Agricultural and food waste provide bountiful opportunities for diverting energy and nutrients for other uses. But how to best capture the benefit from these untapped resources? Dr. Anju Krivov, who teaches courses on energy and nutrient recovery at UVM, is passionate about identifying the best technologies for a variety of applications, and sharing the discovery process with her students.
Compost Capacity Upgrade
How does an industrial composting facility prepare for an increase in organic matter headed its way, without knowing exactly what scale of increase to expect? That’s the question UVM student Patrick Singleton and Holly St Jean hoped to help the Chittenden Solid Waste District answer last semester, as part of a service learning class project. Singleton and St Jean were students in Krivov’s “Waste to Energy” course, which she designed to provide students with an understanding of the opportunities for harnessing energy from various kinds of waste.
Vermont’s Universal Recycling Law requires the diversion of food waste and other organic matter from landfills. What happens to that diverted material is somewhat up to who ends up with it. The Department of Environmental Conversation has a hierarchy to express the preference for the highest uses first, human consumption and animal consumption, followed by composting and energy production.
The Green Mountain Compost Facility faces a decision of whether to expand its capacity or install biodigesters at $8 million a pop. Expansion would be the less expensive option, but biodigesters, which utilize microbes to produce combustible gases, provide the option of generating electricity for the power grid. With enough input, such a system could produce a valuable revenue stream for the company. Plus, the effluent left behind would still contain valuable nutrients, like nitrogen and phosphorus, to add back into the composting system.
“Working with Patrick and Holly was valuable because they provided a fresh prospective," says Josh Tyler, Project Manager at Chittenden Solid Waste District. "They asked informed questions around the development of the project expectations, which made me think more critically in terms of our project objectives as a district.”
Don’t let that phosphorus get away!
Krivov’s interest in capturing value from waste permeates her work. In addition to teaching at UVM, she has been leading projects through her company that develops technologies to capture nitrogen and phosphorus from manure.
“Managing excess nutrients is one of the colossal challenges in this century,” says Anju Krivov. “Wouldn’t it be nice to turn that problem around and create value out of it, while improving quality of life now and for our future generations? That’s why I’m drawn to this work.”
Krivov teaches another class at UVM, "Nutrient Recovery Solutions for Improving Water Quality of Natural Aquatic Systems," which focuses on diverting nutrients from entering waterways and turning them into fertilizer. Nutrient runoff is a key concern for Vermont and other regions dealing with water quality challenges. Students learn about the various mechanical, chemical, and biological methods for extracting phosphorous and nitrogen from water—and which technologies are best suited for different scales and contexts.
One potential application of the technology is on large dairy farms, where farmers must process large amounts of manure on an annual basis. Farmers generally have two options available to them: spreading the manure on their fields or employing a biodigester to convert the manure to energy. The first option is relatively inexpensive, but regulations limit the times of year that manure can be spread, and the process can pollute waterways, especially if the manure is applied shortly before storm events.
Biodigesters, as mentioned above, convert manure into combustible gasses, which in turn generate energy. However, biodigesters require a significant up-front investment, and even after the biodigestion process, nitrogen and phosphorus still remain in the effluent byproduct.
One process the students are investigating utilizes organics separation implemented at several farms. Separated organics can be processed into cow bedding material or fertilizer products, which could be a valuable benefit for farmers, either as a revenue source or as a means to offset their own fertilizer expenditures. Other students are looking a potential ways to treat municipal wastewater, and the possibility of converting from chemical treatments to biological approaches.
Krivov hopes to continue the students’ involvement in real world scenarios involving nutrient management through a class she is teaching this fall, “Food Waste to Value: Community Development Applications.” The class will focus on understanding how the nutrient resources embedded in food waste can generate value for the economy.
With global challenges related to natural resource use, we need these solutions more than ever.