Engineering, Materials

The design hierarchy

The problem of toxic substances has roots that can be traced back through the organizational levels of industrial systems: from the design and manufacture of products to the design and manufacture of the materials from which products are fashioned, and ultimately to the level of chemical production and molecular design. The results of design and engineering decisions at each level are taken up as finished products for use in ‘higher’ levels of design and engineering. Product design rarely involves creating new materials or synthesizing new chemicals; rather, it most commonly involves selecting among available existing materials. Those materials, in turn, are made of chemical ingredients selected from already-available options. To a large extent, the entire chemistry-based system of production is shaped by the available transformations of mineral and petrochemical resources.

This view highlights a multi-level hierarchy in the way things are made—we might call it a design hierarchy, illustrated here with the example of a hypothetical PVC-containing building product.

The design hierarchy

We can use the design hierarchy to trace the decisions that have led to the presence of toxic chemicals in products, and to identify opportunities for substitution. This concept is adapted from the ‘nested relationship’ of chemicals, materials, and products that the Lowell Center for Sustainable Production articulated in their Alternatives Assessment Framework. That relationship expressed a hierarchy of inclusion: “products consist of materials and/or chemicals, materials consist of chemicals, and chemicals are constituents of materials or products.” The design hierarchy also expresses the relationships of different actors involved in designing technological artifacts and systems—and these relationships are interesting from the perspective of systems change.

As we follow toxic problems deeper into the design hierarchy, the main actors at each level—the designers, engineers, and manufacturers who make each discrete item what it is—become further and further removed from each other and their respective design goals and knowledge networks. For example, it’s difficult for architects who want to design ‘green’ buildings to influence what goes on in the domains of materials science and chemistry. They lack the resources and technical expertise necessary to delve into issues of the molecular composition of products, and they can’t easily modify products to make them less toxic.

Designers could try to select safer products, by asking what alternatives are available and how these compare in terms of environmental health impacts. But answering such questions is a challenge in itself. There are structural and organizational barriers to information flow in supply chains, especially across different levels of this hierarchy. For any given item, there may be a complex, globally-distributed network of suppliers; who is responsible for its chemical makeup? For that matter, what is its chemical makeup? Product makers don’t necessarily even know. Concerns about chemical risks upstream in the supply chain are simply not negotiable in markets where detailed knowledge of product chemistry is lacking.

One way to advance a safer material economy is to bring more technical resources to bear on the problem at deeper levels of design. This could be approached in a number of ways:

  • Specialized groups of design professionals could take on the challenge of developing innovative technologies that are inherently benign. At the chemical and material design levels, this corresponds to green chemistry and green engineering. Green product design is even more complex and nebulous.
  • Proponents of clean production can develop green design tools—decision support tools intended to inform and guide users in the technical aspects of eliminating toxic substances. Green design tools have been developed and used at all levels of the design hierarchy: to reduce the environmental health impacts of the synthesis and properties of molecules (e.g., the GreenScreen), to optimize the chemical composition of materials and the manufacture of parts and components (e.g. the Sustainable Apparel Coalition’s Higg Index), and to select safer and less environmentally costly products (e.g. Healthy Building Network’s Pharos Project). Different kinds of expertise, and different design tools, are brought to bear at each level. The idea is that well-informed decisions may, in aggregate, help shift production systems to more sustainable trajectories.
  • Stakeholders can advocate for greater access to knowledge of the chemical constituents of products and materials—in other words, transparency of chemical information—to support informed design choices. This idea has gained considerable traction in the green building space, through projects like the Health Product Declaration open standard. Meanwhile, broader initiatives like the BizNGO Guide to Safer Chemicals and the Chemical Footprint Project aim to help companies address systemic problems of supply-chain chemical management.

These are all valid approaches to the challenge of getting toxic substances out of products and production systems. But they all share some common assumptions: that the key problem to solve is a deficit in the technical abilities or knowledge resources of various kinds of design specialists (chemists, architects, etc.); and that these specialists, if well-equipped, could take on all the responsibility for fixing unsustainable technical systems. Taking a different view, we might see the causes and potential solutions to this ‘wicked’ problem as distributed throughout society, in addition to being submerged in technicalities. That will be the subject of another post…

This post originally appeared on the author’s personal blog and is reposted under a Creative Commons Attribution license.

Engineering, Environmental Chemistry, Materials, Policy

Chemical Footprinting: New tools for tracking green chemistry business practices

Chemical Footprinting: Identifying Hidden Liabilities in Manufacturing Consumer Products

In an unassuming low-rise in the Boston suburbs, Mark Rossi tinkers with a colorful dashboard on his laptop screen while his border collie putters around his feet. Rossi is the founder of BizNGO and Clean Production Action, two nonprofit collaborations of business and environmental groups to promote safer chemicals. He’s also the creator of tools that he hopes will solve a vexing problem—how to get a handle on companies’ overall toxic chemicals usage.

Consider the screen of Rossi’s laptop. Chances are the company that manufactured the product has crunched the numbers on the total amount of carbon, water, and land associated with getting it into the office—from the manufacturing of the electronic components to the packaging and transportation to retail outlets. But the total amount of toxic chemicals that contributed to the screen’s design and production might be a more difficult question to answer….

