Plastic pollution transcends national boundaries and is not just a global environmental concern but a legal and infrastructural nightmare with plastic waste accumulating in oceans, lakes, landfills, and rivers in the millions of tonnes.
Fig. 1. Typical ocean plastic waste of single use F&B packaging found during an Ocean Purpose Project beach cleanup
Source: Ocean Purpose Project
At the same time, the development of critical IT and AI infrastructure globally has sparked a trade war between China, Europe and the United States following China’s export restrictions from 1st August 2023 on key metals used in semiconductors and other products, to protect national security interests. Semiconductors are the backbone of modern technology, powering everything from computers and smartphones to renewable energy systems. Traditionally, the production of semiconductors has heavily relied on trace metals like silicon, germanium, and gallium arsenide. However, recent advancements in nanotechnology have paved the way for an exciting alternative: carbon nanotubes (CNTs). With their remarkable properties and potential applications, CNTs have emerged as a promising substitute for trace metals in semiconductor manufacturing. In this blog post, we will explore the reasons why carbon nanotubes can revolutionize the semiconductor industry and how ocean plastic waste can become an untapped source for the technology revolution. Carbon Nanotubes: A Dual Solution for Plastic Waste and Clean Energy
Researchers have developed a novel approach of converting plastic waste into higher-value products, including hydrogen and carbon nanotubes. Ocean Purpose Project works with researchers from India, Singapore, Germany and the United States to help realise our dream of turning unwanted ocean plastic pollution into hydrogen while producing a valuable byproduct - carbon nanotubes. Carbon nanotubes, with their unique properties, offer a range of applications, while hydrogen is a versatile and clean energy source, presenting a dual solution to plastic pollution and clean energy production.
Fig. 2. Ocean Purpose Project’s proposed Plastic-To-Fuel unit Source: Ocean Purpose Project
Carbon nanotubes are nano-sized cylindrical structures composed of carbon atoms. These tubes possess remarkable physical and chemical stability, along with high electrical conductivity and tensile strength. Such unique properties make carbon nanotubes suitable for a wide range of applications, including conductive paints and coatings, microelectronic transistors, energy storage systems, biosensors, and medical devices. Incorporating carbon nanotubes derived from plastic waste provides a sustainable approach to harnessing this valuable material. Researchers at the University of Maryland in College Park discovered that the mobility of carbon nanotubes is about 70 times higher than that of silicon used to currently manufacture processors and 25 percent higher than any other known semiconductor material. Mobility is calculated by dividing the conductivity of a particular material by the number of charges it carries, or the amount of current flowing through the material. The result is a measure of how fast electrons move through a transistor.
Fig 2. Picture of carbon nanotube Source: Evannovostro/Shutterstock.com
"It's probably the most useful number to know about a semiconductor," said Michael Fuhrer, assistant professor of physics at the University of Maryland, and leader of the team of researchers who published a report online week in Nano Letters, a scientific journal.
Here are key reasons why carbon nanotubes or CNTs derived from plastics could rival existing materials used in computer chips:
1) Superior Mechanical Strength:
Another compelling characteristic of carbon nanotubes is their exceptional mechanical strength. CNTs possess an extraordinary tensile strength, several times higher than that of steel, while maintaining remarkable flexibility. This outstanding mechanical property makes them highly resilient to bending, stretching, and breaking. Incorporating carbon nanotubes into semiconductor materials can enhance the durability and reliability of electronic devices, ensuring longer lifetimes and reducing the need for frequent replacements.
Fig 3. Picture of CNT fabric stopping a 9MM, jacketed round in controlled ballistics testing Source: Nanocomp Technologies
2) Chemical Stability and Environmental Friendliness:
Trace metals used in semiconductor manufacturing, such as arsenic and cadmium, pose significant environmental and health risks due to their toxicity. In contrast, carbon nanotubes exhibit excellent chemical stability and are considered environmentally friendly materials. They are non-toxic and do not release harmful substances during production or disposal. By replacing trace metals with CNTs, we can reduce the environmental impact associated with semiconductor manufacturing, promoting sustainability and eco-friendliness in the industry.
