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by Robert McKay
April/May 2008
What is the definition of “green?” This is a question often asked by design firms, marketing departments and corporate offices as businesses wrestle with how to respond to increasing demands for green products. The U.S. Green Building Council (USGBC) has estimated that the value of new construction that is LEED certified (Leadership in Energy and Environmental Design) surpassed $12 billion in 2007 while Mintel’s Green Living report estimates the number of consumers who often buy “green products” has tripled in the 16 months prior to December 2007. Within this explosion of activity, how is the definition of green evolving and what will it be like in the future?
The value of a good or service has traditionally been defined as the benefits received in exchange for the financial cost incurred. Recently, an additional cost has been gaining increased attention: the “cost to earth and health.” This cost has always been present — it’s just that our understanding and awareness has been steadily increasing. The ideal definition of green is reducing the net cost to earth and health to zero, allowing us to grow our economies indefinitely without running out of resources, harming the environment or diminishing our health. The often quoted former Prime Minister of Norway, Gro Harlem Brundtland eloquently put this into words: “Sustainability is meeting the needs of the present without compromising the ability of future generations to meet their own needs.” This definition of green may seem simple and intuitive.
Unfortunately, this ideal is very difficult to achieve in practice and there are many paths toward this end. For example, one person may reduce the amount of energy they consume without changing how it was generated, while another person may consume the same amount of energy but switch to a cleaner generation technology. Both could have the same environmental footprint, but get there in two very different ways. Our ideal definition becomes blurred in real life.
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1. Plastics are traditionally fabricated using hydrocarbons (containing carbon and hydrogen atoms) extracted
from fossilized biomass.
2. Bio-based materials propose to extract the carbon and hydrogen atoms required to make plastics directly
from biomass before it has been fossilized by geological forces.
3. Theoretically, it is the imbalance between the rate of combustion (annual) and the rate of fossil fuel creation
(hundreds of millions of years) that creates the build-up of CO2 in the atmosphere commonly tied to global
warming. Bio-based materials and fuels may reduce this imbalance, but side-effects such as land, water,
and fertilizer use also need to be considered.
4. Recycling, especially of post-consumer waste using advanced technologies, is another option to reduce
environmental burden.
5. To effectively compare design changes, the effects of the use phase should not be ignored. |
Bio-plastics
One form of green is bio-materials. Theoretically, the concept is simple: plants absorb CO2 as they grow. Those plants are harvested for their carbon and hydrogen atoms, which are converted into bio-based materials and bio-fuels through either chemical or bio-chemical processes. When these materials or fuels degrade or are incinerated, the carbon atoms then combine with oxygen to form CO2 in the atmosphere — closing the loop. If the rate of carbon absorption matches the rate of carbon release at the end-of-life through biodegradation or incineration, there theoretically would be little risk of CO2 build-up in the atmosphere. As Joel Bourne writes in the National Geographic (October 2007), “In theory, burning a tank of [bio-fuel] could make even an Indy car carbon neutral.”
As with the ideal definition of green, the ideal benefit promised by bio-based materials is also elusive in practice. Replacing fossil resources with agricultural crops requires more land area, competing with food production and other land uses. For example, many first generation bio-based plastics are based on starch (e.g. corn), leading to the “food versus fuel” debate. Green alternatives usually come with trade-offs, and objectively evaluating these trade-offs can be difficult and complicated.
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High performance connectors made from Valox iQ* PBT resin — each contains nearly one PET water bottle (SABIC Innovative Plastics photo). |
Recycling
Another alternative is to close the loop through recycling instead. Rather than incinerating, biodegrading or land filling materials at the end of life, we may harvest the carbon and hydrogen atoms required to make new polymers from waste plastics. Again, just as with bio-based plastics, first generation recycled plastics were far from ideal.
Traditional techniques involve mechanical recycling or grinding of plastic waste and compounding the recycled materials back into a useable form. However, each heat history, or melt-cool cycle, slowly degrades, or shortens, the polymer molecules. Since many of the benefits of a polymer are derived from long molecular chains, their shortening reduces the usefulness of the material. Over time, the material can become almost unusable, except for perhaps the least demanding applications. A second problem is removing the pigments, additives and reinforcement. This is virtually impossible through mechanical recycling.
A relatively new alternative is to use chemical processes to depolymerize, purify, and then rebuild the polymer back into its original high performance state. Sometimes these processes can also be used to upgrade the material. For example, SABIC Innovative Plastics depolymerizes post-consumer PET (polyethylene terephthalate) and combines the reclaimed chemicals with another building block to create a PBT (polybutylene terephthalate), an engineering thermoplastic with up to 65 percent post-consumer content. Another way to look at this process is to imagine that the post-consumer PET bottles, which had a useful life ranging from minutes to hours in your hand, are being upgraded for use in durable goods like cars and buildings with useful lives ranging from months to over 40 years.
