Our initial exploration began in our home country Germany, where our Human Practices Team delved into the local plastic waste management system and its limitations. After engaging with various stakeholders in the waste management sector, we identified mixed plastic waste as a significant concern, leading us to tailor our research efforts accordingly.
Drawing inspiration from Valerie Bürstner of Interzero Zero Waste Solution, we extended our focus to countries with diverse waste management systems to assess the adaptability of our platform. We conducted interviews with NGOs and start-ups specializing in waste management across eight countries, gathering valuable feedback.
While exploring our project's impact, we also considered the broader implications from the perspective of Sustainable Development Goals, specifically SDGs 9, 11, 12, and 13. We critically examined the social, environmental, and economic aspects of our project and integrated feedback from SDG stakeholders into our initiatives.
Our initial step involved the identification of stakeholders associated with our project, with a particular focus on the plastic value chain, to better understand the plastic life cycle. This way, we could identify areas where ReMixHD could lead to meaningful change.
In addition to conducting a comprehensive literature review, we also engaged in interviews with stakeholders from waste collection centers, the German Dual System, plastic sorting facilities, and plastic recycling factories. Furthermore, we visited the local waste collection center and a plastic sorting plant near Heidelberg, affording us an authentic firsthand experience of the practical aspects of plastic waste treatment.
Here, we present our research results to the plastic value chain in the following chart:
The material of our yogurt cup, polypropylene (PP), is generated from raw materials like natural gas and oil. Monomers such as ethylene and propylene are produced by cracking ethane and propane. After polymerization and pelleting, PP pellets are shipped to factories, which are further melted and molded into yogurt cups.
After, the yogurt company filled the yogurt cup with yogurt. A label made of PE is also wrapped around the PP cup. Here, we have two different plastic materials used together. Afterward, it is transported to the supermarket, where it is bought and consumed.
If consumers do not separate the PE label from the PP yogurt cup when they discard the waste, mixed plastic waste ocurrs. The packaging waste is put into the yellowbags in Germany. The yellow bags are further collected by the waste truck and driven to the nearby waste collection center.
We had a informative visit to the waste collecting center in Heidelberg and a great conversation with our guide Stephan.
Companies that use plastic packaging in their product must pay the German Dual System. German Dual System further uses the money to employ sorting plants to sort the packaging waste.
We talked to Valerie Bürstner, expert from Interzero , one leading company in the German Dual System.
Our yogurt cup enters the waste sorting plant. If the label was well separated from the yogurt cup, these two different plastic materials would be separated into their plastic waste fraction with near-infra-red (NIR) technology.
We visited a waste sorting plant near Heidelberg and had a deeper understanding of current plastic waste sorting technology.
The pure plastic fractions will be transported to another processor. There, they are cleaned, shredded, and melted. Recycled pellets are made out of it.
We talked to Dr. Mark Reichenberger from Graf Polymer and gained more insights in mechanical recycling.
Many companies buy recycled pellets and create new products, like benches, rail, and garden furniture.
The mixed plastic waste fraction usually has less value since it is made of heterogeneous materials and is difficult to process. Most of the time, they are used as fuel for power plants.
Waste export One leading action is to close materials loops to achieve responsible consumption and production. However, Germany was the leading export country of plastic waste in 2019, with 1 million tons (Strobel et al., 2023). Even though only sorted plastic and recyclable plastic have been allowed to be exported to certified recycling facilities since 2021, still 800,000 tons of plastic waste were exported from Germany. The reasons for this high amount of export lie in Germany's cost and lack of workforce (Strobel et al., 2023).
We had an enlightening conversation with Jakob Kluchert from Greenpeace, exploring the pressing issue of waste export.
In addition to yogurt cups, which serve as an example of mixed plastic waste when various plastic materials aren't adequately separated, multi-layered packaging also poses a significant challenge in terms of mixed plastics (Read more).
ReMixHD represents an advanced synthetic upcycling platform technology, distinguished by its capacity to convert mixed plastic materials into valuable chemical molecules. When employed as a bioreactor system, it exhibits the potential to seamlessly harmonize with the system of German waste management, facilitating the degradation of mixed plastic waste originating from waste sorting procedures.
In contrast to mechanical and chemical recycling methods, which impose specific requirements regarding the composition of plastic waste feedstock, our solution can effectively degrade a broad spectrum of prevalent mixed plastics, including PP, PE, PET, PS, and PVC. This versatility can prolong the life cycle of plastic material, thus fostering the principles of a circular economy.
Compared to current plastic waste treatment methods, which predominantly rely on downcycling or waste-to-fuel strategies, our solution has the advantage of producing higher-quality chemical molecules from mixed plastic intermediates.
