Microalgae harvesting and processing: a literature review

Abstract

This report is a literature review on microalgal harvesting and processing submitted as partial fulfillment of subcontract XK-3-03031-01. The work was performed under subcontract to SERI with funds provided by the Biomass Energy Technology Division of the U.S. Department of Energy.~t

Microbial Biodiesel Production - Oil Feedstocks Produced from Microbial Cell Cultivations

“…How to harvest microalgae cells is dependent on the characteristics of the microalgae, such as size and density (Olaizola 2003). All of the available harvest approaches, which include flocculation, flotation, centrifugal sedimentation, and filtration, have limitations for effective, cost-efficient production of biofuel (Shelef, Sukenik et al 1984). For instance, flotation methods, based on the trapping of algae cells using dispersed micro-air bubbles, is www.intechopen.com very limited in its technical and economic viability.…”

Paving the Road to Algal Biofuels with the Development of a Genetic Infrastructure

“…Not only do microalgae fully address each of the disadvantages of land-based biofuel crops, but they also are amenable to genetic engineering for the enhanced biosynthesis of a wide range of advanced biofuels and high-value added products. Currently, three fundamental objectives remain critical to the implementation of economically-and technologically-feasible algal biofuel production: [1] increase of biological productivity through species selection and genetic engineering as well as optimization of culture conditions; [2] development of low-cost vessels for cultivation, whether they be closed photobioreactors or open pond systems; and [3] improvement of inexpensive downstream processing techniques for algal biomass, including harvesting, dewatering, and extraction of biofuel metabolites (Hejazi et al, 2004a;Shelef et al, 1984;Danquah et al, 2009). As with many novel sources of bioenergy, the complexity of the microalgal biofuel production process calls for a multidisciplinary approach in which biotechnological progress will be accompanied by advances in process engineering.…”

Advantages and Challenges of Microalgae as a Source of Oil for Biodiesel

“…Algal lipids must be separated from the rest of the biomass (carbohydrates, proteins, nucleic acids, pigments) and water. Common harvesting methods generally produce a slurry or paste containing between 5 and 25% solids (Shelef et al, 1984). Removing the rest of the water is thought to be one of the most expensive steps with literature values ranging from 20 to 75% of the total processing cost (Uduman et al, 2010, Molina Grima et al, 2003.…”

“…Removing the rest of the water is thought to be one of the most expensive steps with literature values ranging from 20 to 75% of the total processing cost (Uduman et al, 2010, Molina Grima et al, 2003. Shelef et al (1984) highlight a number of possible techniques for drying biomass: flash drying, rotary driers, toroidal driers, spray drying, freeze-drying and sun drying. Because of the high water content, sun-drying is not an effective method and spray-drying is not economically feasible for low value products (Mata et al, 2010).…”