"Sustainability isn’t just a scientific problem—it’s an ethical responsibility."

For more than four decades, Roger Ruan, PhD, professor in the Department of Bioproducts and Biosystems Engineering, has dedicated his career to transforming waste into resources and challenges into opportunities. In this conversation, he reflects on invention as a deeply human endeavor, the evolving role of engineering in sustainability, and the power of curiosity and purpose to shape a better world.

What kind of research do you do? Is there a common theme or thread that runs through all of your projects? 

My research focuses on developing innovative processes and systems for agricultural and food by-product utilization, and for converting solid and liquid wastes into valuable products. Whether it’s renewable energy, environmental technology, or food engineering, the common thread is sustainability: finding practical, science-based ways to close the loop between production, processing and waste management. 

Ultimately, our goal is to turn challenges into opportunities: transforming what would otherwise be discarded or even polluting our environment into new resources that support a sustainable circular economy. For me, sustainability isn’t just a scientific problem, it’s an ethical responsibility. The way we design systems today determines the kind of world we leave to the future generations.

Can you share a project, invention, or accomplishment that you consider to be the most significant in your career?

One of them is the invention of catalytic microwave pyrolysis technology. This work involves integrating microwave-absorbing materials into microwave reaction systems to achieve rapid, uniform, and energy-efficient heating, while advancing catalytic reforming systems to extend catalyst life and performance.

These systems have been applied in areas ranging from circular plastics economy development to PFAS and micro- and nano-plastic remediation, as well as broader environmental cleanup and solid waste utilization. What makes this work meaningful is that innovative solutions make significant practical impact possible, such as helping convert waste into valuable chemicals, fuels, materials and cleaner energy, while addressing some of our most persistent environmental problems.

Several of our technologies have been successfully transferred to industry and are being scaled for commercial applications. Seeing research evolve from an idea in the lab into real-world impact has been one of the most fulfilling parts of my career.

You’ve worked as an engineer—mechanical, agricultural, biological—for more than 40 years. What have been the biggest changes you’ve seen?

The most profound change has been our growing awareness of the unintended consequences of industrial and agricultural progress. Decades ago, engineering often focused on efficiency and output, building systems that worked. Now, we must also understand how those systems affect climate, ecosystems, and human health.

We’ve learned that sustainability must be built into the design of the processes and systems from the start. The overuse of fertilizers, pesticides, plastics, and other chemicals has improved productivity but also caused lasting harm to the environment and human health. Engineers today must be innovators and caretakers—designing solutions that support both human development and environmental integrity.

In addition to the National Academy of Engineering, you were recently inducted into the National Academy of Inventors. Can you talk about your process of invention? 

Invention, for me, is not an isolated act. It is the natural result of complete problem-solving. It always begins with the understanding and defining the real need, the true essence of the problem. From there, I draw upon a broad base of mechanical, chemical, biological, environmental knowledge to explore effective solutions.

The key of the invention process lies in what we in Chinese call 心无旁骛, that is to devote oneself entirely, without distraction. It is a state of focus where your mind lives with the problem until the path forward emerges. Real invention often happens at the intersection of clear definition, cross-disciplinary thinking, and unwavering dedication. The invention process is both deeply technical and deeply human, which requires not just intelligence, but patience, empathy, and persistence.

How does your research contribute to the College's mission? 

The CFANS’ mission to feed the world while caring for the planet requires both scientific understanding and engineering ingenuity. My work provides the engineering solutions that make sustainability tangible, for example, biological and thermochemical technologies that eliminate PFAS, micro- and nano-plastics from soil and water, biorefining technologies that recover resources, minimize/eliminate waste, and produce value-added products, while protect ecosystems and improve human health at the same time.

But beyond engineering technology, it’s about perspective. Feeding the world sustainably means thinking in systems, respecting natural cycles, and recognizing that environmental stewardship and human well-being are inseparable. Science and engineering give us the tools; compassion and responsibility give us the direction.

What qualities do you look for when you recruit students and researchers to your lab or into the Department of Bioproducts and Biosystems Engineering?

I look for curiosity, self-motivation, and resilience. A good researcher is not someone who knows all the answers, but someone who keeps asking questions and has the drive to find answers.

I value students who are lifelong learners, problem-solvers, and resourceful, those who can adapt, seek knowledge across disciplines, and find creative ways to achieve their goals. Integrity and collaboration are also essential, because great research is developed on trust and teamwork.

In the end, I want students who don’t just acquire knowledge but use it—to make a difference in the world.

What advice do you give to CFANS students who are just starting their education and career? 

Stay curious and stay humble. Learn how to learn—that is the most powerful skill you can develop. The world is changing rapidly, and what matters most is not how much you know now, but how well you can grow, adapt, and lead.

Cultivate strong communication and leadership skills, because science and engineering are collective endeavors. Most importantly, keep a sense of purpose. Ask yourself not only what you are doing, but why it matters. When your work serves a greater good, it will give you both direction and strength.

Could you talk a little bit about your path to where you are today? How did you get your start as an engineer and inventor? 

My journey began at China Agricultural University, where I earned my bachelor’s degree in mechanical engineering. About forty years ago, I came to the United States to pursue graduate studies and to apply engineering principles to food, energy, and environmental systems.

I was fortunate to study under exceptional mentors at UC Davis, Oklahoma State University, and the University of Illinois at Urbana–Champaign, many of whom went on to become Regents Professors, National Academy members, and even a Nobel Laureate. They taught me not only how to do research but how to think, lead, and contribute to society.

Since joining the University of Minnesota, I’ve had the privilege to mentor outstanding students and postdocs, many of whom are now faculty members, scientists, and industry leaders around the world. Watching their growth and success has been one of the most rewarding parts of my career. Each generation builds upon the last, that’s how knowledge and progress continue.

Who has had the biggest influence on your career?

It’s impossible to name just one. The collective influence of my parents, and my mentors and advisors across my academic journey profoundly shaped who I am. Their dedication, curiosity, and humanity left a lasting impression. I try to honor their influence by paying it forward—by mentoring my own children and students with the same care and belief that they showed in me.

You joined the University of Minnesota as a faculty member in 1991. What do you think about that decision now?

It was one of the best decisions I’ve made in my life. The University of Minnesota has been an extraordinary place to grow with an open, collaborative culture and a strong commitment to solving real-world problems.

I am deeply grateful to my advisors and mentors, who trusted me and supported my early work here. Over the years, CFANS and BBE have given me opportunities to innovate, to collaborate with remarkable colleagues, and to make contributions that matter. I feel both proud and humbled to have spent my career here.

What might someone be surprised to learn about you?  

People are often surprised to learn how much I value quiet reflection in my daily life. I enjoy spending quiet time reading and thinking about history and philosophy, as they remind me that science and engineering are part of a much larger human story. I also make time to exercise regularly—swimming daily when possible—not only for physical health but also to keep a clear mind. Hiking gives me time outdoors to think freely, often without even realizing I’m thinking at all.

These simple, rhythmic, and grounding activities are not separate from my work; they are part of the same process. They teach patience, focus, and balance, which are essential for discovery. Many of my ideas have surfaced during those quiet moments of stillness and movement. I believe that innovation comes not only from intellect, but from attention, discipline, and an open, reflective mind. In that sense, how I live is inseparable from how I work.