Sustain. Chem., Volume 5, Issue 4 (December 2024) – 5 articles

Brewer’s spent grains (BSG) are a by-product of the beer industry and can be used to produce biofuels. In this case, the objective of this study was to obtain reducing sugars from this biomass by subcritical water hydrolysis in a semi-continuous mode after steam explosion. Temperatures of 120–180 °C, reaction times of 1–5 min, and pressures of 15–25 MPa were used for the steam explosion without CO₂. Moistures of 10–50% (w/v), temperatures of 120–180 °C, reaction times of 1–5 min, and pressures of 15–25 MPa were used for the steam explosion with CO₂. Subcritical water hydrolysis of solid-exploded material was developed at 210 °C, 15 MPa, a solid/feed ratio of 16 g/g, and a flow rate of 20 mL/min. The characterization of BSG, reducing sugar yields, kinetic profiles, the composition of monosaccharides and furanic moieties, and the characterization of remaining solid by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) were performed. For steam explosion with CO₂, the significant variables were the temperature and moisture, and the optimized conditions were moisture of 50% (w/v), 120 °C, pretreatment for 1 min, and 15 MPa, with a reducing sugars yield of 18.41 ± 1.02 g/100 g BSG. For steam explosion without CO₂, the significant variables were the time and temperature, and the optimized conditions were 120 °C, pretreatment for 1 min, and 15 MPa, with a reducing sugars yield of 17.05 ± 0.48 g/100 g BSG. The process was successful because the steam explosion ruptured the lignocellulosic matrix, and the subsequent process of subcritical water hydrolysis could dissociate the polymers into low-chain saccharides. Full article

Biochar, produced through the pyrolysis of biomass and green waste, offers significant potential as a soil amendment to enhance soil health and sustainability in agriculture. However, the current Measurement, Reporting, and Verification (MRV) systems for biochar predominantly focus on carbon credits/offsets, neglecting crucial aspects related to its usability and suitability as a soil amendment on agricultural fields. Through an examination of recent findings, this perspective explores the integration of geochemical tracers, functional group (hydroxyl, carboxyl, phenolic, lactonic, etc.) analysis, and nutrient dynamics into MRV procedures/systems to create a more comprehensive framework. By examining the applicability of these indicators, this paper identifies key gaps and proposes a more robust MRV approach. Such a system would not only facilitate better assessment of biochar’s agronomic benefits but also guide its optimal use in various soil types and agricultural practices. Full article

In this study, several professional cleaning products were analyzed for their impact on local air and sewage contamination. The products were first analyzed for their content of potentially harmful ingredients, their biodegradability, and the potential for the mobilization of hazardous substances from the floorings that were cleaned. The contribution of the cleaning products to sewage pollution with environmentally hazardous substances was studied at full scale. All commercially available cleaning products studied were declared to be environmentally friendly (labeled with the EU Ecolabel). However, despite being labeled as “green” products, between 16 and 24 volatile harmful ingredients were identified. An optimized experimental product, produced completely from natural raw materials, also contained several harmful substances originating from the herbal raw materials themselves. During the field study, we identified a range of trace substances in the sewage. Eight of these substances (e.g., p-cymene, butanone, eucalyptol) significantly originated from the cleaning products. Several others may have originated from the cleaning products, but other sources were also possible. The flooring materials that were cleaned contained several harmful substances themselves. The release of some substances (e.g., toluene) into the sewage significantly increased during the cleaning process. Full article

Phosphorus mainly exists in the form of phosphate in water. Excessive phosphorus can cause eutrophication, leading to algae reproduction and the depletion of oxygen in water, destroying aquatic ecology. This study prepared quaternized polyaniline (PN) and quaternized polyaniline with lanthanum hydrate (HLO-PN), and a new nanocomposite for removing phosphate from wastewater was proposed. The results of adsorption experiments show that HLO-PN can effectively remove phosphate in the range of pH 3~7; the maximum adsorption capacity is 92.57 mg/g, and it has excellent anti-interference ability against some common coexisting anions (${\mathrm{F}}^{-},$ ${\mathrm{C}\mathrm{l}}^{-},$ ${\mathrm{NO}}_3^{-},$ ${\mathrm{SO}}_4^{2-}$) other than ${\mathrm{CO}}_3^{2-}$. After five adsorption–desorption cycles, the phosphate adsorption capacity (60 mg/g) was still 74.28% of the initial adsorption capacity (80.85 mg/g), indicating that the HLO-PN nanocomposites had good reusability and recovery of phosphorus. The characterization results show that phosphate adsorption is realized by electrostatic adsorption and ligand exchange. Full article