tag:theconversation.com,2011:/us/topics/chemical-engineering-21799/articlesChemical engineering – The Conversation2023-11-08T19:05:23Ztag:theconversation.com,2011:article/2170352023-11-08T19:05:23Z2023-11-08T19:05:23ZHow animals get their skin patterns is a matter of physics – new research clarifying how could improve medical diagnostics and synthetic materials<figure><img src="https://images.theconversation.com/files/558150/original/file-20231107-15-ksvdj8.png?ixlib=rb-1.1.0&rect=0%2C0%2C2121%2C1412&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Color patterns seen in fish and other animals evolved to serve various purposes.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/close-up-of-the-eye-of-a-yellowspot-rabbitfish-royalty-free-image/691700228">Lagunatic Photo/iStock via Getty Images Plus</a></span></figcaption></figure><p>Patterns on animal skin, such as zebra stripes and poison frog color patches, serve various biological functions, including <a href="https://doi.org/10.1080/00222933.2019.1607600">temperature regulation</a>, <a href="https://doi.org/10.1098/rsos.160824">camouflage</a> and <a href="https://doi.org/10.1111/j.1558-5646.2011.01257.x">warning signals</a>. The colors making up these patterns must be distinct and well separated to be effective. For instance, as a warning signal, distinct colors make them clearly visible to other animals. And as camouflage, well-separated colors allow animals to better blend into their surroundings.</p>
<p>In our newly published research in Science Advances, my student <a href="https://scholar.google.com/citations?user=ZYQyHkYAAAAJ&hl=en">Ben Alessio</a> <a href="https://scholar.google.com/citations?user=oiMqxxoAAAAJ&hl=en">and I</a> propose a <a href="http://www.science.org/doi/10.1126/sciadv.adj2457">potential mechanism</a> explaining how these distinctive patterns form – that could potentially be applied to medical diagnostics and synthetic materials.</p>
<p>A thought experiment can help visualize the challenge of achieving distinctive color patterns. Imagine gently adding a drop of blue and red dye to a cup of water. The drops will slowly disperse throughout the water due to the <a href="https://bio.libretexts.org/Learning_Objects/Worksheets/Biology_Tutorials/Diffusion_and_Osmosis">process of diffusion</a>, where molecules move from an area of higher concentration to lower concentration. Eventually, the water will have an even concentration of blue and red dyes and become purple. Thus, diffusion tends to create color uniformity.</p>
<p>A question naturally arises: How can distinct color patterns form in the presence of diffusion?</p>
<h2>Movement and boundaries</h2>
<p>Mathematician Alan Turing first addressed this question in his seminal 1952 paper, “<a href="https://doi.org/10.1098/rstb.1952.0012">The Chemical Basis of Morphogenesis</a>.” Turing showed that under appropriate conditions, the chemical reactions involved in producing color can interact with each other in a way that counteracts diffusion. This makes it possible for colors to self-organize and create interconnected regions with different colors, forming what are now called Turing patterns. </p>
<p>However, in mathematical models, the boundaries between color regions are fuzzy due to diffusion. This is unlike in nature, where boundaries are often sharp and colors are well separated.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/558105/original/file-20231107-20-d6d55o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Close-up of head of moray eel with dark brown patches separated by uneven white boundaries." src="https://images.theconversation.com/files/558105/original/file-20231107-20-d6d55o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/558105/original/file-20231107-20-d6d55o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/558105/original/file-20231107-20-d6d55o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/558105/original/file-20231107-20-d6d55o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/558105/original/file-20231107-20-d6d55o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/558105/original/file-20231107-20-d6d55o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/558105/original/file-20231107-20-d6d55o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Moray eels have distinctive patterns on their skin.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/laced-leopard-moray-in-indian-ocean-during-a-scuba-royalty-free-image/1306632894">Asergieiev/iStock via Getty Images</a></span>
</figcaption>
</figure>
<p>Our team thought a clue to figuring out how animals create distinctive color patterns could be found in lab experiments on micron-sized particles, such as the <a href="https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Biology_(Kimball)/03%3A_The_Cellular_Basis_of_Life/3.22%3A_Chromatophores">cells involved in producing the colors</a> of an animal’s skin. <a href="https://doi.org/10.1039/D0SM00899K">My work</a> and work from <a href="https://doi.org/10.1073/pnas.1511484112">other labs</a> found that micron-sized particles form <a href="https://doi.org/10.1103/PhysRevLett.117.258001">banded structures</a> when placed between a region with a high concentration of other dissolved solutes and a region with a low concentration of other dissolved solutes.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/558109/original/file-20231107-17-u1tewc.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Diagram of a large blue circle moving to the right as it's swept along with the medium-sized red circles surrounding it also moving to the right, where there is a higher concentration of small green circles" src="https://images.theconversation.com/files/558109/original/file-20231107-17-u1tewc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/558109/original/file-20231107-17-u1tewc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=551&fit=crop&dpr=1 600w, https://images.theconversation.com/files/558109/original/file-20231107-17-u1tewc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=551&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/558109/original/file-20231107-17-u1tewc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=551&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/558109/original/file-20231107-17-u1tewc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=693&fit=crop&dpr=1 754w, https://images.theconversation.com/files/558109/original/file-20231107-17-u1tewc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=693&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/558109/original/file-20231107-17-u1tewc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=693&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The blue circle in this diagram is moving to the right due to diffusiophoresis, as it is swept along with the motion of the red circles moving into an area where there are more green circles.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Schematic_of_particle_illustrating_diffusiophoresis.png">Richard Sear/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>In the context of our thought experiment, changes in the concentration of blue and red dyes in water can propel other particles in the liquid to move in certain directions. As the red dye moves into an area where it is at a lower concentration, nearby particles will be carried along with it. This phenomenon is <a href="https://doi.org/10.1039/C6SM00052E">called diffusiophoresis</a>. </p>
<p>You benefit from diffusiophoresis whenever you <a href="https://doi.org/10.1103/PhysRevApplied.9.034012">do your laundry</a>: Dirt particles move away from your clothing as soap molecules diffuse out from your shirt and into the water.</p>
<h2>Drawing sharp boundaries</h2>
<p>We wondered whether Turing patterns composed of regions of concentration differences could also move micron-sized particles. If so, would the resulting patterns from these particles be sharp and not fuzzy? </p>
<p>To answer this question, we <a href="http://www.science.org/doi/10.1126/sciadv.adj2457">conducted computer simulations</a> of Turing patterns – including hexagons, stripes and double spots – and found that diffusiophoresis makes the resulting patterns significantly more distinctive in all cases. These diffusiophoresis simulations were able to replicate the intricate patterns on the skin of the ornate boxfish and jewel moray eel, which isn’t possible through Turing’s theory alone.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/pU-EB6fa0As?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This video shows small particles moving due to a related phenomenon called diffusioosmosis.</span></figcaption>
