Navid R. Moheimani

Sustainable biofuels from algae

There is currently great interest in microalgae as sources of renewable energy and biofuels. Many algae species have a high lipid content and can be grown on non-arable land using alternate water sources such as seawater. This paper discusses in detail the issue of sustainability of commercial-scale microalgae production of biofuels with particular focus on land, water, nutrients (N and P) and CO2 requirements and highlights some of the key issues in the very large scale culture of microalgae which is required for biofuels. The use of genetically modified algae is also considered.

The long-term culture of the coccolithophore Pleurochrysis carterae (Haptophyta) in outdoor raceway ponds

The calcareous marine haptophyte algae, the coccolithophorids, are of global environmental significance because of the impact of their blooms on the carbon cycle. The coccolithophorid, Pleurochrysis carterae was grown semi-continuously in paddlewheel-driven outdoor raceway ponds over a period of 13 months in Perth, Western Australia. The mean total dry weight productivity of P. carterae was 0.19 g.L−1.d−1 with cell lipid and CaCO3 contents of up to 33% and 10% of dry weight respectively, equivalent to an annual total biomass productivity of about 60 t.ha−1.y−1 and 21.9 t.ha−1.y−1 total lipid and 5.5 t.ha−1.y−1 total calcium carbonate production. Throughout the culture period there was little protozoan contamination or contamination by other algae. The pH of the growth medium increased to pH 11 during the day and was found to be a useful variable for monitoring the state of the culture. A comparison of the growth of P. carterae and Dunaliella salina in the raceway ponds showed no significant differences between these two species with regard to areal total dry weight productivity and lipid content.

Algae for biofuels and energy

Microalgae are one of the most studied potential sources of biofuels and bioenergy. This book covers the key steps in the production of renewable biofuels from microalgae - strain selection, culture systems, inorganic carbon utilisation, lipid metabolism and quality, hydrogen production, genetic engineering, biomass harvesting, extraction. Greenhouse gas and techno-economic modelling are reviewed as is the 100 year history of microalgae as sources of biofuels and of commercial-scale microalgae culture. A summary of relevant basic standard methods used in the study of microalgae culture is provided. The book is intended for the expert and those starting work in the field.​

Production of biofuels from microalgae

The production of biofuels from microalgae, especially biodiesel, has become a topic of great interest in recent years. However, many of the published papers do not consider the question of scale up and the feasibility of the various processes to be operated at the very large scale required if algal biofuels are to make a meaningful contribution to renewable fuels. All the steps in the process must also be very low cost. This paper discusses the unit processes required for algal biofuels production (i.e., growing the algae, harvesting, dewatering, extraction and conversion to biofuel) and their scalability. In many cases, especially in the lipid extraction step, little is known as yet as to the scalability and economic feasibility of the various processes proposed. We also highlight the key engineering and biological issues which must be resolved for the production of biofuels from microalgae to become an economic reality.

Potential use of algae for heavy metal bioremediation, a critical review

Algae have several industrial applications that can lower the cost of biofuel co-production. Among these co-production applications, environmental and wastewater bioremediation are increasingly important. Heavy metal pollution and its implications for public health and the environment have led to increased interest in developing environmental biotechnology approaches. We review the potential for algal biosorption and/or neutralization of the toxic effects of heavy metal ions, primarily focusing on their cellular structure, pretreatment, modification, as well as potential application of genetic engineering in biosorption performance. We evaluate pretreatment, immobilization, and factors affecting biosorption capacity, such as initial metal ion concentration, biomass concentration, initial pH, time, temperature, and interference of multi metal ions and introduce molecular tools to develop engineered algal strains with higher biosorption capacity and selectivity. We conclude that consideration of these parameters can lead to the development of low-cost micro and macroalgae cultivation with high bioremediation potential.

Standard Methods for Measuring Growth of Algae and Their Composition

The purpose of this chapter is to present a summary of techniques for measuring growth and analysing chemical composition of microalgae. There are perhaps as many methods and modifications to these methods as there are active phycologists today. Investigators generally employ their own particular adapted methodology. Here, we have attempted to include in this chapter those methods generally employed by several investigators, as well as having general applicability to different laboratories. Among the major methods discussed here are: cell counting, measuring growth techniques and biochemical compositions (lipid, carbohydrates and protein). The audience for whom this chapter is intended is diverse and includes junior to experienced phycologist and/or non-phycologists.

Open Pond Culture Systems

Open pond culture systems are the main type of culture system used in the commercial-scale culture of microalgae and because of their relatively low cost are the systems most likely to be used for the production of microalgae for biofuels. These ‘open’ systems can be broadly classified as shallow lagoons and ponds, inclined (cascade) systems, circular central-pivot ponds, simple mixed ponds, and ‘raceway’ ponds. The raceway ponds are by far the most commonly used. This Chapter describes these systems in detail as well as their advantages and disadvantages. The management of such systems to achieve reliable, long-term, high-productivity cultures is a challenge, especially on the large scale and the various options and strategies available are reviewed as are options for maximizing algae productivity.

Coccolithophorid algae culture in closed photobioreactors

The feasibility of growth, calcium carbonate and lipid production of the coccolithophorid algae (Prymnesiophyceae), Pleurochrysis carterae, Emiliania huxleyi, and Gephyrocapsa oceanica, was investigated in plate, carboy, airlift, and tubular photobioreactors. The plate photobioreactor was the most promising closed cultivation system. All species could be grown in the carboy photobioreactor. However, P. carterae was the only species which grew in an airlift photobioreactor. Despite several attempts to grow these coccolithophorid species in the tubular photobioreactor (Biocoil), including modification of the airlift and sparger design, no net growth could be achieved. The shear produced by turbulence and bubble effects are the most likely reasons for this failure to grow in the Biocoil. The highest total dry weight, lipid and calcium carbonate productivities achieved by P. carterae in the plate photobioreactors were 0.54, 0.12, and 0.06 g L−1 day−1 respectively. Irrespective of the type of photobioreactor, the productivities were P. carterae > E. huxleyi > G. oceanica. Pleurochrysis carterae lipid (20–25% of dry weight) and calcium carbonate (11–12% of dry weight) contents were also the highest of all species tested. Biotechnol. Bioeng. 2011;108:2078–2087.

Techno-economic assessment of CO2 bio-fixation using microalgae in connection with three different state-of-the-art power plants

Large-scale microalgae cultivations for CO2 bio-sequestration from power plants can be an alternative process to conventional technologies if the capital investments associated with carbon capture, transport and storage can be reduced or avoided. In order to counterbalance the costs required to operate massive microalgae cultivations, it is necessary to create additional revenues through biomass sales. This manuscript examines the techno-economics of microalgae cultivations for the integration with three power plant technologies using an artificial neural network model. The economics are estimated using the net present value approach. The assessment is carried out at photosynthesis efficiencies ranging from 2% to 6%. The sensitivity assessment shows microalgae selling prices in the range of

Sustainable cultivation of microalgae by an insulated glazed glass plate photobioreactor

440–1028/t at a photosynthetic efficiency of 4% for low and high cost scenarios in order to achieve an electricity price similar to that from a conventional power plant without a CO2 capture and storage.