Types of biofuels: a comparison of solid, liquid, gaseous

An alternative to traditional energy resources are various types of biofuels, for the manufacture of which used vegetable or animal raw materials, industrial waste and the results of life organisms.

We propose to understand the advantages and disadvantages of the use of such fuel, learn the features production, functional characteristics, as well as evaluate the effectiveness of using different types biofuels. This information will help to navigate in the selection of alternative energy sources.

What is biofuel

The most promising areas in the energy sector are technologies that use renewable resources, which include biofuels.

As a raw material for its production, you can take biomass of plant / animal origin, including industrial wastes or animal residues.

Processing of such substances is thermochemical or biological method, in the latter case, the fuel is obtained using various types of microorganisms.

In many countries, there are special programs to increase the share of biofuels in national and regional energy consumption. In a number of states there are also mandatory norms for the use of this energy source.

The advantages and disadvantages of biofuels

Biological types of fuel have their positive and negative sides. Interest in the use of this type of raw material due to its undoubted advantages.

These include:

• Budget value. Although at the moment the price of biofuels practically coincides with the cost of gasoline, biological substances are considered to be a more profitable type of fuel, since they produce less emissions when burning. Biofuels are suitable for use in various conditions, while it can be adapted to engines of different designs. Another advantage is the optimization of the engine, which stays clean longer due to the small amount of soot and exhaust gases.
• Mobility. Biofuel differs from other alternative energy options by its mobility. The design of solar and wind power plants usually include heavy batteries, so they are often are used permanently, while bio-fuel can be transported from one region to other.
• Renewable energy. Although, according to researchers, the existing deposits of crude oil will last for at least a few hundred years, the mineral reserves are still finite. Biofuels made from plants and animal waste are among the renewable resources that are not threatened with extinction in the foreseeable future.
• Earth Atmosphere Protection. A major disadvantage of traditional hydrocarbons is a large percentage of CO.₂that is released during combustion. This gas creates a greenhouse effect in the atmosphere of our planet, creating conditions for global warming. During the combustion of biological substances, the amount of carbon dioxide is reduced to 65%. In addition, crops used in the production of biofuels consume carbon monoxide, reducing its share in the air.
• Economic security. Hydrocarbons reserves are unevenly distributed, therefore, some states are forced to buy oil or natural gas, spending large amounts of money to purchase, transport, and store. Different types of biological fuel can be obtained in almost any country. As for its manufacture and processing it will be necessary to create new enterprises and, accordingly, jobs will benefit the national economy and have a positive effect on well-being of people.

Improving technology and developing new methods will enhance the positive effects of biofuels. Thus, the development of technologies using plankton and algae will significantly reduce its price.

At the same time, at the present stage of development of science and technology, the production of biofuels is associated with a number of difficulties and inconveniences. First of all, these are natural limitations in growing plants.

For the growth of crops used for biomass production, a number of factors need to be considered, namely:

• Water use. Agricultural plants consume a lot of water, which is a limited resource, especially in dry places.
• Invasiveness. Cultures grown for fuel are often aggressive. They drown out the authentic flora, which may affect the biodiversity and ecosystem of the region.
• Fertilizers. The growth of many plants requires the addition of nutrients that can harm other crops or the general ecosystem.
• Climate. Separate climatic zones (for example, desert or tundra) are not suitable for growing biofuel crops.

The active cultivation of agricultural plants is associated with the depletion of agricultural resources. Non-compliance with the rules of agricultural engineering can lead to a decrease in the content of beneficial soil components and, consequently, to their depletion, which will cause an aggravation of food Problems.

Ecosystem disturbance occurs. For the production of biomass usually requires the expansion of the territories involved in agriculture.

Often, for this purpose, the area is cleaned up, which leads to the destruction of the microecosystem (for example, forests), the death of plants and animals.

There are problems with growing monocultures. To get more biomass yield, producers often sow the land with a certain plant. This practice is not very well reflected in the state of agricultural land, since monoculture leads to a change in the environment.

On the fields occupied by one species of plants, special species of pests usually parasitize. An attempt to control them with insecticides and pesticides only leads to the development of resistance to these agents.

To avoid the problems described above, scientists advise not to neglect the biodiversity of crops, combining several plants in the fields, as well as use local varieties of flora.

Generations of alternative fuel

A wide range of vegetable raw materials used for biomass can be divided into several generations.

First generation. This category includes crops that contain a high percentage of starch, sugars, fats. These are such popular plants as corn, sugar beet, canola, soy.

Since the cultivation of these crops is detrimental to the climate, and their removal from the market affects the pricing of products, scientists are trying to replace them with other types of biomass.

