How Does Biofuel Work?
Last updated: 15th January, 2023
Biofuels have gained popularity in recent years as a way to reduce our dependence on fossil fuels for energy and decrease greenhouse gas emissions. They are particularly popular in the transport sector, where they are blended with gasoline and diesel fuel to make the standard fuel more sustainable.
In general, the popularity of this alternative energy source varies by region and country and depends on factors such as government policies and the availability of feedstocks. For example, in the United States, ethanol made from corn is the most widely used type and is blended into gasoline to produce a fuel called E10. Biodiesel application has also been increasing in recent years.
In Europe is a biodiesel made from rapeseed oil, and ethanol made from sugar beet or cereal crops. In Brazil, ethanol made from sugarcane is blended with gasoline to produce a fuel called gasohol.
In many developing countries, biofuels are not yet widely used, and the majority of energy still comes from fossil fuels or increasingly from solar energy. However, with growing concerns about energy security and climate change, many countries are beginning to invest in biofuels as a source of renewable and sustainable energy for the future.
What is a biofuel?
Biofuel is a term that refers to a number of liquid, solid or gaseous fuels produced from biomass using biological (as opposed to geological) processes. Biomass refers to the plant material or organic matter that is used to produce biofuels such as ethanol, biodiesel, and biogas.
Examples of biomass include:
- Corn, sugarcane, rapeseed, and wheat – used to produce ethanol
- Soybeans, palm oil, and animal fats – for biodiesel
- Agricultural waste, such as straw and corn stover, and sewage – for production of biogas through anaerobic digestion
The main advantage of using biomass as a source of fuel is that it is renewable resource and can be sustainably produced.
The two most common types of liquid biofuels are ethanol and biodiesel. Ethanol is usually derived from sugarcane and corn starch, while biodiesel is processed from vegetable oils (primarily palm oil) or animal fat.
There are other, more exotic varieties as well, such as algae biofuel, and biofuels derived from jatropha (mostly biodiesel), fungi, or animal gut bacteria.
Materials, such as wood and its byproducts, as well as waste and agricultural residue can also serve as a source of biomass. There is a lot of ongoing research focused on looking for new sources for biofuels and improving existing ones, and developing new techniques for their production.
The main types of biofuels
There are several types of biofuels, each with their own specific origin and method of production. Some of the most common types include:
Ethanol is a type of biofuel made by fermenting sugar or starch crops such as corn, sugarcane, and wheat. It is the most widely used biofuel in the world and is commonly blended with gasoline to produce a fuel called E10 (10% ethanol, 90% gasoline). The largest ethanol-producing countries are the United States, Brazil, and China.
Biodiesel is a type of biofuel made by converting vegetable oils, animal fats, or recycled cooking grease into a diesel-like fuel through a process called transesterification. It is commonly used as a direct replacement for diesel fuel in vehicles. The largest biodiesel-producing countries are the European Union, the United States, and Brazil.
Biogas is a type of biofuel made by the breakdown of organic matter through anaerobic digestion. It is primarily used to generate electricity and heat in power plants. Biogas can be produced from a variety of organic materials such as agricultural waste, sewage, and landfills.
Biomethanol is a type of biofuel made by converting biomass into synthesis gas or syngas (a mixture of carbon monoxide CO and hydrogen H2) and then converting it into methanol. Biomethanol is made from a variety of biomass sources such as wood, agricultural waste, and sewage.
#5 Synthetic biofuels
Synthetic biofuels are not made directly from biomass but are derived from it. They are made by converting biomass into liquid hydrocarbons. The most well-known synthetic biofuel is biojet fuel, which is created by converting biomass into hydrocarbons that can be used as jet fuel.
Overall, biofuels can be produced from a wide range of biomass sources, and the most commonly used feedstocks vary by region and country. Every country has a different climate and is abundant resources. The biofuels depend on this factor.
The production process of liquid biofuels
Liquid biofuels are primarily used in the transport industry in the form of ethanol and biodiesel.
The process of making ethanol starts with the cultivation of crops such as corn, sugarcane, wheat, rapeseed, or soybeans. These crops are then harvested and processed to extract the sugars or oils that will be used to make the biofuel.
For example, corn can be ground up and mixed with water to create a mixture of starch and water. Enzymes are then added to the mixture to break down the starch into simple sugars, which are then fermented with yeast to produce ethanol.
The process of preparing biomass for fuel production is typically referred to as “conversion.” The most common method of conversion is through fermentation. Fermentation is the process of breaking down sugars or starches into ethanol using enzymes and yeast.
To use ethanol in car engines, most of the water has to be removed, so the liquid has to go through the process of distillation and dehydration. The final process of dehydration has a purpose of removing the final small percentage of water from the mixture to make it suitable for engine use.
