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The feasibility of pretreatment involving soaking in aqueous ammonia (SAA) for the anaerobic digestion (AD) of eight different types of agricultural biomass of Ugandan origin was investigated. Moderate pretreatment temperatures of 60 and 90 °C were employed, and the NH3 concentration, solid-to-liquid ratio, and pretreatment time were fixed at 15.0% (w/w), 1:6, and 6 h, respectively. The delignification efficiencies of the SAA pretreatment ranged from 51.1 to 76.6%, and the maximum value was observed for maize bran pretreated at 90 °C. Biochemical methane potential experiments proved that the breaking of the complex bonds of lignin made fermentable sugars easily accessible to microorganisms. In all cases, the SAA pretreatment enhanced the methane potential of the eight types of Ugandan biomass compared with its untreated counterparts. The pretreated maize bran exhibited the highest methane yield of 291.5 mL CH4/g COD, which is 83.1% of the theoretical conversion. SAA followed by AD is useful for employing Ugandan agricultural biomass as a renewable energy source. [ABSTRACT FROM AUTHOR]

Corn stover was pretreated with aqueous ammonia in a flow-through column reactor, a process termed ammonia recycled percolation (ARP). This method was highly effective in delignifying of the biomass, reducing the lignin content by 70–85%. Most lignin removal occurred within the first 20 min of the process. Lignin removal by ARP was further confirmed by FTIR analysis and lignin staining. The ARP process solubilized 40–60% of the hemicellulose but left the cellulose intact. The solubilized carbohydrate existed in oligomeric form. Carbohydrate decomposition during the pretreatment was insignificant. Corn stover treated for 90 min exhibited enzymatic digestibility of 99% with 60 FPU/g of glucan enzyme loading, and 92.5% with 10 FPU/g of glucan. The digestibility of ARP treated corn stover was substantially higher than that of α-cellulose. The enzymatic digestibility was related with the removal of lignin and hemicellulose, perhaps due to increased surface area and porosity. The SEM pictures indicated that the biomass structure was deformed and its fibers exposed by the pretreatment. The crystallinity index increased with pretreatment reflecting removal of the amorphous portion of biomass. The crystalline structure of the cellulose in the biomass, however, was not changed by the ARP treatment. [Copyright &y& Elsevier]

Abstract: NaOH catalyzed steam explosion was applied to improve the enzymatic digestibility of Eucalyptus grandis. The impregnation of wood chip with NaOH solutions before steam explosion was carried out to investigate the effects of alkaline catalysis on solid recovery, enzymatic digestibility, and glucose recovery. The lignin removal was significantly affected by NaOH as a catalyst and the glucose recovery increased with increased severity index. The use of NaOH showed higher enzymatic digestibility than the use of water at most severity indexes due to the delignification of biomass and the increase of accessibility to cellulose of enzyme. The maximum glucose recovery was 65.55% having 4.4361 of severity index with 7wt.% of NaOH catalyzed steam explosion at 210°C during 9min. NaOH catalyzed steam explosion was effective to enhance the enzymatic digestibility due to the removal of lignin. [Copyright &y& Elsevier]

• Soaking in aqueous ammonia enhanced methane production from maize bran biomass. • Optimal pretreatment conditions were found as 72.5 °C, 7 h, and a S/L of 1:6.2. • The maximum methane yield was 293.8 mL CH 4 /g COD. • Validation experiments confirmed the accuracy of response surface methodology. In this study, maize bran biomass was subjected to soaking in aqueous ammonia (SAA) pretreatment to reduce and eliminate lignin, a major component that hinders biological digestibility. The effect of SAA pretreatment on the mesophilic anaerobic digestion of maize bran were investigated by using statistical techniques on batch anaerobic test. Response surface methodology by the central-composite design has verified the effects and the interactions of three variables, pretreatment temperature (10–110 °C), pretreatment time (1–11 h) and solid to liquid (S/L) ratio (0.068–0.307) on the responses: methane yield (MY), methane productivity rate (MPR), delignification and sugar recovery were monitored keenly. The optimal regions predicted via overlay plots for the multiple response falls within the following ranges: pretreatment temperatures between 55 and 70 °C, pretreatment time of 5 to 8 h and S/L ratio of 0.14 to 0.185. The optimal conditions were found at 72.5 °C, an S/L ratio of 0.14, and 7.02 h resulting to an MY of 293.8 mL/g COD, and an MPR of 106.0 mL CH 4 /g VSS-day. The model equations for the multiple responses were within p < 0.05 meaning it is significant and is fitted to the data sets. Validation experiments has confirmed that the pretreatment conditions with optimal responses presented are in close agreement comparing the ones obtained from the experiment and that as estimated by the model. [ABSTRACT FROM AUTHOR]

Abstract: Rice straw was utilized for the cultivation of Phanerochaete chrysoporium to produce cellobiose dehydrogenase. The composition of the rice straw after fermentation was found to be 28.77% glucan, 19.05% xylan and 54.81% other lignin containing sugars. The glucan and xylan content decreased due to the consumption of glucan and xylan by P. chrysoporium. After fermentation, the rice straw waste was subjected to chemical pretreatment to remove lignin. The effect of dilute acid pretreatment was not notable because of the glucose loss. However, when the rice straw after fermentation was treated with aqueous ammonia, the composition changed to 44.73% glucan, 25.43% xylan and 29.52% other lignin containing sugars. The aqueous ammonia pretreatment was optimized and an ammonia concentration, reaction time and temperature of 20%, 6 h and 60 °C, respectively, were determined to be the optimal pretreatment conditions After removal of lignin, the initial reaction rate was increased to 0.009583 g/L s, which was about 3 fold higher than the rice straw after fermentation. X-ray diffractometry was performed to investigate the crystallinity index, and the XRD results showed that biological treatment and the combination of both biological treatment and chemical pretreatment decreased the crystallinity index. [Copyright &y& Elsevier]

Abstract: Liberation of fermentable sugars from recalcitrant lignocellulosic biomass is one of the key challenges in production of cellulosic ethanol. Here we developed a two-stage pretreatment process using aqueous ammonia and dilute sulfuric acid in a percolation mode to improve production of fermentable sugars from rice straw. Aqueous NH3 was used in the first stage which removed lignin selectively but left most of cellulose (97%) and hemicellulose (77%). Dilute acid was applied in the second stage which removed most of hemicellulose, partially disrupted the crystalline structure of cellulose, and thus enhanced enzymatic digestibility of cellulose in the solids remaining. Under the optimal pretreatment conditions, the enzymatic hydrolysis yields of the two-stage treated samples were 96.9% and 90.8% with enzyme loadings of 60 and 15FPU/g of glucan, respectively. The overall sugar conversions of cellulose and hemicellulose into glucose and xylose by enzymatic and acid hydrolysis reached 89.0% and 71.7%, respectively. [Copyright &y& Elsevier]