Second generation. The biomass group includes wood, grass, agricultural waste (shell, husk). Obtaining biofuels from such raw materials is costly, however, it solves the problem of disposing of non-food residues with the simultaneous production of combustible materials.

A feature of the cultures included in this variety is the presence of lignin and cellulose in them. Thanks to them, biomass can be burned and gasified, and also subjected to pyrolysis, obtaining liquid fuel.

The main disadvantage of the second generation biomass is the lack of return per unit area, which is why significant land resources have to be allocated for such crops.

Third generation. The raw material for the production of biofuels are algae that are grown on an industrial scale, for example, in open water.

This practice has great prospects, but at present such technologies are only being developed. Scientists are also conducting research on the creation of techniques that allow obtaining fourth- and even fifth-generation biofuels.

Three types of biofuels

Depending on the state of aggregation of the substance, there are three main types of biofuels:

1. Solid: firewood, peat, animal waste and agricultural production.
2. Liquid: biodiesel, dimethyl ether, bioethanol, biobutanol.
3. Gaseous: biogas, methane, biohydrogen.

Each type of substance has its own specifics, which will be discussed below.

Type # 1: Solid

The most popular solid varieties of biofuels are wood, peat, animal waste.

Wood (firewood, chips, sawdust)

The ancient form of biofuels are well-known firewood, which has long been used for heating homes and cooking. Until now, they are actively used in different countries to produce heat / electricity, in particular, a large Austrian thermal power plant with a capacity of 66 megawatts operates on firewood.

At the same time, such raw materials have disadvantages. The energy value of firewood is relatively small: when burning, a part of the substance accumulates in the form of soot, due to which the fireplaces and stoves must be regularly cleaned. In addition, it takes time to replenish the stock of wood - new trees will grow only in 15-20 years.

An excellent alternative to conventional firewood is pellets (granules), for the production of which substandard wood is used: bark, chips, pressed sawdustboughs

For the production of fuel pellets, the raw materials are ground to dust, which is then dried and pressed at high temperature. Due to the lignin contained in the wood, a sticky mass is formed, from which small cylinders with a length of 5-70 mm and a diameter of 6-10 mm are formed.

You can set up the production of pellets by yourself. briquette press.

Among the popular types of biofuels are wood chips, which often serve as an energy source for European thermal power plants. The production of this raw material is carried out at logging sites or at special production lines equipped with shredding machines.

Marsh and forest fuel peat

This is a common form of biofuels, used in domestic and industrial purposes for centuries. Peat is a layer of moss that has not completely decomposed in the swamp conditions, and is harvested in many countries around the world: Russia, Belarus, Canada, Sweden, Indonesia and others.

For the convenience of the production process, biomass is usually processed at the extraction site. The process consists in cleaning (screening) the raw materials from extraneous shutdowns, followed by drying and molding in the form of briquettes or granules.

Agricultural Waste Fuel

In agricultural production, as a rule, a large number of diverse plant waste accumulates: the outer shells of plants, nutshells, straw.

Such raw materials can also be pressed and granulated to obtain fuel pellets, the characteristics of which practically do not differ from pellets made from woody biomass.

Biofuels of animal origin

Along with firewood in ancient times, people began to use fuel of animal origin, namely, manure - dried manure of domestic animals. Modern technologies of drying and processing of similar raw materials make it possible to obtain solid varieties of biofuels, completely devoid of an unpleasant odor.

Since at present animal waste is accumulated on an industrial scale, the production of fuel from them simultaneously solves the problem of their utilization.

Type # 2: liquid

Liquid biofuel variants that are safe and environmentally friendly are mostly used as a substitute for gasoline and other similar means. The most common options include bioethanol, biomethanol, biobutanol, biodiesel, dimethyl ether.

Bioethanol from plants

This is a common liquid biofuel that is used to refuel cars. Although the pure substance is not used as a fuel, its addition to gasoline improves performance. engine, increasing its power, monitoring the heating of the engine, reducing exhaust emissions gases.

Bioethanol was also appreciated by fireplace lovers. This substance has a good heat transfer, moreover, when it is burned, no soot or smoke is formed, and the amount of carbon dioxide emitted is minimized.

Thanks to such features, fuel can be used even for heating the hearth in apartment buildings. Read more about biofuels for fireplaces written in this article.

Bioethanol is produced from the first generation raw materials containing starch or sugar. Cereals, corn, sugar cane, beets are processed by the technology of alcoholic fermentation.

Biobutanol for refueling cars

Biobutanol is a biologically produced butanol analog. The colorless liquid, which has a characteristic odor, is widely used as a chemical raw material in industry, and can also be used as a transport fuel.

