A Superior Shade of Green: Making Sustainable Materials Better and Cheaper
There’s an engineering adage that if something is green, it can also be good or cheap — but not both.
However, my Purdue Materials Engineering colleagues and I are turning that thinking on its head to bring about a new triple bottom line. Our goal is to discover and develop novel solutions — using new materials, processes and designs — that check the boxes for sustainability, as well as performance and cost-effectiveness. Best case, performance will improve, and costs will decline.
We’re challenging popular misconceptions — flaws that occur because people misperceive the impact of a change, target issues that don’t significantly affect sustainability, and miss data points that disprove common notions.
Numbers can help us refocus. For example, students are surprised when I tell them that taking just one less transatlantic flight per year has about the same carbon impact as eating vegan for two years or going car-free for six months. And in another head-scratcher, plastic shrink wrap used to extend food life (e.g., from four days to two weeks for a cucumber) generally offers a net benefit because it reduces food waste, including the carbon used to produce the food.
Studying materials engineering through the lens of sustainability for some 15 years has convinced me that we can make the materials green in just about everything we use, and innovations can help us create more effective products and save money at the same time.
The main ways to enhance sustainability are to:
- See what’s toxic and remove it.
- Identify materials and processes that use fossil fuels, and then eliminate or reduce that fuel consumption.
- Develop new materials that can operate more efficiently, for example, by being stronger or performing at a higher temperature.)
To the last point, introducing new materials generally involves one of these alternatives:
- Consume less stuff– reduce, reuse, recycle. This is the path we are mostly taught and why we put things in the recycling bin. Unfortunately, we recycle only one-third of our stuff, and most people do not want to reduce consumption and sacrifice quality of life.
- Make things lighter — improve efficiency. For instance, if a car weighs less, it doesn’t require as much power or as much fuel to make it go, so we get the same functionality by consuming less fuel. However, we can push reductions only so far with the materials we have as most things are fairly optimized for economic reasons. So again, to make materials lightweight with current designs requires sacrificing size or amenities.
- Or — and this is my preference — make the product inherently greener. Do so by changing materials, processes or designs without forfeiting (and if possible, by enhancing) properties, functionality or performance. If we replace aluminum in an aircraft with composite, while composite isn’t as green a material, the aircraft becomes lighter so it is more efficient, which makes the overall system greener.
Another path is to tap natural materials, which tend to start out more sustainable. Also, because biomass (think trees or grass) is abundant, it is cheap. In addition, it turns out that nature has had a billion years to optimize structure, so in many cases, natural alternatives can be just as good as or better than synthetic options. Sustainable, good and cheap — the triple bottom line!
For example, a research team on which I participate has discovered that tannic acid — a relatively inexpensive material used for medicine and for beverage flavoring — can be added to epoxy polymers as an effective hardening agent and a flame retardant. This enhancement can produce more environmentally-friendly and durable adhesives, coatings, insulation manufacturing composites, and electronic components, while at the same time eliminating toxic compounds added for safety.
In another project, Purdue researchers including myself have collaborated with Oregon State University and the U.S. Forest Service to create a way to add cellulose nanocrystals, which are wood nanoparticles, to concrete in order to increase its strength, functionality and efficiency. The improved concrete has proved useful in a Wisconsin sidewalk and a South Carolina parking lot, and it’s scheduled for use in a California bridge.
Concrete is the most common synthetic material in the world, and its use by humans is second only to water, so upgrading its quality can have far-reaching benefits. For instance, in another Purdue project, we found that 3D printing of cement paste, a key concrete ingredient, can help concrete become tougher — potentially reducing the frequency of bridge and road replacement.
Engineers need to get out in front of the trend toward the new triple bottom line. Near term, we can expect new government incentives and imperatives, such as a carbon tax or cap and trade system, as well as requirements to design materials so they can be recycled effectively.
In the next 100 to 150 years, our society will move to totally closed-loop solutions. For starters, we need to ask: What if we could substitute natural materials that are more sustainable, effective and efficient than those used today? And what if we could genetically engineer and grow grass and trees to make better materials? We look forward to collaborating with engineers across disciplines and with scientists, such as biologists, to begin developing and implementing answers to these questions.
Jeffrey Youngblood, Ph.D. is a Professor of Materials Engineering at Purdue University, and former Editor-in-Chief of Green Materials
