The demand for alternative fuels has increased in the past several years. Several substitutes have come into existence in the recent years and many more are on their way to get established as a sustainable fuel alternative. Biodiesel is gaining importance as one of the most important substitutes for the depleting fossil fuels. There are many advantages of using biodiesel as an alternative form of energy. It can be used as such in the diesel engine without any engine modification indicating that it has comparable physical and chemical properties as conventional diesel.
Combustion of Biodiesel
The combustion properties of biodiesel are also very close to those of petroleum diesel . Biodiesel is highly biodegradable and is nontoxic as well as renewable. The exhaust of biodiesel during combustion has lesser carbon monoxide, hydrocarbon, particulate matter and sulfur dioxide as compared to those of petro-diesel. However, the problems like increased NOx emissions, poor cold flow and poor oxidative stability need to be solved. Therefore, a lot of research is focused on control of these NOx emissions.
Sources of Biodiesel
Biodiesel can be derived from edible oil seed crops such as sunflower, palm, rapeseed, soybean, coconut, etc. which are considered as first generation biodiesel feed stocks. However, use of such feed stocks for biodiesel production has faced problems as they disturb the overall worldwide balance of food reserves and safety. The non-edible seed crops of jatropha, karanja, jojoba, mahua and waste cooking oil, grease, animal fats, etc. have gained importance in the last few years as second generation feed stocks for biodiesel production. However, these second generation feed stocks are not sufficient to entirely substitute the present transportation needs.
Algae/Micro algae Biodiesel
Recent focus is on microalgae as the third generation feedstock. Using microalgae has several advantages like high photosynthetic efficiency and higher biomass production. Microalgae do not compete for land and can grow anywhere, even in brackish saline water. The current research efforts have been concentrated on increasing lipid content in microalgae and culturing of algae.
In order to establish the potential of microalgae biomass as an alternative for biodiesel production, more concentrated attempts are needed for detailed characterization of algae biomass, algae oil and algae biodiesel as very little information in literature is available around the world on the same.
Three different species of algae i.e. Chlorella, Spirulina and pond water algae shows significant potential for biodiesel production. The natural pond water algae biomass is expected to be a cheaper feedstock for biodiesel production as compared to pure cultures of Chlorella and Spirulina. The growth patterns of the three algae species were studied with an aim to determine the maximum productivity of algae species. The algae biodiesel production was attempted by some researcher via oil extraction and transesterification both in single stage and two stage reactor units in order to get the maximum biodiesel yield.
Some works done to investigate the usefulness of techniques like Fourier transform infrared (FTIR), NMR, GC and proximate and elemental analyses to understand the chemical properties of algae biomass, algae oil and algae biodiesel. The fuel properties of algae biodiesel were also investigated by some researcher.