My company wants to measure the carbon footprint for our booth. Do you have any suggestions?

Making a baseline measurement is a good idea because it helps quantify your progress. It's a good step, that is, if you understand what the measurement means…and what it doesn't mean. They say numbers don't lie. But when it comes to environmental impacts, facts and figures aren't always what they seem.

The Missing Data Problem
Let's take an example. Typical exhibit walls and cabinets are made of plywood, which starts as trees. Measuring the carbon footprint of harvesting forests is tricky. Trees absorb carbon dioxide during life, but release carbon when they decompose. Some of this carbon is stored in the soil, some escapes into the air, and the balance for forests and harvesting techniques varies. So we can't measure the trees.

Trees are commodities, traded worldwide every day of the week. The plywood factory might be next door or an ocean away. So the carbon pollution from logging and shipping varies too. We don't have these data points either.

At the factory, logs are cut into sheets and glued together under high pressure. The laminated sheets are sanded and trimmed — voila, it's plywood! This we can measure. But no two factories are identical, and few factories even report emissions. European factories do — the law requires them to — but this is not true worldwide. So we rely on averages based largely on European examples.

Finally, a stack of plywood makes its way from the factory to your builder via ship, train, or truck. It travels a short distance or around the world. Surprisingly, thousands of miles aboard ship might cause less pollution than a relatively short ride on the highway. So we are left with estimated emissions based on relatively small data sets. Resource extraction is left out. The rest is averaged and rounded off.

The Boundary Problem
We ignored forests in the plywood footprint. When it comes to transportation fuels, the U.S. Environmental Protection Agency ignores oil extraction and refining, too. Instead, the EPA measures emissions from burning a gallon of fuel — the so-called "tailpipe emissions."

We must apply these same boundary limitations to every material in an exhibit; otherwise we'd be mixing apples with oranges. This means we are dealing with a partial picture. That's fine for our purposes, but it isn't comprehensive or precise.

Opportunities for Abuse
Unfortunately, people often present the carbon footprint results as if they are absolute. Or they fail to apply boundary limitations consistently. Beware: These errors can lead you astray. But carbon footprint metric was never intended to give you an absolute, precise number. It was meant for something else altogether. Used properly, it helps you see and choose lower carbon options.

Stay tuned because the carbon metric is an amazingly effective tool. We'll explore how to use carbon as a decision-making tool in the next installment of Ask Mr. Green. E