Biodiesel fuel has a little bit different method of production. Instead of fermentation, the transesterification is applied. Transesterification is a process of breaking down the triglycerides in the oil or fat into fatty acid methyl esters (FAMEs), which are the chemical compounds that make up biodiesel.
During transesterification, the oil or fat is mixed with an alcohol, such as methanol, and a catalyst, such as sodium hydroxide. The mixture is heated and agitated, which causes the triglycerides to break down into FAMEs and glycerin. The glycerin is removed, and the remaining liquid is biodiesel.
Whether it is ethanol or biodiesel, the resulting biofuel has to be purified and blended with gasoline or diesel fuel to make it suitable for use in vehicles.
A wide spectrum of sources and a range of processing techniques reflect the complexity of what is collectively called “biofuels.” The final products, ethanol or biodiesel, then work exactly as other liquid fuels. They both are primarily used to fuel cars, although they also have use in aviation and trains.
Ethanol is commonly added to gasoline in small amounts to create a fuel blend known as E10 (10% ethanol, 90% gasoline). Higher ethanol blends such as E85 (85% ethanol, 15% gasoline) can also be used in vehicles specifically designed to run on flex-fuel. Biodiesel can be used as a direct replacement for diesel fuel in vehicles.
Ethanol is very popular in the US and in Brazil. Biodiesel is more popular in Europe for cars, while in North America it is mostly used to power trucks.
The biggest issue with the use of biofuels is their low efficiency compared to fossil fuels. This means that higher amount of biofuel is needed for the same performance. That is why bioethanol and biodiesel are frequently used as mix-ins and additives.
How is biogas produced?
Biogas is typically used to generate electricity and heat in power plants.
For biogas production, biomass is broken down through anaerobic digestion, which is the process of breaking down organic matter in the absence of oxygen. The process of anaerobic digestion produces a mixture of methane, carbon dioxide and other gases which are used as fuel for power generation.
How does a biofuel work to produce energy?
How do these biofuels actually work to produce energy as desired? Let’s break down each one of them.
Ethanol is a type of biofuel that is made from fermented plant material, such as corn or sugarcane. The process of producing ethanol involves breaking down the sugars in the plant material through fermentation, and then distilling the resulting liquid to purify it. The purified ethanol can then be blended with gasoline to create a fuel that can be used in internal combustion engines.
Ethanol is approximately 30% less efficient per unit of volume than gasoline, which means more pure ethanol is required to fuel the same mileage than gasoline. Furthermore, use of pure ethanol in engines is restricted to automobiles, lights-duty trucks and motorcycles, and only when engines were specifically adapted for the use.
In most cases, however, ethanol is used in mixtures with gasoline. At gas stations, such mixed fuels are marked with an “E” sign followed by the percentage of ethanol in the mixture.
E70 would mean a mixture with 70% of ethanol and 30% of gasoline. Adding ethanol increases an octane number of the fuel, which is better for higher performance of combustion engines.
Mixtures E5-E20 are also called gasohol and do not require any adaptation of the engine . The higher the percentage of ethanol in the mix, the more modifications are required.
An E85 mixture is commonly used in the US and Europe for flexible fuel vehicles.
According to the International Energy Agency (IEA), the United States is the largest producer and consumer of ethanol in the world, followed by Brazil and Canada. The US produces more than 20 billion gallons of ethanol per year, most of it is made from corn.
In the European Union, ethanol is also widely used as a transportation fuel, but it is used in smaller quantities than in the US. The EU has set a target of achieving a 10% share of renewable energy in transport by 2020, which has led to the development of a ethanol industry in the region. However, the EU production is only around 8 billion gallons per year.
In other parts of the world, ethanol use is much more limited. In Asia, for example, ethanol is primarily used for industrial and chemical purposes rather than as a transportation fuel.
Biodiesel can be used in diesel engines as an alternative to traditional diesel fuel as its renewable, biodegradable, and sustainable alternative.
However, the output of biodiesel is also lower than that of gasoline, even though, it highly depends on the blend and quality of the fuel. Biodiesel comes is blends commonly referred under “B” sign followed by the percentage of biodiesel in the fuel mix.
Same as in case of bioethanol, the lower the number – the less need there is for modifications of the engine. Use of pure biodiesel (B100) may lead to maintenance and performance problems in the long run. Although, in Europe, there are provisions to use B100 in agricultural engines .
Biodiesel is used in many other countries around the world, but the specific applications vary widely depending on the country and region.
In general, the use of biodiesel is highest in countries with strong government support for biofuels and a developed biofuels industry, such as in the European Union and United States. In the EU, biodiesel is the most widely used biofuel and it has been mandated by the EU’s Renewable Energy Directive that at least 6% of energy used in transport should come from renewable sources by 2020, and this has led to the development of a large biodiesel industry.