</figure>
<p>Further supporting our hypothesis, our model was able to reproduce the findings of a <a href="https://doi.org/10.1038/s41567-021-01213-3">lab study</a> on how the bacterium <em>E. coli</em> moves molecular cargo within themselves. Diffusiophoresis resulted in sharper movement patterns, confirming its role as a physical mechanism behind biological pattern formation. </p>
<p>Because the cells that produce the pigments that make up the colors of an animal’s skin are also micron-sized, our findings suggest that diffusiophoresis may play a key role in creating distinctive color patterns more broadly in nature.</p>
<h2>Learning nature’s trick</h2>
<p>Understanding how nature programs specific functions can help researchers design synthetic systems that perform similar tasks. </p>
<p>Lab experiments have shown that scientists can use diffusiophoresis to create <a href="https://doi.org/10.1038/ncomms15181">membraneless water filters</a> and <a href="https://doi.org/10.1002/adma.201701516">low-cost drug development tools</a>.</p>
<p>Our work suggests that combining the conditions that form Turing patterns with diffusiophoresis could also form the basis of artificial skin patches. Just like adaptive skin patterns in animals, when Turing patterns change – say from hexagons to stripes – this indicates underlying differences in chemical concentrations inside or outside the body. </p>
<p>Skin patches that can sense these changes could diagnose medical conditions and monitor a patient’s health by detecting changes in biochemical markers. These skin patches could also sense changes in the concentration of harmful chemicals in the environment.</p>
<h2>The work ahead</h2>
<p>Our simulations exclusively focused on spherical particles, while the cells that create pigments in skin come in varying shapes. The effect of shape on the formation of intricate patterns remains unclear. </p>
<p>Furthermore, pigment cells move in a complicated biological environment. More research is needed to understand how that environment inhibits motion and potentially freezes patterns in place.</p>
<p>Besides animal skin patterns, Turing patterns are also crucial to other processes such as <a href="https://doi.org/10.1042%2FBST20200013">embryonic development</a> and <a href="https://doi.org/10.1016/j.neo.2020.09.008">tumor formation</a>. Our work suggests that diffusiophoresis may play an underappreciated but important role in these natural processes.</p>
<p>Studying how biological patterns form will help researchers move one step closer to mimicking their functions in the lab – <a href="https://doi.org/10.1038/s41427-021-00322-y">an age-old endeavor</a> that could benefit society.</p><img src="https://counter.theconversation.com/content/217035/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ankur Gupta receives funding from NSF (CBET - 2238412) and ACS Petroleum Research Fund (65836 - DNI9). </span></em></p>Understanding how the intricate spots and stripes, or Turing patterns, of many animals form can help scientists mimic those processes in the lab.Ankur Gupta, Assistant Professor of Chemical and Biological Engineering, University of Colorado BoulderLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2137152023-09-25T12:20:30Z2023-09-25T12:20:30Z‘Design of Coffee’ course teaches engineering through brewing the perfect cup of coffee<figure><img src="https://images.theconversation.com/files/549189/original/file-20230919-29-u8o1mb.jpg?ixlib=rb-1.1.0&rect=7%2C21%2C4785%2C3168&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">UC Davis students learn the fundamentals of both engineering and brewing coffee.</span> <span class="attribution"><span class="source">UC Davis</span></span></figcaption></figure><figure class="align-right ">
<img alt="Text saying: Uncommon Courses, from The Conversation" src="https://images.theconversation.com/files/499014/original/file-20221205-17-kcwec8.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/499014/original/file-20221205-17-kcwec8.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=375&fit=crop&dpr=1 600w, https://images.theconversation.com/files/499014/original/file-20221205-17-kcwec8.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=375&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/499014/original/file-20221205-17-kcwec8.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=375&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/499014/original/file-20221205-17-kcwec8.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=471&fit=crop&dpr=1 754w, https://images.theconversation.com/files/499014/original/file-20221205-17-kcwec8.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=471&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/499014/original/file-20221205-17-kcwec8.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=471&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em><a href="https://theconversation.com/topics/uncommon-courses-130908">Uncommon Courses</a> is an occasional series from The Conversation U.S. highlighting unconventional approaches to teaching.</em> </p>
<h2>Title of course:</h2>
<p>The Design of Coffee: An Introduction to Chemical Engineering</p>
<h2>What prompted the idea for the course?</h2>
<p>In 2012, my colleague professor Tonya Kuhl and I were drinking coffee and brainstorming how to improve our senior-level laboratory course in chemical engineering. Tonya looked at her coffee and suggested, “How about we have the students reverse-engineer a Mr. Coffee drip brewer to see how it works?” </p>
<p>A light bulb went off in my head, and I said, “Why not make a whole course about coffee to introduce lots of students to chemical engineering?” </p>
<p>And that’s what we did. We developed The Design of Coffee as a freshman seminar for 18 students in 2013, and, since then, the course has grown to over 2,000 general education students per year at the University of California, Davis.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/549190/original/file-20230919-25-c9imuf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A student wearing a flannel shirt uses a white microscope, with a pile of coffee beans and a metal scoop sitting next to them on the table." src="https://images.theconversation.com/files/549190/original/file-20230919-25-c9imuf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/549190/original/file-20230919-25-c9imuf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/549190/original/file-20230919-25-c9imuf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/549190/original/file-20230919-25-c9imuf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/549190/original/file-20230919-25-c9imuf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/549190/original/file-20230919-25-c9imuf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/549190/original/file-20230919-25-c9imuf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A student uses a microscope to look at coffee beans in The Design of Coffee lab.</span>
<span class="attribution"><span class="source">UC Davis</span></span>
</figcaption>
</figure>
<h2>What does the course explore?</h2>
<p>The course focus is hands-on experiments with roasting, brewing and tasting in our coffee lab. </p>
<p>For example, students measure the energy they use while roasting to illustrate the law of <a href="https://www.britannica.com/science/conservation-of-energy">conservation of energy</a>, they measure how <a href="https://www.sciencedirect.com/topics/nursing-and-health-professions/ph-measurement">the pH of the coffee</a> changes after brewing to illustrate the kinetics of chemical reactions, and they measure how the <a href="https://doi.org/10.1038/s41598-021-85787-1">total dissolved solids</a> in the brewed coffee relates to time spent brewing to illustrate the principle of <a href="https://en.wikipedia.org/wiki/Mass_transfer">mass transfer</a>. </p>
<p>The course culminates in an engineering design contest, where the students compete to make the best-tasting coffee using the least amount of energy. It’s a classic engineering optimization problem, but one that is broadly accessible – and tasty.</p>
<h2>Why is this course relevant now?</h2>
