. Integrated Human Practices .

Overview

The ongoing climate crisis driven by high levels of carbon dioxide emissions has led to numerous disasters and heavy losses worldwide. Climate-related disasters, such as the alarming melting of glaciers, rising sea levels, and a surge in extreme weather events, have become increasingly frequent and severe over the years. According to incomplete data statistics, these catastrophic weather events resulted in significant economic losses and substantial human casualties, reaching nearly $143 billion annually and approximately 60,951 deaths in the last 20 years (1). So, governments act to alleviate the climate crisis, and their efforts focus on two main strategies: reducing the sources of greenhouse gas (GHG) emissions and improving carbon absorption. Improving carbon absorption relies mostly on natural solutions. The best way is to protect vegetation, especially forests. Therefore, Human Practices are essential to understand the full scope of the problem, find effective solutions, and arouse broad public concern.

1. Investigating the Current Situation and Problems

After discussions with Assistant Professor Liang Dan, we recognized the vital role of trees in global climate regulation. Due to their long growth cycles, trees recover slowly after large-scale deforestation, which worsens the climate crisis. So, promoting the recycling of renewable resources, especially paper, is the best way to protect forest resources and mitigate the climate crisis. After consulting the reference, we know that 129.65-million-ton paper products were produced in 2023, which accounts for 39.5% of total timber consumption in China (2), while the utilization rate of waste paper has decreased from 72.5% (2014) to 52.4% (2023) (3). After a field survey of the paper enterprises, we learned that the inefficiency of deinking and pollution in the paper recycling process continues to limit paper recycling efforts significantly. For waste paper entering the recycling process, removing ink from the waste paper is the main intractable problem, including high cost, environmental pollution, and health risks. Thus, our project focuses on developing a green and sustainable method to overcome this problem.

2. Exploring an Unprecedented Answer

To make paper recycling more environmentally friendly and cost-effective, we plan to optimize the industrial waste paper recycling process using synthetic biology techniques. We developed and refined our project through interviews with experts from both academia and industry. After consulting with Associate Professor Yang Liulin and Ling Chen, we selected an efficient deinking enzyme to remove the ink from the pulp. We consulted with Ms. Zhuang Xiaoyan, and she pointed out that using an autolysis system in industrial applications would require large amounts of expensive inducers, making it cost-prohibitive. She recommended using signal peptides instead, which skip the expensive protein purification and/or inducers. Based on our enterprise survey, we discovered that deinking flotation is the preferred method for removing printed ink from paper during the recycling process. However, this method will cause a loss of fibers, thus lowering the recovery rate. To address this issue, we consulted Associate Professor Sha Yong, an expert in petroleum extraction. He advised us to use a hydrophobic solvent to extract the ink. Therefore, we chose to use limonene, a hydrophobic solvent that can be biosynthesized, from many hydrophobic solvents to extract the ink in the pulp after enzymatic deinking. These human practices have provided theoretical guidance for our project, allowing us to enhance and refine our research continually.

3. Arousing Broad Public Concern

Furthermore, we have actively engaged with the public to raise awareness about recycling. We conducted surveys to understand people's attitudes toward paper recycling and the use of recycled paper. We organized a communication seminar to introduce synthetic biology principles and techniques to the paper enterprise staff, deepening their understanding of synthetic biology. We also held educational activities at the Xiamen Science and Technology Museum and Yanwu Primary School to popularize the importance of recycling renewable resources. These efforts are not just about raising awareness, but also about fostering a sense of collective responsibility. We aim to encourage more people to pay attention to the recycling of paper and other renewable resources, working together to mitigate the climate crisis.