Let’s move beyond bio-plastics and recycling. Narrow goals such as producing products with “X% bio-content” or “X% post-consumer content” are easy to understand, communicate and practice. Unfortunately, experience is showing us that simply focusing on one attribute without considering other factors is somewhat like steering your ship around an iceberg while only looking at its tip: what you can’t see can sink you.
Life cycle thinking and life cycle
assessment
This brings us to the most holistic but complicated measure of green: life cycle thinking and life cycle assessment (LCA).
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Lexan* Constant Clear Film applied to only the top half of a freezer door (SABIC Innovative Plastics photo). |
In life cycle thinking, a designer strives to consider the environmental burden of every step of fabrication ranging from the extraction of resources, through the production of the primary materials, on to the assembly, use, and in the end, disposal or recycling. LCA is an established methodology (ISO 14044) that attempts to quantify a wide range of environmental and social impacts from carbon emissions through land-use of any given product. By considering both the “means” and the “result,” life cycle thinking and LCA attempt to prevent burden shifting and the “iceberg” problem. Life cycle thinking and LCA also allow for the “benefits” of a product during its life to be weighed against the “cost” of manufacturing that product.
In one example, applying polycarbonate film enhanced with anti-fog technology to the glass doors on grocery store frozen food display cases saves energy and reduces the impact of operating those displays. The application of this film may allow the storeowner to turn off the heaters that prevent the doors from fogging as customers open the doors while shopping. The benefits of turning off the heaters and saving electricity far outweigh the energy used to manufacture, distribute and install the film. Not only does the electricity reduction save money, it also reduces the impact on the environment as each MWh of electricity conserved can reduce as much as 690 kg of greenhouse gases to be emitted, depending upon how local power is generated.
In another example, a hotel in Cancun installed polycarbonate glazing with infrared blocking technology to reduce the solar heat entering the building during the day. By using this technology, they expect to reduce the solar heat transmission by as much as 35 percent. During the summers, when temperatures easily hit mid-90°F (mid-30°C), this improvement may contribute to the comfort of guests and staff, save money with reduced cooling costs, while also reducing the environmental costs resulting from the production of electricity at nearby power-plants. Neither of these examples uses a biopolymer or recycled plastic. Instead, they illustrate how today’s technology may be used in infrastructure and product design to significantly increase energy efficiency and decrease the environmental burden during the use phase of the product’s life cycle.
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Lexan* Solar Control IR sheet — Crown Paradise Hotel in Cancun, Mexico (SABIC Innovative Plastics photo). |
Advance life cycle analysis tools
Some material design changes are not as simple and involve many complex tradeoffs, such as switching from a polymer manufactured from petroleum resources to one made from bio-based resources. For these situations, advanced life cycle analysis tools such as SimaPro and GaBI have been designed to simplify the calculations and ensure some level of standardized approach. The current state-of-the-art in these LCA calculators and simulators could be compared with the early days of computer aided engineering (CAE) analysis: the tools are improving rapidly, the competencies for their effective use are developing in the marketplace, and the supporting databases are growing in both breadth and depth. It is possible to envision life cycle analysis becoming as ubiquitous in the future as CAE has become today. When used properly, LCA may facilitate better designs and consumer choices.
Conclusion
We are in a period of increasing awareness of the “cost to earth and health” of the products and services we consume in our everyday lives. As we reach for the ideal goal of reducing these environmental costs to zero and learn more about total environmental impact, we will certainly continue to evolve our definition of green. Guidelines will shift and new regulations will be introduced. Therefore, the more sophisticated the definition of green that we can implement within our design and investment decisions today, without overburdening these processes to the point of ineffectiveness, the more likely our designs will stand up to future expectations.
A pre-recorded presentation on this topic (“Sustainability” – 1 hour in English) is available on the Calendar of Events accessible from the www.sabic-ip.com home page.
Robert McKay is the sustainable polymers project manager for SABIC Innovative Plastics. For information on the examples in this article, please contact SABIC Innovative Plastics at (800) 845-0600. Feedback and questions to the author are welcome at robert.mckay@sabic-ip.com.
For information on product offerings, contact SABIC Polymershapes, 11515 Vanstory Drive, Suite 140, Huntersville, NC 28078 USA; (866) 437-7427, www.gepolymershapes.com.
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