Summary

Throughout our project cycle, guided by the principles of Responsible Research and Innovation, we engaged in continuous dialogue with diverse stakeholders. These interactions shaped our project's trajectory and defined our final product form: a coffee grounds upcycling kit designed for home gardeners, communities, and small-scale horticultural operations. This product embodies a circular economy model, transforming waste into plant nutrients and empowering the public to participate in sustainable practices. Ultimately, our Human Practices work was more than just outreach or discussion; it served as the compass guiding our scientific and entrepreneurial decisions, ensuring our project is not only innovative but also responsible, responsive, and deeply rooted in real-world needs.

Stakeholder	Role/Identity	Key Feedback & Suggestions	Our Response & Project Iteration
Coffee Shops(e.g., Manner, Starbucks)	Provider of core raw material (SCG) & potential partner	1. Expressed strong interest in sustainable, low-cost recycling solutions (like our project). 2. Current disposal methods are limited, primarily discarding as wet waste or giving away to customers/employees.	1. Positioned our project as a solution addressing their needs. 2. Planned a community collection network partnered with coffee shops within our product concept, establishing them as eco-hubs to solve their waste disposal pain points and enhance their environmental image.
Paques-Skion Water	Professional environmental technology solution provider	1. Highlighted drawbacks of traditional disposal methods (landfilling, physico-chemical). 2. Suggestion: Adopt a biological, aerobic treatment process for more complete SCG conversion and reduced final waste.3. Affirmed the value of recovering nutrients from SCG to reduce fertilizer reliance.	1.Systematically compared method pros/cons via a table, arguing the necessity of our biological approach. 2. Strengthened our project's value proposition regarding "resource cycling" and "reducing chemical fertilizer dependence".
Dr. Tong Zhou(Fermishan Technology)	Bio-fertilizer & agricultural technology expert	1. Noted the high cost and low farmer acceptance of bio-fertilizers. 2. Suggestion:- Target high-value sectors first (e.g., home gardening, premium flowers).- Build trust through demonstration and process transparency.- Use differentiated marketing (e.g., coffee scent).	1. Adjusted Target Market: Focused the final product form on home/small-scale gardening, not traditional agriculture. 2. Conducted Education: Implemented targeted education in communities, elderly universities, etc., based on suggestions, to pave the way for market entry.
Professor Fu	Synthetic Biology Expert	1. After failed gene synthesis for B. subtilis, suggested switching to more common, tractable E. coli strains. 2. Facing instability with the single-plasmid system, suggested a modular, multi-plasmid co-transformation strategy.	1. Iterated Chassis: Switched from B. subtilis to E. coliBL21, ultimately settling on E. coli DH5α, which successfully improved degradation efficiency. 2. Optimized Genetic Circuit: Changed genetic load from single plasmid to a three-plasmid system, significantly enhancing system stability and performance.
Gardening Enthusiasts	End-potential users	1. Core focus is fertilizer efficacy; environmental aspect is a bonus. 2. Concerned about convenience & safety (e.g., odor, pests, root burn).3. Suggestion: Provide "conversion powder", clearly label components, enhance education.	1. Designed Product Form: Developed the "ready-to-use lyophilized bacterial powder" kit directly, meeting convenience needs. 2. Established Safety Protocols: Emphasized the inactivation step in the process guide for safety.3. Planned Product Packaging: Will clearly label nutritional content and compare safety pre/post-treatment in educational materials.
Shaanxi Tian Ren Xue Bio-Tech Co., Ltd.	Agricultural microbial high-tech enterprise; Industrialization advisor	1. Identified three key productization challenges: genetic stability, process scale-up, application method. 2. Emphasized safety core: Final product must contain no live engineered bacteria, suggesting a "relay baton" inactivation process.	1. Defined R&D Focus: Listed genetic stability and process scale-up as future priorities. 2. Adopted Safety Design: Made "no live engineered bacteria" a core safety promise of the product. 3. Planned Product Pathway: Acknowledged composite microbial fertilizer as a future direction.
Yum China	Corporate benchmark in ESG/SDG performance	1. Suggested engaging waste processors, fertilizer companies, corporate ESG depts., government agencies, and NGOs. 2. Inspired us to construct a complete "coffee - consumption - recycling - fertilizer - planting" carbon cycle loop.	1. Clarified Partnership Path: Listed the suggested organization types as key future partners. 2. Elevated Project Vision: Elevated the project's value from simple "waste-to-resource" to a "carbon cycle loop" aligning with circular economy and carbon neutrality principles, making it a core narrative.

