Algae have recently received growing attention given its prospects as a source of renewable energy and its potential for CO2 capture. Algae culture is of increasing value given that: (i) algae can be cultivated on non-agricultural land using wastewater, (ii) algae can provide a high yield on a per unit of light irradiated area, (iii) algae growth requires CO2 and nutrients that can be obtained from wastewater and fossil fuel combustion and (iv) algae contains high oil and starch making possible the production of high quality biodiesel. Thus, algae culture can contribute to CO2 fixation, wastewater treatment and can be a source of bioenergy. This article presents a critical review, focusing on various microalgae species that consume CO2 and nutrients from wastewater, and provide high quality biofuel. In this respect, a number of relevant topics are discussed in this review: (a) the media for algae culture, (b) the photobioreactor, (c) the associated wastewater treatment processes, (d) the CO2 capture mechanism and (e) microalgal harvesting. This review also considers various aspects of the biomass processing such as (a) lipid extraction, (b) thermodynamics of the produced biomass conversion, (c) biomass gasification, (d) biodiesel production, (e) catalysts, (f) reaction pathways/mechanisms and (g) reaction kinetics.

Integrated CO2 capture, wastewater treatment and biofuel production by microalgae culturing—A review

Development of suitable photobioreactors for CO2 sequestration addressing global warming using green algae and cyanobacteria.

Microalgae metabolites: A rich source for food and medicine

Microalgal species are recently in the spotlight for biofuels production like biodiesel, bioethanol and biohydrogen. Algae are also used as a biofertiliser, source of nutrient and for controlling pollution. Algae being a photosynthetic organism are produced in the photo bioreactors. Hence the design and development of photobioreactors for maximum production of algae is very important. Apart from maximum production, other factors such as design, cost effectiveness of the bioreactor, purity of the algae produced, user friendly, low maintenance and space convenience need to be optimized. The bioreactors which are used for the purpose of growing algae are bubble column photobioreactor, airlift photo bioreactor, flat panel bioreactor, horizontal tubular photobioreactor, stirred tank photobioreactor etc. These bioreactors have their own advantages and disadvantages. Work is on for developing hybrid type of bioreactors which may overcome the limitations of the developed photobioreactors. This paper covers the salient features, limitations of developed photobioreactors and recent developments in the field of photobioreactors.

Development of suitable photobioreactor for algae production – A review

Global warming caused by anthropogenic CO2 emission has been one of the most important issues in the fields of science, environment and even international economics and politics. To control and reduce CO2 emissions, intensive carbon dioxide capture and storage (CCS) technologies have been comprehensively developed for sequestration of CO2 especially from combustion flue gas. Microalgae-based CO2 biological fixation is regarded as a potential way to not only reduce CO2 emission but also achieve energy utilization of microalgal biomass. However, in this approach culture process of microalgae plays an important role as it is directly related to the mechanism of microalgal-CO2 fixation and characteristics of microalgal biomass production. The aim of this work is to present a state-of-the-art review on the process effect, especially on the effects of photobiochemical process, microalgal species, physicochemical process and hydrodynamic process on the performance of microalgal-CO2 fixation and biomass production. Also, the perspectives are proposed in order to provide a positive reference on developing its fundamental research and key technology.

Process effect of microalgal-carbon dioxide fixation and biomass production: A review

Acceleration-stat (A-stat) cultivations in which the dilution rate is continuously changed at a constant acceleration rate, leading to different average light intensities inside the photobioreactor, can supply more information and reduce experimental time compared with chemostat cultivations. The A-stat was used to optimize the biomass and product yield of continuous cultures of the microalgae D. tertiolecta in a flat-panel reactor. In this study, four different accelerations were studied, a pseudo steady state was maintained at acceleration rates of 0.00016 and 0.00029 h-2 and results were similar to those of the chemostat. An increase in the acceleration rate led to an increase in the deviation between results obtained in the A-stat and in the chemostats. We concluded that it is advantageous to use the A-stat instead of chemostats to determine culture characteristics and optimize a specific photobioreactor. The effect of average light intensity inside the photobioreactor on the production of vitamins C and E, lutein, and β-carotene was studied using the A-stat. The highest concentrations of these products were 3.48 ± 0.46, 0.33 ± 0.06, 5.65 ± 0.24, and 2.36 ± 0.38 mg g-1 respectively. These results were obtained at different average light intensities, showing the importance of optimizing each product on light intensity. © 2004 Wiley Periodicals, Inc.

Jan Willem Zijffers

Papers

Optimization of biomass, vitamins, and carotenoid yield on light energy in a flat-panel reactor using the A-stat technique.