As the core force for policy guidance and resource coordination, they construct the framework for sustainable development. Through regulations and incentives, governments activate the entire chain, determine industrial direction, and act as system facilitators.

• For the Food Service Industry: Through "Regulations & Incentives," governments promote standardized waste cooking oil management in catering enterprises, reduce illegal dumping, ensure the achievement of the "reduce pollution and health hazards" goal, and simultaneously provide source assurance for resource recovery.
• For Waste Management Entities: Using regulations and incentives, governments encourage efficient collection and pre-processing of waste oil, advancing the SDG 12 target of "sustainable waste management."
• For Biodiesel Producers: Policy support fosters the development of the biodiesel industry, accelerating the conversion of waste oil into clean energy (Biodiesel), directly contributing to SDG 7 "Affordable and Clean Energy."

They are the source participants for waste oil. The "Waste Oil" they generate can pollute water bodies and soil if discharged improperly; standardized transfer to Waste Management entities enables resource recovery (SDG 12), reduces harm to health (SDG 3) and the environment, and is a key link in "waste reduction and resource utilization" under SDG 12 "Responsible Consumption and Production."

Acting as the "process hub," they receive "Waste Oil" from the food service industry. Through the "Pre-processed Oil" stage, they ensure waste oil compliantly enters biodiesel production (Biodiesel Producers), avoiding environmental pollution from illegal disposal. They directly serve SDG 12 "Sustainable Waste Management" and act as a bridge between resource cycling and pollution prevention.

As the "value conversion end," they receive "Pre-processed Oil" and, combined with "Tech Optimization" (e.g., enzymatic catalysis, process improvements) from Research Institutions, convert waste oil into biodiesel. This promotes SDG 7 "Affordable and Clean Energy," reducing reliance on fossil fuels. Through resource cycling (SDG 12), they are the core of the "waste-to-clean-energy" closed loop, achieving synergy between SDG 12 "Responsible Consumption and Production" and SDG 7 "Affordable and Clean Energy."

As "technology enablers," they use "Tech Optimization," such as synthetic biology for enzyme engineering and upgrading production processes, to enhance biodiesel conversion efficiency, promoting SDG 9 "Industry, Innovation and Infrastructure." By providing technical support to Biodiesel Producers, they accelerate the conversion of waste oil into clean energy (SDG 7) and cycled resources (SDG 12), directly embodying SDG 9's "foster innovation for sustainable development" within the industry.

As "awareness disseminators," they can use "Awareness" initiatives to educate Local Communities about waste oil resource utilization and the value of biodiesel, promoting SDG 4 "Quality Education" for sustainable development. They foster public awareness for SDG 12 "Responsible Consumption" (e.g., supporting biodiesel, supervising compliant waste oil disposal) and help realize SDG 13 "Climate Action" awareness. They are a key force in building "social consensus" for goals like SDG 12 and SDG 13.

As "end-user feedback providers," communities provide "Demand/Feedback" regarding biodiesel (e.g., usage willingness, environmental concerns) and waste oil management demands. This guides Biodiesel Producers in product optimization while encouraging communities themselves to practice SDG 12 "Responsible Consumption," ensuring the realization of SDG 3 "Good Health and Well-being" (healthy environment) and SDG 7 "Affordable and Clean Energy" on the public side.

In summary, the various stakeholders, through the closed loop of "waste oil recovery → clean energy production → social awareness feedback," collaboratively achieve:

• Environmental Dimension: Reducing oil pollution and promoting clean energy.
• Economic Dimension: Building a "waste oil-to-biodiesel" circular economy and stimulating industrial innovation.
• Social Dimension: Enhancing health and well-being, and disseminating awareness of sustainable development.

These interactions have refined our approach—such as optimizing lipase compatibility with high-acid WCO and designing scalable collection networks—strengthening our project’s potential to drive meaningful progress toward global sustainability goals.

Our project is highly relevant to SDG 3.9, which aims to reduce deaths and illnesses from pollution and hazardous chemicals.

• Alternative to traditional chemical processes: Traditional waste oil treatment (such as random dumping, landfill) or chemical production of biodiesel often uses strong acids, strong alkalis and other dangerous chemicals, which are easy to cause leakage and residue, and pollute soil and water bodies. Biological enzyme technologies act as biocatalysts, usually under mild conditions, significantly reducing or avoiding the use of these hazardous chemicals, reducing their risk of leakage and environmental contamination at the source.
• Reduced waste toxicity: Waste grease itself contains harmful substances and microorganisms. The enzymatic conversion process effectively breaks down the oil and converts it into clean biodiesel, preventing waste oil from entering the environment without treatment (polluting water and soil) or being illegally reused for food (health hazards) Due to the complexity of the composition, we were not sure how to pre-treat the waste oil to achieve better conversion efficiency and how to protect the environment from the organic solvents such as methanol or ethanol that we would use in the conversion process. In this regard, we asked Professor Li Jin to answer for us.

