WHAT IS BIODIESEL?
Biodiesel is any biomass-derived diesel fuel substitute. Today, biodiesel has fuel substitute. Today, biodiesel has come to mean a very specific chemical modification of natural oils. Oilseed crops such as rapeseed and soybean oil have been extensively evaluated as sources of biodiesel.
Oilseed crops yield natural oils, generally present in the form of Triacylglyc4erols (TAGs). TAGs consist of three long chains of fatty acids attached to a glycerol backbone. The algae species can produce up to 60% of their body weight in the form of TAGs, holding potential as an alternative source of biodiesel. It does not compete with the existing oilseed market, which is already on the verge of meeting demands.
The use of vegetable oils as alternative fuels has been around for 100 years when the inventor of the diesel engine Rudolph Diesel first tested peanut oil in his compression ignition engine. The rapid introduction of cheap petroleum quickly made petroleum the preferred source of diesel fuel, so much so that today's diesel engines do not operate will when operated on unmodified TAGs. Natural oils, it turns out, are too viscous to be used in modern diesel engines.
In the 1980s, a chemical modification of natural oils was introduced that helped to bring the viscosity of the oils within the range of current petroleum diesel. By reacting these TAGs with simple alcohols (a chemical reaction known as "transesterification"), we can create a chemical compound known as an alkyl ester, but which is known more generically as biodiesel. Its properties are very close to those of petroleum diesel fuel.
Commercial experience with biodiesel has been very promising. One of the biggest advantages of biodiesel compared to many other alternative transportation fuels is that it can be used in existing diesel engines without modification, and can be blended in at any ratio with petroleum diesel. Biodiesel performs as well as petroleum diesel, while reducing emissions of particulate matter, CO (Carbon monoxide), hydrocarbons and Sox (Oxides of sulphur). Emissions of NOx (Oxides of nitrogen) are, however, higher for biodiesel in many engines. Biodiesel virtually eliminates the notorious black soot emissions associated with diesel engines. Total particulate matter emissions are also much lower. Other environmental benefits of biodiesel include the fact that it is highly biodegradable and that it appears to reduce emissions of air toxics and carcinogens (relative to petroleum diesel). Suffice it to say that, given many of its environmental benefits and the emerging success of the fuel in Europe and USA, biodiesel is a very promising fuel product.
Why should we use microalgae for diesel? There are a number of benefits, four of which are outlined here.
1. Energy Security: Affordable energy contributes to reducing poverty, increasingly productivity and improving the quality of life. India meets nearly 30% of its total energy requirements through imports. With the increase in share of hydrocarbons in the energy supply/use, this share of imported energy is expected to increase. The challenge, therefore, is to secure adequate energy supplies at the least possible cost.
Our almost complete reliance on petroleum in transportation comes from the demand for gasoline in passenger vehicles and the demand for diesel fuel in commerce. Bioethanol made from terrestrial energy crops offers a future alternative to gasoline, biodiesel made from algal oils could do the same for diesel fuel.
2. Climate Change: CO2. Thus, is recognized as the most important (at least in quantity) of the atmospheric pollutants that contribute to the greenhouse effect. The burning of fossil fuels is the major source of the current build up of atmospheric CO2. Thus, identifying alternatives to fossil fuels must be the key strategy in reducing greenhouse gas emissions. While no one single fuel can substitute for fossil fuels in all the energy sectors, biodiesel from algal oils could make major contribution to the reduction of CO2 generated by power plants and commercial diesel engines.
3. Synergy of Coal and Microalgae: Many of our fossil fuel reserves, especially coal, are going to play significant roles for years to come. On a worldwide basis, coal is, by far, the largest fossil energy resource available. It will remain the mainstay of world baseline electricity generation, accounting for half of electricity generation by the year 2015. A typical coal-fired power plant emits flue gas from stacks containing up of 13% CO2. As pressure to reduce carbon emissions grows, this will become an increasingly acute problem for the world.
Algal farms could help recycle the carbon emitted. Large algal farms could be located adjacent to power plants. the bubbling of flue gas from a power plant into these ponds provides a system for recycling of waste CO2 from the burning of fossil fuels. The concept of coupling a coal fired power plant with an algae farm provides an elegant approach to recycle the CO2 from coal combustion into a useable liquid fuel.
4. Terrestrial versus Aquatic Biomass: Algae grow in aquatic environments. In that sense, microalgae technology will not complete for the land already being eyed by proponents of other biomass-based fuel technologies. More importantly, many of the algal species can grow in brackish water – that is, water that contains high levels of salt. Algae technology will thus not put additional demand on freshwater supplies needed for domestic, industrial and agricultural use. Land use needs for microalgae complement, rather than compete, with other biomass-based fuel technologies.