Can Biochar Couple with Algae to Deal with Desertification?

In order to improve man-made biological soil crusts (BSCs) for desertification control and develop value-added utilization of bioenergy byproducts, preliminary experiments were carried out to understand the effect of biochar addition on algae growth in sand. Microcoleus vaginatus was chosen as the model algae and cultivated in sand with various contents of biochar (0%, 2%, 5%, 8%, and 10% weight of sand) that were made by rice hull gasification. Results showed that when the content of biochar in sand was 2%, both algal biomass (indicated by chlorophyll-a content) and the fixed sand weight in the BSC were significantly higher than that of the control (without biochar addition) and other treatments (with >2% biochar additions). Results from this pioneering research indicate that appropriate amount of biochar addition could increase BSC formation in sand under dry conditions and can potentially enhance sand fixation in deserts for desertification control.

Short Report: Effects of Biochar Addition on Manure Composting and Associated N₂O Emissions

Recent interests in biochar stem from its agronomic benefits and carbon sequestration potentials in soil applications. As a not fully understood newer concept, adding biochar as a bulking agent to animal manure composting has the potential to enhance the performance of composting process and reduce associated N2O emissions. This short report presents emerging trends and knowledge gaps in this research area, and provides an introduction to understand the mechanism by which biochar impacts manure composting performance and N2O fluxes.

Bacterial Lysis of Microalgal Cells

This short communication reports a pioneering research of using bacteria for simultaneous algal cell disruption and cell wall/membrane utilization. Microalgae are regarded as one of the most promising feedstock that can potentially address the twin challenges of energy security and environmental protection due to their fast growth rate, high lipid content and CO2 biofixation capabilities. However, different from their terrestrial oil crops, the extracellular coverings of algae vary significantly, ranging from multiple layers of elaborate scales to highly mineralized coats to complex cell walls consisting of structural fibrils enmeshed in complex matrices. These strong cellular walls and membranes are resistant to disintegration, which makes lipid extraction from microalgae difficult. A bacteria-assisted algal cell disruption and lipid extraction method was studied here. The bacteria Sagittula stellata showed strong algicidal activity against two microalgae, Nannochloropsis oculata and Dunaliella salina. The algicidal rate reached 64.7% on N. oculata and 52.4% on D. salina in six days. A decrease in chlorophyll-a fluorescence density of both algae and bacteria addition was also observed. After 6-day treatment by S. stellata, hexane-extracted crude lipid contents increased from 32.9% to 45.7% and from 19.6% to 36.4% for N. oculata and D. salina, respectively, when compared with no bacterial addition. The preliminary results concluded that S. stellata was effective in the lysis of microalgal cells for effective lipid recovery.

Effective syngas cleanup and reforming using Ni/γ-Al_(2)O_(3) catalyst

This work reports the performance of a selective Ni-based catalyst in tar removal and syngas reforming.Benzene was used as the model tar to optimize catalytic reaction conditions.Parameters investigated were reaction temperature(700℃ to 900℃),gas residence time(0.1 s to 1.1 s),and catalyst loadings(3%to 21%of the weight of γ-Al_(2)O_(3) support).On the basis of the benzene test,a reaction temperature of 800℃,catalyst loading of 15wt%,and residence time of 0.3 s were chosen as optimum reaction conditions.Testing of these conditions showed that the Ni/γ-Al_(2)O_(3) catalyst removed more than 99%of tars in syngas in the downdraft gasifier and 98%in the updraft gasifier.Concentrations of combustible compounds of syngas also increased significantly.H_(2) concentration increased from 19.96%to 51.78%in the downdraft gasifier and from 23.97%to 37.39%in the updraft gasifier;CO concentration increased from 16.26%to 21.10%in the downdraft gasifier and from 22.95%to 25.64%in the updraft gasifier.The results indicate that the Ni/γ-Al_(2)O_(3) catalyst and associated catalytic conditions could not only effectively eliminate tars but also improve the quality of syngas in biomass gasification.

In-chamber thermocatalytic tar cracking and syngas reforming using char-supported NiO catalyst in an updraft biomass gasifier

The objective of this study was to evaluate the performance of an in-chamber tar cracking and syngas reforming unit.This unit was composed of a two-stage tubular reactor placed within the combustion zone of an updraft biomass gasifier.Heat generated in the exothermic combustion reactions of biomass gasification drove tar cracking and syngas reforming in the tubes,eliminating the need of external heating.The performance of the unit was evaluated using char-supported NiO catalysts and was found to be very effective in tar removal and syngas composition enhancement.A tar removal rate of 95% was achieved at 0.3 s residence time and 10%nickel loading.This condition also gave syngas high-heating value increment of 36%(to 7.3 MJ/m^(3)).The effect of gas residence time and Ni loading on tar removal and syngas composition of the unit was also studied.Gas residence of 0.2-0.3 s and Ni loading of 5%-10% were found appropriate to produce clean syngas with tar content appropriate for industrial applications(<0.6 g/m^(3))in an updraft biomass gasifier without external heating.

