Artificial Photosynthesis and Biodegradability: Combating Plastic Menace with Sustainability in Mind

CO2 emission and the presence of non-biodegradable plastics on Earth are both dangers that cause irreversible damage. Significantly, carbon dioxide, being a heat-trapping gas, warms the planet and eventually results in climate change. 

This warming effect is underscored by NASA's estimates, which reveal that human activities have raised the atmosphere's carbon dioxide content by 50% in less than 200 years. Further worsening the situation are non-biodegradable plastics sourced from materials like styrofoam, disposable plastic bags, and plastic water bottles, which pose another grave threat as they contaminate the groundwater and food chain and pollute the air.

Addressing these intertwined challenges, researchers from Osaka Metropolitan University have now devised a breakthrough that deals with both these challenges through a single route. It has emerged with an innovative and efficient way to produce fumaric acid that will bring down carbon dioxide emission levels while repurposing the waste to make biodegradable plastics. Let us delve deeper into understanding what this innovation means and how it works.

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Sustainable Production of Fumaric Acid

Fumaric acid is a component of biodegradable plastics. It traditionally comes from petroleum, carbon dioxide, and biomass-derived compounds. Now, the researchers have come up with a solution wherein one can produce fumaric acid sustainably and efficiently. There have been two studies towards the same end goal. 

In the first one, a research team led by Professor Yutaka Amao of the Research Center for Artificial Photosynthesis at the Osaka Metropolitan University (OMU) exhibited the ways of synthesizing fumaric acid from bicarbonate and biomass-derived pyruvic acid. The energy used in the process was renewable solar energy. 

The scientists also achieved success in producing fumaric acid with carbon dioxide that contributed as a raw material to the process, coming directly from the gas phase. However, the experiment faced one limitation. It could not produce a substantial volume of fumaric acid. The production remained low. 

However, in the following research, the scientists overcame the challenge. They developed a new photosensitizer and made advances in artificial photosynthesis that could double fumaric acid's yield in comparison with the traditional methods. 

The scientists developed an effective way to produce visible-light-driven fumarate from gaseous CO2 and pyruvate with the system consisting of triethanolamine, cationic water-soluble zinc porphyrin, zinc tetrakis(4-N, N, N-trimethyl aminophenyl)porphyrin, pentamethylcyclopentadienyl coordinated rhodium(III) 2,2′-bipyridyl complex, NAD+, malate dehydrogenase (NAD+-dependent oxaloacetate-decarboxylating) and fumarase.

The research, titled “An effective visible-light-driven fumarate production from gaseous CO2 and pyruvate by the cationic zinc porphyrin-based photocatalytic system with dual biocatalysts,” was supported by the Institute of Fermentation, Osaka. 

Overall, the research has empirically established that it was possible to manufacture an advanced artificial photosynthesis catalyst that could use carbon dioxide more efficiently in producing biodegradable plastics. 

But, if we think further and try to assess why artificial photosynthesis and its contribution to sustainably and efficiently produce biodegradable plastics is seen as a breakthrough, we will see that plastics have been a menace, and any effort to make it sustainably-produced biodegradable should be appreciated and encouraged. 

One of the most severe plastic-related damages on planet Earth is caused by microplastics. The United States National Oceanic and Atmospheric Administration defines microplastics as small plastic pieces that are less than five millimeters long and cause harm to our health, ocean, and aquatic life. The category also includes plastics that are intentionally designed to be small. Called microbeads, these are used in many health and beauty products. These microplastics carry several harmful implications.

Microplastics enter our body through different pathways, including the water we drink, the food we consume, and the food containers we use, all of which are avenues of microplastic oral intake. Additionally, we inhale microplastics through the air, and our personal care products and mobile phone cases, which contain microplastics, create leeways for them to come into our personal contact.

Once inside the human body, these microplastics can cause a host of health issues. They are known to induce oxidative stress and DNA damage, lead to metabolic disorders, and cause dysfunctions in vital organs such as the liver, intestines, brain, and airways. Furthermore, the toxicity of microplastics can damage our reproductive and developmental capabilities, illustrating the severity of their impact on human health.

The issue of microplastics extends beyond human health, as these particles also harm marine life. They exert a toxic effect on fish and other aquatic organisms, inhibiting their growth and development, increasing mortality rates, causing inflammation, decreasing swimming speed, reducing vitality and body length, and causing intestinal injuries. This evidence underscores the pressing need to address and halt the pollution of our environment with microplastics.

In light of this, recent underwater dive surveys have highlighted the urgent need for innovative waste collection solutions. For example, a groundbreaking survey conducted by researchers from the Desert Research Institute at Lake Tahoe's lakebed revealed an alarming average of 83 pieces of plastic litter per kilometer, with not a single stretch of the lakebed found to be free of plastic litter. Common items identified include food containers, bottles, plastic bags, and toys, with the six most common types of plastic being polyvinyl chloride (PVC), polystyrene, polyester/polyethylene terephthalate, polyethylene, polypropylene, and polyamide.

While several solution providers who offer viable alternatives to clean underwater plastics are present, researchers are also interested in assessing the potential of a ‘sustainability metric‘ to curb plastic pollution. The Woods Hole Oceanographic Institution's researchers developed a sustainability metric for the ecological design of plastic products that have low persistence in the environment. The researchers believed that this metric could deliver environmental and societal benefits. 

The study showed an innovative and inventive way to tackle the menace of plastic pollution. The approach could be seen as somewhat similar to the social impact accounting exercises we are familiar with. It compared indices for the environmental impact of plastics as well as their substitutes that demonstrated that accounting for the environmental persistence of plastic and replacing them efficiently could mean gains of hundreds of millions of dollars for a single consumer product. 

