Team:KEYSTONE/Hardware
The final product
Abstract
The hardware we created is a plastic degrading trash bin that incorporates many functional parts such as a shredder and a decomposing reactor. Our concept is to make a sustainable machine that can be implemented in any environment, meaning it is unprecedented in plastic recycling. Therefore, it can be interpreted as a mini plastic recycling station. This idea is conceptual, but we valued practicality. To put our concept into practice, we first interviewed many experts in the field of plastic recycling to identify the position where our product can help the best. According to the investigations done, we decided to focus on plastic issues in remote areas. From the focus, we introduced supporting parts such as solar panel to improve the practicality form the technical perspective. Later, we created a 3D model to specify the product. Using the model, we commissioned a factory to produce the trash bin for us.
Introduction
The purpose of hardware is to put the concept and approach of our iGEM project into practice. Thus, we created a developing process mainly including investigation, product specification, product design, and product development to provide a solution to the global issue we aimed to solve.
Product background
In our community, we are educated to be aware of global issues around us, especially issues related to sustainable development goals. There is a total of 17 sustainable development goals that the United Nations has carried out. After a few discussions, we found ourselves very much interested in global goal number 14, Life underwater. In particular, the UN emphasized the importance of reducing ocean plastic pollution.
According to research, the world produces 270 million tons of plastic pollutants every year which is 13% of the world’s annual waste. Among all, 79% are discarded to the natural environment. In fact, plastic takes more than 400 years to degrade in the natural environment, drastically harming the ecosystem and hence jeopardizing the sustainability of human society. (Hannah, 2018)
To solve this issue, we chose to produce a machine containing genetically modified bacteria that can degrade plastic, thus, contributing to the promotion of our world’s sustainability.
Investigation
After continuous brainstorming, we had come up with a research method that helped us to develop our project mindfully and effectively. We believe a Q&A style research can strongly focus our practices on the global issue we are targeting and hence make our project more coherent.
Our project had evolved along this process. At first, we determined the aim of the project and later used the Q&A style research method where we deeply investigated plastic pollution issues and luckily acquired important knowledge regarding the plastic recycling industry which later helped our project to become more precise and more useful.
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What plastic can we degrade with bacteria? How?
According to our research, we learned that there is a wide range of different kinds of plastics such as PE, PET, PVC, PP, and PS. Due to new studies, we found out that PET (polyethylene terephthalate) is practically biodegradable. Also, it is a type of plastic that bottles are often made with. Fortunately, a Nature article called an engineered PET depolymerase to break down and recycle plastic bottles (Tournier, 2020) was found during research. The passage pointed out that LCC (leaf-branch compose cutinase) is a newly discovered PET-depolymerizing enzyme, and, proven by experiments, the most effective one available. Besides, researchers also discovered a new mutation of the enzyme, increasing its heat endurance. Because of the superior qualities this enzyme has comparing to similar enzymes, we choose to utilize this enzyme and knowledge from the article as the means of achieving our project (and hardware). -
Is biodegradation of plastics practical in all areas?
To make plastic-degrading hardware practical, we need to find out the most suitable spot for our hardware to carry out its function. Therefore, we interviewed Xue Yang, the Secretary-General of Waste Plastics Recycling Association. In his opinion, our product is not suitable to apply in major cities in China, because the plastic recycling systems there are well-developed and fully functional. For example, in Beijing, the government builds special facilities that have a complete processing line involving assembling, shredding, cleaning, melting, and packaging. According to him, this system, or industry, is playing an important role in the local economy, generating a considerable amount of money each year for all social statuses. As result, in these areas, the conventional plastic recycling system is way preferable comparing to our project.