1. Background & Inspiration

Discussions within our school and local community frequently centered on how to reduce waste and repurpose resources. This prompted us to examine commonplace yet voluminous waste streams in daily life. Coffee, as an essential consumer product, came into focus. We learned that global coffee consumption exceeds 10 million tons annually, generating approximately 6-8 million tons of Spent Coffee Grounds (SCG) (Campos-Vega et al., 2015). The vast majority of SCG is landfilled or incinerated, which not only wastes resources but also emits greenhouse gases, exacerbating environmental pollution (Karmee, 2018), conflicting with Sustainable Development Goals 11 and 13.

This discovery sparked our inspiration: Could we transform this common waste into beneficial organic biofertilizer? Literature review confirmed that SCG is rich in cellulose, nitrogen, phosphorus, potassium, and other nutrients, making it a potential high-quality raw material for organic fertilizer. However, a key scientific fact blocked this "waste-to-treasure" path: residual caffeine (approx. 1-2%) in SCG is a natural phytotoxin that inhibits plant development by disrupting cell division and root growth (Ashihara et al., 2008). Field experiments show that directly composting SCG significantly reduces germination rates and yields in crops like lettuce and tomatoes (Cervera-Mata et al., 2020; Cruz et al., 2015).

Consequently, we realized that effective decaffeination is an indispensable step for safely converting SCG into biofertilizer (See Figure 1). This established the scientific foundation of our entire project.

Figure 1. The idea of recycling SCG. Our idea introduces a solution: to detoxify SCG by making the phytotoxic caffeine a neutral molecule. This process transforms SCG from a harmful waste product into a high-value, plant-safe organic fertilizer. Some of the visual elements in this figure are generated by AI.

2. Current SCG Disposal Status & Demand

● Coffee Shops (e.g., Manner, Starbucks)

○ Expressed strong interest in sustainable, low-cost recycling solutions (like our project itself).

○ Current disposal methods are basic: SCG is mostly discarded as wet waste or given away to interested customers/employees.

● Paques-Skion Water

Paques is a Dutch specialist solution provider for industrial anaerobic wastewater treatment, gas desulphurization, nutrient removal and metals recovery.

○ Current SCG Disposal Methods：

Method	Landfilling/Incineration	Physico-chemical Decaffeination	Home Composting	Our Project - Synthetic Biology Decaffeination
Description	Treated as municipal solid waste for landfilling or incineration.	Uses chemical solvents (e.g., dichloromethane) or supercritical CO₂ extraction.	Individuals mix SCG with other kitchen waste for natural composting.	Uses genetically engineered E. coli expressing Ndm enzyme system to specifically degrade caffeine during fermentation.
Advantages	- Simple, most common method.- Requires no extra tech/cost.	- High efficiency: removes >90% caffeine.- Relatively mature tech: used in food industry (e.g., decaf coffee).	- Low cost, eco-friendly: no special equipment, in-situ processing.- Increases public engagement.	- Efficient & Specific: Targeted enzymatic reaction efficiently removes caffeine while retaining other nutrients. - Environmentally Friendly: Operates under mild T&P, no hazardous solvents. - Resource Cycling: Converts harmful waste into safe, valuable biofertilizer, fitting circular economy. - Broad Application Potential: Adaptable for centralized or decentralized processing.
Disadvantages	- Wastes resources: Fails to utilize SCG nutrients. - Pollutes environment: Landfilling emits GHGs (methane); incineration can release harmful gases. - Conflicts with SDGs.	- High cost: Especially SC-CO₂ requires expensive high-pressure equipment. - Chemical residue risk: Solvent extraction may leave harmful residues, affecting fertilizer safety. - Nutrient loss: May remove/destroy other beneficial SCG nutrients. - Unsuitable for decentralized treatment: Hard to promote in communities/small farms.	- Inefficient & incomplete: Slow natural fermentation (months). - Fails to degrade caffeine effectively: Incomplete fermentation leaves phytotoxic caffeine, inhibiting germination/root growth. - Unstable fertilizer quality: Highly variable, influenced by environment.	- High technical barrier: Involves synthetic biology, fermentation engineering. - High initial R&D cost: Strain construction & process optimization require investment. - Public perception & regulation: Requires addressing public GMO concerns & meeting biosafety regulations.

This demonstrates clear shortcomings of traditional SCG disposal methods in economy, environmental friendliness, or safety. Ordinary home composting cannot solve the core problem of caffeine phytotoxicity.