In the United States, the Renewable Fuel Standard (RFS) requires a certain amount of biofuels, including biodiesel, to be blended into the fuel supply each year. In 2020, The U.S. Environmental Protection Agency (EPA) proposed a rule to increase the biomass-based diesel volume requirement to 2.43 billion gallons for 2022 and 2.52 billion gallons for 2023.
In developing countries, the use of biodiesel is more limited and is often used for specific applications such as powering vehicles in rural areas or for electricity generation in remote communities.
Overall, the exact amount of biodiesel used globally is difficult to estimate because it is not tracked in a centralized manner, but it is estimated that the total global biodiesel production capacity was around 24 billion gallons per year as of 2021.
Biogas is typically produced through the process of anaerobic digestion, which involves breaking down organic matter such as agricultural waste, sewage, or food waste in the absence of oxygen. The resulting biogas is a mixture of methane (CH4) and carbon dioxide (CO2).
The most common feedstocks used to produce biogas include:
- Manure from livestock
- Food waste and other organic waste from households and commercial sources
- Sewage and wastewater
- Crops such as corn, wheat, and grass
- Energy crops such as willow, poplar, and miscanthus
- Industrial waste like food processing waste, paper mills waste
- Landfill waste
The specific feedstocks used will depend on the location and availability of resources, as well as the specific goals of the biogas operation. Biogas production can happen at small scale (household, farm) or large scale (industrial, municipal)
Biogas can be used in a variety of ways, including:
- As a fuel source for heating and electricity generation in homes, businesses, and power plants.
- As a transportation fuel, either alone or in a mixture with diesel or natural gas.
- In industrial processes such as the production of fertilizer, chemicals, and bioplastics.
- To treat and purify wastewater.
Biogas can also be upgraded to pure methane, or “biomethane”, which can then be used as a pipeline-quality gas.
Overall, biogas is a versatile and sustainable energy source that can help to reduce greenhouse gas emissions, improve air quality, and promote energy independence.
The use of biogas varies widely between countries and regions. Its purpose depends on the location. According to the International Energy Agency (IEA), biogas is most widespread in Europe, where it is primarily used for electricity generation, heat production, and transportation. In Germany, for example, biogas is used to generate electricity for millions of households and businesses.
In the United States, the use of biogas is also growing, but it is primarily used for electricity generation, as well as to produce heat and transportation fuel (CNG- compressed natural gas).
In Asia, the use of biogas is also growing, especially in China and India, where it’s used for electricity generation and cooking in rural areas.
In Africa and Latin America, the use of biogas is more limited and is often used for specific applications such as powering vehicles in rural areas or for electricity generation in remote communities.
It’s difficult to estimate the exact amount of biogas used, but it is estimated that the total global biogas production capacity was around 370 billion cubic meters per year as of 2021, of which around 60% is used for electricity generation and heat production, 25% for transportation and 15% for other uses such as industrial processes and cooking.
Solid biofuels are fuels that are made from solid biomass, such as wood, crops, and waste materials. They can be used in a variety of ways, including being burned to produce heat and electricity through their combustion.
In the combustion process, the solid biofuel is burned in a boiler, which generates heat. This heat then creates steam that is used to power a turbine. The turbine generates electricity, which can then be distributed to homes and businesses through the power grid.
Combustion of solid biofuels in specially designed power plants is also an alternative to traditional fossil fuels and can help to reduce greenhouse gas emissions. The efficiency of the process and the environmental impact of the biofuel depends on the type of biofuel used, its production process (how sustainable it is), and the technology used for combustion.
Solid biofuels are commonly used in industrial and power generation applications, as well as in residential and commercial heating systems.
They can also be used as a feedstock for the production of biofuels like bioethanol and biodiesel.
Solid biofuels are still the main source of energy for households in many developing countries, particularly in Africa and Asia, where they are used for cooking and heating. In these regions, it is estimated that solid biofuels account for more than 30% of total primary energy consumption.
In more developed countries, the use of solid biofuels is more limited, but it still plays an important role in certain sectors such as the residential and commercial heating, and small-scale power generation. In the EU, for example, solid biofuels account for around 5% of total primary energy consumption.
It is estimated that the total global solid biofuels consumption was around 150 Exajoules per year as of 2021, of which around 60% is used for residential and commercial heating, 25% for electricity generation and 15% for other uses such as cooking and industrial processes.
Biofuels are as old as car engines; however, low price and wide availability of fossil fuels over the twentieth century made them less competitive and reduced their share of the market. Currently, biofuels are considered to be an alternative energy source.
Further reading: Advantages and disadvantages of biofuels