14
Alternative Green Biofuel from
Microalgae
A Promising Renewable Resource
Katkam N. Gangadhar,
1,2,3
João Varela
1
and F. Xavier Malcata
2,3,
*
Introduction
Energy is essential and an important factor of production in the global economy, and approximately 90%
of the commercially produced energy is from fossil fuels such as crude oil (36%), coal (27.4%), and gas
(23%) (Demirbas 2010; Chen et al. 2011), of which 58% is consumed by the transport sector (Daroch
et al. 2013). The world energy consumption, including oil, natural gas, nuclear, and coal has decreased
around 1.1% (BP 2010). At the same time, the production of natural gas and crude oil has lessened about
2.1% and 7.3%, respectively (Emma and Rosalam 2012). This suggests that the world energy supply met
by fossil fuels is not sustainable and will diminish in the middle of the century (Chisti 2007). Fossil fuels
are non-renewable in nature and were formed millions of years ago from the remains of ancient algae
(e.g., diatoms), plants, and animals, a process that usually requires long periods of time. In addition,
fossil fuel is directly related to air pollution, water degradation, and climate change due to greenhouse
gas (GHG) emissions, which can significantly contribute to global warming (Rojas-Downing et al. 2017).
The constant rising of global demand of transportation fuels and electricity generation, in which these two
sectors have played an important role in improving human living standards. Most of the energy sources,
such as solar, wind, hydroelectric, geothermal, and nuclear power which are mainly used to generate
electricity and heat. Electricity is considered to be a secondary energy resource that is used to convey
and distribute energy over large distances. Moreover, these renewable resources such as solar, wind,
and hydrothermal have several drawbacks. For instance, solar energy can only be produced in places
with ample sunlight; solar energy can only be generated at daytime; wind technologies generate noise
pollution and require suitable locations where wind is frequent. Due to the reduction of oil resources and
1
CCMAR – Centre of Marine Sciences, University of Algarve, Campus de Gambelas, P-8005-139 Faro, Portugal.
2
Department of Chemical Engineering, University of Porto, Rua Dr. Roberto Frias, s/n, 4200-465 Porto, Portugal.
3
LEPABE – Laboratory of Process Engineering, Environment, Biotechnology and Energy, Rua Dr. Roberto Frias, s/n,
P-4200-465 Porto, Portugal.
* Corresponding author: fmalcata@fe.up.pt
Alternative Green Biofuel from
Microalgae
A Promising Renewable Resource
Katkam N. Gangadhar,
1,2,3
João Varela
1
and F. Xavier Malcata
2,3,
*
Introduction
Energy is essential and an important factor of production in the global economy, and approximately 90%
of the commercially produced energy is from fossil fuels such as crude oil (36%), coal (27.4%), and gas
(23%) (Demirbas 2010; Chen et al. 2011), of which 58% is consumed by the transport sector (Daroch
et al. 2013). The world energy consumption, including oil, natural gas, nuclear, and coal has decreased
around 1.1% (BP 2010). At the same time, the production of natural gas and crude oil has lessened about
2.1% and 7.3%, respectively (Emma and Rosalam 2012). This suggests that the world energy supply met
by fossil fuels is not sustainable and will diminish in the middle of the century (Chisti 2007). Fossil fuels
are non-renewable in nature and were formed millions of years ago from the remains of ancient algae
(e.g., diatoms), plants, and animals, a process that usually requires long periods of time. In addition,
fossil fuel is directly related to air pollution, water degradation, and climate change due to greenhouse
gas (GHG) emissions, which can significantly contribute to global warming (Rojas-Downing et al. 2017).
The constant rising of global demand of transportation fuels and electricity generation, in which these two
sectors have played an important role in improving human living standards. Most of the energy sources,
such as solar, wind, hydroelectric, geothermal, and nuclear power which are mainly used to generate
electricity and heat. Electricity is considered to be a secondary energy resource that is used to convey
and distribute energy over large distances. Moreover, these renewable resources such as solar, wind,
and hydrothermal have several drawbacks. For instance, solar energy can only be produced in places
with ample sunlight; solar energy can only be generated at daytime; wind technologies generate noise
pollution and require suitable locations where wind is frequent. Due to the reduction of oil resources and
1
CCMAR – Centre of Marine Sciences, University of Algarve, Campus de Gambelas, P-8005-139 Faro, Portugal.
2
Department of Chemical Engineering, University of Porto, Rua Dr. Roberto Frias, s/n, 4200-465 Porto, Portugal.
3
LEPABE – Laboratory of Process Engineering, Environment, Biotechnology and Energy, Rua Dr. Roberto Frias, s/n,
P-4200-465 Porto, Portugal.
* Corresponding author: fmalcata@fe.up.pt