Guiding Principles for More Sustainable Plastics

The shifting of the resource base for organic chemicals from fossil fuels to renewable resources creates a unique opportunity for shifting plastics from their current unsustainable course to a more sustainable life cycle. Our core principles for designing a more sustainable plastic product are:

• Sustainable Resources: grow, harvest and/or collect natural resources in a sustainable manner.
• Green Chemistry: strive to manufacture plastics based upon the 12 Principles of Green Chemistry.
• Closed Loop Systems: for plastics that meet the above two principles, manufacture and use plastics that either a) contain a very high percentage of post-consumer recycled content or b) are biodegradable into safe and usable organic matter.

Sustainable Resources

The goal of the Sustainable Resources Principle is to transform the resources used to produce plastics from unsustainable fossil fuels to a sustainable renewable resource base. The challenge in the transition from fossil fuel to biological feedstocks for plastics is how to do so sustainably, without creating environmental damage that is equal to or worse than the existing impacts of fossil fuel extraction and processing. To date, the renewable resource for plastics is agricultural crops and their byproducts, primarily corn, soy, sugar cane and sugar beets. But the renewable resources available for industrial products are likely to increase, including: non-food plant crops (for example, switchgrass) and organic wastes (for example, yard waste, food waste or biosolids).

To date, there are no widely accepted principles of sustainable agriculture for commodity crops. The principles for sustainable biomass developed by the Institute for Agriculture and Trade Policy and Friends of the Earth set a foundation for specifying more sustainable commodity crops, including growing crops that should:

• Be sustainable for local communities, including:
  • not imposing unjust burdens on economically or socially marginal communities,
  • not jeopardizing food security and
  • promoting local ownership and control over crop production and processing facilities.
• Be sustainable for the climate, environment and public health, including:
  • significantly reducing greenhouse gas emissions across the life cycle of the material,
  • maintaining and building soil structure and fertility,
  • conserving water quantity and quality,
  • not encroaching on forests and other intact ecosystems,
  • improving biological diversity (which encompasses not using genetically modified crops) and
  • minimizing, and eliminating whenever possible, the use of dangerous agrochemicals.

These are the principles that growers of biobased feedstocks need to adopt and implement. When the sources of biological feedstocks are biological wastes (for example food, yard, animal or human waste), the relevant sustainability principles for that waste stream would apply. For example, if it is animal waste, then the animals need to be raised according to sustainable animal husbandry practices -- including the appropriate use of antibiotics and the humane treatment of animals.

In addition to ensuring that the transition to renewable materials is sustainable, it is critical to preserve natural capital - to do more with less by increasing resource efficiency and productivity, reducing our material throughput.

Green Chemistry in Manufacturing

Today’s fossil fuel-based plastics are not manufactured according to the Principles of Green Chemistry. They rely primarily upon inherently hazardous chemicals -- chemicals that are likely to be carcinogens, neurotoxicants or endocrine disruptors. In short, chemicals that are unhealthy for humans and the environment. Examples abound of the inherent toxicity of the fossil fuel-based plastics. Polyvinyl chloride plastic is made from the carcinogens -- vinyl chloride monomer and ethylene dichloride. Polystyrene plastic is made from a carcinogen, benzene. Polycarbonate is made from the endocrine disruptor, bisphenol A.

The most effective means for reducing the risks from toxic chemicals is to reduce hazard, that means, to prevent the use of inherently hazardous chemicals in the first place. Green chemistry as defined by Anastas and Warner (1999) is the “the utilization of a set of principles that reduces or eliminates the use or generation of hazardous substances in the design, manufacture and application of chemical products.” The 12 Principles of Green Chemistry define an alternative path to manufacturing plastics that is based on the pursuit of processes that reduce and eliminate the use or generation of hazardous substances in the design, manufacture and application of chemical products. Principles of Green Chemistry that are especially important to moving plastics manufacturing to inherently less toxic chemicals are:

• Principle #2 - Design safer chemicals and products: Design chemical products to be fully effective, yet have little or no toxicity.
• Principle #3 - Design less hazardous chemical syntheses: Design syntheses to use and generate substances with little or no toxicity to humans and the environment.
• Principle #8 - Use safer solvents and reaction conditions: Avoid using solvents, separation agents, or other auxiliary chemicals. If these chemicals are necessary, use innocuous chemicals.
• Principle #10 - Design chemicals and products to degrade after use: Design chemical products to break down to innocuous substances after use so that they do not accumulate in the environment.
• Principle #12 - Minimize the potential for accidents: Design chemicals and their forms (solid, liquid, or gas) to minimize the potential for chemical accidents including explosions, fires, and releases to the environment.³

The goal of integrating chemistry into plastics manufacturing is to create a production system that uses inherently less hazardous chemicals for each step in the process of converting basic chemicals into complex polymers.

Closed Loop Material Flows

Closed loop systems minimize waste by keeping materials in the economy and out of landfills and incinerators. Our goal is to close the materials loop, most preferably by keeping environmentally preferred materials in circulation as long as possible. This entails maximizing the reuse and recycling of environmentally preferred materials. Less preferred, but certainly better than landfilling or incinerating plastics, is to biologically degrade them to create soil amendments and feedstocks for new materials (for example, through anaerobic digestion). For plastics, the ideal is to either create plastics that are easily recycled back into the same product or can be composted into nutrients healthy for the soil. McDonough and Braungart refer to these as technical nutrients (materials that are readily recycled or reused) and biological nutrients (materials that are designed to return biological cycles).

The Plastics Scorecard integrates each these three life cycle principles -- Sustainable Resources, Green Chemistry in Manufacturing and Closed Loop Material Flows -- into the criteria for evaluating and identifying more sustainable plastics. By implementing each of these principles, the carbon footprint of plastics will be greatly diminished.

ENDNOTES
¹ Institute for Agriculture and Trade Policy and Friends of the Earth. 2008. Sustainable Biomass Principles (accessed July 30, 2008).
² Paul Anastas and John Warner. 1999. Green Chemistry: Theory and Practice, Oxford University Press: New York.
³ Ibid.
⁴ William McDonough and Michael Braungart. 2002. Cradle to Cradle: Remaking the Way We Make Things. New York: North Point Press.