Manjinder Singh

An efficient system for carbonation of high-rate algae pond water to enhance CO2 mass transfer

High-rate algal ponds have the potential to produce 59 T of dry biomass ha(-1)year(-1) based on the specific productivity of 20 g m(-2) day(-1). Atmospheric air provides only 5% of the CO(2) to the pond surface required for photosynthesis. Hence, CO(2) is usually provided via bubbling of concentrated CO(2)-air mixture into the algae ponds. This process is, however, not significantly effective in terms of mass transfer. Use of bubble column to increase the interfacial area of contact available for gas exchange is proposed as an efficient alternative. A carbonation column (CC) was modeled and designed to measure CO(2) absorptivity in-pond water at various pH regimes. The CC performed at 83% CO(2) transfer efficiency. An air-to-pond mass transport coefficient of 0.0037 m min(-1) was derived. The proposed device can be used with any exhaust gas stream with higher concentrations of CO(2) in conjunction with raceways for optimizing algae production.

Microalgal system for treatment of effluent from poultry litter anaerobic digestion

The potential of mixotrophic microalgae to utilize poultry litter anaerobic digester (AD) effluent (PLDE) as nutritional growth medium was evaluated. Three algal strains viz. Chlorella minutissima, Chlorella sorokiniana and Scenedesmus bijuga and their consortium showed significant biomass productivity in 6% (v/v) concentration of PLDE in deionized water. Multiple booster dosage of PLDE supported better growth relative to a single dose PLDE. The maximum biomass productivity of 76 mg L(-1) d(-1) was recorded. The biomass was rich in protein (39% w/w) and carbohydrates (22%) while lipids (<10%) were low, making it most suitable as an animal feed supplement. The mixotrophic algae showed sustainable growth against variations in PLDE composition in different AD batches, thus proving to be a suitable candidate for large scale wastewater treatment with concomitant production of renewable biomass feedstock for animal feed and bioenergy applications.

Effect of cell rupturing methods on the drying characteristics and lipid compositions of microalgae.

This paper investigated the effect of cell rupturing methods on the drying characteristics and the lipid compositions of a green algae consortium grown in an open raceway pond. The ruptured microalgae samples obtained from French press, autoclave and sonication methods were used for conducting thin layer drying experiment at four drying temperatures (30, 50, 70 and 90 °C). The rate of moisture removal at each drying condition was recorded until no change in moisture loss. A typical drying curve for a microalgae consortium indicated that the rate of drying was limited by diffusion. Among three drying models (Newton, Page and Henderson-Pabis) used to fit the drying data, Page model fitted well on the experimental drying data with a coefficient of determination (R(2)) of 0.99. Solvent extraction of French press ruptured cells produced the highest total lipid yield with no significant change in lipid compositions.

Low Cost Nutrients for Algae Cultivation

Microalgae are aquatic microorganisms growing phototrophically using sunlight and inorganic nutrients viz. carbon, nitrogen, phosphorus and other micronutrients. Sustainable production of microalgae biomass as feedstock for renewable biofuels is facing important bottlenecks in nutrient and water requirements that may hinder commercial scale development of algal systems. Fertilizer nutrients and fresh water contribute up to 50 % of the total biomass production cost that eventually impact the economical feasibility of algal fuels. In the algae-biofuels industry, nutrients must be found in lower-value sources like wastewaters and other waste streams and for sustainable production, those nutrients be recycled within the system. Integration of algal wastewater treatment with biofuel production has been strongly promoted recently. Utilizing nutrient rich wastewaters and animal wastes like poultry litter can greatly reduce the water and fertilizer demands for alga culture. Additionally, producing algal feedstock from low-cost waste based nutrient media has multiple benefits including improved water quality, N and P recycling from animal waste, reduced environmental footprints, and economic efficiency. This approach appears very attractive, since the impacts of releasing N and P and greenhouse gases into the environment could be mitigated, while conserving nutrients and simultaneously producing a material that can replace crude oil as a fuel feedstock.

Optimization of Protein Extraction from Spirulina platensis to Generate a Potential Co-Product and a Biofuel Feedstock with Reduced Nitrogen Content

The current work reports protein extraction from Spirulina platensis cyanobacterial biomass in order to simultaneously generate a potential co-product and a biofuel feedstock with reduced nitrogen content. S. platensis cells were subjected to cell disruption by high pressure homogenization and subsequent protein isolation by solubilisation at alkaline pH followed by precipitation at acidic pH. Response surface methodology (RSM) was used to optimize the process parameters - pH, extraction (solubilisation/precipitation) time and biomass concentration for obtaining maximum protein yield. The optimized process conditions were found to be pH 11.38, solubilisation time of 35 min and biomass concentration of 3.6 % (w/w) solids for the solubilisation step, and pH 4.01 and precipitation time of 60 min for the precipitation step. At the optimized conditions, a high protein yield of 60.7 % (w/w) was obtained. The protein isolate (co-product) had a higher protein content (80.6 % (w/w)), lower ash (1.9 % (w/w)) and mineral content and was enriched in essential amino acids, the nutritious γ-lenolenic acid and other high-value unsaturated fatty acids compared to the original biomass. The residual biomass obtained after protein extraction had lower nitrogen content and higher total non-protein content than the original biomass. The loss of about 50 % of the total lipids from this fraction did not impact its composition significantly owing to the low lipid content of S.platensis (8.03 %).