Oil Algae Extraction of Selected Microalgae Species Grown in Monoculture and Mixed Cultures for Biodiesel Production

Microalgae is an attractive feedstock for sustainable biodiesel production. The harvesting step of microalgae needs technology, which saves energy and time. One of the low cost strategies for addressing this problem is the use of flocculation-sedimentation process as an initial step. The aim of the present study is to evaluate the flocculation-sedimentation of selected microalgae species grown in monoculture (Nannochloropsis sp.) and mixed cultures (South Coast of Yogyakarta) using modified chitosan. The effect of flocculant dosage and sedimentation time that might affect the percentage of microalgae cell removal was investigated. Chitosan has proved to be highly effective for dewatering of the microalgae, Nannochloropsis sp. and Yogyakarta mixed cultures, with the optimum flocculation efficiency reaching over 72.09 % (25 ppm of chitosan dosage; 10 min of sedimentation time) and 87.25 % (25 ppm of chitosan dosage; 30 min of sedimentation time) of biomass removal. The characteristics of chitosan in term of high positive charge density and long chains allow the microalgae to aggregate to form flocs and settle to the bottom due to gravitational effect.

Chitosan Flocculation-sedimentation for Harvesting Selected Microalgae Species Grown in Monoculture and Mixed Cultures

Abstrac t -  The production of microalgae biodiesel is one solution to solve the energy problem in the future, especially in the transportation sector. Some advantages of the development of the production of biodiesel from microalgae is high productivity, food security friendly and  global warming problem-solving . The main problem in the production of microalgae biodiesel is the high production cost due to the high cost of lipid extraction. Several studies have been conducted to find a low cost extraction process. In this research, the Nannochloropsis sp. microalgae lipid extraction utilizing hydrodynamic cavitation has been studied. Effects of the concentration of solids, specific energy and time on the extraction have been examined. The study was conducted in a batch with a combined solvent of methanol and hexane. The influence of specific energy given at the same level of cavitation of increasing specific energy would increase the yield where it would be higher at the beginning and remain stable at the end of the process. At the same specific energy and  level of cavitation, the value of concentration that provides the lowest extraction energy requirement was 0.105 g/g. The optimum of cavitation levels for the same specific energy and  concentration at the value of cavitation number was 0.126. The optimum temperature for the extraction process was 42°C. The  lowest extraction energy requirement was 16.743 MJ/kg lipid.

https://www.ijrer.ijrer.org/index.php/ijrer/article/download/6887/pdf

Optimum Extraction of Algae-oil from Microalgae using Hydrodynamic Cavitation

Abstract Microalgae have been considered as a potential candidate for biodiesel feedstock. Single-stage simultaneous extraction–transesterification process is proposed for simpler and more effective biodiesel conversion. In this study, the experiment of biodiesel production from microalgae Spirulina sp. was performed in a batch-stirred reactor using palm oil as a co-solvent of methanol and catalyzed by potassium hydroxide at a percentage of 1 wt% (w/w of palm oil). The effects of methanol–palm oil molar ratio, palm oil–microalgae weight ratio, and temperature on biodiesel yield were investigated. The results showed that the best biodiesel yield was 85.28% (99.01% of partial biodiesel yield from palm oil and 16.69% of partial biodiesel yield from dry microalgae), obtained at a methanol–palm oil molar ratio of 10:1, a palm oil–microalgae weight ratio of 5:1, and at a temperature of 60°C. Upon comparison, the overall yield increased by 34.59% (37.73% of partial biodiesel yield from palm oil and 13.00% of partial biodiesel yield from dry microalgae) than that of the two-stage (conventional) method. Single-stage simultaneous extraction–transesterification process also reduced the number of unsaturated fatty acid components in biodiesel that will lower the biodiesel quality.

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Advancing biodiesel production from microalgae Spirulina sp. by a simultaneous extraction–transesterification process using palm oil as a co-solvent of methanol

The increasing use of fossil fuels causes the depletion in supply and contributes to climate change by GHG emissions into the atmosphere. Microalgae indicate as renewable and sustainable energy sources as they have a high potential for producing large amounts of biomass for third-generation biofuels (bioethanol and biodiesel) feedstock. However, there are several parameters which should be considered for microalgae cultivation, such as environmental conditions, medium composition and microalgae species. The aim of this research was to study cultivation of mixed microalgae cultures (Glagah consortium and Arthrospira maxima) in a thin layer photobioreactor. Farmpion medium, Bold's Basal Medium (BBM) and Thoriq Eko Arief (TEA) medium were investigated as cultivation medium for bioethanol feedstock for 7 days. The results showed that the highest dry weight concentration of microalgae was in Farmpion medium (0.35 mg/ml) and the highest carbohydrate concentration of microalgae was in BBM (0.14 mg/ml). Thus, the optimum medium of microalgae cultivation for bioethanol feedstock was BBM because of the highest carbohydrate-dry weight ratio (0.88). In addition, mathematical approach by using Contois model was used to find out the growth rate of microalgae cultivation in each medium.

https://iopscience.iop.org/article/10.1088/1742-6596/1022/1/012051/pdf

Study of cultivation and growth rate kinetic for mixed cultures of local microalgae as third generation (G-3) bioethanol feedstock in thin layer photobioreactor

Nowadays, energy is one of human basic needs. As the human population increased, energy consumption also increased. This condition causes energy depletion. In case of the situation, alternative energy is needed to replace existing energy. Microalgae is chosen to become one of renewable energy resource, especially biodiesel, because it contains high amount of lipid instead of other feedstock which usually used. Fortunately, Indonesia has large area of water and high intensity of sunlight so microalgae cultivation becomes easier. Nannochloropsis sp., one of microalgae species, becomes the main focus because of its high lipid content. Many ways to break the cell wall of microalgae so the lipid content inside the microalgae will be released, for example conventional extraction, ultrasonic wave extraction, pressing, and electrical method. The most effective way for extraction is electrical method such as pulsed electric field method (PEF). The principal work of this method is by draining the electrical current into parallel plate. Parallel plate will generate the electrical field to break microalgae cell wall and the lipid will be released. The aim of this work is to evaluate two-stage procedure for extraction of useful components from microalgae Nannochloropsis sp. The first stage of this procedure includes pre-treatment of microalgae by ethanol solvent extraction and the second stage applies the PEF extraction using a binary mixture of water and ethanol solvent. Ethanol is chosen as solvent because it’s safer to be used and easier to be handled than other solvent. Some variables that used to study the most effective operation conditions are frequency and duty cycle for microalgae. The optimum condition based on this research are at frequency 1 Hz and duty cycle 13%.

Perwitasari Yekti Mumpuni

Papers

Combination pulsed electric field with ethanol solvent for Nannochloropsis sp. extraction