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We’ve captured carbon. Now what?

Before the industrial revolution the world removed carbon from the air all by itself. With global carbon emissions breaking records in 2022 and potential risks of storing carbon underground, however, companies are getting creative and repurposing captured carbon in unexpected ways.

The Paris Agreement in 2015 had countries all over the world commit to take part in the race to net-zero emissions. Those countries are working toward the agreement’s renewable-energy goals, but more can be done to control greenhouse gases. One solution is carbon capture.

Natural or human-made

Carbon capture is the process of retrieving carbon emissions from the air and storing them. The process can be natural or manmade.

Natural carbon capture and storage is achieved by elements of the planet’s ecosystems. Trees, for example, are an effective carbon-capture and storage mechanism: Their leaves absorb carbon dioxide from the air through photosynthesis. But if trees are cut and burned for firewood — or even if the tree dies naturally — stored carbon is released back into the atmosphere.

The largest source of natural carbon capture is the world’s oceans. The United Nations estimates that the oceans soak up about 25 percent of all greenhouse-gas emissions and 90 percent of the surplus heat those emissions cause.

This natural carbon-capture process is called the carbon cycle. The problem is the world’s ecosystems can’t keep up with the greenhouse gases that are being produced by humans.

Enter man-made carbon capture.

Carbon-capture processes are designed to remove carbon from industrial waste or from the air outside. Carbon-capture plants typically have walls of giant fans, sucking in air. They remove the carbon from the air, convert it to liquid, store it underground or use it to inject into oil fields to simplify oil extraction. But there are challenges with carbon capture.

These large plants require a lot of energy in the form of materials to build the facilities and the energy to run them. Additionally, once the carbon dioxide is stored, there are risks. The carbon dioxide could leak out of the stored areas, polluting water sources and eventually reaching the surface — once again polluting the air.

Reasons for concern

There is also concern that pressure from injecting the carbon underground could cause seismic activity and controversy over whether carbon capture and storage might embolden fossil-fuel use. The 2022 report from the Institute for Energy Economics and Financial Analysis says, “Captured carbon has mostly been used for enhanced oil recovery” and “enhancing oil production is not a climate solution.”

While easing oil removal is the most common use of captured carbon, some companies are getting creative and managing carbon in other unusual ways.

Many large companies purchase carbon offsets to reduce their footprints. But individuals can purchase them as well. One company selling to individuals is Climeworks, a Swiss-based carbon-removal company that captures 900 tons of carbon annually. Buyers can even offer this as a “green gift” in the name of someone else. Climeworks also produces the bubbles for carbonated beverages for such clients as Coca-Cola.

Also getting off the ground is E-Jet fuel from carbon-capture company Twelve. The company says this fuel lowers greenhouse-gas emission of traditional fuels by 80 percent. Twelve entered into a memorandum of understanding with Alaska Air Group and Microsoft to work toward testing the fuel on a commercial flight.

Taking Off

In an announcement of the partnership, Nicholas Flanders, co-founder and CEO of Twelve said, “By producing our drop-in E-Jet fuel from captured CO2, we can rapidly and efficiently close the carbon cycle and allow businesses to sustainably use emissions to power their own business travel.” No date for the testing of the commercial flight has been announced. Air Transport Action Group reports that aviation makes up 12 percent of emissions from all transport sources.

After returning home from a green, commercial flight, weary travelers might do some green laundry with laundry capsules made from captured carbon.

In 2010, Unilever, which produces over 400 household brands such as Omo, Ben and Jerry’s and Dove, began a decades-long commitment to halve its environmental impact by 2030. One of the ingredients used to make foam in Omo (Persil) laundry capsules is fossil fuels. But on World Earth Day in 2021, Unilever launched a limited-edition capsule that used captured carbon instead of fossil fuels in a new process that makes the capsule 82 percent less carbon intensive. Unilever aims to achieve net zero emissions from its product line by 2039.

