Upcycling food waste into microporous biosorbent for hydrogen storage

While environment is significantly impacted by the greenhouse gas emission during landfill disposal of waste, there is concurrent depletion of water and energy in the process of recycling and reusing it. In the United States, 30-40% of food supplied is ultimately destined to be food waste as estimated by U.S Department of Agriculture (USDA). The monumental challenge associated with the methods of discarding FW urges for its appropriate management. In recent years, various conversion techniques, such as biochemical (e.g., composting, anaerobic digestion), thermochemical (e.g., pyrolysis, hydrothermal carbonization), etc. have been utilized to upgrade wet biomass wastes into value-added products. However, finding an avenue in upcycling food waste into microporous biosorbent with its potential application as hydrogen (H2) storage material, while the world is transitioning towards sustainable hydrogen energy economy, was the novel scope of this study. Moreover, various research efforts have been undertaken to store H2 in MOFs, COFs etc. due to their large specific surface area, small pore size, and large pore volume. However, it is not economically feasible to store significant amounts of H2 in MOFs or COFs, as that could be cost intensive. As food waste could be a very low-cost feedstock to synthesize porous adsorbent materials, the objective of this study was to produce superactivated hydrochars from food waste for storing H2. Hydrochar from food waste was produced at 260 °C and activated using KOH at 800°C using KOH: Hydrochar mass ratio of 4:1. BET analysis was conducted of the activated chars to determine the surface morphology parameters (specific surface area, pore type, pore volume). In addition, all the samples underwent ultimate and proximate analysis to determine the physicochemical properties. In addition, High-Pressure Volumetric Analyzer (HPVA) was used to measure the volumetric uptake of H2. Analyses showed that the superactivated hydrochars were developed with a large fraction of micropores (0.95) as well as high surface area of 2800 m2/g and total pore volume 1.8 cm3/g. The gas storage capacity of the developed materials was substantially high with 6.2 wt% of H2. In addition, the structural integrity of the materials was analyzed by storing H2.