○ To achieve complete cycle in the project's value chain, they suggested using a biological engineering approach with aerobic treatment, which would be more advantageous than traditional methods, enabling more thorough SCG conversion and reducing final waste for disposal.

○ Currently, farmers primarily rely on synthetic fertilizers for NPK nutrients. Recovering these nutrients from SCG could reduce this dependency, further affirming our project's value.

3. Biofertilizer Market Prospects

Dr. Tong Zhou,

Ph.D. in Biology from Shanghai Jiao Tong University, is a modern biotechnology expert spanning seeds, soil, fertilizers, processing, and testing. Dr. Tong founded Fermishan Technology Co., successfully cultivating the world's first batch of high-altitude polyphenol lettuce, achieving the perfect integration of scientific technology for ecological agriculture industrialization and synthetic biology with modern agriculture.

l Biofertilizer Pros and Cons

○ Pros: Biofertilizers improve soil microecology, avoid soil compaction and degradation of water retention caused by chemical fertilizers, aligning with sustainable agricultural trends.

○ Cons: Higher cost, farmer acceptance influenced by traditional chemical fertilizer habits.

○ Limitations: Cost pressure and farmer mindset hinder large-scale promotion; need to demonstrate yield increase and pest/disease resistance effects.

l Biofertilizers are expensive and hard for average farmers to accept; consumer education is needed. Dr. Tong suggested we:

○ First promote use in high-value industries (e.g., home gardening, premium flowers), conducting pilot education campaigns to lay the groundwork for later market entry.

○ Process Transparency: Emphasize control of harmful bacteria (e.g., packaging anti-microbial tech), provide quality inspection certificates.

○ Demonstration Promotion: Select demonstration farmers for free trials, persuade with actual yield increase data.

○ Analogous Success Cases: Use applications like bean dregs, coconut husk fertilizer to reduce fear of "bacteria".

○ Marketing:

■ Participate in international projects like UNIDO's carbon reduction initiatives for authoritative endorsement.

■ Composite & Synergize: Combine with mature products like coconut husk fertilizer to reduce costs and broaden application scenarios.

■ Differentiated Promotion: Highlight the uniqueness of "coffee-scented fertilizer", spread via case studies (e.g., home gardening).

Our Feedback:

Following Dr. Tong's advice, to increase consumer acceptance and strengthen product education, we conducted basic project introductions targeting home gardening enthusiasts in communities, elderly universities, and other venues. These sessions specifically explained how synthetic biology transforms SCG from chemically harmful waste into safe and valuable fertilizer, conducting market education for the future product. （Details in Education）

4. Technical Iteration - Chassis & Genetic Circuit Design

Professor Fu,

Synthetic Biology Expert

● From Bacillus subtilis to Escherichia coli

We initially chose Bacillus subtilis for its natural competence and safety profile, making it an ideal potential chassis for environmental release. Collaborating with a gene synthesis company revealed an inability to synthesize our target gene for B. subtilis.

Therefore, we consulted Professor Fu, who suggested that as a high school team, we prioritize using more common, tractable lab strains like E. coli BL21 or DH5α.

First, we tried E. coli BL21, a strain optimized for high-level protein expression. Experimental results showed that although Ndm was successfully expressed in BL21, we found its caffeine degradation efficiency was very low. Prioritizing functional efficiency over mere expression levels, we focused on E. coli DH5α. Although not a classic expression strain, DH5α is engineered for genetic stability and robust growth, which we hypothesized might better support our multi-enzyme pathway's synchronous activity. Ultimately, we were pleased to find that caffeine degradation efficiency increased significantly in the DH5α chassis.

Our Solution:

Focused on E. coli DH5α.

● Genetic Circuit Design

Initially, for simplicity, our genetic design placed the three key genes ndmA, ndmB, and ndmC-D-E on a single plasmid vector.

However, we encountered issues of genetic instability and low overall pathway performance. We suspected a single, large plasmid imposed a significant metabolic burden on the host, and concurrent expression of three complex genes in one construct could cause transcriptional interference or enzyme ratio imbalance.

Our Solution:

To solve this, we consulted Professor Fu, who suggested we consider a modular and distributed approach. We could clone the three gene fragments onto three separate, compatible plasmids and introduce them into E. coli DH5α via co-transformation.

This strategy yielded benefits:

Reduced Metabolic Burden: Distributed genetic load lightened the cellular machinery's load.

Independent Optimization: Allowed independent fine-tuning of each enzyme module's expression level.

Increased Stability: The system was more genetically stable over multiple generations.