Even with the volume of removal, storage and creative ways carbon is being repurposed, carbon neutrality remains out of reach. The 2021 Global Status of Carbon Capture and Storage Report estimates that in order to reach mid-century goals, the number of carbon-capture facilities would have to increase by 100 times. There are currently 27.

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Polluted oceans:
Let the trash take itself out

Up to 12.7 million tons of waste makes its way into the world’s oceans each year, forming massive “plastic islands” in oceanic gyres and devastating birds and marine life in the process.

Cleanup, in which plastics are currently collected at sea, stored and shipped to shore for disposal, is estimated to take from 50 to 130 years with annual costs expected by some at nearly US $37 million. In the meantime, the trash is degrading faster than it can be gathered, disintegrating into harmful and even more difficult to mitigate microscopic forms.

Listen to the Deep Dive

Now a team of researchers from Massachusetts in the United States is suggesting a new approach: self-powered cleanup vessels that turn the trash they harvest from the seas into the fuel they use for the job.

RELATED: Microplastics: The invisible threat

The “blue diesel”-powered ships could reduce the amount of fuel and roundtrips needed to remove ocean waste, the researchers write in a paper published in the Proceedings of the National Academy of Sciences of the United States of America.

The researchers, representing Harvard University, the Woods Hole Oceanographic Institution and the Worcester Polytechnic Institute, suggest using high temperatures and high pressure in a process called hydrothermal liquefaction to depolymerize the plastics into a harnessable energy, creating self-powered cleanup that eliminates the need to refuel or unload plastic waste and potentially reduces total cleanup times.

Of course, it isn’t enough to clean up the oceans faster and with less fuel waste. The world needs to address the amount of garbage that makes it into the oceans in the first place, the researchers write. “Reducing or eliminating the amount of plastic waste generated is critically important, especially when the current loading may persist for years to even decades,” they say.

 COVID’s toll on the oceans 

Meanwhile, researchers from China’s School of Atmospheric Sciences at Nanjing University and the Scripps Institute of Oceanography at the University of California-San Diego say the COVID-19 pandemic is making an already bad situation in the oceans even worse.

Also writing in the Proceedings of the National Academy of Sciences of the United States of America, the scientists say that of the 8 million tons of plastic waste generated until recently in the fight against the virus, about 25,000 tons of medical waste, mostly from hospitals, has entered the world’s oceans. And more is expected to come, not only damaging marine species but potentially spreading contaminants including the COVID-19 virus.

The hospital trash, they say, dwarfs the amount of waste from discarded personal-protective equipment (PPEs) and plastic packaging produced by a surge of online shopping in the wake of the pandemic. For a little perspective, the authors cite another study estimating that 1.56 million face masks made it to the oceans in 2020.

Plastics that wash into the oceans are endangering wildlife. IMAGE: Shutterstock

Five of the top six rivers associated with medical-waste discharge are in Asia (Shatt al Arab, Indus, Yangtze,Ganges Brahmaputra and Amur). The other, the Danube, is in Europe.

The authors call for increased public awareness of plastics’ environmental impacts; better collection, treatment and recycling of plastic waste; and improved waste-management practices at pandemic epicenters, particularly in developing countries.

 Microbots to the rescue? 

A solution to microplastics in water might come in an equally small package: microbots.

The bacterium-size bots when added to water with a little hydrogen peroxide attach to microscopic bits of plastic and begin to break them down. The research was recently published in ACS Applied Materials & Interfaces.

“They can sweep a much larger area than you would be able to touch with stationary technology,” says study co-author Martin Pumera, a researcher at the University of Chemistry and Technology, Prague.

Pumera envisions setting the microbots loose in the oceans to collect microplastics, but Win Cowger, an expert in plastic pollution at the University of California, Riverside, who was not involved with the study, tells Scientific American that closed systems such as those for drinking-water or wastewater treatment would probably be better potential targets.