Background

The climate crisis, a pressing issue of our time, is primarily driven by greenhouse gas (GHG) emissions, such as carbon dioxide, trapping heat in the atmosphere. This results in global warming, leading to the alarming melting of glaciers, rising sea levels, and a surge in extreme weather events. The El Niño phenomenon, which has become increasingly erratic and destructive, is a stark example of these changes. It has caused severe flooding in countries like Peru and Ecuador in South America, and devastating droughts in places like Australia, Indonesia, and parts of Southeast Asia. These weather disasters have had profound impacts on agriculture, infrastructure, and national economies. The global climate crisis is rapidly worsening, with countries facing escalating crop failures, higher economic costs, and more frequent natural disasters.

In response to this growing threat, governments worldwide have implemented various policies to mitigate the effects of climate change. One key initiative is the Paris Agreement, which aims to keep the increase in global average temperature well below 2 °C above pre-industrial levels. These efforts focus on two main strategies: reducing the sources of greenhouse gas (GHG) emissions and improving carbon absorption. Reducing emissions focuses on energy conservation and cutting emissions, like using energy more efficiently and switching to renewable sources such as solar and wind power. Improving carbon absorption relies mostly on natural solutions. The best way is to protect vegetation, especially forests. Therefore, many countries are now investing in reforestation projects and promoting sustainable land use to strengthen the Earth's natural ability to absorb emissions. However, the growth rate of wood is far from enough to meet the human demand for wood. So, promoting the recycling of renewable resources, especially paper, is the best way to protect forest resources and mitigate the climate crisis.

Project Design

1. Brainstorming

Based on a preliminary understanding of the relationship between climate crisis and paper manufacturing, our team initiated many brainstorming sessions to discuss the project design. Some of the questions below are critical and should be ascertained first.

(1) What important role do forests play in climate regulation?

(2) How does paper production impact the climate and environment?

(3) Can paper be recycled?

(4) How does paper recycling contribute to addressing the climate crisis?

(5) What is the current status of paper recycling? What is the main challenge?

So, we carried out some Human Practices to find answers to our doubts.

2. Theoretical and Practical Investigation

2.1 What important role do forests play in climate regulation?

After searching for information from the literature, we found that forests are vital in regulating the global climate. They absorb large amounts of carbon dioxide, which helps slow down global warming. Statistics indicate that forests absorb a net 7.6 billion metric tons of carbon dioxide each year (4). However, in a discussion with Assistant Professor Liang Dan, he highlighted that about 13 million hectares of forests are lost each year due to human activities, mainly for essential uses like paper production. The official data indicated that 129.65-million-ton paper products were produced in 2023, which accounts for 39.5% of total timber consumption in China (2), confirming the conclusion from Prof. Liang. This puts immense pressure on forest resources and worsens ecological imbalances and climate crises. Following his advice, we focused on investigating the paper industry and paper recycling to alleviate its dependence on forests and help mitigate the climate crisis.

2.2 How does paper production impact the climate and environment?

It is known that paper production and consumption require the felling of many trees. In 2023, China produced 129.65 million tons of paper and paperboard, equivalent to cutting down over 20 billion trees (2). To better understand the impact of paper production on the climate and environment, we held discussions with the Zhangzhou Municipal Ecology and Environment Bureau. The Bureau staff noted that the paper industry not only accelerates the depletion of forest resources but also contributes significantly to carbon emissions and environmental pollution, such as black liquor waste and wastewater containing high levels of ammonia, nitrogen, and total phosphorus. Many paper enterprises have been classified as "pollutant discharging entities." This made us realize that the paper industry urgently needs to adopt a more sustainable development approach, reducing its heavy dependence on forest resources and minimizing environmental pollution to address future climate challenges better.

2.3 Can paper be recycled?

Of course! We got a clear answer at the Xiamen Low-Value Recyclable Sorting Center. In cities like Xiamen and across China, recycling renewable resources like paper is strongly encouraged to reduce waste and support sustainable development.

The Xiamen Low-Value Recyclable Sorting Center is the first demonstration project for low-value recyclable materials in China. Ms. Liu, a staff member, explained that the center uses advanced technology to automatically identify and sort different types of waste, such as paper, plastics, and metals. This technology speeds up the recycling process and greatly reduces the amount of waste sent to landfills. The center focuses on recycling low-value materials like used paper, playing a key role in helping Xiamen become a more resource-efficient city.