<p>Coffee plays <a href="https://www.smithsonianmag.com/videos/the-history-of-coffee-culture-in-america/">a huge role in culture</a>, <a href="https://doi.org/10.3945/jn.116.233940">diet</a> and <a href="https://www.ncausa.org/Research-Trends/Economic-Impact">the U.S.</a> and <a href="https://icocoffee.org/">global economy</a>. But historically, relatively little academic work has focused on coffee. There are entire academic programs on wine and beer at many major universities, but almost none on coffee. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/549191/original/file-20230919-15-46yjz8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A student wearing a black UC Davis sweatshirt holds a glass cup of coffee" src="https://images.theconversation.com/files/549191/original/file-20230919-15-46yjz8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/549191/original/file-20230919-15-46yjz8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/549191/original/file-20230919-15-46yjz8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/549191/original/file-20230919-15-46yjz8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/549191/original/file-20230919-15-46yjz8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/549191/original/file-20230919-15-46yjz8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/549191/original/file-20230919-15-46yjz8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Many students who don’t like coffee develop a taste for it over the course of the class.</span>
<span class="attribution"><span class="source">UC Davis</span></span>
</figcaption>
</figure>
<p>The Design of Coffee helps fill a huge unmet demand because students are eager to learn about the beverage that they already enjoy. Perhaps most surprisingly, many of our students enter the course professing to hate coffee, but by the end of the course they are roasting and brewing their own coffee beans at home.</p>
<h2>What’s a critical lesson from the course?</h2>
<p>Many students are shocked to learn that black coffee can have <a href="https://doi.org/10.1111/1750-3841.16531">fruity, floral or sweet flavors</a> without adding any sugar or syrups. The most important lesson from the course is that engineering is really a quantitative way to think about problem-solving. </p>
<p>For example, if the problem to solve is “make coffee taste sweet without adding sugar,” then an engineering approach provides you with a tool set to tackle that problem quantitatively and rigorously. </p>
<h2>What materials does the course feature?</h2>
<p>Tonya and I originally self-published our lab manual, <a href="https://www.amazon.com/Design-Coffee-Engineering-Approach/dp/B09FSCDY18">The Design of Coffee: An Engineering Approach</a>, to keep prices low for our students. </p>
<p>Now in its third edition, it has sold more than 15,000 copies and has been translated to <a href="https://www.amazon.com/dise%C3%B1o-del-caf%C3%A9-aproximaci%C3%B3n-ingenier%C3%ADa/dp/B08TQ42NS2/">Spanish</a>, with Korean and Indonesian translations on the way.</p>
<h2>What will the course prepare students to do?</h2>
<p>Years ago, a student in our class told the campus newspaper, “I had no idea there was an engineering way to think about coffee!” Our main goal is to teach students that there is an engineering way to think about anything. </p>
<p>The engineering skills and mindset we teach equally prepare students to design a multimillion-dollar biofuel refinery, a billion-dollar pharmaceutical production facility or, most challenging of all, a naturally sweet and delicious $3 cup of coffee. Our course is the first step in preparing students to tackle these problems, as well as new problems that no one has yet encountered.</p><img src="https://counter.theconversation.com/content/213715/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>William D. Ristenpart receives funding from the National Science Foundation, the Coffee Science Foundation, and the Specialty Coffee Association. </span></em></p>In an engineering course at UC Davis, students learn all the nuances that go into brewing ‘a truly excellent cup of coffee.’William D. Ristenpart, Professor of Chemical Engineering, University of California, DavisLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2130252023-09-07T18:00:25Z2023-09-07T18:00:25ZSeparating molecules is a highly energy-intensive but essential part of drug development, desalination and other industrial processes – improving membranes can help<figure><img src="https://images.theconversation.com/files/546739/original/file-20230906-15-1tywxl.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2121%2C1412&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Molecules are often separated by their size, shape or other properties.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/abstract-spheres-flowing-through-a-circle-shaped-royalty-free-image/1336236614">twomeows/Moment via Getty Images</a></span></figcaption></figure><p>Separating molecules is critical to producing many essential products. For example, in <a href="https://www.britannica.com/technology/petroleum-refining">petroleum refining</a>, the hydrocarbons – chemical compounds composed of hydrogens and carbons – in crude oil are separated into gasoline, diesel and lubricants by sorting them based on their molecular size, shape and weight. In the <a href="https://doi.org/10.1038/s41586-022-05032-1">pharmaceutical industry</a>, the active ingredients in medications are purified by separating drug molecules from the enzymes, solutions and other components used to make them. </p>
<p>These separation processes take a substantial amount of energy, accounting for <a href="https://doi.org/10.1038/532435a">roughly half of U.S. industrial energy use</a>. Traditionally, molecular separations have relied on methods that require intensive heating and cooling that make them very energy inefficient. </p>
<p>We are <a href="https://scholar.google.com/citations?user=wiZJ2yAAAAAJ&hl=en">chemical and</a> <a href="https://scholar.google.com/citations?user=ryUNRywAAAAJ&hl=en">biological engineers</a>. In our newly published research, we designed a new type of <a href="https://www.science.org/doi/10.1126/science.adh2404">membrane with nanopores</a> that can quickly and precisely separate a diverse range of molecules under harsh industrial conditions.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/mxqOPdEUNTs?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Membranes are one method to desalinate water.</span></figcaption>
</figure>
<h2>Membrane technology</h2>
<p><a href="https://en.wikipedia.org/wiki/Membrane">Membranes are physical barriers</a> that can separate molecules in a mixture like a sieve based on their size or affinity – such as charge or polarity – to the membrane material. For example, <a href="https://www.genome.gov/genetics-glossary/Cell-Membrane">your cells</a> are surrounded by a membrane that transports nutrients into it and transports toxins out of it. <a href="https://en.wikipedia.org/wiki/Membrane_technology">Membrane technology</a> include synthetic barriers that can separate molecules in industrially important mixtures at a lower energy cost than traditional methods. </p>
<p>Currently available membranes, including those used in large-scale <a href="https://doi.org/10.1126/science.abb8518">seawater desalination</a>, suffer from instability at high temperatures and when exposed to <a href="https://www.cdc.gov/niosh/topics/organsolv/default.html#">organic solvents</a> – carbon-based chemicals that dissolve other substances. This has limited the use of membranes in many industrial separations. </p>
<p><a href="https://doi.org/10.1126/science.aax3103">Inorganic materials</a> are more stable and better able to survive industrial conditions. Previous studies have focused on making inorganic membranes that are ultrathin in order to allow specific molecules to pass through. But thinness increases the likelihood of creating defects and pinholes in the membrane, and would be difficult to make on an industrial scale. </p>
<h2>Improving membrane separation</h2>
<p>We developed a technique to make a new inorganic material called <a href="https://www.science.org/doi/10.1126/science.adh2404">carbon-doped metal oxide</a> that can separate organic molecules smaller than one nanometer (for scale, a <a href="https://www.nano.gov/nanotech-101/what/nano-size">gold atom</a> is a third of a nanometer in diameter).</p>
<p>Taking inspiration from an existing technology that manufacturers use to make semiconductors, called <a href="https://doi.org/10.3762/bjnano.5.123">molecular layer deposition</a>, we worked with two low-cost reactants from that process and generated thin films. These films contain nanopores that can be precisely tuned to control the separation of molecules ranging from 0.6 to 1.2 nanometers in diameter.</p>
<p>One of the key features of our membrane is that it can <a href="https://www.science.org/doi/10.1126/science.adh2404">withstand harsh conditions</a>. These membranes are stable up to 284 degrees Fahrenheit (140 degrees Celsius) and pressures up to 30 atmospheres (around 441 pounds per square inch) in the presence of organic solvents. This stability is critical, as many industrial separation processes can save tremendous amounts of energy when carried out under high temperatures. </p>
