Goes Around, Comes
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Cows in the Loop– Cradle to Cradle comcepts supported by Materials Innovation.

by Cynthia Tyler, PhD.


The Cradle to Cradle design philosophy is a very holistic one, incorporating a wide variety of factors that come together to establish responsible materials and products.  Within the framework, there are a number of elemental concepts and practices, and we will touch on some recent developments in materials and processing that support these specific concepts in this article.

Waste Equals Food

In the Cradle-to-Cradle approach, waste becomes food by use of biological or technical nutrients.  Biological nutrients support growth of additional biobased materials by nourishing the soil from which they grow. 

Materials that are capable of returning to the earth as nutrients themselves are the core of sustainable development.  A recent development in biodegradable plastics is a novel process created by Professor Keith Kyler at Indiana University of Pittsburg.  Instead of using corn or other edible feedstocks, his process converts switchgrass, a fast-growing prairie grass, into cellulose and then into sugar, the main ingredient in the biodegradable plastic.   The plastic biodegrades in soil in about one to six months, and applications include plastic wrap, packaging and possibly beverage bottles.  The next step is to scale-up the laboratory process at an affordable price.

How does a synthetic material or technical nutrient become food?  Shaw Industries, the producer of Cradle-to-Cradle certified carpets, offers a take-back program for their carpeting, illustrating a way in which technical nutrients can be used as food. 

Shaw owns Evergreen Nylon Recycling LLC in Augusta, Georgia, which uses patented technology to convert post-consumer nylon-6 carpet by depolymerizing the waste into caprolactam, the monomer raw material or ‘food’ for new nylon-6 carpet fiber production.  The depolymerization process uses high temperature steam to convert carpet waste (typically landfilled) into a technical nutrient for new carpet fiber production without loss of any aesthetic or performance properties.  

 Research into another depolymerization technology is underway at Georgia Institute of Technology in Atlanta by Professor John D. Muzzy’s research group.  In this process, a small amount of potassium hydroxide liquid catalyst (1%) is added to post-consumer carpet and mixed in an extruder/reactor depolymerizing nylon-6 at a temperature of 350°C (662°F) and in less than 10 minutes (the ionic liquid process requires several hours).  The low cost equipment and significantly shorter reaction time offset the additional processing step needed to purify the ‘crude’ caprolactum.  Suitability for economically processing low volumes presents the possibility of localized operation near waste carpet sources.  Instead of shipping the entire carpet to one centralized location, depolymerization occurs locally followed by shipment of the crude caprolactum to another location such as the Evergreen plant for further purification, significantly lowering transport costs.      

Use Current Solar Income

Another goal of Cradle-to-Cradle design is the use of current solar income for energy requirements during manufacture and assembly of the entire product and individual components.  In addition to solar, forms of current solar income include other clean renewable energy sources such as wind, biomass, and hydropower.  Materials developments are also contributing to the advancement of these alternative energy sources, especially solar energy. 

BioSolar, Inc. is developing bioplastic materials from renewable plant sources that will reduce the cost of backsheet materials by 50 percent.  The backsheet is the bottom layer that supports the solar cell array and its various layers.  Their innovative manufacturing process and proprietary blend of additives produces a bioplastic film prototype with the necessary durability to meet processing and installation requirements of solar cell applications.   

Another materials innovation uses waste from the semiconductor industry to produce solar cells.  IBM was recently honored by the The National Pollution Prevention Roundtable for a reclamation process that allows them to reuse millions of scrap silicon wafers in the production of solar cells rather than throwing them away – a process that required them to be crushed (for security purposes) and sent to a landfill.  The process allows the company to save as much as 90% of the energy required to manufacture new wafers, and reduced costs by more than $1 million over the course of 2007.  Green thinking leading to green rewards.

Celebrate Diversity

 Another precept of Cradle to Cradle is the reinforcement of mixed species in the environment.  Natural systems thrive on diversity where each organism interacts with other organisms sustaining the ecosystem on a local level by exchanging materials and energy.  A remarkable example of one such system is the closed-loop Genesis ethanol plant in Mead, Nebraska operated by E3 BioFuels, LLC.

 Instead of relying on fossil fuels to heat fermenting corn to produce ethanol, the plant uses power, generated from cow manure at a nearby feedlot, combined with waste from the ethanol process.  The two main by-products of ethanol production are wet distillers grain or “wet cake”, a high-protein animal feed, and a heated milky liquid, “thin stillage.”  Rather than dry the wet distillers grain for transport to distant farms raising livestock, the system avoids the energy intensive drying step by feeding wet cake to the nearby cows.  Manure from the cows combined with thin stillage from the plant provides feedstock and some thermal energy from the thin stillage for an anaerobic digester, generating all necessary fuel required by the ethanol plant.  

Anaerobic digestion is the same process occurring naturally in landfills where microorganisms in the absence of oxygen convert organic waste material to biogas consisting of methane and carbon dioxide.  As with composting, another by-product of anaerobic digestion is the formation of a soil conditioner, providing nutrients to grow the next seasons’ corn.    


e2e Materials LLC, is taking a similar approach, with plans to co-locate near a soy-based biodiesel plant and farms growing soybeans and flax.  The company manufactures bio-composite panels composed of resin made from soybean protein, water and other natural materials and reinforced with fiber from fast-growing flax plants.  The process complements manufacturing of biodiesel fuel from soybeans where, after soy oil extraction, the soy protein by-product becomes raw material for the bio-composite.  The composites contain no formaldehyde, may be recycled, or will biodegrade in six months.  According to Pat Govang, President of e2e Materials, the material is safe and you could eat it (if you could chew it).  The mechanical properties of the bio-composites are comparable in certain aspects to existing glass-fiber-reinforced composites. Current applications include skateboards and an alternative to particleboard for cabinetry.

The materials innovations in this article are just a few examples of advancements we are continuously monitoring at Material ConneXion, with many emerging from university research laboratories.  We recognize that the transition from manufacturing based on the Industrial Revolution to one embracing Cradle-to-Cradle is a gradual process.  These developments are definitely a step in the right direction.


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