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To date limited work has focused on assessing the economic viability of scCO2 extraction to obtain waxes as part of a biorefinery. This work estimates the economic costs for wax extraction from maize stover. The cost of manufacture (COM) for maize stover wax extraction was found to be € 88.89 per kg of wax, with the fixed capital investment (FCI) and utility costs (CUT) contributing significantly to the COM. However, this value is based solely on scCO2 extraction of waxes and does not take into account the downstream processing of the biomass following extraction. The cost of extracting wax from maize stover can be reduced by utilizing pelletized leaves and combusting the residual biomass to generate electricity. This would lead to an overall cost of € 10.87 per kg of wax (based on 27% combustion efficiency for electricity generation) and €4.56 per kg of wax (based on 43% combustion efficiency for electricity generation). A sensitivity analysis study showed that utility costs (cost of electricity) had the greatest effect on the COM.

Wax extraction has been achieved from an abundant and sustainable waste residue, date palm leaves (or leaflets). Supercritical carbon dioxide extraction was utilised as a clean and efficient extraction technology in this process. Extraction conditions including pressure and temperature have been optimised using response surface methodology ( via a 2 × 2 factorial experimental design). The highest yield obtained was 3.49% at 400 bar and 100 °C, which is significantly higher than other reported agricultural residues. The wax obtained at optimum condition (400 bar, 100 °C) exhibited a comparable melting point (78 °C) to carnauba wax, making it a suitable alternative or replacement for this overexploited commercial plant wax. The supercritical process required significantly shorter extraction times (with a 97% isolated wax yield after 120 min), as compared to soxhlet systems which typically required extraction times of up to 5 h to obtain comparable yields. Supercritical carbon dioxide was utilised to tailor the extraction process and obtain waxes with different textural properties, chemical composition and melting profile (35–78 °C). An economic study for the date palm leaf wax extraction estimated a lowest cost of manufacture (COM) at €3.78 kg −1 wax. The low cost of the manufacturing, combined with high wax recovery, the thermal properties of the extract and abundance of this waste resource, makes date palm leaf an attractive feedstock for the natural wax industry. [ABSTRACT FROM AUTHOR]

The decline in petrochemical wax supply coupled with the ever-growing demand for bio-products means that the development of a sustainable process to renewably sourced waxes is paramount. This review focuses on recent advances in supercritical extraction as a clean efficient process for extracting waxes from waste biomass as a part of a holistic biorefinery. The use of supercritical carbon dioxide leads to reductions in solvent waste and leaves no solvent residues meaning that the biomass can further processed without the need for energy-intensive solvent removal steps. This technology crucially improves the downstream conversion of residual cellulosic biomass for the sustainable production of sugars, consumer products and biofuels (up to a 40% increase in ethanol production) leading to higher energy efficiencies and higher economic returns. Supercritical carbon dioxide extraction is not only an important technology for the cleaner production of waxes, it is a sustainable pre-treatment of biomass as part of an integrated holistic biorefinery and significantly, it can improve the safety of products, e.g. less off gassing of wood pellets. [ABSTRACT FROM AUTHOR]

Up to 33% of hemp by mass can be lost in the form of dust during processing for fibre production. Heptane Soxhlet extractions and supercritical carbon dioxide extractions (scCO 2 ) of hemp dust samples yielded significant quantities of high value lipophilic molecules including fatty acids, policosanols (fatty alcohols), fatty aldehydes, hydrocarbons, sterols, triterpenoids and cannabinoids (cannabidiol (CBD)). Dust collected from different stages of the mechanical processing of hemp fibres gave rise to lipophilic extractives with varying compositions, thus making the isolation and purification of these compounds easier. Of particular interest is CBD (5832.5 ± 118.9 μg/g of dust), which has attracted much attention for clinical-level studies due to its therapeutic efficacy in the treatment of a variety of central nervous system (CNS) disorders. Factorial experimental design was carried out to optimise the scCO 2 extraction, with 350 bar and 50 °C yielding the selective extraction of higher value components. [ABSTRACT FROM AUTHOR]

Extraction of high-value products from agro-industrial waste is an important component for the development of a sustainable bioeconomy. In this work, natural wax extraction was carried out on different types of sugarcane waste (rind, leaf and bagasse) using supercritical CO 2 (scCO 2 ). Substantial quantities of long-chain aldehydes and n -policosanols (nutraceutical compounds) were found in the rind (83% of total composition). Interestingly, the wax obtained from the leaf residues varied from other types of waxes from sugarcane waste, with low aldehyde and n -policosanol contents (normally found in high quantities) and considerable amounts of high-value triterpenoids (169 ±6 mg/g wax), which have well-known medicinal properties. The use of sugarcane leaf residues for the extraction of waxes has not been previously considered, though the amount of these residues increased significantly after the switch to green harvesting. Sugarcane bagasse wax showed the highest ester composition (37 ± 1.5 mg/g of wax), which can be useful in a host of applications, ranging from cosmetics to hard wax polishes, lubricants, coatings and plasticisers. [ABSTRACT FROM AUTHOR]

This work demonstrated that supercritical carbon dioxide extraction is effective as a pre-treatment technology to generate soot particles with the fullerene-like structure and increase syngas yield from extracted residues during coupled microwave activation with gasification. Supercritical carbon dioxide extraction removes over half of the fatty and resin acids from needles and branches, whereas the extraction of needles generates greater yields of value-added compounds. The high yields of extractives indicate the effective conversion of waste wood for the sustainable production of value-added chemicals. The wood extraction did not influence the solid residue yields during pyrolysis/gasification emphasizing the significant potential of integrating the extraction process into the holistic biorefinery. Interestingly, supercritical carbon dioxide extraction had a significant effect on the structure and quality of soot particles formed. The differences in the extractives composition led to the formation of needle soot particles with a porous and less ordered nanostructure, whereas the soot branches obtained a ring graphitic structure. The greater yields of steroids and terpenes during the extraction of needles compared to the branches pretreatment indicated the influence of the extractives type on the soot nanostructure. • Wood and MW char were reacted at fast pyrolysis or gasification conditions in a DTF. • The reactivity of soot from original wood and scCO 2 treated sample was similar. • The removal of extractives increased gas yield at CO 2 gasification conditions. • Soot particles from scCO 2 extracted wood obtained a fullerene-like structure. • Gasification product yields were not influenced by combined scCO 2 and MW processes. [ABSTRACT FROM AUTHOR]