Prof. Li advised us that we could prioritize simple solid-liquid separation for waste valorization economics. Handling methanol/ethanol demands extreme caution: use a fume hood, full PPE, explosion-proof equipment, and strictly follow all safety procedures.

In conclusion, biocatalytic technology provides a core solution for the efficient and green recycling of waste oils and fats. By avoiding the use of hazardous chemicals, effectively eliminating waste oils and fats as a significant source of pollution, and producing clean renewable fuels (biodiesel) to replace highly polluting fossil fuels, this technology directly contributes to the achievement of SDG 3.9 across multiple stages. Starting from source prevention and process control, the technology significantly reduces the risks of air, water, and soil contamination by hazardous chemicals and waste oils and fats, thereby effectively decreasing the disease burden and premature deaths caused by these pollutants. It is one of the key technological pathways to achieving a healthier environment and improved public well-being.

Our product is designed to deliver environmentally friendly green fuels. From sourcing raw materials to large-scale bioenzymatic production of green fuels, we actively align with relevant government policies.

Our product embodies the following characteristics that fulfill SDG 7 criteria:

• Cleanliness

Reducing Pollution at Source & Achieving Carbon-Neutral Cycling

- Low-Carbon Emission Profile:

Waste oils are carbon-cycle byproducts. Their conversion releases no net additional atmospheric carbon. Compared to fossil fuels, enzymatic biodiesel emissions can be as low as 20g CO₂eq/MJ (IEA data), reducing emissions by >80%.

- Eco-Efficient Process Synergy:

Enzymatic catalysis operates under mild conditions, slashing energy consumption by 60% versus conventional chemical methods, further cutting indirect emissions.

- Co-Treatment of Pollutants:

Engineered microbes co-express enzymes , degrading carcinogens like benzopyrene and PAHs in waste oil , avoiding dioxin generation from traditional incineration.

- Zero Hazardous Byproducts:

Enzymatic transesterification produces no acidic wastewater or heavy metal residues (unlike sulfuric acid catalysts in chemical processes).

• Resource Circularity

Closed-Loop Waste Valorization

- Converts waste oil into energy, epitomizing the “Waste-to-Value” circular economy model.

- Byproduct glycerol is upgraded to high-value chemicals (e.g., propanediol, surfactants), enhancing economic viability while minimizing environmental impact.

● SDG 9.4 Upgrade Infrastructure and Retrofit Industries for Sustainability: The project leverages synthetic biology to innovate traditional waste cooking oil treatment methods. By screening and optimizing specific lipases, an efficient expression element library is constructed to enhance lipase production in Pichia pastoris, thereby converting waste cooking oil into biodiesel. This process improves resource efficiency in the waste oil treatment industry, reduces the high energy consumption and pollution associated with chemical treatment methods, and promotes the industry's shift toward sustainability.

● SDG 9.5 Enhance Scientific Research and Upgrade Technological Capabilities: Throughout the project implementation, the team conducted in-depth research on lipase screening, promoter and signal peptide optimization, involving multidisciplinary knowledge and cutting-edge technologies. For instance, studies on lipases from different sources and optimization experiments on promoters and signal peptides have strengthened the team's research capabilities in the field of synthetic biology and provided valuable insights for technological upgrades in related industries.

● SDG 9.b Support Domestic Technology Development and Innovation in Developing Countries: As a student team from China, this project addresses local practical issues by applying synthetic biology to tackle waste cooking oil pollution and resource wastage, reflecting domestic technological development and innovation. The project’s outcomes have the potential to be promoted both domestically and internationally, offering transferable experiences for other regions and fostering technological advancement in related fields.

In response to the 2030 target of SDG 11 on "Make cities and human settlements inclusive, safe, resilient and sustainable" – in particular Goal 11.2 (Provide safe, affordable, accessible and sustainable transport systems) and Goal 11.6 (Reduce the negative environmental impact per capita in cities, with special attention to air quality, including waste management, and municipal and other waste management) – bioenzyme technologies, In particular, the lipase production technology based on Pichia pastoris is becoming the core driving force to promote the recycling of urban waste oil and the greening of transportation fuels. Pichia pastoris, as an excellent eukaryotic protein expression host, is widely used for the efficient and large-scale production of highly active and stable recombinant lipases due to its strong secretion capacity, high cell density growth characteristics, precise protein processing ability, and good adaptability to inexpensive media. These lipases, "customized" by Pichia pastoris, are able to specifically and efficiently catalyze triglycerides in waste oils and fats and convert them into biodiesel by transesterification under mild conditions.