<p>As a demonstration, we used our membrane in the molecule separation step during the manufacture of the pesticide boscalid. By tailoring the pore sizes of our membranes to match the sizes of the molecules in the mixture, we were able to <a href="https://www.science.org/doi/10.1126/science.adh2404">separate each individual component</a> of reactant, product and catalyst. Because of the stability of our membrane, we were able to carry out the whole process at 194 F (90 C), the temperature at which the reaction takes place, eliminating the need to reduce the temperature during the separation process. This can significantly reduce energy consumption and, in turn, reduce the carbon footprint of the industrial process. </p>
<p>We believe our membrane can be used in many similar industrial processes, including those involving harsh conditions where traditional membranes would fail, and are confident that it can be quickly scaled up. This can open the door for researchers and manufacturers to use membranes in previously unexplored applications.</p><img src="https://counter.theconversation.com/content/213025/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Miao Yu receives funding from National Science Foundation.</span></em></p><p class="fine-print"><em><span>Bratin Sengupta does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Around half of US industrial energy use goes toward separating molecules in industrial processes. Developing materials that can withstand harsh industrial conditions can help increase efficiency.Bratin Sengupta, Ph.D. Candidate in Chemical and Biological Engineering, University at BuffaloMiao Yu, Professor of Chemical and Biological Engineering, University at BuffaloLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1404412020-06-11T19:56:52Z2020-06-11T19:56:52ZWhat makes pepper spray so intense? And is it a tear gas? A chemical engineer explains<p>In recent weeks, the world has looked on as governments use chemical irritants to control protesters and riots. Whether it’s tear gas, pepper spray, mace or pepper balls, all have one thing in common: they’re chemical weapons. </p>
<p>Chemical warfare agents have been used twice in Sydney in the past week alone. Police <a href="https://www.abc.net.au/news/2020-06-07/sydney-police-defend-pepper-spray-use-on-protesters/12330558">pepper-sprayed</a> demonstrators at Central Station, following Saturday’s major Black Lives Matter protest. </p>
<p>The next day, tear gas <a href="https://www.abc.net.au/news/2020-06-08/tear-gas-fired-into-exercise-yard-of-sydney-long-bay-jail/12332572">was used</a> to break up a fight at Long Bay jail, as prison guards filled an exercise yard with tear gas canisters – also impacting nearby residents.</p>
<p>These events followed the deployment of <a href="https://edition.cnn.com/2020/06/05/politics/park-police-tear-gas/index.html">chemical riot control agents</a> – specifically “pepper bombs” – in Washington DC last week. They were used to clear protesters from a public park so President Donald Trump could walk from the White House to a nearby church for a photo opportunity.</p>
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<p>US Attorney General William Barr said “<a href="https://www.factcheck.org/2020/06/the-continuing-tear-gas-debate/">there was no tear gas used</a>”, claiming “pepper spray is not a chemical irritant. It’s not chemical.”</p>
<p>I’m a chemical engineer and chemist who studies chemicals in the environment. So I thought I’d clear the air about what makes pepper spray such a powerful chemical irritant, and a chemical weapon.</p>
<h2>What’s inside pepper spray?</h2>
<p>The active compounds in pepper spray are collectively known as capsaicinoids. They are given the military symbol OC, for “oleoresin capsicum”. </p>
<p>The most important chemical in OC is capsaicin. This is derived from chilli peppers in a chemical process that dissolves and concentrates it into a liquid. Capsaicin is the same compound that makes chillies hot, but in an intense, weaponised form. </p>
<p>Not all capsaicinoids are obtained naturally. One called nonivamide (also known as PAVA or pelargonic acid vanillylamide) is mostly made by humans. PAVA is an <a href="https://cot.food.gov.uk/committee/committee-on-toxicity/cotstatements/cotstatementsyrs/cotstatements2002/pavastatement">intense irritant</a> used in <a href="https://www.theguardian.com/society/2018/dec/09/pepper-spray-used-in-non-violent-situations-in-prison-pilot">artificial pepper spray</a>.</p>
<h2>Is pepper spray a tear gas?</h2>
<p>We’ve established pepper spray is a chemical, but is it also a kind of tear gas? </p>
<p>“<a href="https://emergency.cdc.gov/agent/riotcontrol/factsheet.asp">Tear gas</a>” is an informal term and a bit of a misnomer, because it isn’t a gas. Rather, tear gas refers to any weaponised irritant used to immobilise people.</p>
<p>More specifically, tear gas is often used to describe weapons that disperse their irritants in the air either as liquid aerosol droplets (such as <a href="https://www.popularmechanics.com/science/health/a28904691/how-tear-gas-works/">gas canisters</a>), or as a powder (such as pepper balls). This definition distinguishes tear gas from personal self-defence sprays which use foams, gels and liquids.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/what-is-tear-gas-139958">What is tear gas?</a>
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</em>
</p>
<hr>
<p>Tear gas canisters typically contain the irritants 2-chlorobenzalmalononitrile (CS) and phenacyl chloride (CN). Both CS and CN are man-made chemicals discovered in a lab, unlike capsaicin (the traditional ingredient in pepper spray).</p>
<p>But despite capsaicin coming from chilli peppers, pepper spray is still a weaponised irritant that can be delivered as an aerosol or powder. It should unequivocally be considered a type of tear gas.</p>
<h2>Pepper spray as a weapon</h2>
<p>The chemical irritants OC, CS and CN have military symbols because they are chemical weapons. They are termed “<a href="https://www.wbur.org/news/2020/06/10/rubber-bullets-protesters-victoria-snelgrove-boston">less-lethal</a>” because they are less likely to kill than conventional weapons. Their use, however, can still <a href="https://www.forbes.com/sites/judystone/2020/06/08/tear-gas-and-pepper-spray-can-maim-kill-and-spread-coronavirus/#47f17a2a725f">cause fatalities</a>.</p>
<p>Technically, pepper spray and other tear gases are classified as lachrymatory agents. <a href="https://theconversation.com/what-is-tear-gas-139958">Lachrymatory agents</a> attack mucous membranes in the eyes and respiratory system. </p>
<p>Pepper spray works almost instantly, forcing the eyes to close and flood with tears. Coupled with coughing fits and difficulty breathing, this means the targeted person is effectively <a href="https://healthland.time.com/2011/11/22/how-painful-is-pepper-spray/">blinded and incapacitated</a>. Because lachrymatory agents work on <a href="https://www.ncbi.nlm.nih.gov/books/NBK544263/">nerve receptors</a> that help us sense heat, they also induce an intense burning sensation. </p>
<p>The combined effects of pepper spray can last anywhere from 15 minutes to more than an hour.</p>
<p>Lachrymatory agents emerged on the <a href="https://www.history.com/this-day-in-history/germans-introduce-poison-gas">battlefields of World War I</a>. Artillery shells were filled with chemicals such as <a href="https://www.compoundchem.com/2014/05/17/chemical-warfare-ww1/">xylyl bromide and chloroacetone</a> and fired at enemy soldiers. Agents that induce choking, blistering and vomiting were added as the <a href="https://www.nytimes.com/2018/11/10/science/chemical-weapons-world-war-1-armistice.html">chemical arms race</a> escalated.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/tear-gas-and-pepper-spray-are-chemical-weapons-so-why-can-police-use-them-140364">Tear gas and pepper spray are chemical weapons. So, why can police use them?</a>
</strong>
</em>
</p>
<hr>