While explaining the significance of the study, the lead author of the study, Bryan James, a material scientist and engineer, said:

“What's important to determine is how can we design functional, sustainable, and benign materials, products, and processes that embody all of the principles of green materials engineering into the future world that we are going to live in.”

Overall, making plastics that are adequately biodegradable and identifying suitable alternatives for them have kept the scientific and technological community busy. There are many businesses, large and small, that are actively working in this area.  

#1. Mitsubishi Chemical Group

Mitsubishi Chemical Group has been an active participant in this space for quite some time now. As a member of the Japan Technological Research Association of Artificial Photosynthetic Chemical Process (ARPChem), established in October 2012, Mitsubishi Chemical Corporation (MCC) participated in an Artificial Photosynthesis project conducted by New Energy and Industrial Technology Development Organization (NEDO). Since then, Mitsubishi has been pushing the envelope to achieve more efficiency and optimization of the process. 

It was about sustainably producing Fumaric acid in the research we had as the opener for our discussion. However, Mitsubishi Chemical Group's efforts are directed towards producing Olefin. 

In this process, a synthetic catalyst plays a critical role by enabling the reaction between separated hydrogen and carbon dioxide. Mitsubishi's innovative work in developing a suitable catalyst and refining the necessary process technologies has significantly enhanced the yield, making Olefin production more efficient. 

As a result, Olefin has become an effectively produced raw material for creating plastics, showcasing Mitsubishi's contribution to advancing sustainable manufacturing practices in the chemical industry.

The Green Innovation Project, run by NEDO, selected Mitsubishi's commercial development of artificial photosynthesis-based chemical raw material production for funding in February 2022. 

In further stages of development, the process will convert raw materials from petroleum and help develop plastic production technology leveraging carbon dioxide by utilizing petrochemical manufacturing technology, catalyst development technology, and other technologies it has cultivated while collaborating with universities and research institutes. 

The Mitsubishi Corporation published an integrated report for the fiscal year ending on March 31, 2023. The company earned more than US$159 billion.

#2. Evonik and Siemens

In what is called technical photosynthesis, two corporations, Evonik and Siemens, are using renewable energy and bacteria to convert carbon dioxide into specialty chemicals. The corporations are carrying out this task under a joint research project called Rheticus. The first phase of the research saw the production of chemicals such as butanol and hexanol, which are both feedstocks for special plastics and food supplements. 

According to Dr. Thomas Haas, responsible for the project in Evonik's strategic research department Creavis: 

“With the Rheticus platform, we want to demonstrate that artificial photosynthesis is feasible.”

To make this claim a reality, both Evonik and Siemens are contributing as per their core competencies. For instance, Siemens is empowering the process with electrolysis technology, which will be used in the first step to convert carbon dioxide and water into hydrogen and carbon monoxide using electricity. 

Evonik's contributions are aimed at strengthening the fermentation process, wherein gasses containing Carbon Monoxide would be converted into useful products by metabolic processes facilitated by special microorganisms. 

While elaborating on its potential to help the plastic and specialty chemical industry, Dr. Haas said:

“Its modular nature and flexibility in terms of location, raw material sources, and products manufactured make the new platform attractive for the specialty chemicals industry in particular. We are confident that other companies will use the platform and integrate it with their own modules to manufacture their chemical products.”

According to the latest available annual financials, Evonik Group registered sales of nearly 18.5 billion Euros in 2022. Of this revenue, specialty additives and nutrition & care contributed 23% each. Revenue from smart materials constituted 26% of the revenue, while performance materials contributed 20%, and technology and infrastructure products and services contributed 8%. 

In the fiscal year 2023, Siemens recorded an annual revenue of close to 22 million Euros, a significant increase from 19.5 billion Euros recorded in FY 2022. 

Plastics and Our Journey Towards Sustainability

Through collective efforts, we need to ensure that we are taking the right steps towards a future replete with bioplastics, which are either biodegradable plastics or biobased materials themselves, deriving energy from renewable resources. These bioplastics, in terms of their durability and usability, would be no less than conventional plastics. They could be processed through conventional plastic machines and kept in traditional warehouses, effectively removing the scope of resource redundancy.

The failure to work out a viable alternative to the menace of plastic waste would translate to grave dangers for several countries across the world. Southeast Asia, for instance, has already become a ‘hot spot' for plastic pollution, a situation exacerbated by rapid urbanization and a burgeoning middle class. Further compounded by the lack of efficient infrastructure, this has resulted in muted efficiency for recyclable plastics.

This issue of mismanagement of waste has been further aggravated during the COVID season due to the consumption of masks, sanitizer bottles, and online delivery packaging. According to data presented by the World Bank, in countries like Thailand, Philippines, and Malaysia, more than 75% of the material value of recyclable plastic is lost – the equivalent of $6 billion a year when single-use plastic is discarded rather than recovered and recycled.

In light of such mismanagement of waste and inadequacy of infrastructure, bioplastics emerge as the most effective alternative that is independent of such mishandlings. Moreover, bioplastics aid in our sustainability efforts since they depend less on conventional fossil fuels. Using biodegradable plastics also means enhanced end-of-life scenarios for disposal and recycling.

Yet, the share of bioplastics is still much less than what it should be for our future to be fully dependent on sustainable means. According to one estimate, out of the 367 million tonnes of plastic produced globally each year, the share of bioplastics is still less than one percent. However, it is expected to witness significant growth in the coming years across a range of application fields, including packaging, consumer goods, building and construction, automotive and transport, textiles, agri and horticulture, electrics and electronics, coatings and adhesives, and more.

Cutting-edge research-backed technologies, such as artificial photosynthesis and sustainable production of plastic components powered by renewable energy sources, will make a significant impact on ways to deal with plastic. These processes will not only mean better environment-friendly plastics but also a production ecosystem that is sustainable and nearly emission-free.