However, in places like islands or mountains, such a system usually does not exist or lacks sufficient facilities. For example, on Mt. Everest, over 140 tons of garbage are present, and a great portion of them are plastic. To look for a more specific example, we interviewed Bali waste disposal experts Rósa Halldórsdóttir and Sally Silverstone, co-sponsors of the Biosphere Foundation. They pointed out that, in most cases, there is not enough space to build plastic recycling factories on islands, and as a result, a significant amount of plastic wastes entered the coastal ecosystem, harming wildlife in the coral region. The results imply that our project might be an alternative to solve the plastic pollution issue in remote tourist attractions where many conventional methods are not available to function.
Tough the conventional method of recycling plastic might be more efficient in terms of quantity; the biodegradation method is potentially more superior in quality due to the following. According to the Nature article we based our project on, we learned, by using LCC, we can depolymerize PET plastic into EG (ethylene glycol) and TPA (terephthalic acid), which are essential materials used to product PET plastic. Yet in the interview with Xue Yang, he mentioned that the conventional PET plastic processing method will reduce many qualities of the plastic and hence reduce its integrated value. In conclusion, we can avoid the reduction of the value of the plastic in a purely environmental-friendly (carbon free) manner by degrading PET using biological means. This will bring our project value and strengthen our approach to the goals.
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What are some projects that share similar function with ours? What can we learn from them?
We analyzed three similar projects, which greatly inspired us.
The first product is from Exeter; a 2019 undergraduate iGEM team from England. The team aims to degrade microplastic using bacteria with a special membrane. To realize that, their hardware can function as a filter that collects micro-plastics in tap water and store them in a container. From their project, we’ve learned that the means of collecting plastic from the environment is very important for the practicality of a product; we also learned that it is necessary to store degraded substances because our degradation process will create valuable material such as EG and TPA.
Second, we analyzed the trash shredder from a plastic recycling company. This shredder can break plastics into small pieces. This piece of machinery strongly inspired the design of our hardware because the function it has converges with our expectations. However, this type of shredder is only present in large factories and itself is on a huge scale as well. This violates our idea of bringing our device to places that are not suitable for big factories. This idea is developed in an interview with Sally Silverstone, a plastic recycling expert in Bali; in the interview, she told us that it is very difficult to execute large scale activities in these remote areas because of multiple reasons. First, it is very expensive to transport such a large amount of material because it usually involves airline transport and a substantial amount of human resources. Besides, some obstacles may hinder the consistent functioning of the facility; for example, it will be very difficult to find a replacement once one piece of your machine is broken because there are no factories to supply you due to remoteness. Fortunately, we found a mini shredder that has the size of a tissue box on YouTube to solve this issue. Also, in the video, the YouTuber clearly demonstrated and proved its ability to shredding plastic bottles; so, we decided to apply this type of machine in our hardware.
Finally, we analyzed is Bali Island,1 which is a famous scenic spot with an extremely high population of tourists. According to national geographic, 52% of all the plastic garbage, there are not managed appropriately. Consequently, 33,000 tons of plastic waste were dumped into the ocean every year. According to the interview we did with local garbage recycling activists, the lack of an advanced plastic recycling system might be the agent of this issue. However, the facilities required to solve this problem are overly expensive and occupying. Besides, according to National Geographic, tourists generate a considerable amount of waste each year, where the collective average waste generation of tourists is 1.7 kg/day. For this reason, our hardware cannot only focus on local populations but also on foreign tourists in remote areas such as Bali island. Since part of the users of our hardware are tourists, our hardware mustn't hinder their touring experience; therefore, our hardware should have a fair appearance, and a method of covering the unpleasant smell of the bacteria working inside is needed. (Amanda, 2019)
Product design
The big picture
Now, due to prior works, we can state the qualities this product should obtain into a product statement that will function as a guideline. To be more specific and accurate, we listed the qualities and formed a product specification to specify the areas that the qualities shall be made practical.
Product statement: The hardware of this project is dedicated to the solution of plastic pollution issues in remote tourist attractions by degrading PET plastic using genetically modified bacteria.
