ABSTRACT
Fast depleting fossil fuels, energy security and environmental concerns are promoting conventional renewable energies, wind, tidal, solar and biofuels as an alternative (IPCC 1991, UK Royal Commission 2000). In
1 Department of Chemical Engineering, Monash University, Clayton, 3800, Australia. Email: ravichandra.potumarthi@monash.edu, pravichandra@gmail.com 2 Department of Biotechnology, National Institute of Technology, Warangal, AP, India. * Corresponding author
comparison with wind, tidal, and solar forms of renewable energy, biomass based biofuels allow solar energy to be converted into lignocellulosics and stored (Hill et al. 2006) which further can be converted into biofuels by physio, chemico, thermal and biological methods. Lignocellulosic biomass, an important feedstock to alleviate greenhouse gas emissions, to replace fossil fuels and to provide energy security (Goldemberg 2000, Yang et al. 2011, Prasad et al. 2007, Singh et al. 2010). Diverse and abundant biomass is available in the form of agricultural residues, forest residues and they have been investigated as the feedstock for the production of different class of second generation biofuels (Yanqun et al. 2008). While second generation biofuels answers concerns about the intricacy generated by the fi rst generation biofuels such as the food security, overall savings energy, greenhouse gas emissions, etc. it fails to answer the competition between bioenergy crops (switch grass) and food crops for arable land which affects food security (Kenneth et al. 2007). In addition, lignocellulosic based biofuels has a signifi cant environmental impact in comparion with fossil fuels by breaking the carbon cycle-conversion of fi xed carbon into CO2. Hence, without proper replantation it may result in massive biomass defi cit which ultimately leads to deforestation (Yanqun et al. 2008). Due to techno-economic non viability of biomass pretreatment technologies, cost of enzymes (ex. cellulases) and lack of viable technology for co-fermentation of glucose and xylose the commercialization of lignocellulosic ethanol (Jay and Timilsina 2010) at industrial level of operation is limited. In addition to these factors nitrogen fertilizers used for crops releases extra N2O into atmosphere contributing more green house gases than by fossil fuel savings (Crutzen et al. 2007). Issues and concerns raised from lignocellulosic based second generation biofuels has directed scientifi c and engineering attention towards research and development in algal biofuels. Although research is carried out on micro and macro algal biofuels, further discussions in this chapter are restricted to micro algae.
