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Burning fossil fuels to produce energy is a significant contributor to the climate crisis. To mitigate its impact, we need to find new ways to produce energy. Biofuels may be the answer.
What is biofuel?
Biofuels are fuels of plant or animal origin. They are supposed to replace traditional fuels from non-renewable resources with those produced from renewable raw materials.
For example, regular firewood or rapeseed oil can be classified as biofuels. However, diesel and gasoline have replaced these fuels because they are cheaper, and mass motorisation requires large volumes of fuel.
Why have people returned to biofuels? The first reason is the climate crisis, which is exacerbated by greenhouse gas emissions from the use of fossil fuels. Transport accounts for almost a quarter of all carbon dioxide emissions associated with energy production. Since 1970, greenhouse gas emissions from the transport sector have doubled, of which 80% come from road transport.
The second reason is the search for renewable energy sources, as oil and coal reserves may soon be completely exhausted. We can also add to this the price hikes for hydrocarbons.
Types of biofuels: Solid, liquid, gaseous
Solid biofuels
The most typical and ancient type of solid biofuel is firewood. However, now in its pure form and on a large scale, it is almost no longer used. The most popular solid type of biofuel is pellets obtained from sawdust or bark, straw, olive pits, nut shells, or sunflower seed husks. Pellets are also made from cattle manure.
Pellets replace coal, firewood, and diesel fuel. When burned, they do not emit harmful substances and practically do not smoke (unlike coal and diesel). In addition, they are more energy efficient than regular firewood. Another advantage of pellets is the minimal ash content, which reduces the need for servicing furnaces and boilers. In addition, they have the lowest price compared to other types of biofuels.
Liquid biofuels
Bioethanol is the most popular and widely used liquid biofuel. It is produced by fermenting starch or sugar. Brazil and the United States are among the leaders in bioethanol production. In the United States, ethanol-based biofuels are produced from corn and are usually mixed with gasoline to produce a hybrid fuel. Overall, biofuels account for 5% of all energy consumption in the United States. In Brazil, ethanol-based biofuels are made from sugar cane, and in England, they are even produced from sugar beets.
Biodiesel is the second most popular liquid biofuel. Biodiesel is made primarily from oil plants such as soybeans or oil palm, and to a lesser extent from other oil products such as waste cooking fat from deep frying. Biodiesel is used in diesel engines and is usually mixed with petroleum diesel in varying proportions.
Biobutanol is a four-carbon alcohol that is also a biofuel. It is made from the same raw materials as ethanol. The advantages of biobutanol over bioethanol are that biobutanol is not miscible with water, has a higher energy content and a lower vapour pressure, which means lower volatility due to evaporation.
Dimethyl ether. It can be obtained from biomass, but on an industrial scale, the feedstock for it remains natural gas. The advantage of this fuel is that its energy efficiency is almost equal to diesel fuel, but the energy density of dimethyl ether is half that of diesel fuel, so it requires a fuel tank twice as large. In addition, vehicles need a specially designed system to run the engine on dimethyl ether.
Currently, engineers are actively developing a new generation of liquid biofuel obtained using algae. Algae are grown in large pools or on farms, and they convert sunlight into energy and store it in the form of oil. The oil is extracted mechanically (by pressing the biomass) or using chemical solvents that destroy the cell walls. Further processing and purification produce biofuel suitable for use as an alternative to traditional fuels.
Gaseous biofuel
Biogas is a gas consisting mainly of methane and carbon dioxide in varying proportions depending on the composition of the organic matter from which it was obtained. The main sources of biogas are livestock and agricultural waste, wastewater, and organic matter from household waste. Biogas is formed as a result of biological decomposition processes without oxygen (anaerobic fermentation).
Biohydrogen is an analogue of ordinary hydrogen, which is obtained from biomass. The thermochemical method involves heating the feedstock without oxygen to high temperatures, for example, wood waste, which releases hydrogen and other associated gases. In the biochemical method of obtaining biohydrogen, special microorganisms are added to the biomass, which decompose it with the release of hydrogen.
Pros and cons of biofuels
Advantages
• Renewability of the resource: Fossil fuels are a finite energy source that will eventually run out. Since biofuels are made from plant matter, they are theoretically renewable
• Reduced environmental impact: When biofuels are burned, the amount of carbon dioxide is reduced by up to 65%, which reduces the industry’s contribution to climate change. In addition, bioethanol and biodiesel contain lower concentrations of chemicals such as chlorine and sulfur. This means that biofuels help reduce emissions of these pollutants into the atmosphere
• Economic security: Biofuels can be produced locally, creating jobs in the same region where they will be consumed, thereby reducing transportation costs and emissions. In addition, producing your own biofuels reduces the country’s dependence on oil supplies from other countries
• Engine durability: Since biofuels contain fewer impurities compared to traditional fuels, engines will be less polluted and will fail less often
Disadvantages
• Loss of forests: Biofuel production requires vast areas to grow raw materials. This can lead to massive deforestation to free up space
• Food crisis: Biofuel production can affect the economy related to food prices and availability, as arable land will be allocated to biofuel crops rather than food
• Soil degradation: Growing the same crops (monocultures) will lead to soil depletion and an increase in pests. Chemical pesticides will be used to combat them, resulting in decreased soil fertility and loss of biodiversity
• Resource use: The amount of energy produced by biofuels is significantly less than that produced by burning fossil fuels, meaning that much more land, water, and fertilisers are required to meet the energy needs of the same number of people
• Energy costs: When assessing the economic benefits of biofuels, the energy required to produce them must be taken into account. For example, the process of growing corn for ethanol uses fossil fuels in the production of fertilisers, transportation of corn, and distillation of ethanol. In this regard, ethanol obtained from corn provides a relatively small gain in energy
Where is biofuel used
So far, we are mainly talking about its consumption at home. Usually, solid types of biofuel are used in poor countries where there are no other energy sources, for cooking, washing, and cleaning, or for heating the house itself. 80% of all biofuels consumed today are used for these purposes. 18% of biofuels are used in industry as a source of energy and lubricants. Biofuels are often mentioned as an alternative to gasoline for cars, but now only 2% is used in the transport industry.
Biofuel prospects
Today, the United States is the largest producer of biofuels among developed countries, accounting for almost 40% of the global market. In total, in 2019, global biofuel production exceeded 1.8 thousand barrels, with a market share of $136 billion. So far, this has become a record. Due to the coronavirus pandemic, the global biofuel market fell by about 8% for the first time in 20 years.
Biofuels have a chance to occupy part of the market, since their potential is artificially limited. For example, the EU has rules prohibiting the use of more than 7% of food crops as raw materials for biofuels. In the short term, biofuels do not require replacing existing infrastructure and engines, but it is unlikely that the entire energy complex will be able to switch exclusively to them.
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