<p>In the 1920s, the <a href="https://www.un.org/disarmament/wmd/bio/1925-geneva-protocol/">Geneva Protocol</a> was enacted to ban the use of indiscriminate and often ineffective chemical weapons on the battlefield. Today, the unjustified use of chemical riot control agents <a href="https://www.aljazeera.com/indepth/opinion/2012/04/201242913130963418.html">threatens to erode</a> the systems that are meant to protect us from the most dangerous weaponised chemicals.</p><img src="https://counter.theconversation.com/content/140441/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gabriel da Silva does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Pepper spray uses a chemical called capsaicin. It’s the same compound that makes chillies hot, but in a more intense, weaponised form.Gabriel da Silva, Senior Lecturer in Chemical Engineering, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1311472020-02-11T19:08:45Z2020-02-11T19:08:45ZSmall world: atom-scale materials are the next tech frontier<figure><img src="https://images.theconversation.com/files/314662/original/file-20200211-146686-19pb781.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C7976%2C4500&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Could graphene - shown here as an illustration of its molecular structure - come to define the next phase of the information revolution?</span> <span class="attribution"><span class="source">Rost9/Shutterstock</span></span></figcaption></figure><p>Every age in the history of human civilisation has a signature material, from the Stone Age, to the Bronze and Iron Ages. We might even call today’s information-driven society the Silicon Age. </p>
<p>Since the 1960s, silicon <a href="https://www.sciencedirect.com/topics/engineering/silicon-nanoparticles">nanostructures</a>, the building-blocks of microchips, have supercharged the development of electronics, communications, manufacturing, medicine, and more.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-nanotechnology-is-more-than-just-a-buzzword-97376">Why nanotechnology is more than just a buzzword</a>
</strong>
</em>
</p>
<hr>
<p>How small are these nanostructures? Very, very small – you could fit <a href="https://www.extremetech.com/extreme/191996-zoom-into-a-computer-chip-watch-this-video-to-fully-appreciate-just-how-magical-modern-microchips-are">at least 3,000 silicon transistors onto the tip of a human hair</a>. But there is a limit: below about 5 nanometres (5 millionths of a millimetre), it is hard to improve the performance of silicon devices any further.</p>
<p>So if we are about to exhaust the potential of silicon nanomaterials, what will be our next signature material? That’s where “atomaterials” come in. </p>
<h2>What are atomaterials?</h2>
<p>“Atomaterials” is short for “atomic materials”, so called because their properties depend on the precise configuration of their atoms. It is a new but <a href="https://lniconference.com.au/">rapidly developing</a> field.</p>
<p>One example is <a href="https://theconversation.com/graphene-and-the-atomic-crystals-that-could-see-next-big-breakthrough-in-tech-99156">graphene</a>, which is made of carbon atoms. Unlike diamond, in which the carbon atoms form a rigid three-dimensional structure, graphene is made of single layer of carbon atoms, bonded together in a two-dimensional honeycomb lattice.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/harder-than-diamond-stronger-than-steel-super-conductor-graphenes-unreal-5123">Harder than diamond, stronger than steel, super conductor ... graphene's unreal </a>
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</em>
</p>
<hr>
<p>Diamond’s rigid structure is the reason for its celebrated hardness and longevity, making it the perfect material for high-end drill bits and expensive jewellery. In contrast, the two-dimensional form of carbon atoms in graphene allows electron travelling frictionless at a high speed giving ultrahigh conductivity and the outstanding in plane mechanical strength. Thus, graphene has broad applications in medicines, electronics, energy storage, light processing, and water filtration. </p>
<p>Using lasers, we can fashion these atomic structures into miniaturised devices with exceptional performance.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/JtmQi-eJQfg?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Using atomaterials, <a href="https://www.swinburne.edu.au/research/translational-atomaterials/">our lab</a> has been working on a range of innovations, at various stages of development. They include:</p>
<ul>
<li><strong>A magic cooling film</strong>. This film can cool the environment by up to 10°C without using any electricity. By integrating such a film into a building, the electricity used for air conditioning can be reduced by 35%, and summer electricity blackouts effectively stopped. This will not only save electricity bills but also reduce greenhouse emissions.</li>
</ul>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/314664/original/file-20200211-146700-cz8xg2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/314664/original/file-20200211-146700-cz8xg2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/314664/original/file-20200211-146700-cz8xg2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/314664/original/file-20200211-146700-cz8xg2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/314664/original/file-20200211-146700-cz8xg2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/314664/original/file-20200211-146700-cz8xg2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/314664/original/file-20200211-146700-cz8xg2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/314664/original/file-20200211-146700-cz8xg2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Baohua Jia and Han Lin with the graphene cooling film.</span>
<span class="attribution"><span class="source">CTAM Global OpenLab</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<ul>
<li><strong>Heat-absorbing film</strong>. Some 97% of Earth’s water is in the oceans, and is salty and unusable without expensive processing. Efficiently removing salt from seawater could be a long-term solution to the growing global freshwater scarcity. With a solar-powered graphene film, this process can be made very efficient.</li>
</ul>
<p>The film absorbs almost all the sunlight shining on it and converts it into heat. The temperature can be <a href="https://www.sustainabilitymatters.net.au/content/energy/case-study/ultrathin-graphene-film-offers-new-concept-for-solar-energy-738586419">increased to 160°C within 30 seconds</a>. This heat can then distil seawater with an efficiency greater than 95%, and the distilled water is cleaner than tapwater. This low-cost technology can be suitable for domestic and industry applications.</p>
<ul>
<li><p><strong>Smart sensing film</strong>. These flexible atomaterial films can incorporate a wide range of functions including environmental sensing, communication, and energy storage. They have a broad range of applications in healthcare, sports, advanced manufacturing, farming, and others. For example, smart films could monitor soil humidity near plants’ roots, thus helping to make agriculture more water-efficient.</p></li>
<li><p><strong>Ultrathin, ultra-lightweight lenses</strong>. The bulkiest part of a mobile phone camera is the lens, because it needs to be made of thick glass with particular optical properties. But lenses made with graphene can be mere <a href="https://newatlas.com/optical-lens-one-billionth-meter-thick/41588/">millionths of a millimetre thick</a>, and still deliver superb image quality. Such lenses could greatly reduce the weight and cost of everything from phones to space satellites. </p></li>
<li><p><strong>Near-instant power supply</strong>. We have developed an environmentally friendly supercapacitor from graphene that <a href="https://freshscience.org.au/2016/fast-charging-everlasting-battery-power-from-graphene">charges devices in seconds</a>, and has a lifetime of millions of charge cycles. By attaching it to the back of a solar cell, it can store and deliver solar-generated energy whenever and wherever required. You will be free and truly mobile.</p></li>
</ul>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/314665/original/file-20200211-146678-1lakcot.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/314665/original/file-20200211-146678-1lakcot.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/314665/original/file-20200211-146678-1lakcot.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/314665/original/file-20200211-146678-1lakcot.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/314665/original/file-20200211-146678-1lakcot.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/314665/original/file-20200211-146678-1lakcot.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/314665/original/file-20200211-146678-1lakcot.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/314665/original/file-20200211-146678-1lakcot.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The graphene supercapacitor could help mobile power truly live up to its name.</span>