Ms. Liu also mentioned that both China and the international community are working to build a resource-efficient society. This project is not only part of China's environmental efforts but also contributes to global goals for sustainability. These initiatives are improving local waste management and positively impacting the environment worldwide.

2.4 How does paper recycling contribute to addressing the climate crisis?

We further conducted a field investigation at Nine Dragons Paper Limited. The staff explained that recycling waste paper can not only optimize the raw material structure and reduce environmental pollution but also significantly decrease petrochemical energy consumption, making it an important way to promote the sustainable development of the paper industry. According to statistics, producing recycled paper from waste paper greatly benefits the earth (5).

(1) Recycling 1 ton of waste paper could save 17 trees.

(2) Recycling 1 ton of waste paper could save 100 tons of water.

(3) Recycling 1 ton of waste paper could save 600 kWh of electricity.

(4) Recycling 1 ton of waste paper could reduce the emission of 11.37 tons of carbon dioxide.

2.5 What is the current status of paper recycling? What is the main challenge?

To better understand this issue, we visited the Fuxing Renewable Resources Recycling Store, a small recycling center, for an on-site investigation. The owner told us that small recycling centers like theirs can collect about 600 kg of waste paper daily, while larger recycling centers can collect up to 2000 kg of waste paper daily. The official data also indicated that 64.35 million tons of paper pulp were produced from waste paper in 2023, accounting for 54% of the total annual paper pulp production (2), while the utilization rate of waste paper has decreased from 72.5% (2014) to 52.4% (2023) (3). Thus, some bottlenecks challenge paper recycling.

At the paper enterprise, the worker showed us the paper recycling process. For the waste paper entered into the recycling process, removing ink from the waste paper is the main intractable problem in the recycling industry. We summarize the issues, include but is not limited to the following points:

(1) High cost: Plenty of water and chemical reagents were used to remove the ink from waste paper, and the effluent treatment also incurred many processing fees.

(2) Environmental pollution: The improper process mode (incinerate or landfill solid sludge) may result in severe pollution.

(3) Health risk: Using many chemical reagents, such as hydrogen peroxide and sodium hydroxide, poses significant health risks to workers in paper enterprises.

In conclusion, this conventional approach requires a substantial amount of toxic chemicals. It also releases poisonous organic agents and heavy metals that may cause environmental contamination.

3. Summary

After the serious Human Practices with the professors, staff in street waste recycling stations, the government sector, and paper enterprises, we explore the comprehensive information about paper recycling. As climate change continues to accelerate, the need to preserve our forests has never been more critical. Deforestation, driven by commercial purposes such as paper production, exacerbates this issue by the destruction of vital carbon sinks. Thus, Paper recycling is an effective way to protect the forests and mitigate the climate crisis. However, the current methods for pulp deinking and heavy metals treatment in recycled paper are inefficient and highly polluted, which are the key bottlenecks in improving the utilization rate of recycled pulp and realizing the greening of the paper production process. Therefore, by focusing on optimizing the pulp deinking and heavy metal treatment processes, we can improve the utilization rate of recycled pulp, reduce carbon emissions and environmental pollution, and provide a more effective solution to address environmental and climate crises.

Project Design Improvement

1. Pulp Deinking

To better understand the current state of paper recycling, we visited the Xiamen Renewable Resources Industry Association. The senior staff told us, “Removing the stains, especially ink, is a serious problem that blocks waste paper recycling for many enterprises.” Standard deinking methods, such as chemical and physical methods, are highly polluted and inefficient, affecting the quality and yield of recycled paper. This made us realize that the low efficiency of deinking is a significant obstacle to waste paper recycling. As a result, we began to consider the possibility of using synthetic biology technology to develop a more eco-friendly and efficient deinking method. By overcoming these challenges and optimizing key steps in the recycling process, we can promote paper recycling, reduce deforestation, and mitigate the climate crisis.

