Algal biomass conversion to bioethanol – a step‐by‐step assessment

Abstract

The continuous growth in global population and the ongoing development of countries such as China and India have contributed to a rapid increase in worldwide energy demand. Fossil fuels such as oil and gas are finite resources, and their current rate of consumption cannot be sustained. This, coupled with fossil fuels' role as pollutants and their contribution to global warming, has led to increased interest in alternative sources of energy production. Bioethanol, presently produced from energy crops, is one such promising alternative future energy source and much research is underway in optimizing its production. The economic and temporal constraints that crop feedstocks pose are the main downfalls in terms of the commercial viability of bioethanol production. As an alternative to crop feedstocks, significant research efforts have been put into utilizing algal biomass as a feedstock for bioethanol production. Whilst the overall process can vary, the conversion of biomass to bioethanol usually contains the following steps: (i) pretreatment of feedstock; (ii) hydrolysis; and (iii) fermentation of bioethanol. This paper reviews different technologies utilized in the pretreatment and fermentation steps, and critically assesses their applicability to bioethanol production from algal biomass. Two different established fermentation routes, single-stage fermentation and two-stage gasification/fermentation processes, are discussed. The viability of algal biomass as an alternative feedstock has been assessed adequately, and further research optimisation must be guided toward the development of cost-effective scalable methods to produce high bioethanol yield under optimum economy.

Microalgal biomass pretreatment for bioethanol production: a review

“…Currently there are over fifty companies that produce some types of aquatic biomass either for use as supplement, additives, colorants, food or bioenergy (Klöck, 2010 In the production of bioenergy from aquatic biomass, as in any types of biorefineries, a very important step is the pretreatment of the raw materials, where the objective is to make available the intracellular compounds such as carbohydrates, proteins, lipids, and added-value compounds such as short chain oligosaccharides, antioxidants, pigments, etc. (Harun et al, 2014;Demuez et al, 2015). The two main objectives for which pretreatment of microalgae biomass is necessary are the breakdown of the cell wall and the modification of the structure of intracellular carbohydrates.…”

Development of nickel based catalysts for the transformation of natural triglycerides and related compounds into green diesel: a critical review

“…The above processes constitute the SDO resulting to hydrocarbons with almost the same number of carbon atoms. Depending on the experimental conditions and the catalyst used the CO and CO 2 produced in the gas phase may react with hydrogen to form CH 4 and CO respectively whereas the propane could be cracked to smaller hydrocarbons. Therefore, the determination of the gaseous phase composition is not sufficient to discriminate deCO 2 from deCO.…”

Process application of Subcritical Water Extraction (SWE) for algal bio-products and biofuels production

“…Additional benefits of algae over food crops include fast growth rates, less water intake, adaptation to various water sources (fresh, seawater, saline/brackish and wastewater), high photosynthetic efficiency, carbon dioxide (CO 2 ) biosequestration, phytoremediation, inexpensive cultivation techniques using non-arable land and short harvesting periods. Notwithstanding these benefits, algal biofuel development faces a few drawbacks which include low biomass densities and high operating costs for biomass generation and conversion [6]. Although algal based biofuels generate approximately 13% CO 2 lower emissions from combustion relative to CO 2 emissions from petroleum diesel [7], in terms of absolute emission levels, algal biofuels can be significantly high for full-scale applications.…”