▲ Intro video showcasing Professor Jehng-Jung Kao’s reflection on his 17-year journey from a horticultural novice to a pioneer in green innovation, leading the development of the DIYGreen Zero-Waste Circular Urban Farming System ©NYCU ELITE
Seventeen years ago, a university professor who began as a layman in horticulture and couldn’t even recognize what pak choy (or bok choy) inspired his students to pursue green innovation. Together, they focused on addressing the Heat Island Effect, improving waste recycling, and managing water resources. Professor Jehng-Jung Kao of the Sustainable and Peer Education Center (SPEC) and Institute of Environmental Engineering of National Yang Ming Chiao Tung University (NYCU) led a team researching and developing the “DIYGreen Zero-Waste Circular Urban Farming System” (hereinafter referred to as “DIYGreen”). This innovative solution not only overcomes the waterproofing and nighttime heat dissipation problems of traditional earth-sheltered green roofs but is also more in line with United Nations’ Sustainable Development Goals (SDGs), including projects such as Zero Hunger (SDG 2), Responsible Consumption and Production (SDG 12), and Climate Action (SDG 13), etc. Prof. Kao’s eyes still shine when he looks back on this challenging and innovative research journey.
From Green Roof to City Farmer
Prof. Kao pointed out that Taiwan’s high-temperature issue is influenced not only by global warming but also closely by the Urban Heat Island Effect. In addition, the staggering number of PET bottles recycled each year, the challenge of food waste disposal, and the underutilization of rainwater recycling are some of the environmental challenges that have been his research focuses. Initially, he tried to mitigate the Heat Island Effect through green roofs, which are popular overseas. However, he discovered that traditional green roofs have several limitations – they require additional waterproofing construction, are susceptible to earthquake cracking, and can be expensive to repair. Moreover, the earth-sheltered design can hinder nighttime heat dissipation, and watering processes may lead to pollution. After three years of experimentation, Prof. Kao confirmed that traditional green roofs were unsuitable for Taiwan’s environment and began looking for alternatives, eventually developing the DIYGreen system.
In the demonstration farm on the top floor of NYCU’s Environmental Engineering Building, various plants, such as strawberries, tomatoes, and Italian oregano, are cultivated in several square pots and frames arranged in blocks. At first glance, the pots may appear to be ordinary plastic baskets, but Prof. Kao highlights the ingenuity of their design. He pointed out that every component of the DIYGreen system, including materials, structure, drainage, air permeability, soil retention, etc., has been researched, developed, and tested many times by the team and even undergone 21 refinements before finalizing the system, which has been operating steadily for over 10 years now. This system adopts the “capillary micro-irrigation method,” which is designed to save more water compared to traditional drip irrigation. To accommodate the water storage height of recycled PET bottles, Prof. Kao spent more than half a year visiting major non-woven fabric factories across Taiwan to test water-absorbent materials with different materials and lengths. Through the recommendation of a Taiwanese manufacturer, he finally found the patented, high-tech “wicking strips” (Note 1) produced by a German company. This material can absorb up to 41cm of water by capillary action with a slow water absorption speed, making it an ideal fit for the DIYGreen system.
The DIYGreen system has a minimum unit size of 25 square centimeters and is infinitely expandable. Its elevated design prevents plants from directly contacting the roof and reduces the risk of roof seepage by storing water in recycled PET bottles. Additionally, the air layer formed between the bottles not only insulates and dissipates heat but also regulates nighttime temperatures while ensuring the necessary air space for plant growth. “Experiments have shown that this system can reduce floor temperatures by approximately 2 to 4 degrees, and small recycled bottles can provide plants with water for 7 to 14 days (while large ones can provide water for at least a month).” Prof. Kao mentioned that the team plans to conduct a detailed inventory of the system’s carbon-negative benefits in 2025 and then assess the long-term benefits of applying it to the urban environment.
Recycling for Zero-Waste Cycle
To further promote the concept of a “green cycle,” Prof. Kao also leads his students to raise chickens and earthworms. These earthworms help decompose food, producing nutrient-rich fertilizer. During the COVID-19 pandemic, they cared for seven chickens that provided them with “rich and free” eggs during Taiwan’s egg shortage.
Prof. Kao mentioned that food waste disposal is a significant challenge in environmental protection. Chickens, earthworms, and even gadfly larvae can effectively decompose food waste and turn it into organic fertilizer, which can then be reused at the DIYGreen farm, fostering a zero-waste cycle. The central idea of this recycling model is to maximize resource utilization to minimize environmental waste.
In addition, to meet the demand for planting larger fruit trees, the R&D team has developed a “frame type” for growing fruit trees such as guava, lemon, passion fruit, etc., based on the original “pot” type, as well as a “tree planter” suitable for indoor use. Taking the smallest unit as an example, first, secure the base to four recycled PET bottles. Next, insert the wicking stripe and mount it onto the base. This system is not only easy to implement, but also increases the secondary use value of the PET bottles. To promote the system conveniently, the research team has taken a series of videos of the installation process and uploaded them to YouTube for users can easily reference and set up their own mini-farms anywhere.
User-Friendly: Everyone Can Have Their Own Farm
“Although I specialized in environmental engineering, I aimed to minimize the use of ‘engineering’ from the very beginning.” This statement may sound contradictory, but it illustrates Prof. Kao’s vision. The reason is that only a simple, easy-to-copy design will allow users to get started quickly and gain a sense of achievement, which will promote the system to more homes and businesses. This is the core value and advantage of the DIYGreen system—it is user-friendly and accessible to people of all ages and in any location.
Over the past decade, more than 200 schools in Taiwan have integrated DIYGreen into their teaching experience, with the youngest users being students in senior kindergarten classes. Some corporations have also exclusively ordered the system and are working with the team to expand DIYGreen to communities across Taiwan. In addition, Prof. Kao has collaborated with professors from different fields on campus, such as combining Professor Hsin-Fei Meng’s organic translucent solar photovoltaic device from the Institute of Physics to realize the dual benefits of power generation and farming. Professor Tee-Ann Teo from the Department of Civil Engineering has also led a team of students in planting vegetables and fruits on campus as part of a service-learning course. Students who took the course said, “This is the most interesting and practical course in school!”
In recent years, there has been a lot of interest in food and agriculture education. Still, many teachers lack experience in farming, and the soil conditions in schools vary, making it challenging to implement. Even if teachers are willing to try, improving the soil, pest control, and watering frequency can challenge novices. In contrast, DIYGreen’s capillary micro-irrigation system allows plants to survive without water for a week or two, making promoting food and agriculture education more feasible.
“What I want to solve is Taiwan’s environmental problems,” Prof. Kao said frankly, adding that although he had received orders from Shenzhen, Hong Kong, and even the United States, he was unable to keep up with the supply due to high freight costs. Some professors from Malaysia have also sent students to study in Taiwan. For the time being, DIYGreen is concentrating on the Taiwanese market; however, in the future, it does not rule out the opportunity to collaborate with international academic institutions or businesses.
At the end of the interview, Prof. Kao sincerely invited more people to experience the joy of DIYGreen planting. He hopes to raise public awareness about sustainable development in Taiwan, encouraging environmental awareness to reach every family, school, and enterprise. This way, the green movement can continue to grow and spread.
Note 1: The high-tech wicking strip currently used by Professor Kao is produced by a German company and was discovered through a recommendation from a Taiwanese manufacturer.
Interview ｜ Hui-Fang Cheng
Translation | Yi-Chen Emily Li
Editing | Hsiu-Cheng Faina Chang
Photography | Hao-Yun Peng and Zong-Han Lyu / ZDunemployed Studio