Or, a popular measure reflects our individual lifestyles and the impact of that compared to how much of our "fair share" of the world's resources we consume with that lifestyle. For example, http://www.myfootprint.org/ purports to calculate the amount of land and ocean required to sustain an individual's consumption and absorb their waste based on their reported consumption pattern and lifestyle. It then tells you how many times your share of the earth's resources you consume (based on some estimate of how much is available world wide divided by the world population.) Another one is http://www.carbonfootprint.com/ which is linked to a business site. There are many more. Warning: read carefully and do not assume the same data entered into another calculator will give you the same results!
One that I use in class is from colleagues at UC Berkeley, http://bie.berkeley.edu/files/ConsumerFootprintCalc.swf. It allows much more detailed entry information on types of autos used and gas mileage, flights (long or short- it matters since, I understand, the takeoff and landing have a different impact than a long flight at altitude), and dollar values for expenditures in housing, food, etc.
This is fun when we apply this to our personal lives but it would not help much in manufacturing analysis. That is much more complicated since, as we discussed in an earlier posting, this conversion from consumption to impact varies tremendously depending on the source of energy and, importantly, the bill of materials/supply chain providing the components for your product. We'd like to see the quantitative link between a machine or system design and its performance and impact. Otherwise it is not much help to us as engineers.
It is even more complex than one might envision when we try to determine "how low can you go" in your footprint - that is, how little of the earth's resources can you use?
Overall, energy use scales with disposable income (above a certain base level of income). So, your "footprint" will reflect your consumption of a number of resources:
- energy - heating, lighting, food/cooking
- housing: how big, how many share it, what climate do you live in, do you have air conditioning/heating, etc.
- consumables (in addition to energy) including dietary choices (eating locally raised food rather than out of season food from afar, or food transported some distance to you
- transportation: whether or not you carpool, ride a bike/walk/public transportation, take long airplane trips- business or pleasure (short or long?), have an efficient auto/hybrid
- entertainment/leisure preferences (ie are you a surround sound mini-theater blue-ray junkie or do you take long walks on the beach),
- plumbing/showers/gardening water use, etc.
A friend of mine, a professor at MIT, Tim Gutowski and his students conducted a study as part of a class project assessing life styles and the resources required to sustain them - in the US. (Source: Environmental Life Style Analysis (ELSA) Timothy Gutowski, et al, IEEE Int'l Symposium on Electronics and the Environment, May 19-20, 2008, San Francisco USA). He and his students studied 18 different life styles ranging from homeless people and Buddhist monks to multimillionaires and an "Oprah approximation” (their words!). In many of the cases they also tried to consider variants on the life style (meaning for a given life style, variations in income and variants for a given life style within a fixed income.) Recall the discussion of my father's activities in the depression - that describes an "income variation for a given life style."
The MIT folks used an economic input-output life cycle analysis technique available for such calculations. Sort of a total cost of ownership calculation for the environmental impact. "Services" and subsidies were included in the assessment (such as those provided by the government). I can't summarize the whole study here but one major finding was that housing, transportation and food often dominate the environmental impacts of individuals.
Included in their summary from the assessment is the following - "...by including the subsidies, we identify a floor, below which environmental impacts for people living in the United States do not drop. For example, none of the life styles studied here ever resulted in an energy requirement below 120GJ (in 1997). This includes the life style of a five year old child, a homeless person and a Buddhist monk. [This] is almost double the global average energy use in that year (64 GJ)."
Even Buddhist monks, if living in the US, will consume the equivalent of double the global average energy/person in a year!
This study also re-iterated an important point - if you cut down in one area but use the savings to engage in riotous living in another area ... the impact may be negative. For example - if you buy a hybrid vehicle and then use the savings in gasoline to fund an airplane trip to Paris for vacation, the impact of your airplane ride may wipe out the gains of your energy conscious purchase.
But, you are probably asking at this point, what does this have to do with green manufacturing?!
This is a big issue - one of the key issues I would say. How can you tell whether or not the cure is better than the disease? How do you know your careful system to reduce cutting fluid and lubrication during machining (so called MQL for minimum quantity lubrication) does not require additional part cleaning capability, dust/particle evacuation or chip handling hardware, or specialized tooling that, combined, require an investment in materials and energy (production, installation and maintenance) that exceeds the savings anticipated with the new system?
This is what metrics are for and, if embodied in analytical tools, can give the engineer, designer, and technical specialist the ability to make a "cost-benefit analysis" (except this time it is environmental cost) as part of the due diligence. And insure it covers enough of the life cycle. If we can determine the "footprint" of our product or process or system, and we know what parameters affect it, then we can start to make informed decisions about our manufacturing processes and systems.
This part of the discussion is to be continued in a future posting.
By the way ... my footprint is 5.6 "earths" - meaning if everyone lived like I do we'd need that many earths to support us all. I'm working on it. What's yours?
Green Manufacturing Note: Here is an informative site if you are following green business trends and practice, http://www.environmentalleader.com/.