Bioenergetics. Status and prospects. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Alternative energy sources

 Comments on the article

Shocks such as the energy crisis of 1973 and the Chernobyl disaster of 1986 forced most countries to reconsider their energy policies regarding the pace and prospects for the use of renewable energy sources (RES).

It became clear that it is not enough to develop clean energy only in one's own country, when neighboring countries continue to build and operate nuclear facilities, similar in reliability to the fourth unit of the Chernobyl nuclear power plant. It is necessary to combine the efforts of scientists from different countries in the field of development of non-traditional energy.

The negative trends in the development of traditional energy are mainly due to the presence of two factors - the rapid depletion of natural resources and environmental pollution. According to the UN, the depletion of coal deposits is expected in 2082-2500.

Promising traditional energy technologies increase the efficiency of energy use, but do not improve the environmental situation: thermal, chemical and radioactive pollution of the environment can lead to catastrophic consequences

In this regard, there is a need to identify opportunities for the rational use of traditional energy resources, on the one hand, and the development of scientific and technical work on the use of non-traditional and renewable energy sources, on the other.

All energy resources on Earth are ultimately products of the activity of the Sun. Almost all non-traditional energy is the conversion and use of solar energy by direct and indirect methods.

Direct methods of using solar energy are based on the conversion of solar radiation into electrical or thermal energy.

Indirect methods are based on the use of kinetic and potential energy, which arise as a result of the interaction of solar radiation with the geosphere. The greatest energy potential is characterized by wind energy, energy of rivers, sea tides and waves, biomass energy

A number of foreign countries have adopted national programs for the development of energy from non-traditional sources, work is being carried out on the initiative of government agencies, private firms, and low-interest loans are provided.

Energy production using renewable sources in 1992 in the countries of the European Union is presented in table 1.

The negative factors in the development of traditional energy in Ukraine are especially acute and are exacerbated by an imbalance in the development of the energy complex, so the use of renewable energy sources is of particular importance.

The need and possibility of developing this area of ​​energy are due to the following reasons:

• shortage of fuel and energy resources traditional for Ukraine;
• imbalance in the development of the energy complex of Ukraine, which is focused on a significant (up to 25 - 30%) electricity generation at nuclear power plants in the absence of production of nuclear fuel, waste disposal and processing, as well as production for the modernization of equipment of operating nuclear power plants (nuclear reactors, boiler equipment, etc.);
• favorable climatic and meteorological conditions for the use of the main types of renewable energy sources;
• the presence of an industrial base suitable for the production of almost all types of equipment for non-traditional energy.

Table 1. Energy production using RES in 1992 in the EEC countries

Resources of renewable energy sources in Ukraine are significant, their efficient use can make up a very significant share in the energy sector.

So - when using reasonable volumes of energy from renewable sources and the possibility of replacing oil products with them, the percentage ratio of this energy to the total amount of oil products consumed per year in the country (300 million tons of reference fuel per year) is 0,2% for biogas.

The location and operating characteristics of operating power plants are shown in Table 2.

Table 2. Basic installations in Ukraine

Biomass is an efficient renewable energy source.

Biomass resources in various forms are available in almost all regions, and in almost every of them its processing into energy and fuel can be arranged.

At the present level, biomass can cover 6-10% of the total energy needs of industrialized countries.

About 120 billion tons of dry organic matter are formed annually on Earth with the help of photosynthesis, which is energy equivalent to more than 400 billion tons of oil. The use of biomass is carried out in the following areas: direct combustion, gasification, production of ethyl alcohol for motor fuel, biogas production from agricultural and household waste. Biomass, mainly in the form of wood fuel, is the main source of energy for approximately 2 billion people. For most people living in rural areas of the "Third World", it represents the only available source of energy. Biomass, as a source of energy, plays an important role in developed countries as well. In general, biomass provides a seventh part of the world's fuel, and in terms of the amount of energy received, it ranks third along with natural gas. Biomass produces 4 times more energy than nuclear power.

In the countries of the European Union, the share of biomass energy in 1992 was about 55% of the total renewable energy production. Biomass energy is used most efficiently in Portugal, France, Germany, Denmark, Italy and Spain.

In T986, the EU Commission decided to finance 153 projects for the use of biomass and waste. The amount of financing amounted to 70,6 million ECU.

The EU Directorate has launched a new 4-year research program in the field of non-nuclear energy sources. For research on the use of biomass allocated for 2 years 12 million dollars. USA. Biomass resources in Europe in 2000 were: wood fuel - 75, wood waste - 70, agricultural waste - 250, urban waste - 75 million tons.

In addition, biomass grown on energy plantations will provide 250 million tons per year.

In connection with the need to drastically reduce the harmful effects of vehicles on the environment, attention was drawn to the use of biomass in this area. Here, a number of directions have been outlined for replacing environmentally hazardous gasoline with environmentally friendly fuel.

Brazil has developed a program to use ethanol as an alternative fuel, replacing up to 22% (by volume) of gasoline.