Aesthetics: According to the product statement, we believe our hardware does not need to look fancy extremely beautiful. The main purpose should be the performance of essential functions. Besides, the major working site of our product will be remote areas where plastic recycling systems are usually lacking. Nevertheless, our product will look neat so it wouldn’t impact the image of the site in a negative way.
Customer: The target audience of this project is the managing company that runs tourist attractions in remote locations.
Environment: Holding the purpose of solving environment issues, it is unacceptable for this product to product hazard to the environment.
Safety: This product must be safe to use in all conditions because it will be exposed lots of people. To ensure that, we will design safety programs that will minimize the potential damage it can cause.
Function: The main function is to degrade PET plastic and solve plastic pollution issue by doing it. Also, we believe we have the potential and ability of generating profits by selling ET and TPA generated by the degrading process.
Material: The material used should be harmless to the surrounding environment. Material used should be strong enough to endure complicated weather in places such as mountains and islands.
According to our specification, we created a modularized hardware design. It allows a clear understanding of the mechanism and function of our hardware to be comprehended.
Each module serves for a distinct function in the machine. The blue region is the shredder module that breaks down PET plastic bottles into little pieces, effectively increasing the surface area of the plastic, hence promoting higher degradation efficiency. The orange region is the motor module, capable of powering the shredder. The green region is where the plastic is supposed fall into. It it basically is degradation can that contains genetically engineered E. coli. At first, the temperature will be maintained at 37 degree Celsius for culturing the bacteria. Later the temperature will be controlled to be 20 degree Celsius to allow the synthesis of LCC. Then the temperature will increase to 72 degree Celsius, which kills the bacteria and breaks down its cell membrane, allowing LCC to enter the environment and mix with degrading buffer. 72 degree is also the optimal temperature for LCC to preform maximum efficiency. Electricity are stored in a battery located in the pink region. The last module is the controller that has a yellow color. It is comprised of controller and circuits, allowing all modules to work together.
In the degradation module, the main structure is the degradation bin made with metal, which won’t be degraded by LCC. The function of the bin is to provide a suitable living environment for bacteria and degradation conditions for LCC. Thus, the condition of the bin will be carefully monitored and controlled. There will be a thermometer to measure the temperature, which will be controlled by a temperature controlled semiconductor. A liquid level sensor will detect the surface level of fluid in the bin. There will be a tube that connects IPTG to the degradation zone, allowing the bacteria to synthesize protein. There will also be a layer of Aeronautical insulation material, which maintains the temperature in the bin. Besides, an electromagnetic stirrer will also be implanted which blends LCC and PET plastic that maximized the rate of degradation. An air fan will be used to blow the fragrance of linalool into the air, which neutralized the unpleasant smell of the environment. In addition, the bin will also be removable, which allows people to change the bacteria in the bin easily.
Product development
Action plan
Partners
A company named Insentek greatly supported our project in many ways. We got in touch with them in an early stage of our project. we learned that they are a technology company focusing in soil humidity sensing devices, and we both were interested in each other’s work. They are a company that has the quality many similar one’s lack, the dedication to create useful products that accuracy benefits. They provided us two engineers who gave us precious advice and inspirations in the development of hardware and team wiki. Through our connection with this company, we were able to access to their factory and use their resources to create the product we needed.
Mr. Zhang Chaofeng, one of the engineers, participated a lot in supporting our hardware development. He helped a lot in 3D modeling of the hardware design and the connected us and the factory. When collaborating, we sent the full design and description of the hardware to him; he used a more standardized modeling program and recreated our design. Of course, he made some changes, yet those changes are additions to improve practicality. Thank to him, the final model was qualitied enough to fulfill the requirement to product an object in a real factory. Without him, we wouldn't be able to realize that we were missing many key parameters because the design was relatively conceptual. His other role is a coordinator between us and the factory. We commissioned him this job due to his solid prior knowledge and connections in working with factories. In the end, this decision turns out to be a wise choice because he was able to communicate very effectively so that our need of modification could be passed on to them in a short period of time, which is what we are in need of. We were continuously modifying our hardware during its production, and, during this time, Mr. Zhang gave us useful advices such as the most proper motor that could provide enough force and be small at the same time with his professional knowledge. In general, he is the man behind many or our successes in hardware. They style he operates with is very much suitable for our working habit and the concept of iGEM because we were able to fully express out creativity and ideas and study the method of realizing that. For many reasons, we are really thankful to his participation and appreciate the experience to work with him.
