Question

Explain about 3rd generation biofuels: microalgae, its potential, constraints and solutions.

Answer 1

Biofuel production from renewable sources is considered to be one alternative to petroleum. Microalgae are recently considered as an ideal third generation biofuel feedstock as their growth rate is rapid, they have CO2 fixation ability and their capacity of lipid production is high. They do not compete with food also, and they can be produced on non-arable land. Microalgae can be used to produce liquid transportation and heating fuels, like biodiesel and bioethanol.

Microalgae: A potential source of biofuels:

There are different ways to convert microalgal biomass to energy sources. These are classified into biochemical conversion, chemical reaction, direct combustion, and thermochemical conversion. That’s why, microalgae can provide feedstock for renewable liquid fuels like biodiesel and bioethanol. The idea of using microalgae as a potent source of biofuel is not new, but now a days it is being taken seriously because of the rising price of petroleum and the emerging concern about global warming which is associated with burning of fossil fuels. The utilization of microalgae for biofuels production shows some advantages. (1) Microalgae grow at high rates and synthesize and accumulate a large quantities of neutral lipids (20–50 % dry weight of biomass). (2) Microalgae are capable of all year round production, thus, oil yield per area of microalgae cultures will be high. (3) Microalgae need less water, thus reducing the load of freshwater sources. (4) Herbicides or pesticides application is not needed in microalgae cultivation. (5) Microalgae sequester CO2 from flue gases which are emitted from fossil fuel-fired power plants and different other sources. (6) As they can grow under harsher conditions and need reduced nutrients, microalgae can be cultivated in saline, brackish water, coastal seawater and do not compete for resources with conventional agriculture. (7) Depending on the microalgae species different other compounds also can be extracted, like, polyunsaturated fatty acids, polysaccharides, pigments, natural dyes, antioxidants, high-value bioactive compounds, and proteins.

Constraints and solutions:

The cost of cultivation in open ponds or photobioreactors, biomass harvest and oil extraction from algal biomass is very high. In fact, many micro algal species are not suitable for industrial cultures. The fatty acid composition of microalgal lipids are not be the optimal for use as biofuel. Sometimes, stress conditions are needed to accumulate lipids, which causes some arrest of cell growth and division, which results a strong limitation of biomass productivity. Thus, biofuel production from microalgae is not yet sustainable, and it is not possible yet to come up with one algal strain, called “an algal crop” for biofuel production.

      Intensive research efforts will be needed in both strain development and technology innovations.