Microalgae: the next best alternative to fossil fuels after biomass. A review

Abstract

It is expected that 84% of the global energy demands will be met through fossil fuels in 2030 due to increasing energy needs. However, due to their impact on the environment through the emission of anthropogenic green house gases, biofuels were introduced as alternative sources of energy. Biofuels of plant origin for the transport sector proved to be controversial due to competition for food production, fertile land and expensive production processes. As a secondary alternative, microalgae such as Scenedesmus obliquus, Chlorella vulgaris and Nannochloropsis sp. were found to be suitable candidates for liquid biofuels production. This review describes the production of transportation liquid biofuels from plant biomass and microalgae. Information is provided on how the controversies related to plant biomass lead to the use of algal biomass. The production processes involved in both generations are discussed and highlighted. Furthermore, details on the production of secondary products such as pigments, feed additives and valuable secondary metabolites are also provided.

Utilization of Biomass Derived from Cyanobacteria-Based Agro-Industrial Wastewater Treatment and Raisin Residue Extract for Bioethanol Production

“…The agro-industrial sector generates considerable amounts of wastewater, most of which are rich with inorganic and organic pollutants [46,47]. Using these pollutants as nutrient material for a microalgae-based cultivation system may minimize their discharge into the natural environment and further reduce a CO2 footprint by utilizing the resulting biomass in energy production processes [2]. Due to the large amounts of carbohydrates contained in their cells, using microalgal/cyanobacterial biomass as feedstock for bioethanol production appears a very promising solution [3,30].…”

“…However, the use of biomass obtained from solid agricultural wastes increases fuel production cost due to its high lignin content that affects the saccharification process [1]. In contrast, many photosynthetic microorganisms (microalgae and cyanobacteria) have high a content of starch and cellulose and therefore constitute excellent substrates for bioethanol production [2][3][4] (Table 1). Microalgae including different phyla such as Chlorophyta (green algae), Rhodophyta (red algae), Heterokontophyta and Cyanophyta (blue green algae, cyanobacteria) are gaining wide attention as alternative renewable sources of biomass as they offer a number of potential advantages compared to plants [5][6][7].…”

Photobioreactor for Microalgae-Based Wastewater Treatment

“…This can be done in methane tanks together with excess activated sludge. Biomass can also be processed into liquid motor biofuels of the third generation, or into phosphate and nitrate fertilizers [11][12][13][14].…”

A practical tool for selecting microalgal species for biodiesel production

“…Although they have been studied for a variety of processes, including thermochemical processes, anaerobic digestion, and fermentation, [1][2][3] most research focuses on the production of biodiesel. 4,5 Microalgal cultures have several advantages over conventional crops used for commercial biodiesels, including their shorter life cycle and the fact that they can be developed in environments unfit for agriculture, thus avoiding the food-fuel conflict. 6 However, microalgae cultivation is still not sufficiently cost-effective to compete with conventional biodiesel sources.…”