bottles, the climate is better off, and if it gets used 500 times, it beats plastic in all the environment-impact categories studied in a life cycle assessment.

Read this statement carefully. First, we’re talking about a thermos-style stainless steel bottle; this is surely a worst-case scenario (I have had a plastic cup I drink water from and have been several times daily for three or four years now). Second, the latter clause of the sentence suggested to me that “it would take 500 uses to make it’s value break even”, but I am not sure that’s what it really says. It could mean that in one of the categories, the break-even point is 500 uses, but not in all of the others. And, while 500 may sound like a big number, two drinks a day makes the worst-case payoff happen in a year or so.

LCA is tightly aligned with sustainability. A sustainable process or material is one whose total LCA cost creates no additional load on the planet’s resources (a more nuanced definition is here). Sustainability is a highly desirable goal, as one would rightly conclude that until we reach it, we are, in effect, “using up” the earth. The degree to which we’re using up the earth at present rate as beyond imagination, so getting to sustainability must be a major goal of almost anything we do.

But my issues with this presentation are not in disagreeing with LCA or sustainability (on the contrary), but recognizing how best to present the issues to the lay public. For example:

  • People may read such articles without the rigor demanded by the topic, and conclude wrongly that a plastic bottle is fine, or at least the better choice.
  • Sustainability is a goal; the question should be “how do we get there” rather than whether any given change is itself sustainable, at least for most people.
  • While the final paragraph of the story presents a good option (a water fountain), this is only one of many, such as my plastic cup, a bike bottle, a hiking bottle, or even re-using the plastic bottle intended for single-use. If this article results in people going back to plastic bottles, or saying “see, all this environmentalist crap was wrong all along” we’re not getting to sustainability.
  • Getting to sustainability requires rather significant changes to our wasteful habits, and changing habits requires awareness, and a touch of discipline. People don’t like change, and look for reasons to avoid it; we need to present facts in a way sensitive to this.

I a glad to see discussions of important topics like this in the Times, and I don’t want to suggest that all articles need to be aimed at the casual reader or dumbed down in any way. The overall point is that you do have to consider the bigger picture using LCA. But I think that misses the bigger bigger picture: per-item LCA is beyond the scope of almost everyone, even the professionals who do the sophisticated measurements to draw numerically reasonable conclusions.

It’s important to recognize the limitations of the science, and in particular that such narrow examples are unlikely to have much merit; LCA makes sense when the results are aggregated, but are increasingly susceptible to error as the use case gets more narrow.

For this important topic, professionals should recognize their responsibility to help lay-people understand that getting to sustainability is a process, it’s not always as obvious what the right path is, and that being aware of some options you may have in your consumption choices can help guide you to make better choices.

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