How do we optimize the process of removing ink from the pulp?

Our survey found that the ink binder is the key factor contributing to the low deinking efficiency, as it causes the ink to adhere tightly to the pulp. To solve this problem, we considered using several enzymes as potential deinking agents, such as cellulase and laccase, to break down the ink binder and remove the ink. So, we consulted Associate Professor Yang Liulin, a polymer expert, to assess the feasibility of this approach. He pointed out that the current enzymatic methods struggle to break down the polymer resin in the ink binder efficiently. He further advised us to use cellulase to degrade the cellulose on the paper surface. Following his advice, we improved the original design by adding cellulase to the list of deinking agents.

During the experiment, we found that the deinking effect of using cellulase and laccase was limited and did not meet our expectations. To find more effective enzymes, we consulted with Associate Professor Ling Chen. After analyzing the treatment system and the main components of the ink binder, he suggested using oxidases, such as monooxygenases, to degrade the ink binder partially. Following his advice, the introduction of monooxygenase significantly improved the deinking effect. Although it still did not fully meet our expectations, it showed great potential in pulp deinking. Therefore, we decided to explore different types of monooxygenases and perform saturation mutagenesis to harvest the most efficient ones and discover more effective variants.

In our initial design, we considered using an autolysis system to release enzymes. To evaluate the feasibility of this approach, we consulted with Ms. Zhuang Xiaoyan. She pointed out that using an autolysis system in industrial applications would require large amounts of expensive inducers, making it cost-prohibitive. She recommended using signal peptides instead, which offers three key advantages. Firstly, it can secrete the target protein extracellularly and avoid the expensive protein purification procedure, significantly reducing production costs. Secondly, engineered bacteria can continuously release enzymes rather than undergoing one-time lysis, thus improving efficiency. Lastly, unlike the autolysis system, which poses a biosecurity risk by potentially releasing plasmids, signal peptides help minimize this risk. Based on her advice, we tested various signal peptides and selected the most effective one.

Based on our survey, we discovered that deinking flotation is the preferred method for removing printed ink from paper during the recycling process. The process is based on the difference between hydrophilic and hydrophobic inks, in which the latter can be removed from the pulp suspension by adhering to bubbles (6). However, this method will cause a loss of fibers, thus lowering the recovery rate. This problem was also verified by the senior staff in the paper enterprise. To address this issue, we consulted Associate Professor Sha Yong, an expert in petroleum extraction. He explained, "Because the scale of ink and pulp fibers is close to each other, flotation methods are difficult to separate them effectively. Using a hydrophobic solvent to extract the ink might be possible." Therefore, we chose to use limonene from many hydrophobic solvents to extract the ink in the pulp after enzymatic deinking. It can be synthesized through synthetic biology and fermentation engineering (7), overcoming the shortage of flotation method that carries away a large number of pulp fibers so as to minimize the loss of fibers. Upon testing, we observed a significant improvement in the deinking process.

2. Safety

In previous conversations with staff at Nine Dragons Paper Limited, we learned that sterilization processes commonly used in enterprises include UV and filtration. However, these processes do not fully meet biosafety standards, posing a potential risk of engineered bacteria escaping into the environment, which could threaten ecological health and biodiversity. We designed a light-triggered kill switch to avoid introducing additional chemicals into wastewater, such as various inducers. After deinking in a dark circumstance, the inbuilt kill switch will be turned to the “ON” state via exposure to a specific wavelength's light illumination to achieve the biocontainment goal. To evaluate the feasibility of the new solution in the industry, we revisited Nine Dragons Paper Limited at the end of the season. After introducing the method in detail to the relevant staff, the staff acknowledged its potential in terms of safety and flexibility. However, there were still concerns: “We need to ensure the reliability and stability of this solution in practical applications. Additionally, we must evaluate its impact on existing equipment and processes. If these issues can be addressed, we believe this proposal is worth pursuing further.”

