Growing Quinoa With Zero Waste
Environmental engineering seniors’ Harvest 365 project envisions a more sustainable future for agriculture through hydroponics
Agriculture pumps an estimated 9.3 billion metric tons of carbon dioxide into the atmosphere each year, contributing nearly 20% of global greenhouse gas emissions annually. But while much of scientific research and the popular press is focused on greener alternatives to cars and other fossil fuel-powered mainstays, humans will continue to need to eat.
With the global population predicted to reach 10 billion people by 2050, crop scientists and environmental engineers alike are working to develop strategies that will help reduce the climate burden of the food system while simultaneously keeping pace with increasing needs.
Two Stevens Institute of Technology environmental engineering majors partnered on their senior design project, Harvest 365, to address this issue. Sabrina Benayoun ’23 and Jagmeet Ashta ’23, working under the advisement of Professor of Environmental Engineering Xiaoguang Meng, focused on hydroponics, or growing plants without the use of soil. They presented their research at Stevens’ annual Innovation Expo on April 28.
For agriculture to be sustainable, the students explained, several different aspects of the process must be considered.
“You need to consider how much water is being used, how much energy is being used by the system and what you’re using to nourish the plants. Fertilizers, for example, are a big issue in terms of runoff,” Benayoun said.
Although hydroponics provides a more environmentally friendly way to grow food than traditional agriculture, the number and types of crops that can be grown with this method is not currently wide enough to sustain the global population’s dietary needs. At present, hydroponics technology simply cannot compete with traditional farming in terms of scale and costs.
Benayoun and Ashta wanted to see if they could start to change that.
The students focused their efforts on growing quinoa, a staple crop in parts of South America that has also become popular elsewhere in the world. While humans have spent thousands of years optimizing the growth of grains such as wheat, rye, barley and oats in soil, quinoa has not undergone such large-scale optimization and therefore remains expensive to grow traditionally. Due to this combination of high cost and small scale, Ashta and Benayoun realized, quinoa cultivation holds significant untapped potential for optimization through hydroponics.
Initially, the team began to grow an actual crop of quinoa hydroponically, but they quickly learned that the time demands for such an endeavor were too great for a two-semester project. Instead, Benayoun and Ashta focused on a small but key aspect of hydroponics: measuring how much fertilizer is lost to water runoff in traditional agriculture.
The lack of runoff with hydroponics is one of the method’s biggest advantages, Ashta said, since hydroponic growers only need just enough fertilizer to nourish the plant without any extra that might wash away and cause eutrophication, in which nutrient-rich runoff spurs the overgrowth of phytoplankton that depletes oxygen in a body of water. Quantifying excess fertilizer use in standard quinoa growing methods will be an important part of convincing farmers and policymakers to adopt hydroponics methods more widely.
“We found that fertilizer really stays on the top level of soil, and if you have rain the next day, a lot of that fertilizer is just going to wash off and pollute surrounding water,” Benayoun explained.
Precisely determining these fertilizer amounts is part of the life cycle assessment that is key to creating a zero-waste hydroponic system that doesn’t use or release excess nitrogen, phosphorus or water, said Benayoun. At each stage of the life cycle assessment, researchers can accurately quantify the environmental impacts of every stage of the hydroponics system, ensuring that as much of the fertilizer and growing medium nutrients reaches the plants as possible and is not wasted.
Even with their scaled-down approach, the students found the project to be highly challenging. Ashta said that his education at Stevens helped enable him to think on his feet and keep the project moving forward as it evolved in new directions.
“I’ve worked in research labs before, but it’s different when you’re coming up with the experiment yourself. I had to quickly adapt and figure out the most optimal solution,” he said. “I relied on the critical thinking and problem-solving skills that have been drilled into me my entire time at Stevens.”
For example, a widely used growing medium in hydroponics is Rockwool, a synthetic mineral fiber that can hold both water and nutrients. But the students discovered that the high moisture and nutrient value of growing media also makes them attractive to mold, and Rockwool is too alkaline for quinoa, which prefers a slightly more acidic environment.
To resolve both issues, Ashta and Benayoun had to pH treat the growing medium in a solution, as well as watch for mold contamination. The pair repeated this process several times, changing a different variable each time. With each iteration, they measured nutrient and water use by the quinoa seedlings and how the chemicals interacted with water.
Advisor Meng praised Benayoun and Ashta’s efforts, saying Harvest 365 opened his eyes both to the world of hydroponics and to the seemingly endless possibilities students can bring to their senior design projects. The experience, in fact, was as valuable to him as to the students.
“This project really reinforced that hydroponics is the future of agriculture. We all learned a lot,” Meng said.
Both Ashta and Benayoun said that the capstone project required far more time and effort than they had initially anticipated, but that the rewards were worth it.
“The project really made me believe in myself, as cheesy as it sounds,” Benayoun said. “It was just the two of us, and there was a lot of struggle. We had to really check in with each other to make sure that what we were doing was actually impactful.”