Tailoring product characteristics in the carbonisation of brewers’ spent grain through solvent selection

Abstract

Agricultural, food and other biomass wastes represent an untapped resource of hydrocarbonaceous material with potential for valorisation into fuels and chemical products. A key challenge in this area is directing the characteristics of the products for different applications. Here, the use of different solventswater and simple alcohols-is shown to directly impact on the products arising from the carbonisation of brewers' spent grain (BSG). Unprocessed BSG was carbonised using water, methanol, ethanol and 2-propanol under pressure. The synthesised biochar was analysed using infrared spectroscopy, thermogravimetic analysis, elemental analysis and bomb calorimetry. Biochar synthesised in alcohol solvents exhibited significantly different properties to that produced via conventional hydrothermal carbonisation (HTC) in water. HTC yielded a biochar with reduced heteroatom content and more favourable properties for application as a solid fuel. The alcohol solvents yielded greater quantities of water soluble oil (WSO), with the yield increasing with alcohol chain length. These trends are correlated with physical properties such as dielectric constant and increased solubility of organics in higher carbon number alcohols. These results show that the choice of solvent can direct the properties of synthesised chars for specific applications or can maximise the yield of bio-oil for fuel.

Sustainable Exploitation of Residual Cynara cardunculus L. to Levulinic Acid and n-Butyl Levulinate

“…In addition, the absorption bands at 1208 cm −1 (C-O stretching), and 795 cm −1 (C-H bending off the plane) further confirm the similarity between the chars produced by hydrolysis/alcoholysis. At this stage of the investigation, the severity of the performed treatments dampens any differences deriving from the use of different reaction solvents, otherwise reported by some authors very recently [51].…”

Hydrochars as Emerging Biofuels: Recent Advances and Application of Artificial Neural Networks for the Prediction of Heating Values

“…Subsequently, steam gasification of the double-processed waste yielded 33 mol H 2 /kg of hydrochar at 1050 • C. Nasir et al (2020) converted spent brewery grains into hydrochars using different solvents during HTC. The group concluded that typical water-based HTC lead to hydrochar with the optimum fuel properties, however the use of methanol, ethanol and 2-propanol resulted in fundamentally different hydrochars, perhaps suitable for soil application or wastewater treatment processes [77]. It is worth noting that such an approach is not often reported in the literature and may be worth investigating further, as part of a multiple-product biorefinery concept.…”

Comparative study of solvothermal and catalytic solvothermal carbonization of rice husk for Fe(iii), Zn(ii), Cu(ii), Pb(ii) and Mn(ii) adsorption, kinetics, surface chemistry and reaction mechanism

“…1,4,10 A previous experimental study on STC of brewers' spent grain presented that solvochars produced at 250 °C with alcoholic solvents (methanol, ethanol, and 2-propanol) contained oxygen-enriched functional groups, including hydroxyl (-OH) and carboxyl (-COOH) groups, and aromatic ketones. 11 The aromatic ketones and oxygencontaining functional groups play a vital role as the π-electron donor for heavy metal ion adsorption via cation exchange. [12][13][14][15] Another study showed that the presence of -OH and -COOH groups accelerated the heavy metal ion adsorption on the char surface due to the abundance of hydrogen bonding.…”