conditions to decompose biomass materials down to smaller molecule materials with
a higher energy density.
1.4.6.4 Pyrolysis (Thermal Cracking)
Pyrolysis is a thermochemical process to convert dry biomass to bio-oil, syngas, and
charcoal by heating the biomass at medium to high temperatures (350–700
C) in
absence of oxygen with the aid of a catalyst (Goyal et al. 2008). It involves cleavage
of chemical bonds to yield small molecules. Flash pyrolysis at moderate temperature
(500–600
C), short hot vapor residence time (about 1 s) is a viable technique for
future replacement of fossil fuels with biomass derived bio-oil. The biomass-toliquid conversion ratio (95.5%) can be achieved through pyrolysis (Demirbas 2006).
Carbon monoxide, alkanes, alkenes, charcoal, phenol formaldehyde resins, carboxylic acid, and wastewater are common byproducts of pyrolysis. Metallic salts are
used as a catalyst in many studies. A few studies on pyrolysis method for the
production of microalgae derived fuel oil have been studied (Miao and Wu 2004;
Miao et al. 2004). High quality bio-oil was obtained through fast pyrolysis of
C. protothecoides (Yield of 18%) and Microcystis aeruginosa (Yield of 24%) at
temperature of 500
C (Miao et al. 2004). The quality and quantity of the pyrolysis
products depend on various factors, such as reaction temperature, heating rate,
pressure, reaction time, etc. Compared to other conversion technologies, pyrolysis
of algal biomass is quite extensive and has achieved promising and reliable
outcomes that could lead to commercial exploitation.
1.5
Use of Natural Resources
To achieve maximum biomass growth regarding both technical and economic
performance towards biofuel production, resource factors must be appropriately
matched. Algal biofuels productions require resource factors such as suitable climate, land, CO 2 supply, water management, and other nutrients for sustainable use
and cost effectiveness. The sustainability of algal production systems can be
evaluated using a system of social, environmental, and economic indicators.
1.5.1 Climate
Climate and temperature elements determine the overall algal productivity. Solar
insolation, temperature, precipitation, evaporation, and weather events are climatic
factors to affect viability of algal biomass production. The availability of adequate
sunlight, climate suitability, and temperature are key factors to determine economic
feasibility of algal growth. Photoautotrophic microalgae growth in open and closed
cultivation systems depends on the availability of abundant sunlight. The average
seasonal insolation factor is the rate-limiting factor for autotrophic algal productivity. The daily, seasonal, and annual variation in solar insolation on spatial surface
area of cultivation systems is needed to achieve a set amount of product, downstream
1 Algal Biofuel: A Sustainable Approach for Fuel of Future Generation
15
a higher energy density.
1.4.6.4 Pyrolysis (Thermal Cracking)
Pyrolysis is a thermochemical process to convert dry biomass to bio-oil, syngas, and
charcoal by heating the biomass at medium to high temperatures (350–700
C) in
absence of oxygen with the aid of a catalyst (Goyal et al. 2008). It involves cleavage
of chemical bonds to yield small molecules. Flash pyrolysis at moderate temperature
(500–600
C), short hot vapor residence time (about 1 s) is a viable technique for
future replacement of fossil fuels with biomass derived bio-oil. The biomass-toliquid conversion ratio (95.5%) can be achieved through pyrolysis (Demirbas 2006).
Carbon monoxide, alkanes, alkenes, charcoal, phenol formaldehyde resins, carboxylic acid, and wastewater are common byproducts of pyrolysis. Metallic salts are
used as a catalyst in many studies. A few studies on pyrolysis method for the
production of microalgae derived fuel oil have been studied (Miao and Wu 2004;
Miao et al. 2004). High quality bio-oil was obtained through fast pyrolysis of
C. protothecoides (Yield of 18%) and Microcystis aeruginosa (Yield of 24%) at
temperature of 500
C (Miao et al. 2004). The quality and quantity of the pyrolysis
products depend on various factors, such as reaction temperature, heating rate,
pressure, reaction time, etc. Compared to other conversion technologies, pyrolysis
of algal biomass is quite extensive and has achieved promising and reliable
outcomes that could lead to commercial exploitation.
1.5
Use of Natural Resources
To achieve maximum biomass growth regarding both technical and economic
performance towards biofuel production, resource factors must be appropriately
matched. Algal biofuels productions require resource factors such as suitable climate, land, CO 2 supply, water management, and other nutrients for sustainable use
and cost effectiveness. The sustainability of algal production systems can be
evaluated using a system of social, environmental, and economic indicators.
1.5.1 Climate
Climate and temperature elements determine the overall algal productivity. Solar
insolation, temperature, precipitation, evaporation, and weather events are climatic
factors to affect viability of algal biomass production. The availability of adequate
sunlight, climate suitability, and temperature are key factors to determine economic
feasibility of algal growth. Photoautotrophic microalgae growth in open and closed
cultivation systems depends on the availability of abundant sunlight. The average
seasonal insolation factor is the rate-limiting factor for autotrophic algal productivity. The daily, seasonal, and annual variation in solar insolation on spatial surface
area of cultivation systems is needed to achieve a set amount of product, downstream
1 Algal Biofuel: A Sustainable Approach for Fuel of Future Generation
15