Product outcome
3D models
These are the primary concept models that was created for the purpose of presentation and discussion in our team meetings or team meet-ups with other teams.
Later, these models are created, analyzed and modified with help from Mr. Zhang Chaofeng.
The model of the shredder is first created according to similar products on the market. In this step, we decided the type of shredder and motor we are going to use. The choice for the shredder is rather simple, because it is a standardized machine. However, the motor used to power this kind of shredder is large, heavy and power-consuming, which is not the best choice for us. Mr. Zhang managed to solve this issue by finding and later purchasing a motor suitable in size though it was proven to be inefficient later.
After the model of the core function module was done, the final concept design was created according to the qualities we listed. In this design, we’ve kept the qualities of the original concept design and altered the unwanted. For the unchanged, we are consistent with the tall rectangular shape and the positioning of the modules. And for the difference, we added solar panel, divided the outer structure into halves, changed the cover of the shedder similar to many trash cans, and put a large funnel on the top of the shredder to prevent harm to the user.
The main reason that this model is considered a concept design is that it lacks practicalities. When scales were added to consideration, problems soon emerge. The final design was created to resolve such problems. The main change was about the composition of the top of the machine. Before, the whole front part of the machine was the entrance of plastic. Now it is moved to the right side, leaving the control system to have the left, because we are now aware of the potential space the control system is going to take. After this modification, the scale of the machine is increase due to that size of the plastic shredding-degrading module could not change.
Hardware development
Due to the Covid-19 situation, we do not have access to local workshops, so we commissioned a factory to product our hardware. They purchases and produced all the parts needed in our demand. The first step was to weld a rack.
In the motor module, we have tested different combinations of motor and blades of shredder to maximize the efficiency
The original motor
At first, our machine struggled to shred a plastic bottle due to the ineffective motor and blade of the shredder.
Quickly, the blade of the shredder was redesigned and made in a new shape to adapt to plastic. However, the power seems to be insufficient to completely break down a plastic bottle.
The powerful new motor
Finally, we were able to achieve the appropriate shredding rate by using a motor that can provide more power.
When we first received the hardware, it was not completed. Thus, we would have to make some modifications. Images bellow show the process of adjusting the angle of the solar panel.
Solar panel adjusted.
Hardware demonstration
Final product
The person in the picture is Jerry Huang. He is responsible for the design and production of the hardware.
Hardware function demonstration
Controller
The conceptual model
The actual product
Product handbook
The purpose of creating hardware parameters is not only to fully display the functionality of our product, but also, just like one of the purposes of iGEM-developing and sharing parts, we want to share it with the world. Due to covid-19, we could not fulfill everything we planned, yet in the future, someone else may carry out the full potential of our idea and help the society.
1. Hardware blueprint
2. Materials & Tools
2.1 Material list
2.2 Tool list
3. Circuit diagrams
3.1 Control circuit
3.2 Power supply circuit:
Assembly procedure:
1. Weld the material together to from a rack according to the blueprint
2. Place the shredder in the proper position according to the 3D model
3. Connect the shredder to the motor and speed reducer
4. Temporarily connect the motor to the battery for testing
5. Join the solar panel to the top of the machine and adjust the angle if needed
6. Connect the motor and solar panel to the battery.
7. Connect all modules needed to the control circuit and add dc contractor and step up converter.
8. Add sensors and light indicators
9. Function test
User feedback
For many reasons, we did not have the opportunity to fully assess the practicality of the hardware. We believe by gathering feedback from potential users might be able to fill in the blank of product evaluation.