<span class="attribution"><span class="source">CTAM Global OpenLab</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Where to next?</h2>
<p>It can take years for some of these laboratory technologies to reach fruition. To try and speed up the process, we established the <a href="https://ctam.org.au/about-ctam/">CTAM Global OpenLab</a> to engage with industry, academia, government and the wider community and to promote sharing and collaboration. The lab was launched earlier this month at the <a href="https://lniconference.com.au/">International Conference on Nanomaterial and Atomaterial Sciences and Applications (ICNASA2020)</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/finding-an-affordable-way-to-use-graphene-is-the-key-to-its-success-32154">Finding an affordable way to use graphene is the key to its success</a>
</strong>
</em>
</p>
<hr>
<p>The world is facing pressing challenges, from climate change, to energy and resource scarcity, to our health and well-being.</p>
<p>Material innovation is more vital than ever and needs to be more efficient, design-driven and environmentally friendly. But these challenges can only be solved by joint effort from worldwide researchers, enterprise, industry and government with a sharing and open mindset.</p><img src="https://counter.theconversation.com/content/131147/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Baohua Jia receives funding from Australian Research Council, Cooperative Research Centres Projects. She is affiliated with Centre for Translational Atomaterials (CTAM), Faculty of Science, Engineering and Technology, Swinburne University of Technology. </span></em></p>Since the 1960s, silicon ‘nanomaterials’ have driven the information revolution. But as their potential is exhausted, is it time for ‘atomaterials’ such as graphene to drive innovation still further?Baohua Jia, Professor, Swinburne University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1040722018-10-01T18:09:26Z2018-10-01T18:09:26ZHow we can turn plastic waste into green energy<figure><img src="https://images.theconversation.com/files/238769/original/file-20181001-195282-u8z9ln.jpg?ixlib=rb-1.1.0&rect=162%2C108%2C5843%2C3511&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/waste-open-burning-site-plastic-396406627?src=mKJMm9U_C1y6bdZAyDtISw-1-98">Shutterstock.</a></span></figcaption></figure><p>In the adventure classic Back to the Future, Emmett “Doc” Brown uses <a href="https://www.youtube.com/watch?time_continue=15&v=7EXOxilOi7Y">energy generated from rubbish</a> to power his DeLorean time machine. But while a time machine may still be some way off, the prospect of using rubbish for fuel isn’t too far from reality. Plastics, in particular, contain mainly carbon and hydrogen, with similar energy content to conventional fuels such as diesel. </p>
<p>Plastics are among the most valuable waste materials – although with the way people discard them, you probably wouldn’t know it. It’s possible to convert all plastics directly into useful forms of energy and chemicals for industry, <a href="https://pubs.rsc.org/en/content/articlelanding/2018/gc/c7gc03662k#!divAbstract">using a process</a> called “cold plasma pyrolysis”. </p>
<p><a href="https://pubs.rsc.org/en/content/articlelanding/2018/gc/c8gc01163j#!divAbstract">Pyrolysis</a> is a method of heating, which decomposes organic materials at temperatures between 400°C and 650°C, in an environment with limited oxygen. Pyrolysis is normally used to generate energy in the form of heat, electricity or fuels, but it could be even more beneficial if <a href="https://pubs.rsc.org/en/content/articlehtml/2018/gc/c7gc03662k">cold plasma</a> was incorporated into the process, to help recover other chemicals and materials.</p>
<h2>The case for cold plasma pyrolysis</h2>
<p>Cold plasma pyrolysis makes it possible to convert waste plastics into hydrogen, methane and ethylene. Both hydrogen and methane can be used as clean fuels, since they only produce minimal amounts of harmful compounds such as soot, unburnt hydrocarbons and carbon dioxide (CO₂). And ethylene is <a href="https://www.intratec.us/analysis/ethylene-e81a">the basic building block</a> of most plastics used around the world today. </p>
<p>As it stands, 40% of waste plastic products in the US and 31% in the EU are <a href="https://www.plasticseurope.org/application/files/5515/1689/9220/2014plastics_the_facts_PubFeb2015.pdf">sent to landfill</a>. Plastic waste also <a href="https://www.plasticseurope.org/application/files/5515/1689/9220/2014plastics_the_facts_PubFeb2015.pdf">makes up</a> 10% to 13% of municipal solid waste. This wastage has huge detrimental impacts on oceans and other ecosystems.</p>
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<p>Of course, burning plastics to generate energy is normally far better than wasting them. But burning does not recover materials for reuse, and if the conditions are not tightly controlled, it can have <a href="https://www.ncbi.nlm.nih.gov/pubmed/19577459">detrimental effects on the environment</a> such as air pollution.</p>
<p>In a circular economy – where waste is recycled into new products, rather than being thrown away – technologies that give new life to waste plastics could transform the problem of mounting waste plastic. Rather than wasting plastics, cold plasma pyrolysis can be used to recover valuable materials, which can be sent directly back into industry. </p>
<h2>How to recover waste plastic</h2>
<p>In <a href="https://pubs.rsc.org/en/content/articlelanding/2018/gc/c7gc03662k#!divAbstract">our recent study</a> we tested the effectiveness of cold plasma pyrolysis using plastic bags, milk and bleach bottles collected by a local recycling facility in Newcastle, UK. </p>
<p>We found that 55 times more ethylene was recovered from [high density polyethylene (HDPE)] – which is used to produce everyday objects such as plastic bottles and piping – using cold plasma, compared to conventional pyrolysis. About 24% of plastic weight was converted from HDPE directly into valuable products. </p>
<p>Plasma technologies have been used to deal with hazardous waste in the past, but the process occurs at very high temperatures of more than 3,000°C, and therefore requires a complex and energy intensive cooling system. The process for cold plasma pyrolysis that we investigated operates at just 500°C to 600°C by combining conventional heating and cold plasma, which means the process requires relatively much less energy.</p>
<p>The cold plasma, which is used to break chemical bonds, initiate and excite reactions, <a href="http://iopscience.iop.org/article/10.1088/1361-6595/26/1/015013/meta">is generated from</a> two electrodes separated by one or two insulating barriers. </p>
<p>Cold plasma is unique because it mainly produces hot (highly energetic) electrons – these particles are great for breaking down the chemical bonds of plastics. Electricity for generating the cold plasma could be sourced from renewables, with the chemical products derived from the process used as a form of energy storage: where the energy is kept in a different form to be used later.</p>
<p>The advantages of using cold plasma over conventional pyrolysis is that the process can be tightly controlled, making it easier to crack the chemical bonds in HDPE that effectively turn heavy hydrocarbons from plastics into lighter ones. You can use the plasma to convert plastics into other materials; hydrogen and methane for energy, or ethylene and hydrocarbons for polymers or other chemical processes. </p>
<p>Best of all, the reaction time with cold plasma takes seconds, which makes the process rapid and potentially cheap. So, cold plasma pyrolysis could offer a range of business opportunities to turn something we currently waste into a valuable product. </p>
<p>The UK is currently struggling to meet a 50% household recycling target for 2020. But our research demonstrates a possible place for plastics in a circular economy. With cold plasma pyrolysis, it may yet be possible to realise the true value of plastic waste – and turn it into something clean and useful.</p><img src="https://counter.theconversation.com/content/104072/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Anh Phan does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>In the EU, 31% of plastic products go to landfill: but a process called “cold plasma pyrolysis” could turn them into clean fuels.Anh Phan, Lecturer in Chemical Engineering, Newcastle UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/961282018-05-14T06:22:31Z2018-05-14T06:22:31ZIf we can’t recycle it, why not turn our waste plastic into fuel?<figure><img src="https://images.theconversation.com/files/218749/original/file-20180514-178746-ba0vjx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Could this be turned into fuel, instead of just more plastic?</span> <span class="attribution"><span class="source">Shutterstock.com</span></span></figcaption></figure><p>Australia’s <a href="https://theconversation.com/au/topics/recycling-crisis-53343">recycling crisis</a> needs us to look into waste management options beyond just recycling and landfilling. Some of our waste, like paper or organic matter, can be composted. Some, like glass, metal and rigid plastics, can be recycled. But we have no immediate solution for non-recyclable plastic waste except landfill. </p>
