Closing the Loop for Swine Wastewater

Across the United States, industrial hog production relies heavily on a lagoon-and-sprayfield system that has remained largely unchanged for decades.

Wastewater from barns is flushed into large anaerobic lagoons, where solids settle, and the liquids are eventually sprayed onto nearby cropland as fertilizer. On paper, this is often described as a closed-loop nutrient recycling model, where waste from hogs fertilizes the crops that feed future hogs. However, this system is nothing but open. Nutrients leak, odors persist, and large volumes of nitrogen and phosphorus escape into the surrounding environment. As climate variability intensifies rainfall and flood risk, these openings in the loop become even larger and harder to control.

This gap between the promise and the performance of swine wastewater systems has led researchers and farmers alike to search for technologies that can tighten nutrient cycles and reduce environmental impact. Among emerging solutions, engineered biochar, particularly metal-modified biochar, has gained significant attention for its ability to capture nutrients, stabilize waste and support soil health. But can this material help transform hog wastewater handling into a more resilient, circular system?

As a FFAR fellow working in Dr. Sushil Adhikari’s lab under the supervision of Dr. Hossein Jahromi, my research is to develop an engineered biochar-based adsorbent that can selectively remove phosphate from swine wastewater and then be reused in fertilizer formulation for crop production.

Wastewater generated from swine farms is stored in lagoons. However, these lagoons are not impermeable nutrient storage units. Nitrogen escapes as ammonia gas, contributing to air pollution and odor issues, while phosphorus accumulates in soils after repeated land application. High runoff events wash both nutrients into local waterways, promoting algal blooms and contributing to hypoxia. These issues are particularly visible in states with dense hog production, such as North Carolina, Iowa and Minnesota, where the scale of operations magnifies the consequences of nutrient loss. Lagoons contain not only nutrients but also pathogens, antibiotics, organic contaminants and trace metals that can spread beyond farm boundaries, while reliance on land availability and favorable weather severely limits disposal options and increases system vulnerability during extreme conditions. To truly close the loop, farms need technologies that capture nutrients reliably, store them safely, and return them to agricultural soils in stable forms. This is where engineered biochar enters the conversation.

Engineered biochar addresses key weaknesses of the current swine wastewater system: its nutrient leakage, its dependence on land availability and its vulnerability to extreme weather. My research is ultimately motivated by a simple belief: waste is only waste when we fail to capture its value. Swine wastewater contains nutrients that farmers pay for every year in commercial fertilizers. If we can intercept those nutrients before they leak into the environment, we can simultaneously reduce pollution, strengthen soil fertility and improve the sustainability of U.S. hog production. Engineered biochar is not a silver bullet. But it is one of the most promising tools we have to fix the open loops in swine wastewater handling, and I am excited to continue advancing this work through my doctoral research.

My involvement in the Foundation for Food & Agriculture Research (FFAR) Fellows Program has played a transformative role in advancing my research on phosphate removal from swine wastewater and translating it into sustainable agricultural applications. Through its focus on professional development, mentorship and interdisciplinary collaboration, the program has enhanced my leadership and science communication skills, deepened my appreciation of agricultural innovation and brought me into a collaborative community of researchers committed to creating meaningful impact. I am sincerely grateful to the Rockey FFAR Fellows Fund, my PI, Dr. Sushil Adhikari, my major advisor, Dr. Hossein Jahromi and my FFAR Fellows cohort for their unwavering support. Their encouragement continues to inspire my pursuit of solutions that tackle environmental challenges while meeting farmers’ needs—contributing to an agricultural future that is sustainable, resilient and farmer-centered.