Thermal hydrolysis of olive leaves and stems to obtain fermentable sugars

Subcritical water hydrolysis was used for the pre-treatment of residues generated in olive groves. Fermentable sugars were produced from the lignocellulosic material found in olive leaves and stems. Firstly, moisture, ash, particle average diameter, and total extracts were measured. Afterward, subcritical water hydrolysis was carried out at 20 MPa in a 50 mL reactor. The influences of two temperatures (180 and 220 °C) and two water flow rates (10 and 20 mL min-1) on the sugars yields were evaluated. The concentration of sugars was 31.3 g L-1 at 180 °C and 10 mL min-1 in a reaction for 3 min, of which glucose was the major sugar (27.64 g L-1). Statistical analysis was performed using Sisvar® 5.6 software and the averages were compared through Tukey’s test, considering a significance level of 95% (p<0.05). For the treatments evaluated in this work, only xylose was statistically different in the treatments with different water flow rates. The highest values of xylose were obtained with 10 mL min-1, which were 1.82 g L-1 (180 °C) and 2.18 g L-1 (220 °C). The total inhibitors were high at 220 °C for all water flow rates, with a significant difference from the averages obtained at 180 °C.

Sustainably Processed Waste Wool Fiber-Reinforced Biocomposites for Agriculture and Packaging Applications

In the EU, sheep bred for dairy and meat purposes are of low quality, their economic value is not even enough to cover shearing costs, and their wool is generally seen as a useless by-product of sheep farming, resulting in large illegal disposal or landfilling. In order to minimize environmental and health-related problems considering elemental compositions of discarded materials such as waste wool, there is a need to recycle and reuse waste materials to develop sustainable innovative technologies and transformation processes to achieve sustainable manufacturing. This study aims to examine the application of waste wool in biocomposite production with the help of a sustainable hydrolysis process without any chemicals and binding material. The impact of superheated water hydrolysis and mixing hydrolyzed wool fibers with kraft pulp on the performance of biocomposite was investigated and characterized using SEM, FTIR, tensile strength, DSC, TGA, and soil burial testing in comparison with 100% kraft pulp biocomposite. The superheated water hydrolysis process increases the hydrophilicity and homogeneity and contributes to increasing the speed of biodegradation. The biocomposite is entirely self-supporting, provides primary nutrients for soil nourishment, and is observed to be completely biodegradable when buried in the soil within 90 days. Among temperatures tested for superheated water hydrolysis of raw wool, 150 °C seems to be the most appropriate for the biocomposite preparation regarding physicochemical properties of wool and suitability for wool mixing with cellulose. The combination of a sustainable hydrolysis process and the use of waste wool in manufacturing an eco-friendly, biodegradable paper/biocomposite will open new potential opportunities for the utilization of waste wool in agricultural and packaging applications and minimize environmental impact.

Assessment of reducing sugars production from agro-industrial wastes by batch and semicontinuous subcritical water hydrolysis

Reducing sugars produced from agro-industrial wastes by means of hydrolysis represent a promising alternative of chemicals and energy. Yet, large scale production still struggles with several factors involving process complexity, sugars degradation, corrosion, enzyme recyclability, and economic feasibility. More recently, sub and supercritical water hydrolysis has been reported for the production of reducing sugars as a readily available alternative to acid and enzymatic biomass hydrolysis. Accordingly, in this work, the results of batch and semicontinuous lab scale subcritical water hydrolysis experiments of agro-industrial wastes of pea pot and corn stover are discussed. Experiments were carried in the temperature range 250 to 300 °C, pressures up to 3650 psi, residence times up to 30 minutes in batch mode operation, or water flowrates up to 12 mL/min in semicontinuous mode operation. Produced sugars were assessed in the effluent of each experimental run by means of dinitrosalicilic acid method (DNS). A maximum total reducing sugar (TRS) yield of 21.8% was measured for batch pea pot subcritical water hydrolysis experiments at 300°C, 15 minutes, 3650 psi, and 1:6 biomass to water mass ratio. Semicontinuous subcritical water hydrolysis of corn stover showed a maximum TRS accumulated yield of 19% at 290 °C, 1500 psi, and water flowrate of 9 mL/min. The results showed the feasibility of producing reducing sugars from agro-industrial wastes currently discarded through subcritical hydrolysis.

Nanoneedle-forest NiCo2O4@nitrogen-doped Carbon-Mo2C/CC as Double Functional Electrocatalysts for Water Hydrolysis and Zn-air Batteries

The construction of efficient and stable non-precious metal electrocatalysts for water hydrolysis and metal-air batteries is a key to tackle the energy shortage and environmental pollution. Herein, a composite consisting of needle-forest nickel cobalt oxide and nitrogen-doped carbon (NDC)-molybdenum carbide loaded on carbon cloth (NiCo2O4@NDC-Mo2C/CC) is synthesized from the hydrothermal method. The introduction of nitrogen-doped carbon and carbon cloth improves the electrical conductivity of the composite, the existence of NDC-Mo2C on CC makes NiCo2O4 produce generous oxygen vacancies. Therefore, NiCo2O4@NDC-Mo2C/CC shows the low overpotentials of HER (120 mV) and OER (220 mV) @10 mA cm-2 and excellent performances for overall water electrolysis in alkaline medium. Also, NiCo2O4@NDC-Mo2C/CC exhibits robust oxygen reduction reaction (ORR) performance and a large specific capacity of 778 mAh g−1 and energy density of 104 mW cm−2 as air cathode in Zn-air batteries. This work enriches knowledge to explore multifunctional electrocatalysts to replace noble metallic catalysts.