3) Compatibility with Existing Processes:
Adopting carbon nanotubes in semiconductor production does not require a complete overhaul of existing manufacturing processes. CNTs can be integrated into conventional fabrication techniques, such as chemical vapor deposition and lithography, with minor modifications. This compatibility ensures a smooth transition from traditional trace metal-based semiconductor production to the use of carbon nanotubes. By leveraging existing infrastructure and processes, the incorporation of CNTs becomes more feasible and cost-effective.
4) Wide Range of Applications:
The versatility of carbon nanotubes extends beyond their use in semiconductor manufacturing. CNTs have shown immense potential in various fields, including electronics, energy storage, and sensors. They can be utilized in flexible electronics, wearable devices, and even in advanced medical technologies. By capitalizing on the multifunctional properties of carbon nanotubes, we can unlock innovative applications and pave the way for future advancements especially in finally finding efficient resource capture for ever increasing plastic waste, especially legacy plastics.
Fig 4. Picture of microchip Source: Shutterstock
How is plastic turned into CNTs- it starts with Hydrogen
The conversion of plastic waste into hydrogen and carbon nanotubes holds significant potential for mitigating plastic pollution and meeting energy demands sustainably, a promising future. By repurposing plastic waste, this approach not only reduces environmental harm but also produces clean fuel and value-added carbon products. Further advancements and research in this field can lead to the development of large-scale industrial processes, revolutionizing waste management and clean energy production.
Hydrogen is a clean and abundant energy source with various applications. It has a long history of use, including as rocket fuel by NASA in the 1950s and as a power source for spacecraft. Hydrogen fuel cells have also been employed to generate electricity for vehicles, particularly in automobiles and transit buses. The conversion of plastic waste into usable hydrogen offers a promising pathway to reduce dependency on fossil fuels and mitigate environmental impact.
Fig 5. Graphic of Fuel cell and Hydrogen energy basics Source: Fuel cell and Hydrogen Energy Association
Catalytic pyrolysis is a method used to convert plastic waste into hydrogen and high-quality carbon nanotubes. This process involves the use of a bimetallic nickel-iron catalyst at a temperature of 800°C in a two-stage fixed bed reactor. The waste plastics undergo pyrolysis, followed by various chemical reactions facilitated by the catalyst. Factors such as reactor design, catalyst type, and operational parameters influence the yield and quality of carbon nanotubes obtained from plastic waste.
In recent collaborations between universities in the United Kingdom, the Kingdom of Saudi Arabia, and China, researchers have developed a novel catalytic method for converting plastic waste into clean fuel and high-value carbon nanotubes. This technique involves pulverizing plastic waste into small particles and adding iron oxide and aluminum oxide catalysts. The mixture is then subjected to microwave treatment, where the catalysts are heated rather than the plastics themselves.
During microwave treatment, the catalysts create hot spots within the plastic, resulting in the extraction of 97% of the plastic's hydrogen and high-quality carbon nanotubes. This one-step process is energy-efficient, cost-effective, and rapid, taking only 30 to 90 seconds. By heating the catalyst particles and producing tiny hotspots through microwave electromagnetic radiation, this method offers an efficient route for transforming plastic waste into valuable products.
Fig 6. Graphic of microwave treatment, transforming plastic waste into valuable products Source: Journal of Environmental Chemical Engineering, Vol 11 Issue 3 The conversion of plastic waste into hydrogen and carbon nanotubes represents a promising solution to the pressing challenges of plastic pollution and clean energy production. Carbon nanotubes offer diverse applications across various industries, while hydrogen serves as a versatile and clean energy source. Carbon nanotubes have emerged as a promising alternative to trace metals in the production of semiconductors. Their exceptional electrical and thermal conductivity, size and structure, mechanical strength, chemical stability, and compatibility with existing processes make them a viable choice for the semiconductor industry. Moreover, their wide range of applications and environmentally friendly nature further bolster their appeal. As research and development in the field of nanotechnology continue to progress, carbon nanotubes are poised to revolutionise the semiconductor industry, powering the next generation of technological advancements.
By utilising innovative techniques such as catalytic pyrolysis and microwave treatment, researchers are making significant strides in transforming plastic waste into valuable resources. With continued research and development, we can expect a future where plastic waste is effectively managed, while clean energy production and sustainable material utilisation flourish. This is precisely why Ocean Purpose Project believes in a future where mountains of ocean plastic waste washing ashore in Asia can be turned into a valuable resource that turns Asia’s embarrassing plastic pollution into new materials that can de-escalate trade wars around the semiconductor industry.