By Marcus Gay, NM WRRI Student Program Coordinator
As the world’s population grows larger, the need for clean water, food, and energy is rising. Food production requires energy, and accounts for a large portion of global freshwater consumption. Due to the amount of energy and freshwater involved in food production, food waste is particularly important to resource management. Currently, the common practice of landfilling wet food waste leads to methane, carbon dioxide, and liquid waste that contaminates soil, groundwater, and rivers. Fortunately, food waste is a readily available biowaste resource. The use of food waste for biofuel production and resource recovery would not only reduce reliance on fossil fuels, but it would also help solve water scarcity issues and environmental challenges.
In addition to the advantages of using food waste as a feedstock for biofuel production, char (a byproduct derived from the food-waste-to-biofuel conversion), can be used to adsorb heavy metals in waste water treatment. Commercial adsorbents are often not cost effective. Using food waste char instead of commercial adsorbents could improve local water quality, and manage local food waste while generating an alternative source of energy.
In 2019, Hengameh Bayat, was awarded an NM WRRI Student Water Research Grant to study food waste conversion to biofuel, and evaluate the feasibility of using treated char as an adsorbent material for wastewater treatment. The project is titled, Wastewater Treatment Using Food Waste Char Obtained from Hydrothermal Liquefaction as a Low-Cost Adsorbent Material. Bayat, a PhD student at New Mexico State University’s Chemical and Materials Engineering department, worked on this project under the guidance of her faculty advisor, Dr. Catherine E. Brewer.
The food waste for the project’s experiment was collected from NMSU’s dining hall, Taos Restaurant. After mixing the food waste with deionized water, the mixture was blended into a slurry. For each experiment a stainless steel Parr batch reactor was then loaded with the food waste slurry and heated. Hydrothermal liquefaction (HTL) uses hot (250-375°C) compressed water to convert waste materials into energy-dense bio-crude oil, non-condensable gases, an aqueous phase, and HTL-char. The HTL-char was separated from the mixture to be used for experiments.
Preliminary results showed that food waste HTL-char has significantly higher lead adsorption capacity compared to commercial activated carbon, and food waste-derived HTL-char may be an effective adsorbent for the remediation of metal contaminated water.
As Bayat explains, “this research provides information about downstream energy recovery of food waste, and the capability HTL-char has for wastewater treatment. Remediation of heavy metals like lead and copper from water is not only important for animal and human health, but using HTL-char from biowaste would also be economical and environmentally friendly.”
Bayat presented this project at the 64th Annual New Mexico Water Conference, and the American Society of Agricultural and Biological Engineers Annual International Meeting.
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 in her home country of Iran. During her time at the University of Tehran she worked on converting microalgae to value-added products like bio-crude oil as a fuel and biochar as an adsorbent for wastewater treatment. Bayat is working toward her PhD in Chemical Engineering, and would like to pursue a career in academia. She is interested in converting waste materials to value-added products to use in water conservation and remediation.