Figure . Design of gene circuits of Ndm expression.

5. Product End: Listening to Industry Professionals' Advice

Gardening Enthusiasts

l For consumers overall, environmental factors are a bonus, but efficacy remains the core concern. They expressed willingness to try new products but highlighted issues needing resolution: strong odor during composting, tendency to attract pests, and risk of root burn due to high potency.

l Packaging Suggestion: Clearly label fertilizer components (e.g., N-P-K ratio) for user-specific selection.

l Product Form Suggestion: Provide a "conversion powder" product, allowing users to process household SCG themselves, enhancing convenience.

l Product Safety Control: When educating consumers, emphasize the hazards of direct SCG use on plants, contrasting with the safety after degradation.

Shaanxi Tian Ren Xue Bio-Tech Co., Ltd.

A high-tech enterprise integrating R&D, development, production, and marketing, specializing in microorganisms. It possesses core technology for high-density fermentation of composite lactic acid bacteria and has achieved industrial-scale, mass production, and commercial application of this technology.

Business areas involve R&D and promotion of microbial technology; R&D and production of microbial agents for agriculture, forestry, animal husbandry, bio-organic fertilizer, bio-feed additives, soil remediation agents; Technical services for agricultural environmental management and improvement; Development and construction of modern high-tech eco-agriculture demonstration parks and comprehensive agricultural tourism parks; R&D and production of urban environmental ecological recycling technology.

This professional agri-tech company provided crucial guidance for our productization path:

l Key Challenges:

○ Genetic Stability: Engineered bacteria must maintain stable traits during subculturing.

○ Process Scale-up: Optimizing from gram-scale lab to ton-scale production requires solving control of nutrition, temperature, pH, etc.

○ Application Method: Designing processes for efficiently and uniformly adding microbial agents to large SCG volumes for fermentation.

l Product Form: Suggested positioning as a Composite Microbial Fertilizer (containing organic matter, NPK nutrients, and functional microorganisms), offering higher value and better market acceptance. SCG can be blended and processed according to final crop needs to meet national standards.

l Product Safety: Experts emphasized that the final product must contain no live engineered bacteria. For your E. coli, after completing decaffeination, it must be thoroughly killed via an inactivation process (e.g., heat treatment) to ensure product safety. Subsequently, safe, nationally approved beneficial bacteria (e.g., Bacillus subtilis) can be inoculated. This "relay baton" process design is key to meeting biosafety approval.

6. Focusing on Circular Economy Development

Yum China

l Suggested focusing on engaging waste treatment companies, agricultural fertilizer companies, corporate environmental departments, government environmental agencies, and relevant NGOs.

l Yum China has received multiple awards in SDG and ESG. We can learn from its development to pave the way for our project's future commercial development.

l Suggested we could construct a perfect "Carbon Cycle" closed loop: Coffee cultivation -> Consumption -> SCG recycling -> Fermentation into fertilizer -> Return to soil for new coffee/crop cultivation. This process cycles carbon within the system, reducing reliance on external fertilizers and carbon emissions from landfilling waste. From a circular economy value perspective, it truly achieves material cycle of use.

7. Market Access Safety Certification Process (China)

Center for Microbial Fertilizer and Edible Fungus Strain Quality Inspection and Testing, Ministry of Agriculture and Rural Affairs

http://www.biofertilizer95.cn/index.htm

1. Provincial Preliminary Review and Application Acceptance

a. Before applying, enterprises must prepare materials according to the "Measures for the Administration of Fertilizer Registration" and submit the application to the provincial-level Department of Agriculture and Rural Affairs in their locality. After accepting the application, the provincial department will assess the enterprise's production conditions and provide a preliminary review opinion.

b. After passing the preliminary review, the provincial-level Department of Agriculture and Rural Affairs will issue a preliminary review opinion form. Subsequently, this provincial preliminary review opinion form, along with other required materials, must be submitted to the Fertilizer Window of the Ministry of Agriculture and Rural Affairs' Administrative Service Hall.

2. Core of Technical Review: Strain Safety Assessment and Inactivation Verification

a. This is a critical step specifically for products containing inactivated engineered microorganisms.

b. Strain Safety Assessment: Microbial fertilizers or products that rely on specific microorganisms must submit a strain safety assessment report. The strain safety assessment can be conducted by sending the strain to the Center for Microbial Fertilizer and Edible Fungus Strain Quality Inspection and Testing, Ministry of Agriculture and Rural Affairs. If the strain is a new species not listed in the official strain classification catalog, the Fertilizer Registration Evaluation Committee of the Ministry of Agriculture and Rural Affairs will typically propose a classification recommendation, and the Ministry of Agriculture will determine the specific safety assessment requirements.

c. Inactivation Verification: For products containing inactivated engineered strains, you must provide sufficient evidence proving that the engineered strains used in the production process are completely inactivated in the final product and pose no environmental safety risks. This may include a detailed description of the inactivation process, the methods used for verifying inactivation effectiveness, and supporting data (e.g., culture tests demonstrating no viable bacteria detected).

