Answer & Enrich Your Learning:
- Biofuels are usually classified into three groups as 1st, 2nd and 3rd
Biofuels are usually classified as follows:
- First-generation biofuels are directly related to a biomass that is generally edible.
- Second-generation biofuels are defined as fuels produced from a wide array of different feedstock, ranging from lignocellulosic feedstock to municipal solid wastes.
- Third-generation biofuels are, at this point, related to algal biomass but could to a certain extent be linked to utilization of CO2 as feedstock.
- First-generation biofuels include ethanol and biodiesel and are directly related to a biomass that is more than often edible.
- Ethanol is generally produced from the fermentation of C6 sugars (mostly glucose) using classical or GMO yeast strains such as Saccharomyces cerevisiae.
- Only a few different feedstocks, mostly sugarcane or corn, are actually used for the production of first-generation bioethanol.
- Other more marginal feedstocks that are used or considered to produce first-generation bioethanol include but are not limited to whey, barley, potato wastes, and sugarbeets.
- Biodiesel is the only other biofuel produced on an industrial scale.
- It uses biomass (oily plants and seeds), but the process itself relies on extracting the oils and converting them into biodiesel by breaking the bonds linking the long chain fatty acids to glycerol, replacing it with methanol in a process called transesterification.
Second-generation biofuels are defined as fuels produced from a wide array of different feedstocks, especially but not limited to non-edible lignocellulosic biomass.
- Biomass used for production of second-generation biofuels is usually separated in three main categories: homogeneous, such as white wood chips, homogeneous, such as agricultural and forest residues, and non-homogeneous, including low value feedstock as municipal solid wastes.
- Such biomass is generally more complex to convert and its production is dependent on new technologies.
The most accepted definition for third-generation biofuels is fuels that would be produced from algal biomass, which has a very distinctive growth yield as compared with classical lignocellulosic biomass.
- Production of biofuels from algae usually relies on the lipid content of the microorganisms.
- There are many challenges associated with algal biomass, some geographical and some technical.
Key facts and concerns:
- First-generation biofuels are well implemented around the world, although they may come with certain restrictions such as energy consumption and utilization of arable lands, as well as the fuel versus food debate.
- They remain a sure and economically viable approach for sustainability and reduction of fossil fuel consumption.
- In all cases, feedstock is getting increasingly expensive, leading to a growing interest toward second-generation biofuels.
- The latter is produced from a generally less expensive biomass such as forest, agricultural, animal, or municipal wastes.
- Numerous techniques are being investigated around the world for the production of second-generation biofuels, but overall they rely on two distinctive pathways: either “thermo” or “bio”
- The major difference between the second and third-generations is the feedstock.
- Algae are known to produce biomass faster and on reduced land surface as compared with lignocellulosic biomass.
- Nevertheless, production of algal biomass presents technical challenges such as lipid extraction and dewatering, as well as geographical challenges in areas where temperature is below freezing for a large part of the year.
- The future of biofuels may not rely solely on one generation, but may be a combination of the three generations to cope with increased worldwide demand as a result of depletion in the world’s oil resources.