On Green Polymers

15 August 2013

Recently, I learned that the Chemical Engineering Department at the University of Delaware is now the Department of Chemical and Biomolecular Engineering. Apparently, the folks at my alma mater regard the green side of chemicals and chemical processes as at least co-equal in importance to the more traditional varieties. Polymers happen to be my favorite area, so this post looks at biopolymers — the green side of polymers and polymer processing. — C.H.

What is a “Biopolymer”?

From the perspective of a plastics or rubber processor, the term “biopolymer” applies to polymeric materials that are: 

    Biodegradable, or

    Made wholly or partially from biological materials, or

    Both [1]


Biodegradable materials, especially compostable materials, resolve disposal concerns in a natural manner, without negative environmental impacts. Materials sourced from living matter — especially plants — make little, if any, net CO2 emissions to the atmosphere and displace materials derived from petroleum or other non-renewable source.

Biopolymeric Raw Materials

Natural biopolymers have a long history. Silk, cotton, wool and natural rubber have been around much longer than nylon, polyesters, polyacrylates and SBR. The synthetics have gained market share for three primary reasons: flexibility in tailoring physical properties, readily scalable production and (often) lower finished product cost.


Dreamstime - Green ChemistrySynthetic polymers can become “bio” because the chemical precursors to synthetic polymers can be sourced from living matter. For example, polyethylene results from polymerizing ethylene. Ethylene can be produced from ethyl alcohol. Ethyl alcohol can be produced by fermentation of grains (or, better yet, from fermentation of bagasse — pulp waste from sugar cane).


The search for viable “bio” routes to commercially important monomers and monomer precursors is an important research area today. As an example, in June of this year, researchers at the University of Massachusetts announced a high yield process for producing p-xylene from lignocellulosic biomass.[2] p-Xylene is a precursor to PET (polyethylene terephthalate), the volume leading polymer for clear plastic bottles.[3]


Biodegradability


According to Wikipedia,  “(b)iodegradable plastics break down (degrade) upon exposure to sunlight (e.g., ultra-violet radiation), water or dampness, bacteria, enzymes, wind abrasion, and in some instances, rodent, pest, or insect attack are also included as forms of biodegradation”.
[4]


Practically speaking, Green end of product life disposal usually means compostability — conversion to saleable compost that can enrich the soil. There aren’t many industrial strength composting facilities. However, there are some, with more on the way. Waste Management Corporation, for example, reports 36 organic wastes processing facilities, as well as a venture that converts waste plastics to synthetic crude oil. Increased attention to the 30% of America’s solid waste stream that is food wastes will require many more composting facilities.[5]


For Smaller Manufacturers


From the perspective of a plastics or rubber processor who aspires to Sustainability, however, there is more to consider. Dow Chemical usefully cites four pillars of Sustainable Chemistry (hence sustainable polymeric products): [6]


Holistic Design
– Assessing environmental impacts from production, to use, and disposal or reuse


Atom Economy
– Processes where the amount of starting material equals the amount of all products generated. No waste.


Energy Footprint
– Minimizing the amount of energy required throughout its lifecycle.


Reduced Hazard
– Designing safety into products and processes.


Dow’s four pillars offer a good guide to Green practice, ‘bio” or not. Remember that polymer processors usually process compounds, not just polymers. The four pillars apply to the entire compound — the fillers, UV blockers, pigments, heat stabilizers, etc. — as well as the polymer. The fourth pillar, by the way, includes toxicity, be it acute or latent.


====================


Pragmatics


The entire world capacity for producing synthetic biopolymers is projected to grow about five fold, from 1,163,000 metric tons in 2011 to 5,778,000 metric tons in 2016. The great majority of that growth is projected to be in “Bio-PET 30” bottles (30% bio-based polyethylene terephthalate, balance petroleum based PET), similar to the bottles touted by Coca Cola’s bottled water business. And most of the growth is expected to be in Asia and South America, not North America.[7]


For almost all smaller processors, “bio” products are niche markets; best approached hand-in-hand with your customer (and eyes wide open). Much of the materials technology is new, as the research citations mentioned above suggest. Materials costs for “bios” are generally higher than corresponding conventional materials, only in part due to the relatively low volumes. With the advent of “fracking”, especially in North America, the supply of ethylene precursors from natural gas liquids and light petroleum crudes has mushroomed, meaning that the cost of many petroleum based polymers will remain low in North America, and that supply interruptions due to overseas crude oil sources are now much less likely than in past years.


Chuck - BrittanyThoughtful comments and experience reports are always appreciated.


…  Chuck Harrington (
Chuck@JeraSustainableDevelopment.com)


P.S
: Contact me when your organization is serious about pursuing Sustainability … CH


This blog and associated website (
www.JeraSustainableDevelopment.com) are intended as a resource for smaller manufacturers in the pursuit of Sustainability. While editorial focus is on smaller manufacturers, all interested readers are welcome. New blog posts are published on Wednesday evenings.

Green chemistry image: www.dreamstime.com


[1] Environmental Leader, “EL Insights: Green Plastics”, 30 May 2013, page 4 http://www.environmentalleader.com/wp-content/uploads/2013/05/EL-insights-green-plastics-special-Issue-48-may-20131.pdf

 [2] Lignocellulosic biomass resembles the wood pulp that paper manufacturers process. For more on lignocellulosic biomass, see: http://en.wikipedia.org/wiki/Lignocellulosic_biomass

[5] From Waste Management’s 2012 Sustainability Report (which should be required reading for all manufacturers interested in the business possibilities Sustainability offers):  http://www.wm.com/sustainability/pdfs/2012_Sustainability_Report_Executive_Summary.pdf

[7] Statistics from “EL Insights: Green Plastics”, op cit, page 33f