Biofuel and its Types: An Overview

Biofuel is a renewable fuel, which can be used as an alternative to fossil fuels. They are produced from biomass- plant or algae material or animal waste. These sources of biofuel are also known as feedstock. A few examples of feedstock used to produce biofuels are: Vegetable/ Edible Oils (like Canola oil, Safflower oil), Non-Edible Oils (like Almond oil, Salmon oil), Animal fat (Lard, Tallow) and other sources such as Algae, Fungi and Bacteria.

There are four categories in which Biofuels are classified. They are: First Generation, Second Generation, Third Generation and Fourth Generation.

  • First Generation Biofuels: They are made from starch, sugar or animal fats using conventional methods such as fermentation, distillation and transesterification. Hence, they are also called conventional biofuels.
  • Second Generation Biofuels: They are made from woody biomasses as well as agricultural residues and wastes like corn stalk and bagasse.
  • Third Generation Biofuels: They are made from oil extracted from algae.
  • Fourth Generation Biofuels: They are made from electro fuels and solar fuels. Electro fuels are obtained by storing electricity produced from renewable sources in the chemical bonds of liquid or gaseous fuels. Solar fuels are obtained from common materials (example: Carbon dioxide) by the action of solar energy.

There are four common types of Biofuel. They are Bioethanol, Biodiesel, Biogas and Biobutanol

Bioethanol

It is a type of biofuel used as an alternative automobile fuel source. It is produced from feedstocks like sugarcane, algae, corn or various other biomass. The feedstocks are treated with enzymes and undergo the process of fermentation. Bioethanol, along with carbon dioxide, is a by-product released during the whole process. It is majorly used as an alternative fuel to gasoline in internal combustion vehicles.

Advantages of Bioethanol:

  • Ethanol undergoes complete combustion and hence bioethanol burns more clearly in air than petroleum fuels
  • It is a renewable energy resource
  • Any fuel spills are more easily biodegradable

Disadvantages of Bioethanol:

  • Typical automobile engines may need to be modified to use biofuel
  • The production process is slightly expensive
  • Some amount of carbon dioxide gets released along with bioethanol in the production process

Biodiesel

Biodiesel is obtained from natural sources such as triglyceride containing vegetable oils and animal fats. It is produced by transesterification. It is used in vehicles, aircrafts, railways, as a heating oil and for cleaning oil spills. The structure of biodiesel is similar to that of petroleum diesel fuel. Apart from that, in engines, it operates similarly to petroleum diesel fuel. Thus, it can be used easily in engines requiring little modifications to the engines.

Advantages of Biodiesel:

  • It helps to lubricate the engine which in turn decreases engine wear
  • It does not have sulfur content hence it doesn’t contribute to acid rain

Disadvantages of Biodiesel:

  • Biodiesel can release nitrogen oxide which can lead to the formation of smog
  • Its cost varies according to feedstock used and market conditions

Biogas

Biogas is a renewable energy source; a natural fuel. It is produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste or food waste. It is produced by the aerobic digestion of organic matter. Biogas comprises of primarily methane (CH4), carbon dioxide (CO2) and may have small amounts of hydrogen sulfide (H2S), moisture and siloxanes.

Advantages of Biogas:

  • The slurry produced after the production of biogas can be used as manure
  • There is less emission of greenhouse gases
  • It is a renewable energy source as it is produced from waste which gets generated everyday in enormous quantities
  • It is a healthier alternative to the use of firewood for cooking in rural areas

Disadvantages of Biogas:

  • The production process is temperature dependent, as the bacteria need a temperature of around 37°C for digestion. As a result, in areas with a cold climate, there is an extra requirement of heat supply
  • Biogas contains methane, a highly flammable material. If proper care is not taken while handling, it may come into contact with oxygen and violently produce carbon dioxide
  • Despite purification, biogas still contains impurities which may lead to metal corrosion
  • It is unable to be used on a large scale as there is no efficient production system

Biobutanol

Biobutanol is an alcoholic biofuel gaining traction. It is produced by the fermentation of sugar in biomass through the action of microbes. Clostridium acetobutylicum is a commonly used microorganism species. The sugars then get broken down into various alcohols, including butanol. Since it is obtained from biomass it is called Biobutanol. Its major use is as a fuel in internal combustion engines. It also shows potential as an industrial solvent.

Advantages of Biobutanol:

  • Biobutanol has a low vapor pressure, which means that it has a low volatility and a lower risk of evaporation
  • It has fewer emissions than other petroleum fuels. Compared to gasoline, it reduces carbon emissions by 85%

Disadvantages of Biobutanol:

  • The yield obtained and the speed of production are partially dependent on the microorganism used
  • The separation of butanol from the fermentation broth is slightly costly

In the age of global warming, it is necessary for governments and scientists to carry out more research into different biofuels and ways to harness them efficiently. This will not only reduce global warming to an extent, but also helps conserve fossil fuel and build towards a healthy and green future for our planet.