The modern world is built with concrete: . Yet cement, the key component of concrete, is the source of as much as 10% of all carbon dioxide emissions worldwide.

To address this problem, researchers at the 91Ě˝»¨ and Microsoft developed a new type of low-carbon concrete by mixing dried, powdered seaweed with cement. The seaweed-fortified cement has a 21% lower global warming potential while retaining its strength. And thanks to an assist from machine learning models, the team arrived at this new formulation in a fraction of the time that such work would ordinarily take.

July 8 in Matter.

“Cement is everywhere — it’s the backbone of modern infrastructure — but it comes with a huge climate cost,” said senior author , a 91Ě˝»¨assistant professor of materials science and engineering. “What makes this work exciting is that we show how an abundant, photosynthetic material like green seaweed can be incorporated into cement to cut emissions, without the need for costly processing or sacrificing performance.”

Producing one kilogram of cement emits nearly a kilogram of CO2. Most of those emissions come from the fossil fuels used to heat raw materials and from a chemical reaction called calcination that occurs during the production process. Seaweed, in contrast, is a carbon sink: It pulls carbon out of the air and stores it while it grows. And, remarkably, it can directly replace some of the cement in concrete, giving the result a dramatically smaller carbon footprint.

Arriving at the ideal mixture of ingredients would have taken five years of trial and error, Roumeli estimated, because any concrete sample takes about a month to fully cure before its properties can be evaluated accurately.

To speed up the process, the team built a custom machine learning model and trained it on an initial set of 24 formulations of cement. They then used the model to predict ideal mixtures to test in the lab. By feeding the results of those tests back into the model, they were able to work in tandem with the model and move through formulations rapidly. The outcome was an optimal mixture of seaweed-enhanced cement with a reduced carbon footprint that passed compressive strength tests, discovered in just 28 days.

“Machine learning was integral in helping us dramatically shorten the process — especially important here, because we’re introducing a completely new material into cement,” Roumeli said.

From here, the team plans to deepen their understanding of how seaweed composition and structure affects cement performance. The larger goal is to generalize the work out to different kinds of algae (or even to food waste) so that producers can create local, sustainable cement alternatives around the world — and use machine learning to optimize them rapidly.

“By combining natural materials like algae with modern data tools, we can localize production, reduce emissions, and move faster toward greener infrastructure,” Roumeli said. “It’s an exciting step toward a new generation of sustainable building materials.”

Additional co-authors on this paper are , a 91Ě˝»¨doctoral student studying materials science and engineering; , a former 91Ě˝»¨postdoctoral researcher in the materials science and engineering department who is now an R&D engineer at the iPrint Institute; and , a principal researcher at Microsoft Research.

This research was funded by Microsoft Research.

For more information, contact Roumeli at eroumeli@uw.edu.

We use plastics in almost every aspect of our lives. These materials are cheap to make and incredibly stable. The problem comes when we’re done using something plastic — it can persist in the environment for years. Over time, plastic will break down into smaller fragments, called microplastics, that can pose significant environmental and health concerns.

The best-case solution would be to use bio-based plastics that biodegrade instead, but many of those bioplastics are not designed to degrade in backyard composting conditions. They must be processed in commercial composting facilities, which are not accessible in all regions of the country.

A team led by researchers at the 91Ě˝»¨ has developed new bioplastics that degrade on the same timescale as a banana peel in a backyard compost bin. These bioplastics are made entirely from powdered blue-green cells, otherwise known as spirulina. The team used heat and pressure to form the spirulina powder into various shapes, the same processing technique used to create conventional plastics. The 91Ě˝»¨team’s bioplastics have mechanical properties that are comparable to single-use, petroleum-derived plastics.

The team June 20 in Advanced Functional Materials.

“We were motivated to create bioplastics that are both bio-derived and biodegradable in our backyards, while also being processable, scalable and recyclable,” said senior author , 91Ě˝»¨assistant professor of materials science and engineering. “The bioplastics we have developed, using only spirulina, not only have a degradation profile similar to organic waste, but also are on average 10 times stronger and stiffer than previously reported spirulina bioplastics. These properties open up new possibilities for the practical application of spirulina-based plastics in various industries, including disposable food packaging or household plastics, such as bottles or trays.”

The researchers opted to use spirulina to make their bioplastics for a few reasons. First of all, it can be cultivated on large scales because people already use it for various foods and cosmetics. Also, spirulina cells sequester carbon dioxide as they grow, making this biomass a carbon-neutral, or potentially carbon-negative, feedstock for plastics.

