Developing Technologies For Fossil Fuel - 1100 Words

ESL Course: Bioenergy from microalgae Introduction: The past two decades biofuels hold much promise in alleviating climate change, greenhouse effect and in finite amount. Their combustion produces gaseous products: carbon dioxide (CO2) and methane (CH4) that increase the amount of solar heat trapped within the planet× ³s atmosphere (T.R. Karl, 2003). It has also been predicted that the oil reserves may run out by 2050 (Harun et al., 2010). First generation bioethanol seemed to be alternative for fossil fuel. However, production of bioethanol from food crops leads to impact on food supplies, as well as rainforest and arable land. It leads to increased deforestation and food vs fuel debate (Cassman and Liska, 2007 and Fargione et al.,†¦show more content†¦Furthermore, the cultivation of lignocellulosic biomass may occupy the arable land, which is required for the production of edible crops. On the other hand, bioethanol produced from microalgae considered as third and fourth generation feedstock which is less resista nt to conversion from plant biomass into simple sugars. Some microalgae have high carbohydrates contents in their cell wall and there is no lignin and hemicelluloses content, in their cytoplasm with starch as the main carbohydrates source (Rosenberg et al., 2008 and Subhadra and Edwards, 2010). Consequently, the conversion of carbohydrates contained in seaweeds into ethanol does not require delignification. Moreover, the cultivation of seaweeds does not invade arable land and potable water (Mitsunori Yanagisawa). Based on these characteristics, seaweeds have been proposed as some of the most promising raw materials for efficient bioethanol production that would not compete with food. Carbohydrate composition in microalgae: Starch: Starch acts as an energy reserve in mostly green algae and some other groups of algae. Starches contains ÃŽ ±-glucans and are constituted of two molecules: amylose,and amylopectin (Stick and Williams, 2009). Chlorophyta, Cryptophyta, and Dinophyta, contains starch as their main energy resource and its composition varies with the division. Chlorophyta composed of amylopectin and amylose and based on amylose content Cryptophyta is