Read the entire story, by Lindsey Konkel, at  http://ehp.niehs.nih.gov/123-a130/

Materials, Synthesis

A “Designer” Surfactant for Cross Couplings of Hydrophobic Reagents in Room Temperature Water

“TPGS-750-M: A Second-Generation Amphiphile for Metal-Catalyzed Cross-Couplings in Water at Room Temperature” Lipshutz, B. H.; Ghorai, S.; Abela, A. R.; Moser, R.; Nishikata, T.; Duplais, C.; Krasovskiy, A.; Gaston, R. D.; Gadwood, R. J. Org. Chem. 201176, 4379-4391. DOI: 10.1021/jo101974u

I occasionally run reactions in water, and it is awesome. I LOVE not worrying as much about cancer. Unfortunately many interesting chemicals are simply too hydrophobic to allow reactions to be run in aqueous solution. As anyone who has ever scrubbed a greasy pan will know, one way to get around the solubility problem is with soap. Also called emulsifiers, surfactants, amphiphiles, a soap by any name is pretty much the same thing in my mind (though others will disagree I’m sure). Molecules with hydrophilic and hydrophobic ends can form micelles in water, creating variously-shaped and sized particles with hydrophobic cores. Using those hydrophobic cores as reaction media is a concept known as micellar catalysis. The Lipshutz group was not the first player in this arena, but they have been at it for some time. They recently teamed up with the medicinal chemistry company Kalexsyn and came out with a new amphiphile that caught my eye, dubbed TPGS-750-M. 

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Materials, Synthesis

Nanoparticle Salad: A general route to Metal Oxide Nanoparticles using Green Chemistry

“Green Nanochemistry: Metal Oxide Nanoparticles and Porous Thin Films from Bare Metal Powders” Engelbert Redel, Srebri Petrov, Ömer Dag , Jonathon Moir, Chen Huai, Peter Mirtchev, and Geoffrey A. Ozin, Small2011DOI: 10.1002/smll.201101596

Advocates for green chemistry and nanotechnology have both promised technological solutions to society’s great challenges. Some of the barriers to widespread adoption of nanotechnology have been outlined by Jim Hutchison, and many of these barriers can be addressed by green chemistry. In particular the two issues that the current paper addresses are the excessive waste and the potential hazards associated with the metal precursors.

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Materials, Synthesis

Inherently Flame-Retarding Polymers

“Preparation of flame-retarding poly(propylene carbonate)” Cyriac, A.; Lee, S. H; Varghese, J. K.; Park, J. H.; Jeon, J. Y.; Kim, S. J.; Lee, B. Y. Green Chem. 2011, 13, 3469-3475. DOI: 10.1039/C1GC15722A

During graduate school in California I was very aware of the tremendous amount of household furniture loaded with flame retardant polybrominated diphenyl ether chemicals. Those chemicals do a great job of reducing the flammability of numerous petroleum-based products. Unfortunately their non-covalent incorporation in the polymers speeds their environmental release.  Once in the environment, they break down slowly and bioaccumulate. Additionally there are numerous human health and ecological concerns with these chemicals, including their association with decreased fertility in humans (ref). That is why this paper on flame-retarding poly(propylene carbonate) (PPC) caught my eye. Another reason could have been the flames in their graphical abstract!

TDI = toluene 2,4-diisocyanate; TPU = thermoplastic polyurethane

As luck would have it the chemistry is neat too, flames aside. The researchers begin by highlighting (bragging about?) the fact that they have an actual pilot plant in which they use their cobalt-salen-based catalyst to polymerize CO2 and propylene oxide to PPC (Note: experiments from this study were not performed in the pilot plant). The catalyst displays high turnover frequency (15,000/h) and produces high molecular weight polymers (Mn = 300,000).

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Materials, Synthesis

Oxygen, Nature’s Oxidant for Nature’s Feedstocks.

“Selective catalytic conversion of biobased carbohydrates to formic acid using molecular oxygen”R. Wolfel, N. Taccardi,  A. Bosmann, P. Wasserscheid, Green Chemistry, 2011, DOI: 10.1039/c1gc15434f

Graphical abstract: Selective catalytic conversion of biobased carbohydrates to formic acid using molecular oxygen

All of us have a very personal relationship to the oxidizing power of oxygen. We use oxygen to turn our food into energy, CO2 and water. There are a number of enzymes and pathways that aid this process, each aiding the reaction of food and oxygen toward the creation of CO2 and water.  Now the key to turning complex biomass into usable small molecules is the ability to control this reaction so that we can extract usable chemical building blocks without ending up back at CO2 and water. As you can see in this video over-oxidation can be a real concern.  This paper demonstrates the use of a polyoxometalate (POM) catalyst to promote the oxidation of biomass to formic acid.

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Environmental Chemistry, Materials

How Robots Can Help Us Understand the Environmental Fate of Nanoparticles

“Assessment of the physico-chemical behavior of titanium dioxide nanoparticles in aquatic environments using multi-dimensional parameter testing” von der Kammer, F.; Ottofuelling, S.; Hofmann, T. Environ. Pollut. 2010, 158, 3472-3481. DOI: 10.1016/j.envpol.2010.05.007

In order to rationally design nanoparticles that are environmentally benign, we need to be able to accurately predict their environmental fate (i.e. will they travel long distances through waterways, get stuck in soils or sediments, etc?).  Though relatively robust modeling tools are available for predicting the environmental fate of organic chemicals, analogous tools for nanoparticles are in their infancy.  This is largely due to the insane variety of nanoparticle properties (e.g., composition, size, shape, surface chemistry, etc) that can be varied, resulting in an equally insane variety of nanoparticles to study.  In addition, we know very little about any of these nanoparticles.  One important property that controls the environmental fate of nanoparticles is their propensity to aggregate together and fall out of suspension, potentially limiting their environmental mobility.

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