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Microplastics:
The invisible threat

Over 300 million tons of plastics are produced each year, out of which only up to 40 percent are recycled or incinerated. The majority end up in landfills or are improperly discarded in the environment, leading over time to their fragmentation into smaller plastic items.


CREDIT: Khalifa University
Ludovic Dumée

Ludovic (Ludo) Dumée is an assistant professor within the Chemical Engineering Department at Khalifa University who leads the Advanced Separation Materials team. Read more›››

His research interests span from functional and reactive materials engineering to their application across environmental applications. In 2020, he received the Membrane Society of Australasia Science award for his work on microplastics separation. He can be reached at Ludovic.dumee@ku.ac.ae.‹‹‹ Read less

Such “microplastics,” whose maximum dimension falls below 5 millimeters, are ultimately released into waterways and represent a major threat to global ecosystems, the entire food chain as well as many human industrial activities that rely on river or sea-water intake.

The fragmentation of such microplastics may also lead to the formation of nanoplastics, with dimensions below the micrometer level. These are much more difficult to quantify and identify, and they represent key challenges for engineers and researchers.

Why may microplastics enter the food chain and affect humans? Microplastics are reported in the guts of multiple avian or sea-life species that often mistake microplastics for food. Ingested microplastics may accumulate in their digestive system. Besides representing a major source of pain, it can lead to the animals’ premature death. Scavengers then feed on their carcasses, leading to further ingestion of microplastics up the food chain.

Over time microplastics contamination carries over to greater predators and human beings. It is estimated that humans ingest between 50,000 and 100,000 microplastics every year, arising from overusage of plastic bottles for soft drinks or packaged-water consumption, but also through uncontrolled fragmentation and release from packaging materials.

Examples of risks associated to plastic ingestion for human and their uptake by our body through diffusion in the blood system are multiple and daunting, not only due to the increased risk of cancer for exposed organs, but also because microplastics may carry over pathogenic contaminants, such as heavy metals or persistent organic pollutants. Such surface-contaminated microplastics, given the high buoyancy of plastic materials and their ability to float, may therefore act as cargos to further disseminate other contaminants over much larger distances than the single contaminants could achieve.

How can microplastics impact human industrial activities? Besides the food industry, a key area affected by the presence of micro or nanoplastics is the water industry.

Microplastics that enter the waterways may carry over pathogenic contaminants, such as heavy metals or persistent organic pollutants. CREDIT: Unsplash

The intake waters, feeding wastewater-treatment and desalination plants, may contain, depending on their location and origin, various levels of nano or microplastics, which may damage existing treatment processes.

For instance, the presence of microplastics in microbial-digestion bioreactors would disturb the microbial ecosystem and floc formation, that is the size of the colonies and their stability, thus reducing the efficiency of the process.

Deposits of nano or microplastics may directly damage membrane-separation steps, potentially leading to mechanical abrasion, as well as to accumulation onto the membranes, reducing the separation and flux performance. These phenomena were found to increase substantially the cost of water desalination and processing, sometimes detrimentally affecting the quality of produced water.

In addition, studies showed also that, depending on the treatment trains in place, microplastics may be further concentrated across the treatment units, leading to discharge of sludge or downstream waters richer in microplastics at the end of the water-treatment process.

How can you help? Discard your plastic wastes properly and ensure that you put them in the right bin without leaving a chance for discarded items to get into our beautiful waterways. Also privilege sustainable-packaging options and limit your usage of single-use items.

What is needed at this point to better understand risks? Researchers are developing advanced tools and platforms to detect nano and microplastics in wastewaters, to better understand their interactions with microbial organisms, water-treatment operations and assess their health and economic impact. We develop strategies to reveal the true extent of pollution within local ecosystems and understand the impact of plastic fragments of various sizes or shapes on the performance of separation systems. We also study the impact of microplastics on human health and their potential diffusion into our bodies to better prevent long-term diseases.