3. Acute Oral Toxicity Test

If the strain passes the safety assessment, microbial inoculant products are generally exempt from submitting a toxicity report. However, for products containing inactivated engineered strains, the evaluation committee may assess whether an acute oral toxicity test is still required based on the specific product characteristics.

4. Product Safety and Efficacy Evaluation

a. Product Quality Inspection Report: Issued by an inspection agency with fertilizer testing capabilities, certified by metrological authentication, and at or above the provincial level.

b. Field Trials: Standardized field trials must be conducted within China. For example, it may be required to submit trial reports for each crop covering at least two different locations for one year or the same location for two or more years, according to relevant technical requirements. Based on a 2015 notice, applying enterprises can conduct fertilizer field trials themselves in accordance with the requirements or commission relevant institutions to carry them out.

5. Comprehensive Evaluation and Certificate Issuance

a. The Fertilizer Registration Evaluation Committee of the Ministry of Agriculture and Rural Affairs will evaluate the product applying for registration.

b. After the evaluation is passed, the Department of Plantation Management of the Ministry of Agriculture and Rural Affairs will proceed with the approval according to the procedures and issue the Fertilizer Registration Certificate.

8. Proposed Framework for a DIY Coffee Grounds Fertilizer System

Through extensive dialogue with various experts and potential users, we realized that for synthetic biology technology to truly benefit the public, beyond producing a final fertilizer product, providing a solution that allows users to personally participate in and witness the "waste-to-treasure" process holds greater educational significance and community appeal. Therefore, we have conceptualized a coffee grounds upcycling kit aimed at home gardening enthusiasts, communities, and small-scale horticultural operations.

8.1. Product Core: Ready-to-Use Lyophilized Bacterial Powder

8.2. Product Form:

The product core is a ready-to-use lyophilized bacterial powder. It contains our project-optimized engineered bacteria (carrying the multi-plasmid Ndm enzyme system), along with pre-mixed stabilizers and nutrients to initiate fermentation.

8.3. Comprehensive Biosafety Strategy

Our product is designed with a full-lifecycle safety approach:

1. Market Access & Certification: Our engineered strains and final product will undergo rigorous national safety assessments to secure all required certifications before market entry.

2. Closed-Loop User Safety: We provide integrated hardware with a UV-C sterilization lamp. After fermentation, this ensures the complete inactivation of all engineered bacteria, delivering a safe, "microbe-free" fertilizer and preventing environmental release.

Strictly adhering to the biosafety principles discussed with Shaanxi Tian Ren Xue Bio-Tech Co., Ltd., the final fertilizer contains no active engineered bacteria, ensuring environmental and user safety.

8.4. Usage Process:

● Obtain SCG: Users acquire fresh spent coffee grounds for free from partner coffee shop collection points.

○ Partnership Model: We provide partner coffee shops with customized collection bins and promotional materials, establishing them as community "Eco-Hubs".

○ Visual Map: We have initially created a static map. In the future, we plan to develop a simple online map, allowing users to check nearby partner coffee shop locations, real-time SCG availability, and collection times via a WeChat Mini Program or.webp)age, facilitating convenient local access to raw materials.

● Mix Powder: At home, users mix a specified ratio of the bacterial powder with the SCG in a provided container, following simple instructions.

● Self-Service Fermentation: Place the mixture in a warm location for approximately 24-48 hours of fermentation. During this process, the engineered bacteria in the powder revive and work to efficiently degrade caffeine. Using our team's developed Smart Constant-Temperature Bioreactor in conjunction is recommended. The reactor contains a UV sterilization lamp, which ensures no live bacteria remain in the final product, preventing engineered bacterial leakage and addressing safety concerns.

（Details in Hardware）

● Direct Use: The processed coffee grounds can be directly used as safe and efficient organic fertilizer for houseplants or small vegetable gardens.

