NMSU Student Receives Water Research Grant to Study Uses for the Byproducts of Hydrothermal Liquefaction

By Marcus Gay, NM WRRI Sr. Student Program Coordinator

Nitrate is one of the major pollutants of concern in New Mexico water. Ingesting high concentrations of nitrate can cause harmful effects in humans, including an increased risk of cancer. In recent years, increases in nitrate concentrations have been observed in the Rio Grande. These nitrates are likely from agricultural fertilizers and wastewater effluents from large cities like Albuquerque, Las Cruces, and El Paso. Current methods for nitrate removal are ion exchange, reverse osmosis, and electrodialysis, which can have high energy requirements and high costs. Hydrothermal liquefaction-char (HTL-char) is a promising adsorbent for the removal of lead and copper from wastewater*, but to evaluate HTL-char as an adsorbent for anions like nitrate, more information is needed on its ability to adsorb anions.

Fortunately, Hengameh Bayat, a PhD candidate at New Mexico State University’s Chemical and Material Engineering Department, is working on research evaluating nitrate removal from water using food waste HTL-char. NM WRRI has awarded Bayat a Student Water Research Grant for a project titled, Wastewater treatment and water recycling through the use of byproducts from hydrothermal liquefaction of food waste.

Hydrothermal liquefaction (HTL) is a technology used to produce bio-crude oil from food waste. Byproducts of HTL are a nutrient-rich aqueous phase (HTL-AP), and char. HTL implementation has been limited by the lack of value of these byproducts. Therefore, Bayat’s research not only evaluates the use of HTL-char to remove nitrate from water, but also evaluates the use of HTL-AP to provide needed moisture and additional carbon and nutrients to compost.

Under the guidance of her Faculty Advisor, Dr. Catherine Brewer, Bayat’s project has four objectives: 1) Produce and characterize the surface properties and ion adsorption capacity of HTL-chars prepared through co-HTL of food waste and red mud; 2) Quantify the effects of water pH, contact time, and initial nitrate concentration on adsorption performance and mechanisms for nitrate adsorption; 3) Characterize food waste HTL-AP for compost-relevant properties, including pH, total carbon, total-N, ammonia-N, phosphorus, salinity, metals, and organics composition; and 4) Evaluate the feasibility of HTL-AP addition to compost in terms of microbial activity, nutrient availability (C/N ratio), moisture, and quality of the finished compost.

According to Bayat, using HTL-char produced from food waste would reduce nitrate removal energy use and costs while also helping to meet waste management and energy needs. The use of HTL-AP in compost systems will provide moisture, adjust the pH, and increase the amount of nutrients in compost while maintaining the advantages of compost as a fertilizer. Bayat presented her work at the 66th Annual New Mexico Water Conference and the 2021 AlChE annual meeting in Boston.

Originally from Iran, Bayat received her bachelor’s degree in Chemical Engineering from Arak University, and a master’s degree from the Material and Energy Research Center at the University of Tehran. Bayat plans to graduate with her PhD from NMSU in Chemical Engineering in 2022. After graduation, Bayat plans to pursue a career in academia. She is interested in converting waste materials to value-added products for water conservation and remediation.

* Bayat, H., et al., Removal of Heavy Metal Ions from Wastewater Using Food Waste Char. In 2020 ASABE Annual International Virtual Meeting, ASABE: St. Joseph, MI, 2020; p 1.