Efficient bioconversion of rice straw to ethanol with TiO2/UV pretreatment

Effect of alkaline and alkaline-photocatalytic pretreatment on characteristics and biogas production of rice straw

To overcome recalcitrant nature and investigate enhancement of biogas production of rice straw (RS), it was subjected to pretreatment under mild conditions. Alkaline pretreatment using sodium hydroxide (NaOH), photocatalytic pretreatment utilizing titania nanoparticles (TiO₂ NPs) and alkaline-photocatalytic pretreatment was used to disrupt the lignocellulose complex. As compared to raw RS, maximum biogas and methane enhancement due to alkaline pretreatment was observed for 1.5% w/v NaOH pretreated RS which was 50 and 71% respectively. Photocatalytic pretreatment of RS at 0.25 g/L TiO₂ increased biogas and methane yield by 30 and 36% respectively. However, maximum biogas and methane enhancement was observed for alkaline-photocatalytic pretreatment at 1.5% w/v NaOH-0.25 g/L TiO₂ which was 74 and 122% respectively. Comparatively high enhancements were observed during alkaline-photocatalytic combined pretreatment due to increased cellulose and decreased lignin content. Moreover, the experimental data obtained from the experiments were validated using a non-linear kinetic model.

Feasibility of Continuous Pretreatment of Corn Stover: A Comparison of Three Commercially Available Continuous Pulverizing Devices

We determined the potential of three mechanical pulverizers—a continuous ball mill (CBM), an air classifier mill (ACM), and a high-speed mill (HSM)—in the continuous pretreatment of corn stover. The mean diameters of the pulverized biomasses were not significantly different in the three cases, and the glucose yields from the CBM-, ACM-, and HSM-pulverized samples were 29%, 49%, and 44%, respectively. The energy requirements and process capacities for the ACM and HSM were similar. We conclude that the ACM and HSM could be used in the continuous pretreatment of corn stover and would be useful in biofuel production.

Dielectric barrier discharge plasma microbubble reactor for pretreatment of lignocellulosic biomass

A novel lignocellulosic biomass pretreatment reactor has been designed and tested to investigate pretreatment efficacy of miscanthus grass. The reactor was designed to optimize the transfer of highly oxidative species produced by dielectric barrier discharge plasma to the liquid phase immediately after generation, by arranging close proximity of the plasma to the gas-liquid interface of microbubbles. The reactor produced a range of reactive oxygen species and reactive nitrogen species, and the rate of production depended on the power source duty cycle and the temperature of the plasma. Ozone and other oxidative species were dispersed efficiently using energy efficient microbubbles produced by fluidic oscillations. A 5% (w/w) miscanthus suspension pretreated for 3 h at 10% duty cycle yielded 0.5% acid soluble lignin release and 26% sugar release post hydrolysis with accelerated pretreatment toward the latter stages of the treatment demonstrating the potential of this approach as an alternative pretreatment method. © 2018 The Authors. AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers. © 2018 The Authors. AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers. AIChE J, 64: 3803-3816, 2018.

Enhanced biohydrogen and subsequent biomethane production from sugarcane bagasse using nano-titanium dioxide pretreatment

Nano-titanium dioxide (nanoTiO2) under ultraviolet irradiation (UV) followed by dilute sulfuric acid hydrolysis of sugarcane bagasse was used to enhance the production of biohydrogen and biomethane in a consecutive dark fermentation and anaerobic digestion. Different concentrations of 0.001, 0.01, 0.1 and 1g nanoTiO2/L under different UV times of 30, 60, 90 and 120min were used. Sulfuric acid (2%v/v) at 121°C was used for 15, 30 and 60min to hydrolyze the pretreated bagasse. For acidic hydrolysis times of 15, 30 and 60min, the highest total free sugar values were enhanced by 260%, 107%, and 189%, respectively, compared to samples without nanoTiO2 pretreatment. The highest hydrogen production samples for the same acidic hydrolysis times showed 88%, 127%, and 25% enhancement. The maximum hydrogen production of 101.5ml/g VS (volatile solids) was obtained at 1g nanoTiO2/L and 120min UV irradiation followed by 30min acid hydrolysis.