Computational investigation of the effect of biodiesel fuel properties on diesel engine NOx emissions

A detailed numerical spray atomization,ignition,combustion and nitrogen oxides(NOx)formation model was developed for direct injection diesel engines by using KIVA3V code.Several modified or recalibrated sub-models including a Kelvin-Helmholtz Rayleigh-Taylor(KH-RT)spray breakup model,a Shell ignition model,a single-step kinetic combustion model and a Zel’dovich NOx formation model were incorporated into KIVA3V.This modified model was validated by experimental data obtained from a John Deere 4045T direct injection diesel engine that was fueled with a natural soybean methyl ester,a yellow grease methyl ester,a genetically modified soybean methyl ester and No.2 diesel fuel.Errors between predictions of the brake-specific NOx and measured values were less than 1%at full load.For biodiesel fuels,either the Zel’dovich mechanism overpredicted NOx emissions,the ratio of NO to NOx should be less than diesel fuel,or both.As observed from the modeling results,the higher latent heat of vaporization and higher surface tension of biodiesel relative to diesel fuel did not result in increased NOx emissions.The higher viscosity of biodiesel could be one of the reasons for increased NOx,but its effect was relatively small compared with the effect of decreased spray cone angle and advanced start of injection timing on NOx.Decreased spray cone angle and advanced start of injection were the main reasons for increased NOx emissions of biodiesel.

Antioxidant activity of phlorotannins from brown algae

The antioxidant activity of the phlorotannins extracted from five marine algaespecies(Saccharina latissima,Alaria esculenta,Laminaria digitata,Fucus vesiculosusand Ascophyllum nodosum)was studied.Three phlorotannin groups,including soluble,membrane-bound,and extracted membrane-bound phlorotannins obtained by two solvent extraction methods were investigated for their DPPH radical scavenging activity.F.vesiculosusand A.nodosumshowed the highest phlorotannin yield(14.83 mg-extract/g-algae and 12.80 mg-extract/g-algae,respectively)among the five algaespecies.Their soluble phlorophannin(SP),membrane-bound phlorotannin(MP)and extracted membrane-bound phlorotannin(eMP)extracts all showed equal or greater DPPH radical scavenging activity than the commercial antioxidants of butylated hydroxytoluene and ascorbic acid.The antioxidant potential that combines phlorotannin yield and antioxidant activity of the MP extracts of F.vesiculosusand A.nodosum(5890mL/g and 5278 mL/g algae,respectively)were higher than those of SP and eMP,suggesting that the MPs of F.vesiculosusand A.nodosumhad great potential to be used as antioxidants.Different extraction methods also showed significantly different effects on the antioxidant activity of the phlorotannin extracts.

Effects of surface texturing on microalgal cell attachment to solid carriers

The objective of this study was to understand the role of surface texturing in microalgal cell attachment to solid surfaces.Two microalgal species,Scenedesmus dimorphus and Nannochloropsis oculata,were studied on solid carriers made of nylon and polycarbonate.Ridge,pillar and groove at micro-scale were engineered on the solid carriers.Cell response to the textured surfaces was separately described by the Cassie and Wenzel models and the contact point theory.Comparison between measured and model-predicted contact angles indicated that the wetting behavior of the textured solid carriers fell into the Wenzel state,which implied that algal cells could fully penetrate into the designed textures,but the adhesion behavior would be dependent on the size and shape of the cell.Experimental results showed that the attachment was preferred when the feature size was close to the diameter of the cell attempting to settle.Larger or smaller feature dimensions had the potential to reduce cellular attachment.The observation was found to qualitatively comply with the contact point theory.

Effect of nitrogen and extraction method on algae lipid yield

Effects of nitrogen source and concentration as well as lipid extraction method on the lipid yield of autotrophic Scenedesmus dimorphus and heterotrophic Chlorella protothecoides were studied.Three concentration levels of nitrate,urea and glycine/yeast extract as the nitrogen source were investigated.The highest lipid yield of S.dimorphus in the 17-d autotrophic culture was 0.40 g/L from the 1.8 g/L urea medium,and the maximum lipid yield of C.protothecoides in the nine-day heterotrophic culture was 5.89 g/L from the 2.4 g/L nitrate medium.Four different cell disruption methods-bead-beater,French press,sonication and wet milling-were studied for their effectiveness in solvent extraction of algal lipids from S.dimorphus and C.protothecoides.Wet milling followed by hexane extraction was most effective for S.dimorphus lipid extraction,whereas bead-beater disruption followed by hexane extraction was best for C.protothecoides.