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The latest research shows that algal biofuels, at the production levels mandated in the Energy Independence and Security Act of 2007, will place significant demands on water and compete with agriculture meant for food production. Thus, there is a great need to recycle water while producing algal biofuels. This study shows that when using a syntheti...
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... total of three quality control groups using Nannochloropis oceanica (for which the composition is known) were measured alongside each of these measurements to test the accuracy of each of the methods. Table 1 shows that on average 82% of the water was recovered after each growth cycle during the first water recycling experiment (WR1). Water was lost due to evaporation, sampling, and in the pelleted biomass. ...
Citations
Microalgae hold great promise as environmentally sustainable sources of food, animal feed, and fuel. However, large amounts of water are used during microalgae cultivation and this negatively impacts economic viability and environmental sustainability. Reusing cultivation water can reduce the direct impacts of water usage and also reduce nutrient requirements and algal wastewater treatment. However, studies have shown that algae growth in reused water can be compromised, unaffected, or sometimes enhanced compared to controls. This review examines recent studies on water reuse to qualitatively understand these varied effects. Growth inhibitors and stimulators in reused water and their underlying mechanisms are discussed, as well as recent pre-treatment technologies and factors affecting the quality of reused water, such as microalgae taxa, culture conditions, and harvesting methods, are considered. A scheme is proposed for water reuse and harvesting methods based on the desired algal end products. Taking these findings together, here we provide recommendations for further research directions as well as new insights into designing and integrating a cultivation strategy with a harvesting platform to reuse water for more efficient microalgae cultivation.
Microalgae are promising eco-friendly source of food, feed, biofuels, and
chemicals. There has been substantial progress at the lab and industrial scales to
develop efficient and sustainable microalgae culturing techniques. However, several
constraints must be addressed to make the overall process economically viable.
Chemo-genetics elements can play a pivotal role in achieving the commercial
goals because microalgae grow more efficiently in high concentrations of essential
nutrients like nitrogen, phosphorus, and carbon in addition to enhance by-product
formation. Moreover, alteration in culturing conditions also activates lipid accumulation.
Recent strategies have combined these approaches to enhance lipid accumulation
and along with enhanced biomass productivity. It is necessary to optimize
inoculum production and culture management to avoid contamination, especially at
commercial scales. Furthermore, prevailing outdoor conditions of rainfall, variable
temperature, and irradiation, which are entirely different from small lab-scale facilities,
pose additional challenges during outdoor cultivation. This chapter highlights
the nutritional requirements of culturing media and their impact along with possible
challenges on microalgae cultivation to ensure the stable and high productivities of
large-scale cultures. Media recycling not only reduces the dependency on freshwater
but also increases the economic viability of the process. Recent advances regarding
media recycling and strategies to control biological contaminants are also discussed.
Current high costs of commercial-scale algal biofuel production prevent the widespread use of this renewable fuel source. One cost-saving approach is the reuse of algae cultivation water after biomass harvesting, which reduces water pumping and treatment costs. However, dissolved compounds, cell debris, and microorganisms remaining in the water could affect subsequent algae generations. Previous studies demonstrate a variety of effects of recycled medium on algae growth, yet their results have not been collectively analyzed. Here we integrate data across 86 studies to determine the relative importance of different factors influencing algae growth in recycled medium. We found that algae taxa can have the greatest influence, while the harvesting method is less influential on growth outcomes. This meta-analysis identifies favorable taxa and thus provides a tool for algae cultivation decision-making when medium reuse is an important driver. Results can also aid in estimating relative algae yield and growth rates for technoeconomic assessments that incorporate water recycling.