Why our team chose Pichia pastoris:

First of all, because of high-efficiency enzyme production, through genetic engineering, high-efficiency lipase genes from specific sources are introduced into Pichia pastoris, and its strong promoter is used to induce expression, so as to achieve large-scale, low-cost, high-purity fermentation production of target lipases, overcoming the cost and efficiency bottlenecks of chemical catalysts or traditional extraction enzymes. and enzyme performance optimization: The Pichia pastoris system enables appropriate post-translational modifications of expressed lipases, which can help significantly improve the enzyme's catalytic activity, thermal stability, and organic solvent tolerance. This stability is essential for the treatment of waste oils and fats with complex compositions that may contain water and free fatty acids, allowing the enzyme to remain efficient in the actual reaction system. The third is to catalyze the conversion of waste oils: the lipase produced by Pichia pastoris can be effectively hydrolyzed or directly catalyzed for transesterification. In biodiesel production, it precisely catalyzes the reaction of waste oils and fats with short-chain (such as methanol and ethanol), cuts the ester bonds of triglycerides, and generates biodiesel molecules and by-product glycerin. Its high substrate specificity and catalytic efficiency enable high conversion rates and low post-processing costs even for poor-quality waste oil feedstocks.

Finally, the promotion of a circular economy: the technology converts municipal waste directly into valuable clean energy, which is perfectly aligned with SDG 11.6 to improve waste management and reduce environmental pollution. At the same time, the biodiesel produced serves as a renewable, low-carbon fuel that directly contributes to the decarbonization of urban transport systems (SDG 11.2), improves air quality (reducing particulate matter and SOx emissions), and enhances energy security and resilience.

Therefore, based on Pichia pastoris's biological enzyme technology, a closed-loop solution from "municipal waste oil collection (SDG 11.6)→ efficient enzymatic conversion (Pichia pastoris core technology), →clean biodiesel production, → sustainable transportation fuel supply (SDG 11.2)" was constructed. It not only significantly improves the economy and environmental protection of waste oil recycling, reduces the risk of soil and water pollution caused by improper disposal, but also provides a practical technical path for cities to realize the localization and low-carbon transformation of transportation energy, and is one of the important scientific and technological pillars to support cities to achieve the key goals of SDG 11 by 2030.

Our project, focused on the bio-enzymatic conversion of Waste Cooking Oils (WCOs) into biodiesel, is intrinsically aligned with the core objectives of SDG 12. We aim to transform a linear and wasteful consumption model into a circular and sustainable one by addressing the entire lifecycle of cooking oils. Specifically, our work directly advances the following targets:

12.2 By 2030, achieve the sustainable management and efficient use of natural resources

Our project directly contributes to the efficient use of natural resources by converting Waste Cooking Oils, a problematic waste stream, into biodiesel. Instead of relying solely on virgin vegetable oils or fossil fuels, we utilize a synthetic biology approach to engineer robust enzymes that efficiently transform this wasted carbon resource into a valuable energy source. This promotes a circular model, reducing the demand for new agricultural land and fossil fuel extraction, and ensuring that the energy potential of used oils is fully captured and utilized.

12.5 By 2030, substantially reduce waste generation through prevention, reduction, recycling and reuse

We address waste reduction at the recycling and reuse stages by providing a technologically advanced solution for the estimated 10 million tons of WCOs generated annually in China, a significant portion of which is unaccounted for or improperly disposed of. By developing an efficient enzymatic process to recycle this waste into biofuel, we prevent it from polluting waterways and soil. This creates a clear "reuse" pathway, turning an environmental hazard into a product, thereby reducing the overall waste burden and mitigating the associated pollution and public health risks.

12.8 By 2030, ensure that people everywhere have the relevant information and awareness for sustainable development.

Our project's integrated Human Practices, which includes surveys and outreach targeting both the public and restaurants, is designed to raise awareness about the environmental and health hazards of improper WCO disposal. In addition, we have a series of science popularization activities for students, aiming to make young people aware of the hazards of waste oil from an early age.By clearly communicating the scientific process of converting "gutter oil" into clean biodiesel, we aim to demystify synthetic biology and foster public trust in this sustainable alternative. This educational effort is crucial for building a societal consensus on the value of recycling and for encouraging participation in a formal WCO collection system.