<p>At a <a href="http://www.environment.gov.au/system/files/pages/4f59b654-53aa-43df-b9d1-b21f9caa500c/files/mem7-agreed-statement.pdf">meeting last month</a>, federal and state environment ministers endorsed an ambitious target to make all Australian packaging <a href="https://theconversation.com/the-new-100-recyclable-packaging-target-is-no-use-if-our-waste-isnt-actually-recycled-95857">recyclable, compostable or reusable by 2025</a>. But the ministers also showed support for processes to turn our waste into energy, although they did not specifically discuss plastic waste as an energy source.</p>
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<a href="https://theconversation.com/a-crisis-too-big-to-waste-chinas-recycling-ban-calls-for-a-long-term-rethink-in-australia-95877">A crisis too big to waste: China's recycling ban calls for a long-term rethink in Australia</a>
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<p>The 100% goal could easily be achieved if all packaging were made of paper or wood-based materials. But realistically, plastic will continue to dominate our packaging, especially for food, because it is moisture-proof, airtight, and hygienic. </p>
<p>Most rigid plastic products can only be recycled a few times before they lose their original properties and <a href="https://doi.org/10.1016/j.wasman.2017.07.044">become non-recyclable</a>. Even in European countries with strict waste management strategies, only <a href="https://www.plasticseurope.org/application/files/5715/1717/4180/Plastics_the_facts_2017_FINAL_for_website_one_page.pdf">31% of plastic waste is recycled</a>. </p>
<p>Worldwide plastic production is predicted to increase by <a href="http://www3.weforum.org/docs/WEF_The_New_Plastics_Economy.pdf">3.8% every year until 2030</a>. Flexible, non-recyclable plastic materials are used in an increasing <a href="https://doi.org/10.1016/j.wasman.2018.04.023">range of applications</a> like packaging, 3D printing, and construction.</p>
<p>We need to expand our range of options for keeping this plastic waste out of landfill. One potential approach is “plastic to energy”, which unlocks the chemical energy stored in waste plastic and uses it to create fuel.</p>
<h2>How plastic to energy works</h2>
<p>Plastic is made from refined crude oil. Its price and production are dictated by the petrochemical industry and the availability of oil. As oil is a finite natural resource, the most sustainable option would be to reduce crude-oil consumption by recycling the plastic and recovering as much of the raw material as possible. </p>
<p>There are two types of recycling: mechanical and chemical. Mechanical recycling involves sorting, cleaning and shredding plastic to make pellets, which can then be fashioned into other products. This approach works very well if plastic wastes are sorted according to their chemical composition.</p>
<p>Chemical recycling, in contrast, turns the plastic into an <a href="https://doi.org/10.1016/j.ejbt.2017.01.004">energy carrier or feedstock for fuels</a>. There are two different processes by which this can be done: <a href="https://doi.org/10.1016/j.jaap.2017.12.020">gasification and pyrolysis</a>. </p>
<p><strong>Gasification</strong> involves heating the waste plastic with air or steam, to produce a valuable industrial gas mixtures called “synthesis gas”, or syngas. This can then be used to produce diesel and petrol, or <a href="https://doi.org/10.1533/9780857096364.2.146">burned directly in boilers to generate electricity</a>. </p>
<p>In <strong>pyrolysis</strong>, plastic waste is heated in the absence of oxygen, which produces mixture of oil similar to crude oil. This can be further refined into transportation fuels. </p>
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<span class="caption">One of the advantages of plastic waste-to-fuel is that plastic doesn’t have to be separated into different types.</span>
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<p>Gasification and pyrolysis are completely different processes to simply incinerating the plastic. The main goal of incineration is simply to destroy the waste, thus keeping it out of landfill. The heat released from incineration might be used to produce steam to drive a turbine and generate electricity, but this is only a by-product. </p>
<p>Gasification and pyrolysis can produce electricity or fuels, and provide more flexible ways of storing energy than incineration. They also have much lower emissions of sulfur and nitrogen oxides than incineration.</p>
<p>Currently, incineration plants are viewed as an alternative energy supply source and a modern way of driving a <a href="https://theconversation.com/explainer-what-is-the-circular-economy-23298">circular economy</a>, particularly in Japan, South Korea and China, where land is valuable and energy resources are scarce. In other countries, although waste incineration is common practice, the debate around human health impacts, supply issues and fuel trade incentives remains unresolved. </p>
<h2>Can Australia embrace plastic to waste?</h2>
<p>Gasification of plastic waste needs significant initial financing. It requires pre-treatment, cleanup facilities, gas separation units, and advanced control systems. Pyrolysis units, on the other hand, can be modular and be installed to process as little as 10,000 tonnes per year – a relatively small amount in waste management terms. <a href="https://www.planning.act.gov.au/__data/assets/pdf_file/0008/1043657/Appendix-G-Review-of-Pyrolysis-Worldwide-RICARDO.pdf">Plastic pyrolysis plants</a> have already been built in the <a href="http://plasticenergy.net/index.php">UK</a>, <a href="http://www.kleanindustries.com/s/Home.asp">Japan</a> and the <a href="http://www.agilyx.com/">United States</a>. </p>
<p>As pyrolysis and gasification technologies can only process plastics, many councils <a href="http://www.environment.gov.au/system/files/resources/d075c9bc-45b3-4ac0-a8f2-6494c7d1fa0d/files/national-waste-report-2016.pdf">do not see major advantages in using them</a>. But by taking only a specific waste stream, they encourage better waste sorting and help to reduce the flow of mixed waste and plastic litter.</p>
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<p>Australia has invested a serious amount of funding into research, particularly in waste conversion. It has a solid industrialised infrastructure and a highly skilled workforce. The current recycling crisis offers an opportunity to explore some innovative ways of turning our waste into valuable products. </p>
<p>There are direct job opportunities in plastic conversion plants, and indirect jobs around installation, maintenance and distribution of energy and fuels. We might even see jobs in R&D to explore other waste conversion technologies. </p>
<p>In the meantime, the plastic we send to landfill is <a href="http://rstb.royalsocietypublishing.org/content/364/1526/2153">damaging our environment</a> and <a href="http://rstb.royalsocietypublishing.org/content/364/1526/2027">harming wildlife</a>. That needs to change, and Australia should consider plastic waste-to-energy as part of that change.</p><img src="https://counter.theconversation.com/content/96128/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Muxina Konarova receives funding from Advanced Qld Fellowship Scheme and ARENA (Emerging Renewables). </span></em></p>Plastic can only be recycled a few times before it becomes useless. But even non-recyclable plastic can be used to help produce petrol and diesel. Could this process help overcome the recycling crisis?Muxina Konarova, Advanced Queensland Research Fellow, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/707402017-03-27T03:51:04Z2017-03-27T03:51:04ZGreen chemistry is key to reducing waste and improving sustainability<figure><img src="https://images.theconversation.com/files/155790/original/image-20170207-27210-1bbpobt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Chemistry has been getting greener since the '80s.
