They are readily available and are environment-friendly. They obtain energy from both food and nonfood sources. Types of biofuels can be:
- Solid Biofuels (Wood, Energy crops )
- Liquid Biofuels ( Bioethanol, Biodiesel, Biogas)
- Gaseous Biofuels (Syngas)
Types of Biofuels
Same like fossil fuels biofuels come in different forms. They meet different forms of energy needs.
They all come from biomass. They are divided into different types of biofuels based on their source from which they originate.
Fermentation of sugar and starches produces bio alcohols like ethanol and in small quantities propanol and butanol. Ethanol contains almost one-third of the energy density of gasoline.
But mostly they are used as an additive in the vehicles. It is environmentally friendly and produces much less carbon when burn-in vehicles as fuel. So they do not cause the greenhouse effect.
Ethanol belongs to the type of liquid biofuels and is a renewable source of energy.
It also helps to boost economies as it can be produced domestically, and it reduces dependence on foreign fossil fuels.
It affects the production of food and can result in an increase in food prices. More energy is required to produce it in large quantities than it produces.
Biodiesel is another biofuel type which is a renewable source of energy.
- They are prepared from plant oil and animal fats. The primary sources of vegetable oils are rapeseed, palm, or soybean.
- They used the process called transesterification for their production.
- The process involves the exposure of plant oil with alcohol in the presence of a catalyst.
- The main product is then distilled from any byproduct. They can be used as biodiesel in place of petroleum diesel.
- It is a green biofuel example, as green biodiesel is produced during the process of refining.
- This green diesel is similar to, but it does not contain sulfur.
- It is termed as green diesel is not because it is green in color but because it protects against global warming.
- It reduces the emission of gases as well as odor.
There are many advantages of using biodiesel.
One of the most significant advantages is its ‘carbon neutral’ quality.
It emits carbon or greenhouse gases in meager quantities. The amount of carbon it emits is absorbed by plants for photosynthesis.
So it does not result in the greenhouse effect. In fact, it can reduce the greenhouse effect by 65%.
This biofuel type of first-generation is gaseous in nature. It can be produced from any kind of biomass.
- Its composition is just like natural gas. Its main component is methane, and it is produced by the anaerobic decomposition of biomass.
- It is the main reason this gas is gaining popularity and is slowly replacing natural gas.
- It is used as a fuel by households in gas cylinders. Some agricultural firms are also using it.
- It is the most common biofuel which is obtained from both plant and animals.
Like plant contributes hydrogen and carbon whereas animals contribute nitrogen part. These elements altogether then form biogas.
Their primary source is wheat and beat sugar. They can also be prepared from waste glycerol that is produced during the production of biodiesel.
They can be used as an alternative to Petro ether that comes from fossil fuels. They cannot be used as fuel because they are low in energy density.
They are currently replacing lead as a catalyst in fuel to improve the performance of the engine.
Their main advantage is, they decrease the oxygen wear and also reduce the emission of toxin gases in the atmosphere, especially ozone.
It is a type of gaseous biofuel. It is produced with a mixture of other gases include carbon monoxide, carbon dioxide.
- They are collectively called syngas or more commonly synthesis gas.
- Same like biogas it is produced by the process of pyrolysis, gasification or biological fermentation.
- Hydrogen is produced by heating biomass in the process of pyrolysis and gasification.
- Whereas in the fermentation process it uses either dark fermentation or photo fermentation.
- Dark fermentation breaks down biomass using bacteria, as it in the anaerobic process.
- Whereas photo fermentation is just like dark fermentation, the only difference is that it involves light.
- But sadly the efficiency rate of both the processes is low. That is why this process is not used on an industrial scale.
- Fermentation can be done at a lower temperature than a chemical reaction, which made it more preferable.
- Biological fermentation can be used in steel factories and power plants that burn coal.
- But despite all this method is not preferable because of its low throughput, it means it takes a long time to complete.
Cellulose or in simple words, wood is the second generation biofuel type. It belongs to the type of slid biofuels.
- It is one of the most common biofuels which is derived from organic matter.
- It can be obtained from trees as well as from plants and is used for fuel in the form of firewood, sawdust, chips, charcoal, and pellets.
People used wood to warm their houses, cook food, and to power small appliances at the house.
Wood is quite high in energy density. The energy density of hardwood is around 14-15 MJ/Kg if it is burned with 100 percent efficiency.
But when used as the fuel they are not burned completely. Wood is actually the most efficient among all the fuels, and they have 70 percent of the energy content recoverable.
Its major drawback is pollution. It produces the highest amount of carbon dioxide when burned than fuels like methane.
Other pollutants like soot, smoke, and PAHs are also produced with the burning of wood. The most challenging part to burn wood is to provide a spark to it or to ignite it.
7. Energy Crops
It is the primary category of the type of solid biofuels. These crops are usually produced for burning purposes.
Mostly they are grown as wood for combustion. To transport them quickly they are dried and converted into pallets.
They are used in home heating burners. Crops that are grown as liquid biofuels usually have a high content of oils and produce lipids.
Switchgrass or elephant grass are the crops usually grown for combustion.
8. Algae Based Biofuels
Algae are the highest source of energy in the class of biofuels. Because of the food problems, algae gain the most attention to use as a fuel.
The production ability of each alga depends on its type.
Safely we can say that algae have 20 to 80% oil content which can be converted into different fuels.
Production of diesel from algae is the easiest way. Scientists used gene technology to increase the production of oil and biodiesel content from algae.
They are the most advanced form of biofuels. Because of their high energy density, they can produce up to 300 percent more oil per acre than other biofuels.
Algae do not have any impact on food production, so it is safe to grow algae as a biofuel.
Biofuel Types Table
This table explains the feedstock used for the different biofuel types, also what is the production method and applications of each type.
|Fuel||Feed Stock||Production||Energy Density (g)||Applications|
|Ethanol||Starches from wheat, corn, sugar cane, molasses, potatoes, other fruits||Distillation||30||Used as a fuel
Additive in fuel
|Biodiesel||Oils and fats including animal fats, vegetable oils, nut oils, hemp, and algae||Transesterification process||37.8||Used as a fuel|
|Bioethers||Dehydration of alcohols||N/A||N/A||They are used as additives to other fuels that increase performance|
|Biogas||Methane made from waste crop material through anaerobic digestion or bacteria||Fermentation (anaerobic decomposition of biomass)||2.74 (does not take into account the direct effect of methane, which is 23X more effective as a GHG than CO2||Used as a fuel|
|They include everything from wood and sawdust to garbage, agricultural waste, and manure.||By Type|
|This category includes a vast variety of materials. Manure has low CO2 emissions but high nitrate emissions.|
|Biohydrogen||Made from algae breaking down water.||Gasification|
|Hydrogen contains an energy density of|
|Used in place of the hydrogen produced from fossil fuels|
|Cellulose||It is made from wood, grass, or inedible parts of plants||1.5||Cellulose is used as wood, paper and fiber|
|Algae Based Fuel||different kinds of fuels made from algae||Algae-based fuels can be used to produce any of the fuels above, as well as jet fuel||Depend on certain type of fuel derived from algae.||More expensive, but produces 10-100X more fuel than other biofuels.|