To acquire such knowledge, we interviewed plastic degradation expert prof. Liu Luo, which provides multiple suggestions for technical improvements of efficiency and practicality. Detailed information is showed in the section below.
Besides, according to the interview we did with Bali waste disposal expert Sally Silverstone, our hardware is extremely suitable for the local demand. Due to the lack of plastic processing systems in such locations, she especially emphasized how our hardware can directly contribute to solving the issue.
In addition, Lindesay, an activist who is dedicated to the recycling of plastic on the Great Wall, believes our hardware can be used to help the local plastic issue. To clarify, many parts of the Great Wall are located in very remote areas, where visitors occur but very limited protection is given.
Luckily, the experiment results allow the evaluation of partial functions of the hardware. The bacteria we created has been proven to be plastic-degrading which supports our claim on the functionality of the product.
Future vision
Due to technical limitations, many of our vision for the product could not be realized. Still, we want to bring that up, because only by comprehending our project considering these works, a complete understanding can be established. Besides, to make our hardware more effective, we can add functions to it or modify some components in the future.
Before all, we want to clarify that the current condition of the hardware is incomplete. So, the first future work will be to completely establish our concept. The part that was not finished is the decomposing bin. The main reason is because the factory cannot create such precise machine. Also, the creation of the decomposing bin required a lot of test with the our bacteria. However, due to COVID-19 we proven the success of our bacteria in a very late stage, we didn't get a chance to do that.
For example, in the interview with prof. Liu, he pointed out that the current degradation equipment is not optimized for this reaction. A better way is to replace the current degradation can with a tubular reactor that allows the fluid to have a greater surface area. Only in this way, the liquid containing LCC can be heated most effectively. Also, he mentioned the importance of creating water flow in the tube using a pump, because it promotes a better mix of the liquid and plastic pieces.
Another possible improvement we would like to propose is the approach to the sustainability of the biotic portion of the hardware’s functionality. First, a culturing bioreactor is needed to maintain the bacteria population for long-term storge. Also, another method can avoid the complex structure and a large scale of electricity consumption of the bioreactor is powdered bacteria culture. Comparing to the bioreactor, powdered bacteria are much more convenient and simpler, which benefits the sustainability of the machine when placed in a harsh environment. No matter which bacteria culturing method is chosen, the bacteria culture is supposed to be added into the tubular reactor in a controlled timing. After the bacteria is added, it will populate and later boiled for the release of the plastic-degrading enzyme, which is LCC.
.Safety
The bacteria in our device might leak. If the bacteria enter the water system, humans or animals could get sick from drinking contaminated water. To prevent this, the hardware is built majorly by strong materials such as metal, which strengthens the structural force of the machine, hence limiting the chance the hardware to be crushed by natural forces.
The shredder has serious safety concerns. To severe injuries from happening, the feeder of the machine is designed to be steep and deep to maximize the possible distance between the human hand and the blades of the shredder. The height of the feeding window is high as 1.2 meters, which prevents young children from using this machine. Another practice we applied to improve safety is infrared sensors. When equipped with such sensor, the machine will be able to sense whether the door is closed or not and allow the motor to turn on only if the window is fully closed.
Reference
[1]Ritchie, Hannah, and Max Roser. "Plastic Pollution." Our World in Data, Sept. 2018, ourworldindata.org/plastic-pollution.
[2]Tournier, V., Topham, C.M., Gilles, A. et al. An engineered PET depolymerase to break down and recycle plastic bottles. Nature 580, 216–219 (2020). https://doi.org/10.1038/s41586-020-2149- 4
[3] Siddharta, Amanda Tazkia, and Photographs by Nyimas Laula. “Bali Fights for Its Beautiful Beaches by Rethinking Waste, Plastic Trash.” National Geographic, 14 Oct. 2019, www.nationalgeographic.com/science/2019/10/bali-fights-for-its-beautiful-beaches-by-rethinking-waste-plastic-trash/.