“Spirulina also has unique fire-resistant properties,” said lead author , a 91Ě˝»¨materials science and engineering doctoral student. “When exposed to fire, it instantly self-extinguishes, unlike many traditional plastics that either combust or melt. This fire-resistant characteristic makes spirulina-based plastics advantageous for applications where traditional plastics may not be suitable due to their flammability. One example could be plastic racks in data centers because the systems that are used to keep the servers cool can get very hot.”

Creating plastic products often involves a process that uses heat and pressure to shape the plastic into a desired shape. The 91Ě˝»¨team took a similar approach with their bioplastics.

“This means that we would not have to redesign manufacturing lines from scratch if we wanted to use our materials at industrial scales,” Roumeli said. “We’ve removed one of the common barriers between the lab and scaling up to meet industrial demand. For example, many bioplastics are made from molecules that are extracted from biomass, such as seaweed, and mixed with performance modifiers before being cast into films. This process requires the materials to be in the form of a solution prior to casting, and this is not scalable.”

Other researchers have used spirulina to create bioplastics, but the 91Ě˝»¨researchers’ bioplastics are much stronger and stiffer than previous attempts. The 91Ě˝»¨team optimized microstructure and bonding within these bioplastics by altering their processing conditions — such as temperature, pressure, and time in the extruder or hot-press — and studying the resulting materials’ structural properties, including their strength, stiffness and toughness.

These bioplastics are not quite ready to be scaled up for industrial usage. For example, while these materials are strong, they are still fairly brittle. Another challenge is that they are sensitive to water.

“You wouldn’t want these materials to get rained on,” Iyer said.

The team is addressing these issues and continuing to study the fundamental principles that dictate how these materials behave. The researchers hope to design for different situations by creating an assortment of bioplastics. This would be similar to the variety of existing petroleum-based plastics.

The newly developed materials are also recyclable.

“Biodegradation is not our preferred end-of-life scenario,” Roumeli said. “Our spirulina bioplastics are recyclable through mechanical recycling, which is very accessible. People don’t often recycle plastics, however, so it’s an added bonus that our bioplastics do degrade quickly in the environment.”

Co-authors on this paper are 91Ě˝»¨materials science and engineering doctoral students and ; , a 91Ě˝»¨postdoctoral scholar in materials science and engineering; , who completed this work as a 91Ě˝»¨postdoctoral scholar in materials science and engineering and is now at Intel; , a 91Ě˝»¨master’s student studying materials science and engineering; , a 91Ě˝»¨undergraduate student studying chemical engineering; Marissa Nelsen, who completed this work as a 91Ě˝»¨undergraduate student studying biology; and , a principal researcher at Microsoft. This research was funded by Microsoft, Meta and the National Science Foundation.

For more information, contact Roumeli at eroumeli@uw.edu. Note: Roumeli is on Eastern Time this week.

Grant number: DGE-2140004

The very components that make electronics fast and easy to use also make their disposal an environmental nightmare. Components of smartphones, computers and even kitchen appliances contain heavy metals and other compounds that are toxic to us and harmful to ecosystems.

As electronics become cheaper to buy, e-waste has piled up. A 2019 from the World Economic Forum called e-waste “the fastest-growing waste stream in the world” — and for good reason. That same year, people generated more than 50 million metric tons of e-waste, the U.N.’s Global E-waste Monitor. Much of it is incinerated, piled up in landfills or exported to lower-income countries where it creates public health and environmental hazards.

Three researchers in the 91Ě˝»¨ College of Engineering are exploring ways to make electronics more Earth-friendly. , an assistant professor in the Paul G. Allen School of Computer Science & Engineering and researcher in the 91Ě˝»¨Institute for Nano-engineered Systems, will be presenting at the CHI 2022 conference in May. , an assistant professor of mechanical engineering, is indefinitely. And , an assistant professor of materials science and engineering and researcher in the Molecular Engineering & Sciences Institute, uses biological materials, such as seaweeds and other algae, to develop alternatives to plastics that can be 3D-printed.

For Earth Day, 91Ě˝»¨News reached out to these engineers to discuss their projects.

What features do you prioritize when designing sustainable electronics?

Vikram Iyer: There are lots of important problems to tackle in designing sustainable electronics, including reducing the environmental impact of e-waste. Our groups are trying to develop creative solutions to this problem, such as using new and more environmentally friendly materials while building functional devices that don’t compromise performance. For example, the mouse we designed with a biodegradable circuit board works when you plug it into any computer.

What was the design process like for the mouse?