Compared to chemical recycling, ReMixHD functions at a lower temperature of 30 degrees Celsius. Through the upcycling of mixed plastic waste, we have the potential to mitigate plastic waste incineration and its associated CO2 emissions. Furthermore, this approach allows us to bypass the production of virgin plastics, a practice known for its substantial contribution to elevated levels of CO2 emissions.
Furthermore, in regions lacking a centralized waste management infrastructure, ReMixHD is a commendable
solution for mixed plastic waste within local communities. In this context, it enables the on-site
upcycling of waste, avoiding long-distance transportation to landfills, thereby mitigating waste contamination.
However, a decentralized recycling network for every household or community would require small scale
bioreactors that exceed their financial capabilities by far. Even if it would be economically viable,
practical aspects such as mitigated contamination of the bioreactor system would have to be taken into
account, which makes the idea of a decentralised network hard to realised with the current state of technology.
Moreover, ReMixHD's impact aligns with four Sustainable Development Goals (SDGs): SDG 9, SDG 11, SDG 12, and SDG 13.
Using our bioreactor approach, our platform can support countries lacking centralized waste management infrastructure by recycling mixed plastic waste within local communities.
Our platform, not limited to plastics, can help manage growing municipal plastic waste and prevent its export to poorer regions.
By upcycling mixed plastic waste, we contribute to a circular economy and extend the life of plastic materials.
Our energy-efficient recycling platform reduces energy use and CO2 emissions by avoiding producing virgin plastics. For more information, please visit our SDG page.
During the project development phase, we brainstormed various projects including a fungi fertilizer filter, blood substitution, plastic upcycling, and radiation resistant plant to help colonize mars. With help from our PIs, as well as other world class Professors, we discussed the benefits and the challenges with each project. At the beginning, we imagined creating a platform in which bacteria use plastic to create medicine, fertilizers, and other products. However, our professors pointed out the difficulty of for example synthesizing the large insulin molecule in a bacteria. After deciding to focus on plastic bioremediation, we further discussed with our PIs and stakeholders the largest issues, mixed plastic waste, and decided to create our smart co-culture platform using plastic biosensors with the goal of producing polyhydroxyalkanoates (PHA), a bioplastic alternative.
Initially, our project focused on the biological degradation of PET with Ideonella sakaiensis. To better understand the current challenge of plastic recycling in Germany and see where synthetic biology can make a huge difference, our Human Practices team reached out to experts in mechanical recycling. Our current recycling system - mechanical recycling relies on presorting plastic waste into fractions. We were told that mechanical recycling is currently reaching its recycling limit, towards around 50% of collected packaging paste. To raise its limit, we need new recycling solutions for mixed plastic. Therefore, we further brainstormed on modification of our projects to deal with mixed plastic issues instead of pure PET. We finally came to our ReMix system, a platform approach that can degrade mixed plastic waste.
In our ReMix system, the helper strain breaks down mixed plastic in its monomers, which our main strain utilizes as an
energy source for building new molecules, such as bioplastic PHA in our case.
We thought more usage of bioplastics would make Heidelberg a more sustainable city and reduce the adverse environmental
impact of mixed plastic waste. However, after talking to Stephan Knauer, operational deputy manager of the Heidelberg
City waste collection and management center, we recognized the rather tricky role of bioplastic in the current waste
management system in Germany. Stephan mentioned that bioplastic bags are becoming popular as an environmentally friendly
product. However, current bioplastic products cannot be biologically degraded under the conditions in typical composting
plants, such as the one in Heidelberg. Usually, higher humidity and longer time are needed. As a result, bioplastic instead
contaminates the compost product.
We were unaware that bioplastic, a sustainable product with
good will, would instead pose problems to our current waste management system.
As ReMixHD works in moderate conditions and demands less energy than chemical and mechanical recycling, we were keen to determine whether ReMix is actually a sustainable alternative. Therefore, we talked to Sylke Freudenthal, who leads the sustainable development department of the recycling company Veolia GmbH. Sylke drew our attention to a technical report “Environmental and economic assessment of plastic waste recycling” to compare the environmental impact of different recycling methods systematically. From there, we find out that incinerating 1kg of PET produces 2.1kg of CO2. With the help of our metabolic model we are able to predict the amount of CO2 beeing produced by our model. With a value of 1.76 kg CO2 per kg PET, we are below the value of incineration. Nonetheless, there is a significant number of other factors involved in the recycling process, which is why the final evaluation of the sustainability of our recycling platform has not been reached its full scope yet.
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