The energy content of butanol is close to gasoline, which allows partially replacing the latter in fuel cells. Unlike bioethanol, biobutanol can be used independently, without adding traditional types of fuel.

The raw materials for the production of this bio-substance are a variety of plants: beet, cassava, wheat, corn.

Dimethyl ether (C₂H₆O)

It is also environmentally friendly fuel. When it is burned in the exhaust gases there are no sulfur compounds, and the content of nitrogen compounds is 90% lower than during the combustion of gasoline.

Dimethyl ether can be used without special filters, but the design of the car (power system, engine ignition) has to be changed dramatically.

Without any alterations, a combined fuel containing 30% dimethyl ether can be used in machines that are equipped with LPG engines.

Liquid fuel can be produced from various raw materials: natural gas, coal dust, biomass and before total of pulp and paper production residues transforming into a liquid under slight pressure.

Biomethanol from unicellular algae

This substance is similar to conventional methanol, which is widely used to produce a number of chemical compounds (acetic acid, formaldehyde), and is also used as antifreeze and solvent.

For the first time, the question of the production of this type of biofuel was raised in the 1980s, when a group of scientists proposed to produce liquid substance through the biochemical transformation of marine phytoplankton, which will be cultivated in special reservoirs.

Biomethanol has several potential benefits:

• high energy efficiency - 14 upon receipt of methane, 7 in the production of methanol;
• excellent phytoplankton productivity - up to 100 tons per hectare per year;
• undemanding unicellular organisms, for the cultivation of which does not need fresh water, fertile soil;
• conservation of agricultural resourcesbecause phytoplankton is grown in ponds or marine bays.

Although industrial production of biomethanol has not yet been established, persistent research and development of technologies for the development of the production of this type of alternative fuel are currently being conducted.

Biodiesel as an alternative to fuel transport

This is a liquid motor biofuel consisting of a mixture of fatty acid esters. The substance is safe for people and animals, almost completely decomposes in the ground for 28 days, and also has a relatively high (<100) ignition temperature.

Biodiesel reduces the percentage of emissions of harmful gases, and also prolongs the life of the engine, since it contains lubricating components.

Fuel is used to refuel car engines both independently and in combination with conventional fuel. Only a short shelf life of the biological substance should be taken into account: after three months, the decomposition of the biological substance begins with complete loss of properties.

For biodiesel in the EU, a special standard EN14214 was adopted. In a number of countries, the EN590 standard is also in effect, allowing the addition of 5% biodiesel to other fuels.

Type # 3: Gaseous

The main types of gaseous biofuels include biogas and bio-hydrogen.

Biogas as a replacement for natural gas

Biogas is a practically complete analogue of natural gas: it contains 13-50% CO_2, 49-87% methane, as well as impurities H₂ and H₂S. If this substance is cleared of carbon dioxide, you can get biomethane.

Gaseous biofuel is produced from biomass by hydrogen or methane fermentation. The latter is caused by three types of microorganisms: first, the raw material is exposed to the action of hydrolyzing bacteria, which are then replaced by acid-forming and methane-forming microbes.

A variety of materials can be used as raw materials: silage, manure, algae, sewage, litter, fecal residues, household waste. The starting material is brought into a homogeneous state, after which it is placed in the reactor with the help of a loader.

It maintains a comfortable temperature of + 35-38 ° C, necessary for the implementation of the process of methane fermentation.

Raw materials are constantly mixed, with the resulting gaseous product is discharged into the gas tank (storage unit), from where it enters the generator.

More information about obtaining biogas from manure and arrangement of a biogas plant is written in the articles:

1. How to make a biofuel with your own hands from the manure at home
2. Biogas installation for a private house with their own hands: recommendations for the device and an example of homemade equipment arrangement

Biological hydrogen obtained by chemical method

A variety of gaseous biofuel, which is an analogue of ordinary hydrogen, is obtained from biomass using biochemical or thermochemical methods.

In the thermochemical method, the prepared raw material (for example, wood waste) is heated to a temperature of 500–800 ° C without oxygen, and gases of H are emitted.₂, CO, CH₄.

In the biochemical method, the raw material is maintained in comfortable conditions at normal pressure and a temperature of about 30 ° C.

Special microorganisms Enterobacter cloacae, Rodobacter speriodes are introduced into biomass, which decompose the original product, releasing hydrogen. Enzymes are allowed to accelerate production using polysaccharides.

Conclusions and useful video on the topic

On the video below you can see the process of manufacturing a popular type of biofuel - wood briquettes:

Types of biofuels differ not only in the state of aggregation, but also in their characteristics. When choosing such material, it is necessary to take into account their planned use, efficiency, functional properties and cost.

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