VI: This project was a collaboration with , a principal researcher at Microsoft, and , a 91Ě˝»¨doctoral student in the Allen School. We took several steps to make this mouse:

• We optimized our circuit design to use the fewest number of silicon chips possible, because around 80% of carbon emissions associated with manufacturing electronics comes from the energy-intensive processes used to make chips.
• We use biodegradable materials when possible. For example, the circuit board that holds and connects the chips together typically contains toxic flame-retardants, but we instead pattern our circuits on a board made from flax fibers. Also, the casing for the mouse is made out of biodegradable plastics.
• We use general-purpose, programmable chips, like microcontrollers, in our designs so that we can reuse them in new devices.
• We use software to estimate the environmental impact of each stage of production to quantify the environmental impacts and identify which stages of our design to improve next.

This is just a start, and our long-term vision is to develop new materials and methods that help us generate a production cycle for electronics in which all the materials and components can either be recycled and reused, or degraded and regenerated through the natural biological cycle.

Is it really true that the mouse’s case and circuit board dissolve in water?

VI: When we submerge our circuit board in water, the fibers start to come apart and the whole thing just disintegrates. This takes about five to 10 minutes in hot water, or a few hours at room temperature. After this we’re left with the chips and circuit traces which we can filter out. We also designed two different cases, one of these can dissolve in water and the other can be commercially composted.

Would a biodegradable mouse be as durable as a conventional mouse, especially up against the body heat and moisture we produce?

VI: There are definitely sustainable methods to ensure biodegradable components are also durable. For example, you could add a thin coating of water-repellent materials to the mouse — like chitosan, which is found naturally in the outer skeleton of shellfish. We also show that we can print the case out of polylactic acid, a material commonly used to make things like commercially compostable forks. Going forward we’re really excited to partner with researchers like Eleftheria, whose group is making new sustainable materials. And by partnering closely with researchers at Microsoft, we hope to develop solutions that are scalable and deployable for industry.

What types of new materials is the Roumeli group working on?

Eleftheria Roumeli: focuses on developing materials derived from biological matter. In addition to seaweeds and other forms of algae, this includes plant residues and microbial products. Our studies aim to further our understanding of how these natural, versatile materials can be used as composite building blocks for sustainable alternatives to plastics.

How do you manufacture sustainable components — like biodegradable parts — for electronics?

ER: The great thing is that today’s manufacturing methods can be used to create sustainable components for electronics. For example, some of the biologically derived materials my group works with can be made into inks and filaments for manufacturing parts using 3D printing. We recently published a — that’s a type of blue-green algae — both with and without cellulose fibers as a filler. Cellulose is the most abundant natural polymer, and these inks are 100% compostable in soil. There’s no special composting facility required!

What are other alternative filaments you can use for 3D printing?

ER: We can also make hybrid materials that are a blend of both biological matter — such as spirulina cells — and commercial, degradable polymers. For the polymer, we use matrix materials such as polylactic acid, which Vikram mentioned before and is the most widely available industrially compostable polymer, or polybutylene adipate co-terephthalate, a soil-compostable polymer. The particular choice of components determines the properties, performance and the compostability of our filaments.

For example, for packaging, which we usually buy and “consume” very fast and then discard immediately, a material made solely of biological components would be preferable. Then, after we use it, it could be disposed of in a backyard or landfill and it would degrade in a few weeks.

But if we want a filament for the , we would need a polymer binder to ensure that the filament meets the requirements of hot-extrusion based printing.

Are there any other new innovations for sustainable electronics?

Aniruddh Vashisth: One thing we’re working on is recyclable synthetic polymers. Unlike what Eleftheria’s team studies, these polymers are not derived from biological components. Instead, these polymers consist of an adaptive network and can be recycled and reprocessed multiple times.

Unlike other plastics, these materials do not lose their thermo-mechanical properties during reprocessing and recycling. This is exciting since you can reuse the same material again and again! This phenomenon of retaining material properties is possible because the building blocks that make up these materials can detach and reattach, just like Legos.

So when we are recycling, we are disassembling and reassembling the Legos. We have been focusing on aerospace-grade composites, but we are starting to explore other applications with a wide range of target applications.

What impact would that have on the e-waste problem?

AV: Today’s e-waste is usually a complex composite, with plastics, metal and ceramic components all in the same device. Recycling these materials is a challenging task, so they often just end up in landfills and lead to pollution.

Right now there are more than 250 million computers and 7 billion phones in the world. Most of these have polymer components. Just think if the polymers used in these devices could be recycled multiple times. That would be a great step toward sustainability! Our group has been working on how to design and characterize such recycled polymer composites for a more sustainable future.

For more information, contact Iyer at vsiyer@uw.edu, Roumeli at eroumeli@uw.edu and Vashisth at vashisth@uw.edu.