Home General Studies General Science

Biofuels: Generations and Types (Bioethanol, Biodiesel Biogas etc)

news-details Image Source May 07, 2021 15:56 IST , Updated: Jun 08, 2021 15:56 IST · 4 min read

Biofuel is any fuel that is derived from biomass - that is, plant or algae material or animal waste. Since such feedstock material can be replenished readily, biofuel is considered to be a source of renewable energy.

Biofuel is produced through contemporary processes from biomass, rather than by the very slow geological processes involved in the formation of fossil fuels, such as oil.

Biofuel can be produced from plants (i.e. energy crops), or from agricultural, commercial, domestic, and/or industrial wastes (if the waste has a biological origin).

The two most common types of biofuel are bioethanol and biodiesel.

1) Bioethanol

It is an alcohol made by fermentation, mostly from carbohydrates produced in sugar or starch crops such as corn, sugarcane, or sweet sorghum.

Cellulosic biomass, derived from non-food sources, such as trees and grasses, is also being developed as a feedstock for ethanol production.

Ethanol can be used as a fuel for vehicles in its pure form (E100), but it is usually used as a gasoline additive to increase octane and improve vehicle emissions.

2) Biodiesel

It is produced from oils or fats using transesterification and is the most common biofuel in Europe.

It can be used as a fuel for vehicles in its pure form (B100), but it is sually used as a diesel additive to reduce levels of particulates, carbon monoxide, and hydrocarbons from diesel-powered vehicles.

Generations

First-generation

First-generation biofuels are fuels made from food crops grown on arable land. The crop's sugar, starch, or oil content is converted into biodiesel or ethanol, using transesterification, or yeast fermentation.

Second-generation

Second-generation biofuels are fuels made from lignocellulosic or woody biomass, or agricultural residues/waste. The feedstock used to make the fuels either grow on arable land but are byproducts of the main crop, or they are grown on marginal land.

Second-generation feedstocks include straw, bagasse, perennial grasses, jatropha, waste vegetable oil, municipal solid waste and so forth.

Third-generation

Algae can be produced in ponds or tanks on land, and out at sea. Algal fuels have high yields, can be grown with minimal impact on fresh water resources, can be produced using saline water and wastewater, have a high ignition point, and are biodegradable and relatively harmless to the environment if spilled.

Production requires large amounts of energy and fertilizer, the produced fuel degrades faster than other biofuels, and it does not flow well in cold temperatures.

By 2017, due to economic considerations, most efforts to produce fuel from algae have been abandoned or changed to other applications.

Fourth-generation

This class of biofuels includes electrofuels and solar fuels. Electrofuels are made by storing electrical energy in the chemical bonds of liquids and gases.

The primary targets are butanol, biodiesel, and hydrogen, but include other alcohols and carbon-containing gases such as methane and butane.

A solar fuel is a synthetic chemical fuel produced from solar energy. Light is converted to chemical energy, typically by reducing protons to hydrogen, or carbon dioxide to organic compounds.

Types

Biogas

Biogas is methane produced by the process of anaerobic (in the absence of free oxygen) digestion of organic material by anaerobes (organism that does not require oxygen for growth).

It can be produced either from biodegradable waste materials or by the use of energy crops fed into anaerobic digesters to supplement gas yields.

When CO2 and other impurities are removed from biogas, it is called biomethane. Farmers can produce biogas from manure from their cattle by using anaerobic digesters.

Syngas

Syngas, a mixture of carbon monoxide, hydrogen and other hydrocarbons, is produced by partial combustion of biomass, that is, combustion with an amount of oxygen that is not sufficient to convert the biomass completely to carbon dioxide and water.

Syngas may be burned directly in internal combustion engines, turbines or high-temperature fuel cells.

Ethanol (CH3-CH2-OH)

Biologically produced alcohols (ethanol, propanol and butanol) are produced by the action of microorganisms and enzymes through the fermentation of sugars or starches (easiest), or cellulose (which is more difficult).

Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen.

Biobutanol (also called bio-gasoline) is often claimed to provide a direct replacement for gasoline, because it can be used directly in a gasoline engine.

Ethanol fuel is the most common biofuel worldwide, particularly in Brazil.

Alcohol fuels are produced by fermentation of sugars derived from wheat, corn, sugar beets, sugar cane, molasses and any sugar or starch from which alcoholic beverages such as whiskey, can be made (such as potato and fruit waste, etc.).

Ethanol has a smaller energy density than that of gasoline; this means it takes more fuel (volume and mass) to produce the same amount of work.

India has advanced the target date for achieving 20% ethanol-blending in petrol by five years to 2025.

Ethanol extracted from sugarcane as well as damaged food grains such as wheat and broken rice and agriculture waste is less polluting and its use also provides farmers with an alternate source of income.

India is the world's third-biggest oil importer, relying on foreign suppliers to meet over 85% of its demand.

PM Modi launched a pilot project of E-100 (100 per cent ethanol) dispensing stations at 3 locations in Pune.

Biodiesel

Biodiesel is produced from oils or fats using transesterification and is a liquid similar in composition to fossil/mineral diesel. Transesterification is the process of exchanging the organic group R" of an ester with the organic group R' of an alcohol.

Feedstocks for biodiesel include animal fats, vegetable oils, soy, rapeseed, jatropha, mahua, mustard, flax, sunflower, palm oil, hemp, field pennycress, Pongamia pinnata and algae.

Biodiesel can be used in any diesel engine when mixed with mineral diesel.

Popular in General Science