He is the Thrust Leader for Sanitation and Resource Recovery for the Safe Global Water Institute and the Environmental Sustainability Lead for the Soybean Innovation Lab, funded by the U.S. Agency for International Development (USAID). His research focuses on sustainable technologies for engineered water systems, with an emphasis on biotechnology development for resource recovery from wastewater. By integrating experimentation, modeling, and quantitative sustainable design (QSD), Dr. Guests research group leverages fundamental insights into molecular-scale processes to advance systems-scale sustainability, connecting technology innovation with broader societal initiatives for energy, food security, health and nutrition in both technologically advanced and developing communities.