Prediction of methane yield and pretreatment efficiency of lignocellulosic biomass based on composition.

Lignocellulosic biomass is considered a key resource for the future expansion of biogas production through anaerobic digestion (AD), and research on the development of pretreatment technologies for improving biomass conversion is an intensive and fast-growing field. Consequently, there is a need for creating tools able to predict the efficiency of a certain pretreatment on different biomass types, fast and accurately, and to assist in selecting a pretreatment technology for a specific biomass. In this study, seven different types of raw lignocellulosic biomass of industrial relevance were systematically analyzed regarding their composition (carbohydrates, lignin, lipids, ash, extractives, etc.) and subjected to a common pretreatment. The aim of the study was to identify the most important characteristics that make a biomass good receptor of the specific pretreatment prior to AD. A simple ammonia pretreatment was chosen as a case study and partial least squares regression (PLS-R) was used for modeling initially the ultimate methane yield of raw and pretreated biomass. In the sequel, PLS-R was used for modeling the efficiency of the pretreatment on increasing the ultimate methane yield and hydrolysis rate as a function of the biomass composition. The fit of the models was satisfactory, ranging from R2 = 0.89 to R2 = 0.97. The results showed that the most decisive characteristics for predicting the efficiency of the pretreatment were the lipid (r = -0.88), ash (r = +0.79), protein (r = -0.61), and hemicellulose/lignin (r = -0.53) content of raw biomass. Finally, the approach followed in this study facilitated an improved understanding of the mechanism of the pretreatment and presented a methodology to be followed for developing tools for the prediction of pretreatment efficiency in the field of lignocellulosic biomass valorization.

Effects of different treatments of manure on mitigating methane emissions during storage and preserving the methane potential for anaerobic digestion.

Current agricultural practices in regards to storage of manure come with a significant GHG contribution, due, to a big extent, to CH4 emissions. For example, in Denmark, the agricultural sector is responsible for about 11.1 metric tons of CO2 equivalents; only about 0.2 metric tons come directly from CO2, while 6.0 tons come from CH4. The present study aims at evaluating and comparing two methods based on their effect on suppressing CH4 emissions during storage as well as on preserving and enhancing CH4 yield in a subsequent anaerobic digestion step: the commonly applied acidification with H2SO4 as acidifying agent and thermal treatment at the mild temperatures of 70 and 90 °C (pasteurization). Although both treatments effectively suppressed CH4 emissions during storage, they exhibited a significant difference in preserving and/or enhancing the CH4 potential of manure. Specifically, thermal treatment resulted in 16-35% enhancement of CH4 potential, while acidification resulted in decreasing the CH4 yield by 6-23% compared to non-treated manure. Further investigation showed that storage itself positively affected the CH4 potential of treated manure in a subsequent anaerobic digestion step; this was attributed to microbial activity other than biomethanation during storage. In overall and based on the results obtained regarding suppression of CH4 emissions during storage as well as CH4 potential enhancement, pasteurization at the temperatures tested is a promising alternative to the broadly applied acidification of manure.

Structural and functional characterization of a novel biosurfactant from Bacillus sp. IITD106.

Plant saponins are attractive biosurfactants and have been used to enhance phytoremediation. There are only limited reports on saponins produced by bacteria. Here, we report structural and functional characterization of a novel saponin produced by Bacillus sp. IITD106. Biosurfactant production was determined by emulsion index, drop collapse, oil displacement and hemolytic assays. The biosurfactant was stable over a range of temperature (30 °C to 70 °C), salinity (0-150 g liter-1) and pH (4-10). The surface tension of the medium reduced from 58.89 mN/m to 27.29 mN/m using the isolated biosurfactant. Chromatographic analysis revealed the biosurfactant to be a glycolipid. LCMS, FT-IR and NMR analysis identified the biosurfactant to be a saponin containing two sugar groups and a 5 ringed triterpene sapogenin unit. Genome sequencing of the strain revealed the presence of genes responsible for biosynthesis of saponin. Statistical optimization of culture medium resulted in 9.3-fold increase in biosurfactant production. Kinetics study of biosurfactant production performed in a stirred tank batch bioreactor resulted in 6.04 g liter-1 and 6.9 g liter-1 biomass and biosurfactant concentration, respectively. The biosurfactant was found to solubilize polycyclic aromatic hydrocarbons. The potential of cell free biosurfactant containing broth to enhance oil recovery was tested in a sand pack column and recovery of 63% of residual oil was observed. To our knowledge this is the first report of saponin production by any of the strains of Bacillus.

Optimization of Aqueous Ammonia Soaking of manure fibers by Response Surface Methodology for unlocking the methane potential of swine manure.

Swine manure mono-digestion often results to economically non-feasible processes, due to the high dilution and ammonia concentration together with the low degradation rates it presents. The effects of different parameters of Aqueous Ammonia Soaking (AAS) as a pretreatment for improving the digestion of manure fibers when coupled to an ammonia removal step were investigated in this study. Response Surface Methodology was followed and the influence and interactions of the following AAS parameters were studied: NH3 concentration, duration and solid-to-liquid ratio. The mild conditions found to be optimal (7%w/w NH3, 96h, and 0.16kg/L) in combination to a significant increase of the short term CH4 yield (244% in 17days), make this pretreatment a promising solution for improving swine manure mono-digestion. Furthermore, compositional analysis of the manure fibers revealed significant solubilization of hemicellulose, while no lignin removal or loss of cellulose occurred under optimal conditions.