Feedback

1. Communicate with Paper Mills to Evaluate Strategy

At the end of the season, we revisited Nine Dragons Paper Limited to present our proposal and seek feedback. They evaluated our approach based on compatibility, treatment effectiveness, cost, and pollution control. During this process, we noticed that the company had an incomplete understanding of synthetic biology concepts and applications. To address this, we organized a communication seminar to introduce synthetic biology principles and techniques in depth. During the communication, we reported our research throughout the season to the company, in which we constructed an innovative and efficient method for deinking waste paper, continuously optimized the design and established standard operation procedures to solve practical problems. This exchange has enhanced the understanding of synthetic biology and highlighted the advantages of cross-disciplines in solving practical problems.

2. Raise Public Awareness of Environmental Protection

During our discussions with the staff at Xiamen Low-Value Recyclable Sorting Center, we found that the public needs more awareness about the importance of waste paper sorting. We organized educational activities at the Xiamen Science and Technology Museum and Yanwu Primary School to arouse broad public concern. During this science popularization education, we introduced the development and applications of synthetic biology and highlighted the importance of paper recycling. We also engaged children with interactive games to spark their interest in synthetic biology and encouraged the public to pay more attention to the recycling of paper and other renewable resources. Additionally, we posted relevant articles on social media to encourage more people to participate in environmental protection efforts, contributing to addressing the climate crisis.

Summary and Prospect

Following Assistant Professor Liang Dan's suggestion, we used the life cycle assessment (LCA) method to calculate and compare the carbon emissions of enzymatic deinking and chemical deinking methods in recycled paper production (See more details in our LCA page). We want to evaluate the contribution of our project to the emission reduction of wastepaper recycling industry processes. The results indicate that the use of enzymatic methods can reduce carbon emissions by 21.1% and lower the production cost of recycled paper by 31.9%. Currently, we are in close collaboration with Professor Liang, and we value his input in discussing the LCA and the contribution of our project to global environmental sustainability.

Throughout this process, we explored the root causes of the climate crisis, highlighting the critical importance of resource recycling and paper recovery. By collecting data and visiting enterprises, we gained important insights into industrial-scale paper recycling challenges, shaping our project design. The guidance from our professors during the experiments helped us refine our techniques, significantly improving our deinking results and bringing us closer to our objectives. This interdisciplinary collaboration not only sharpened our research skills but also deepened our understanding of the complexity of these issues. To promote our findings further, we actively engaged in public education, reaching out to employees, students, and other groups to spread awareness about synthetic biology and resource recycling. We hope to raise awareness of the climate crisis and encourage more people to get involved in sustainable development efforts, ultimately contributing to mitigating the climate crisis.

References

1. R. Newman, I. Noy, The Global Costs of Extreme Weather that are Attributable to Climate Change. Nature Communications 14, 6103 (2023).
2. China Paper Association, 2023 Annual Report of China's Paper Industry. (2024). (in Chinese)
3. China Paper Association, 2022 Annual Report of China's Paper Industry. (2023). (in Chinese)
4. N.L. Harris, D.A. Gibbs, A. Baccini, et al. Global Maps of Twenty-first Century Forest Carbon Fluxes. Nature Climate Change 11, 234-240 (2021).
5. Y. Zhi, Y. Xiao, Z. Chen, Importing Recycled Waste Paper: A "yin-yang" Discussion on Saving Forest Resources and Pollution from Foreign Garbage. China Weekly 1, 46-53 (2016).
6. S. Jamnicki Hanzer, B. Lozo, L. Barušić, Producing Direct Food Packaging Using Deinked Office Paper Grades—Deinkability and Food Contact Suitability Evaluation. Sustainability 13, 12550 (2021).
7. X. Kong et al., Efficient Synthesis of Limonene in Saccharomyces Cerevisiae Using Combinatorial Metabolic Engineering Strategies. Journal of Agricultural and Food Chemistry 71, 7752-7764 (2023).