8.5. Product Opportunities & Challenges

Aspect	Positive Analysis (Advantages)	Negative Analysis (Challenges) & Coping Strategies
Cost	Low Usage Cost: Powder is a one-time input, SCG is free, much cheaper than buying equivalent organic fertilizer. Coffee Shop Welcome: Helps shops reduce waste disposal costs and enhances their eco-image.	High R&D & Production Cost: Strain construction, fermentation, lyophilization process costs are high.Coping: Cover initial costs via iGEM funding, apply for green venture capital; costs can decrease significantly after scale-up.
User Experience	High Engagement & Educational Value: Users personally participate in the circular economy, high sense of achievement. Convenience: Networked collection points, simple process, aligns with DIY trend.	Operation Barrier: Risk of users not following guidelines (e.g., skipping steps). Coping: Design extremely simple pictorial guides/video tutorials; highlight/repeat safety warnings on packaging/guide; establish online customer service community for Q&A.
Effect	Efficacy & Safety: Completely removes caffeine phytotoxicity, retains all SCG nutrients. Visible Results: Home trial feedback can be used to collect real data, build case library.	Effect Fluctuation: Uncontrolled home environment (e.g., temperature) may cause unstable fermentation. Coping: Provide clear condition guidance (e.g., suggest using yogurt maker for constant temp); optimized strains have certain environmental tolerance.
Business Model	Light Asset: No need to build large fermentation plants, easily replicable model. Creates New Value Points: Powder sales, eco-education services, corporate CSR partnerships.	Logistics & Inventory: Powder requires cold chain transport and storage. Coping: Partner with cold chain logistics; design packaging with insulating materials; set up small refrigerated cabinets at partner points.

9. Future Plan

9.1. Experimental Module

Currently, at the experimental stage, we have successfully achieved 90% caffeine degradation after 48 hours. In the future, we will advance our project through a multi-faceted optimization strategy to achieve a 100% caffeine degradation rate.

l Rigorous Safety Certification: Our strain will undergo rigorous safety certification to confirm its non-pathogenic nature and environmental harmlessness, ensuring its biosafety in caffeine degradation applications.

l Enzyme Engineering via Directed Evolution: we will employ directed evolution techniques to modify and screen key degradation enzymes, significantly enhancing their catalytic activity and substrate affinity.

l Metabolic Pathway Optimization: Through strategies such as promoter engineering and RBS optimization, we will precisely regulate the coordinated expression of three functional modules—including enzyme expression, cofactor regeneration, and transport functions—to improve the harmony of the metabolic pathway and overall degradation efficiency.

l Comprehensive System Optimization: We will systematically optimize critical process parameters, such as temperature and substrate concentration.

9.2. Bio-Appliance

In the future, we will iterate and update the first-generation bio-appliance, optimizing details and the device's programs, aiming to provide consumers with a better user experience and simpler operating instructions. By encapsulating the complex synthetic biology process into a simple, reliable, and safe "black box" operation, we aim to break down technical barriers, allowing the upcycling of coffee grounds to safely enter homes, coffee shops, and small horticultural operations, truly enabling the seamless transformation of synthetic biology technology into practical productivity.

Intelligent Caffeine Degradation Bioreactor - Future Version Operation Manual

Reference

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[2] Campos-Vega, R., Loarca-Piña, G., Vergara-Castañeda, H. A., & Oomah, B. D. (2015). Spent coffee grounds: A review on current research and future prospects. Trends in Food Science & Technology, 45(1), 24-36. https://doi.org/https://doi.org/10.1016/j.tifs.2015.04.012

[3] Cervera-Mata, A., Navarro-Alarcón, M., Rufián-Henares, J. Á., Pastoriza, S., Montilla-Gómez, J., & Delgado, G. (2020). Phytotoxicity and chelating capacity of spent coffee grounds: Two contrasting faces in its use as soil organic amendment. Science of The Total Environment, 717, 137247. https://doi.org/https://doi.org/10.1016/j.scitotenv.2020.137247

[4] Cruz, R., Mendes, E., Torrinha, Á., Morais, S., Pereira, J. A., Baptista, P., & Casal, S. (2015). Revalorization of spent coffee residues by a direct agronomic approach. Food Research International, 73, 190-196. https://doi.org/https://doi.org/10.1016/j.foodres.2014.11.018

[5] Karmee, S. K. (2018). A spent coffee grounds based biorefinery for the production of biofuels, biopolymers, antioxidants and biocomposites. Waste Management, 72, 240-254. https://doi.org/https://doi.org/10.1016/j.wasman.2017.10.042

[6] 《肥料登记管理办法》：肥料登记管理办法农业农村部中国政府网