Classification of Biofuels

Classification of Biofuels:

             I.               1^st Generation Biofuels:

·      1st generation biofuels are also called conventional biofuels. They are made from things like sugar, starch, or vegetable oil. Note that these are all food products. Any biofuel made from a feedstock that can also be consumed as a human food is considered a first generation biofuel.

·      1st generation biofuels suffer from the same problems including threatening the food chain, increasing carbon emissions when planted outside traditional agricultural settings, and intense growth requirements. Ultimately, first generation biofuels have given way to second and third generation fuels.

·    Though they will continue to provide biofuel for the foreseeable future, their importance is waning and new, better alternatives are being developed.

·         Eg- Corn, Sugarcane , Soyabean, Jatropha and other seed crops

Different generations of Biofuels based on Feedstock

            II.            2nd Generation Biofuels

·      2nd generation biofuels are produced from sustainable feedstock. The sustainability of a feedstock is defined by its availability, its impact on greenhouse gas emissions, its impact on land use, and by its potential to threaten the food supply.

·      To qualify as a second generation, a feedstock must not be suitable for human consumption and

  Ø  Should grow on marginal (non-agricultural) land

  Ø  Should not require a great amount of water or fertilizer

  Ø  Certain food products can become second generation fuels when they are no longer useful for consumption

  Ø  waste vegetable oil (2nd generation feedstock)

  Ø  Virgin vegetable oil (1st generation feedstock)

·         Second generation biofuels are also referred to as “advanced biofuels”

Second Generation Extraction Technology:

·         Second generation feedstock are processed differently than first generation biofuels

1. Thermochemical Conversion

·    The first thermochemical route is known as gasification. Gasification is not a new technology and has been used extensively on conventional fossil fuels for a number of years. Through gasification, carbon-based materials are converted to carbon monoxide, hydrogen, and carbon dioxide. This process is different from combustion in that oxygen is limited. The gas that result is referred to as synthesis gas or syngas. Syngas is then used to produce energy or heat. Wood, black liquor, brown liquor, and other feedstock are used in this process.

·      The second thermochemical route is known as pyrolysis. Pyrolysis is carried out in the absence of oxygen and often in the presence of an inert gas like halogen. The fuel is generally converted into two products: tars and char. Wood and a number of other energy crops can be used as feedstock to produce bio-oil through pyrolysis.

·    A third thermochemical reaction, calledtorrefaction, is very similar to pyrolysis, but is carried out at lower temperatures. The process tends to yield better fuels for further use in gasification or combustion. Torrefaction is often used to convert biomass feedstock into a form that is more easily transported and stored.

2. Biochemical Conversion

·     A number of biological and chemical processes are being adapted for the production of biofuel from second generation feedstock. Fermentation with unique or genetically modified bacteria is particularly popular for second generation feedstock like landfill gas and municipal waste. 

             III.        3rd Generation Biofuels

·       Biofuel derived from algae is regarded as third-generation biofuel.

·      Algae cultivation uses nonarable land and has an ideal short cultivation period, in addition, algae can provide the widest range of biofuels (range from vegetable oils to jet fuel) compared to other kinds of biomass.

·       Algae produce an oil that can easily be refined into diesel or even certain components of gasoline

·     Algae can be genetically manipulated to produce everything from ethanol and butanol to even gasoline and diesel fuel directly

·     However, algae have one fatal drawback that would limit the development of third-generation biofuel to a very large extent: algae inevitably require large amounts of fertilizers like nitrogen and phosphorus for growth, and this would consequently produce more greenhouse emissions and dramatically increase the cost of the third-generation biofuels because of the extensive fertilizer production.

            IV.         4th Generation Biofuels

·      The recently emerged fourth-generation biofuels are also produced from the feedstock using nonarable land, but based on a new technology termed “synthetic biology.”

·       Such fuels are considered Carbon Negative because their production extracts carbon from the environment.

·       It is expected to convert solar power directly to biofuels in engineered photosynthetic microorganisms though the feedstock itself using the inexhaustible raw materials: sun light, water, and CO2. However, this is a generation of biofuels that is still at the conceptual stage.