Lignocellulosic residue as bio-carrier for algal biofilm growth: Effects of carrier physicochemical proprieties and toxicity on algal biomass production and composition.

Five types of lignocellulosic materials were applied as the bio-carriers for low-cost algal biofilm cultivation of three algal strains. The effects of bio-carrier physicochemical properties and toxicity on algal cells growth and attachment were investigated. Rougher and hydrophilic bio-carrier could yield more algal biomass than smoother and hydrophobic bio-carrier. Pine sawdust (diameter: 0.420-0.595 mm) performed the best when cultured Diplosphaera sp. (9.61 g·m-2·day-1) biofilm. Meanwhile, bio-carriers could be leached by the culture medium during cultivation, and their energy conversion proprieties could be improved due to the reduced ash contents and the decreased crystallinities. In addition, Chlorella vulgaris growth tests indicated that pine sawdust (15.45%) leachate promoted cell growth, whereas rick husk (15.48%) and sugarcane bagasse (13.19%) leachate inhibited cell growth. And bio-carriers leachates also modified the chemical compositions (lipid, protein and carbohydrate) of algal cells and increased the corresponding saturated fatty acids methyl ester content (from 48.71 to 55.58-57.08%).

Model of osmosis in a single-file pore.

Single-file transport of water and other small molecules through narrow pores in osmosis has drawn considerable attention in recent years due to its extensive application in biology and industry. In this work, we propose a discrete model to describe nonideal osmosis through single-file pores. Every site is assumed to be occupied by a molecule according to experiments and simulations. Hence, a dense chain can always be found, and collective hopping is the only movement method enabling the molecular chain to move. The roles of solute in osmosis are clarified in this model. Those molecules reflected at the pore entrance produce osmotic pressure, and those inside the pore contribute to the flow resistance of the molecular chain. The solute molecules that can enter the pore but cannot penetrate it may significantly reduce the osmotic flux, although they are all rejected by the pore. This conclusion can help to clarify the emerging debate about whether the reflection coefficient of the fully rejected solute can be less than 1. The design of highly efficient membrane pores may also benefit from this study.

Vertical-algal-biofilm enhanced raceway pond for cost-effective wastewater treatment and value-added products production.

A win-win strategy by the integration of wastewater treatment with value-added products production through a vertical-algal-biofilm enhanced raceway was investigated in the present study. Raceway pond was enhanced by vertically setting the biofilm in the system with a certain interval distance that could be adjusted for different light conditions and wastewater types. Two types of synthetic wastewater were treated with suitability-proven materials as biofilm carriers under four operation distances. Composition of the harvested algal biomass was analyzed. Coral velvet with 5-8 mm length villus was the optimal carrier, since it was durable and with high biomass productivity (6.95-8.11 g m-2·day-1). Nutrients in the wastewaters were efficiently removed with the COD, TN and TP reduction of over 86.61%, 73.68% and 89.85%, respectively. Wastewater with the low nutrients concentration experienced lower biomass and lipid productivity but larger biodiesel productivity and higher nutrient removal efficiency. In addition, as the operation distance increased, wastewater treatment efficiency was first increased but then decreased, while algal biomass footprint production was decreased. Differences in nutrients removal efficiencies were mainly due to the distance difference, which caused different biofilm culture surface areas and light regimes. The optimal operation distance as a function of the efficient nutrient removal and biodiesel production in this study was 6 cm.

Operation of a vertical algal biofilm enhanced raceway pond for nutrient removal and microalgae-based byproducts production under different wastewater loadings.

In this study, a vertical-algal-biofilm-enhanced raceway pond (VAB-enhanced raceway pond) was designed and assessed for wastewater treatment and algal biomass production under different nutrient loading rates. Results indicated that the maximum removal capacity of the system was accordingly 7.52, 6.76 and 0.11 g·m-2·day-1 for COD, TN and TP, under which the wastewater effluent concentration could be respectively reduced from 106.00, 92.71 and 1.48 mg/L to 43.5, 11.03 and 0.46 mg/L in continuous mode. Meanwhile, about 7.47-10.10 t·ha-1·year-1 of lipid, 14.85-23.01 t·ha-1·year-1 of protein and 10.69-14.20 t·ha-1·year-1 of carbohydrate could be produced from the algae by the system in large scale. The corresponding estimated stoichiometric-methane-potential and biodiesel production of the harvested biomass was 21,471-29,136 m3·ha-1·year-1 and 0.57-1.15 t·ha-1·year-1, respectively. The findings of this study demonstrate the feasibility of using VAB-enhanced raceway pond for economically and cost-effectively recovery of nutrients from the wastewater via algal-based byproducts production.

Cultivation of algal biofilm using different lignocellulosic materials as carriers.

BACKGROUND: Algal biofilm technology is recently supposed to be a promising method to produce algal biomass as the feedstock for the production of biofuels. However, the carrier materials currently used to form algal biofilm are either difficult to be obtained at a low price or undurable. Commercialization of the biofilm technology for algal biomass production extremely requires new and inexpensive materials as biofilm carriers with high biomass production performances. RESULTS: Four types of lignocellulosic materials were investigated to evaluate their performance of acting as carriers for algal cells attachment and the relevant effects on the algal biomass production in this study. The cultivation of algal biofilm was processed in a self-designed flat plate photo-bioreactor. The biofilm production and chemical composition of the harvested biomass were determined. The surface physics properties of the materials were examined through a confocal laser-scanning microscopy. Algal biomass production varied significantly with the variation of the carriers (P < 0.05). All the lignocellulosic materials showed better performances in biofilm production than poly methyl methacrylate, and the application of pine sawdust as the carrier could gain the maximum biofilm productivity of 10.92 g m-2 day-1 after 16-day cultivation. In addition, 20.10-23.20% total lipid, 30.35-36.73% crude proteins, and 20.29-25.93% carbohydrate were achieved from the harvested biomasses. Biomass productivity increased linearly as the increase of surface roughness, and Wenzel's roughness factor of the tested materials, and surface roughness might significantly affect the biomass production through the size of surface morphology and the area of surface (P < 0.05). CONCLUSIONS: The results showed that lignocellulosic materials can be efficient carriers for low-cost cultivation of algal biofilm and the enhancement of biomass productivity.

Catalytic pyrolysis of tobacco rob: kinetic study and fuel gas produced.

The pyrolysis kinetics of tobacco rob (TR) was investigated using thermogravimetric analysis (TGA) under inert atmosphere, adding chemicals (dolomite and NiO) as catalysts by catalytic-mixing method. The TGA results showed that mass loss and mass loss rates were affected by catalysts. The conversion rates increased while the activation energy decreased. Moreover, the thermal decomposition behaviors of TR were studied in the fixed-bed reactor using dolomite and NiO/γ-Al2O3 as catalysts by catalyst-bed method. A series of experiments had been performed to explore the effects of catalysts, and reaction temperature on the composition and yield of fuel gas. The experiments demonstrated that the catalysts had a high activity of cracking tar and hydrocarbons, as well as yielding a high fuel gas production. For both methods, dolomite and NiO revealed better catalytic performance as a view of enhancing conversion rates and increasing product gas yield.