Chandra S. Theegala

Harvesting economics and strategies using centrifugation for cost effective separation of microalgae cells for biodiesel applications.

Inefficient or energy-intensive microalgal harvesting strategies for biodiesel production have been a major setback in the microalgae industry. Harvesting by centrifugation is generally characterized by high capture efficiency (>90%) under low flow rates and high energy consumption. However, results from the present study demonstrated that by increasing the flow rates (>1L/min), the lower capture efficiencies (<90%) can be offset by the larger volumes of culture water processed through the centrifuge, resulting in net lower energy consumption. Energy consumption was reduced by 82% when only 28.5% of the incoming algal biomass was harvested at a rate of 18 L/min by centrifugation. Harvesting algal species with a high lipid content and high culture density could see harvesting costs of

Hydrothermal liquefaction of separated dairy manure for production of bio-oils with simultaneous waste treatment.

0.864/L oil using the low efficiency/high flow rate centrifugation strategy as opposed to

Millifluidics for Time-resolved Mapping of the Growth of Gold Nanostructures

4.52/L oil using numbers provided by the Department of Energy for centrifugation harvesting.

Optimizing a continuous flow lipid extraction system (CFLES) used for extracting microalgal lipids

A bench scale hydrothermal liquefaction (HTL) system was tested using dairy manure to explore biooil production and waste treatment potential. Carbon monoxide was used as the process gas and sodium carbonate (Na(2)CO(3)) as catalyst. At a 350°C process temperature, the HTL unit produced 3.45 g (± 0.21) of acetone soluble oil fractions (ASF), with an average Higher Heating Value of 32.16 (± 0.23) MJ kg(-1). A maximum ASF yield of 4.8 g was produced at a process temperature of 350°C and 1g of catalyst. The best ASF yield corresponded to 67.6% of energy contained in the raw manure. GC-MS analysis of ASF indicated that the highest quantities of phenolic compounds were formed when 1g catalyst was used. Chemical Oxygen Demand (COD) reduction in the dischargeable slurry was as high as 75%. The results point to an alternative dairy waste treatment technology with a potential to generate transportable biooils.

Metals Determination in Biodiesel (B100) by ICP-OES with Microwave Assisted Acid Digestion~!2010-01-27~!2010-03-25~!2010-04-22~!

Innovative in situ characterization tools are essential for understanding the reaction mechanisms leading to the growth of nanoscale materials. Though techniques, such as in situ transmission X-ray microscopy, fast single-particle spectroscopy, small-angle X-ray scattering, etc., are currently being developed, these tools are complex, not easily accessible, and do not necessarily provide the temporal resolution required to follow the formation of nanomaterials in real time. Here, we demonstrate for the first time the utility of a simple millifluidic chip for an in situ real time analysis of morphology and dimension-controlled growth of gold nano- and microstructures with a time resolution of 5 ms. The structures formed were characterized using synchrotron radiation-based in situ X-ray absorption spectroscopy, 3-D X-ray tomography, and high-resolution electron microscopy. These gold nanostructures were found to be catalytically active for conversion of 4-nitrophenol into 4-aminophenol, providing an example of the potential opportunities for time-resolved analysis of catalytic reactions. While the investigations reported here are focused on gold nanostructures, the technique can be applied to analyze the time-resolved growth of other types of nanostructured metals and metal oxides. With the ability to probe at least a 10-fold higher concentrations, in comparison with traditional microfluidics, the tool has potential to revolutionize a broad range of fields from catalysis, molecular analysis, biodefense, and molecular biology.

Reducing electrocoagulation harvesting costs for practical microalgal biodiesel production

A laboratory‐made continuous flow lipid extraction system (CFLES) was devised to extract lipids from microalgae Nannochloropsis sp., a potential feedstock for biodiesel fuel, with a focus to assess the workable temperatures and pressures for future industrial applications. Using conventional solvents, the CFLES recovered 100% of the lipids extracted with conventional Soxhlet extraction. The optimum temperature and pressure were found to be 100 °C and 50 psi, respectively; conditions significantly lower than those normally used in pressurized liquid extractions requiring specialized equipment. Approximately 87% of the extracted oil was successfully transesterified into biodiesel fuel (fatty acid methyl esters). Preliminary calculations based on the tested lab‐scale system indicated savings in energy, solvent consumption, and extraction time as 96%, 80%, and more than 90%, respectively, as compared to Soxhlet extraction. However, the true cost savings can only be assessed at scaled up level. Energy efficiency of CFLES was calculated as 48.9%. Residual water (~70%) in the biomass had no effect on the extraction performance of CFLES, which is expected to help the process economics at scaled up application. The effect of temperature and pressure on the fatty acids profile of Nannochloropsis sp. is also discussed. Based on the existing literature, the authors believe that a pressurized liquid extraction system with continuous solvent flow has not been reported for lipid extraction from Nannochloropsis sp.

Anaerobic biodegradation of polyhydroxybutyrate in municipal sewage sludge.

Elemental composition of biodiesel is required for product quality-control, auto-engine life, emissions control, and researching appropriate additives. The use of microwave assisted acid digestion reaction system to prepare neat biodiesel (B100) samples in an aqueous medium for simultaneous inductively coupled plasma optical emission spectrometer (ICP-OES) analyses is reported. Biodiesel produced by transesterification reaction was subjected to the test method using calibration standards prepared in an aqueous medium. Significant correlation for the spiked B100 samples, instrument detection limits, accuracy, and precision data showed that elemental concentrations can easily be determined within the specified limits. The method avoids switching any of the ICP-OES accessories required for high organic loads. This method is most appropriately devised for biodiesel analysis than petrochemicals analysis. A consistent quality assurance program is necessary to avoid performance issues in vehicle engines and to ensure sustainable growth of biodiesel production. Inorganic constituents in the final product can promote residue build up in the engine, cause corrosion and ultimately affect engine life. Elements introduced during production process (Na, K, Ca, and Mg) are of particular concern, while other elements present in the feedstock (P, S, and Zn), or used as additives (Si, Mn, Cr, Fe, and Ni) require monitoring in order to avoid undesirable combustion products in the engines (6). Since metallic elements in fuel are undesirable even at lower concentrations, their determination in fuel is necessary to evaluate fuel quality, to see their effect on auto engines, and to control environmental pollution.

Lab-on-a-chip devices for gold nanoparticle synthesis and their role as a catalyst support for continuous flow catalysis

Electrocoagulation has shown potential to be a primary microalgae harvesting technique for biodiesel production. However, methods to reduce energy and electrode costs are still necessary for practical application. Electrocoagulation tests were conducted on Nannochloris sp. and Dunaliella sp. using perforated aluminium and iron electrodes under various charge densities. Aluminium electrodes were shown to be more efficient than iron electrodes when harvesting both algal species. Despite the lower harvesting efficiency, however, the iron electrodes were more energy and cost efficient. Operational costs of less than

Algal Cell Disruption and Lipid Extraction: A Review on Current Technologies and Limitations

0.03/L oil were achieved when harvesting Nannochloris sp. with iron electrodes at 35% harvest efficiency, whereas aluminium electrodes cost

Toxicity and biouptake of lead and arsenic by Daphnia pulex

0.75/L oil with 42% harvesting efficiency. Increasing the harvesting efficiencies for both aluminium and iron electrodes also increased the overall cost per litre of oil, therefore lower harvesting efficiencies with lower energy inputs was recommended. Also, increasing the culturing salinity to 2 ppt sodium chloride for freshwater Nannochloris sp. was determined practical to improve the electrocoagulation energy efficiency despite a 25% reduction in cell growth.