Supercritical Carbon Dioxide Extraction of Value-Added Products and Thermochemical Synthesis of Platform Chemicals from Food Waste

Abstract

Immense global generation of food waste calls for advanced technologies to maximize the use of such renewable carbon-based resources. In this study, corn, taro, lettuce, and bean sprout, were valorized for the production of value-added chemicals via sequential supercritical CO2 (scCO2) extraction and thermochemical conversion. The scCO2 extraction was performed at 350 bar and 50 °C for 60 min. The extracts of the lettuce contained sterols (764 μg g–1) that have potential anticancer properties. While bean sprout extracts had a higher content of saturated fatty acids (641 μg g–1), corn extracts comprised polyunsaturated fatty acids (405 μg g–1) as one of the major compounds, which are beneficial to cholesterol control. There were also notable amounts of wax esters (75–774 μg g–1) in these food waste extracts. Taro extracts were rich in both saturated (2313 μg g–1) and unsaturated fatty acids (1605 μg g–1) and, in particular, contained difatty acids that exhibit pharmaceutical activities. Moreover, the solid residues after scCO2 extraction served as the substrates for platform chemical production. The starch-rich substrates, i.e., taro and corn, resulted in 11–20% hydroxymethylfurfural (HMF) after microwave heating at 140 °C for 5–10 min using SnCl4 catalyst. In comparison, due to the high fiber content, lettuce and bean sprout required a higher temperature of 170–190 °C for chemical decomposition over H2SO4, generating a levulinic acid yield of ∼7%, in company with glucose and fructose as the coproducts. This study on the combined technologies suggested good compatibility between scCO2 extraction and subsequent thermochemical conversion, producing a wide spectrum of value-added chemicals from biomass waste. We herein highlight the vast potential of integrated technologies for food waste valorization in achieving sustainable and carbon-efficient biorefineries.

Value-added chemicals from food supply chain wastes: State-of-the-art review and future prospects

“…Integrated biorefinery, i.e., implementing various conversion approaches in tandem or in series, is drawing more attention from scholars in recent studies [215]. In this way, valorization of food wastes forms a circular bio-economy with more efficient recovery of each reusable stream (e.g., higher carbon efficiency) to obtain diverse range of products, such as biofuels, platform chemicals, and advanced biomaterials.…”

“…For instance, a syrup containing 89 g/L fructose was produced from enzymatic saccharification and isomerization of food and beverage waste, which was then subjected to catalytic reaction and produced 71 mol% HMF at 140 °C within 40 min using Amberlyst 36 catalyst [168]. Another recent study proposed the supercritical CO 2 extraction of high-value products (e.g., esters, fatty acids) from vegetables, from which the solid residues were utilized as feedstock for HMF synthesis [215]. Another possibility is to combine waste-to-energy technologies, which are commercially mature in market, with emerging biorefineries.…”

Novel Challenges on the Catalytic Synthesis of 5-Hydroxymethylfurfural (HMF) from Real Feedstocks

“…SnCl 4 was surely the preferred salt for HMF synthesis from raw biomasses, and other researchers have tested it as a catalyst. For example, Yu et al investigated HMF synthesis in the presence of SnCl 4 under MW heating, starting from different food wastes, such as bread waste [103,[107][108][109], unskinned kiwi fruit [104], watermelon flesh [104], rice waste [104,106], corn waste [110], and taro waste [110]. Performing the reaction under the same conditions (140 • C and 20 min) in the solvent system H 2 O/DMSO (1/1 v/v), the authors reported different HMF yields depending on the starting biomass (runs 77-81, Table 4) [103,104].…”

The Food–Materials Nexus: Next Generation Bioplastics and Advanced Materials from Agri‐Food Residues

“…Although FLW minimization is crucial in feeding more people and in reducing the environmental impacts of the food chain, there are unavoidable losses resulting from food production and processing. Hence, FLW valorization is a complementary approach that allows the recovery or upcycling of resources for a variety of purposes, including those associated with energy, [ 15,16 ] animal feed, chemicals, [ 17 ] and materials. [ 18 ] Since the transformations needed for FLW valorization, on their own, might involve additional environmental impacts, one needs to consider the feasibility of each valorization initiative in a holistic manner, for example, by using life cycle assessments (LCA) and other approaches to support decision‐making.…”