</span> <span class="attribution"><span class="source">Chemistry image from www.shutterstock.com</span></span></figcaption></figure><p>The development and evolution of the chemical industry is directly responsible for many of the <a href="http://www.essentialchemicalindustry.org/the-chemical-industry/the-chemical-industry.html#section_2">technological advancements</a> that have emerged since the late 19th century. </p>
<p>However, it was not until the 1980s that the <a href="https://www.acs.org/content/acs/en/greenchemistry/what-is-green-chemistry/history-of-green-chemistry.html">environment became a priority for the chemical industry</a>. This was prompted largely by stricter environmental regulations and a need to address the sector’s poor reputation, particularly due to <a href="http://www.nature.com/news/2011/110104/full/469018a.html">pollution and industrial accidents</a>.</p>
<p>But the industry is now rapidly improving, and this changing mindset has provided the backdrop for the emergence of green chemistry. </p>
<h2>What is green chemistry?</h2>
<p>Sustainability is becoming increasingly important in almost every industry and <a href="http://www.nature.com/nature/journal/v450/n7171/full/450810a.html">chemistry is no different</a>.</p>
<p><a href="https://www.acs.org/content/acs/en/greenchemistry/what-is-green-chemistry/principles/12-principles-of-green-chemistry.html">Green chemistry</a> aims to minimise the environmental impact of the chemical industry. This includes shifting away from oil to renewable sources where possible. </p>
<p>Green chemistry also prioritises safety, improving energy efficiency and, most importantly, minimising (and ideally) eliminating toxic waste from the very beginning. </p>
<p>Important examples of green chemistry include: phasing out the use of chlorofluorocarbons (<a href="https://www.esrl.noaa.gov/gmd/hats/publictn/elkins/cfcs.html">CFCs</a>) in refrigerants, which have played a role in creating the <a href="https://www.environment.gov.au/protection/ozone/ozone-science/ozone-layer">ozone hole</a>; developing more efficient ways of making pharmaceuticals, including the well-known painkiller <a href="https://www.epa.gov/greenchemistry/presidential-green-chemistry-challenge-1997-greener-synthetic-pathways-award">ibuprofen</a> and chemotherapy drug <a href="https://www.epa.gov/greenchemistry/presidential-green-chemistry-challenge-2004-greener-synthetic-pathways-award">Taxol</a>; and developing cheaper, more efficient <a href="http://science.sciencemag.org/content/354/6314/861">solar cells</a>.</p>
<h2>The need to adapt</h2>
<p>Making chemical compounds, particularly organic molecules (composed predominantly of carbon and hydrogen atoms), is the basis of vast multinational industries from perfumes to plastics, farming to fabric, and dyes to drugs. </p>
<p>In a perfect world, these would be prepared from inexpensive, renewable sources in one practical, efficient, safe and environmentally benign chemical reaction. Unfortunately, with the exception of the chemical processes found in nature, the majority of chemical processes are not completely efficient, require multiple reaction steps and generate hazardous byproducts. </p>
<p>While in the past traditional waste management strategies focused only on the disposal of toxic byproducts, today efforts have shifted to eliminating waste from the outset by making chemical reactions more efficient. </p>
<p>This adjustment has, in part, led to the advent of more sophisticated and effective catalytic reactions, which reduce the amount of waste. The 2001 Chemistry Nobel Laureate Ryoji Noyori stressed that <a href="http://www.nature.com/nchem/journal/v1/n1/full/nchem.143.html">catalytic processes</a> represent “the only methods that offer the rational means of producing useful compounds in an economical, energy-saving and environmentally benign way”. </p>
<h2>A secret to cleaner chemistry</h2>
<p>Catalysts are substances that accelerate reactions, typically by enabling chemical bonds to be broken and/or formed without being consumed in the process. Not only do they speed up reactions, but they can also facilitate chemical transformations that might not otherwise occur. </p>
<p>In principle, only a very small quantity of a catalyst is needed to generate copious amounts of a product, with reduced levels of waste. </p>
<p>The development of new catalytic reactions is one particularly important area of green chemistry. As well as being more environmentally friendly, these processes are also typically more cost effective. </p>
<p>Catalysts take many forms, including <a href="http://www.bbc.co.uk/schools/gcsebitesize/science/add_edexcel/cells/enzymesrev1.shtml">biological enzymes</a>, <a href="http://www.nature.com/nature/journal/v455/n7211/full/nature07367.html">small organic molecules</a>, <a href="http://www.nobelprize.org/nobel_prizes/chemistry/laureates/2010/">metals</a>, and particles that provide a better <a href="http://www.catalysts.basf.com/p02/USWeb-Internet/catalysts/en_GB/content/microsites/catalysts/prods-inds/mobile-emissions/how-it-works">surface for reactions to take place</a>. Roughly 90% of industrial chemical processes use catalysts and at least <a href="http://cen.acs.org/articles/91/i36/Nobel-Prizes-Recognized-Notable-Developments.html">15 Nobel Prizes</a> have been awarded for catalysis research. This represents a tremendously important and active area of both fundamental and applied research. </p>
<h2>What’s the outlook?</h2>
<p>In the past 20 years since green chemistry was established, there have been tremendous advances in the industry. Nevertheless, there remains considerable room for improvement.</p>
<p>The chemical industry faces a number of significant challenges, from reducing its dependence on fossil fuels to playing its part in addressing climate change more generally. </p>
<p>Specific challenges include: <a href="https://www.ipcc.ch/pdf/special-reports/srccs/srccs_wholereport.pdf">capturing and fixing carbon dioxide</a> and other greenhouse gases; developing a greater range of <a href="http://journals.sagepub.com/doi/pdf/10.1177/0734242X16683272">biodegradable plastics</a>; reducing the high levels of waste in <a href="http://pubs.rsc.org/en/Content/ArticleLanding/2017/GC/C6GC02157C#!divAbstract">pharmaceutical drug manufacture</a>; and improving the efficiency of <a href="http://pubs.rsc.org/en/content/articlelanding/2009/cs/b800489g#!divAbstract">water-splitting employing visible light photocatalysts</a>. </p>
<p>History suggests that society can develop creative solutions to complex, intractable problems. However, success will most likely require a concerted approach across all areas of science, strong leadership, and a willingness to strategically invest in human capital and value fundamental research.</p><img src="https://counter.theconversation.com/content/70740/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alex Bissember received a 2015 Green Chemistry for Life Grant from PhosAgro/UNESCO/IUPAC.</span></em></p>It was not until the 1980s that the environment became a priority for the chemical industry, and it was the industry’s bid to clean up that gave birth to ‘green chemistry’.Alex Bissember, Senior Lecturer in Chemistry, School of Physical Sciences, University of TasmaniaLicensed as Creative Commons – attribution, no derivatives.