Ethanol is obtained from the processing of specially grown cane. More than 7% of the gasoline offered contains 10% ethanol additive and 80% of this country's fleets use this additive. The US also has a major program to replace gasoline fuels with ethanol, which is made by processing surplus corn and other grains.

The use of alcohol as a fuel has received support in some European countries, in particular in France and Sweden. In Ukraine, the problem of replacing gasoline with alcohol has not yet been considered. The possibility of growing rapeseed in areas contaminated with radioactive elements is being studied in order to obtain rapeseed oil and use it as fuel in diesel engines. This idea is currently being developed by specialists from Ukraine and Germany.

In non-traditional energy, a special place is occupied by the processing of biomass (organic agricultural and domestic waste) by methane fermentation to produce biogas containing about 70% methane and disinfected organic fertilizers. The utilization of biomass in agriculture is extremely important, where a large amount of fuel is consumed for various technological needs and the need for high-quality fertilizers is constantly growing. In total, about 60 varieties of biogas technologies are currently used or developed in the world.

Biogas is a mixture of methane and carbon dioxide, formed in special reactors - digesters, designed and controlled in such a way as to ensure maximum methane release. The energy obtained by burning biogas can reach from 60 to 90% of that which the source material has. However, biogas is obtained from a liquid mass containing 95% water, so that in practice the yield is difficult to determine. Another, and very important, advantage of the biomass processing process is that its waste contains significantly fewer pathogens than the source material.

The production of biogas is economically justified and is preferable when processing a constant stream of waste (effluents from livestock farms, slaughterhouses, vegetable waste, etc.). Cost-effectiveness lies in the fact that there is no need for preliminary waste collection, organization and management of their supply; at the same time, it is known how much and when the waste will be received.

The production of biogas, which is possible in installations of various sizes, is especially effective in agro-industrial complexes, where there is the possibility of a complete ecological cycle. Biogas is used for lighting, heating, cooking, for driving mechanisms, transport, and power generators.

In anaerobic digestion, organic matter decomposes in the absence of oxygen. This process includes two stages (Fig. 1). At the first stage, complex organic polymers (fiber, proteins, fats, etc.) under the influence of a natural community of various types of anaerobic bacteria decompose to simpler compounds: volatile fatty acids, lower alcohols, hydrogen and carbon monoxide, acetic and formic acids, methyl alcohol . In the second step, methane-producing bacteria convert organic acids into methane, carbon dioxide, and water.

Figure 1 Scheme of organic matter digestion

Primary anaerobes are represented by various physiological groups of bacteria: cell-destroying, carbon-fermenting (such as butyric acid bacteria), ammonifying (decomposing proteins, peptides, amino acids) bacteria that decompose fats, etc. Due to this composition, primary anaerobes can use a variety of organic compounds of plant and animal origin , which is one of the most important features of the methane community. The close relationship between these groups of bacteria provides sufficient process stability.

Methane fermentation proceeds at medium (mesophilic) and high (thermophilic) temperatures. The highest productivity is achieved with thermophilic methane fermentation. The peculiarity of the methane consortium makes it possible to make the fermentation process continuous. For the normal course of the anaerobic digestion process, optimal conditions in the reactor are necessary: ​​temperature, anaerobic conditions, a sufficient concentration of nutrients, an acceptable pH range, and the absence or low concentration of toxic substances.

Temperature greatly influences the anaerobic digestion of organic materials. Best fermentation occurs at a temperature of 30-40°C (development of mesophilic bacterial flora), as well as at a temperature of 50-60°C (development of thermophilic bacterial flora). The choice of mesophilic or thermophilic operating mode is based on an analysis of climatic conditions. If significant energy costs are required to provide thermophilic temperatures, then the operation of reactors at mesophilic temperatures will be more efficient.

Along with temperature conditions, the process of methane fermentation and the amount of biogas produced are affected by the time of waste processing.

When operating reactors, it is necessary to control the pH value, the optimal value of which is in the range of 6,7-7,6. The regulation of this indicator is carried out by adding lime.

During normal operation of the reactor, the resulting biogas contains 60-70% methane, 30-40% carbon dioxide, a small amount of hydrogen sulfide, as well as impurities of hydrogen, ammonia and nitrogen oxides. The most efficient reactors operate in thermophilic mode at 43-52°C. With a duration of manure treatment of 3 days, the yield of biogas in such plants is 4,5 liters per liter of useful volume of the reactor. In order to intensify the process of anaerobic manure digestion and release of biogas, organic catalysts are added to the initial mass, which change the ratio of carbon and nitrogen in the fermented mass (optimal ratio C/N=20/1 - 30/1). Glucose and cellulose are used as such catalysts. The approximate nitrogen content and the ratio of carbon and nitrogen content in various wastes by dry weight are presented in table 3.

Table 3. Nitrogen content and C/N ratio in various wastes

The biogas produced during fermentation has a calorific value of 5340-6230 kcal/m3 (6,21+7,24 kWh/m3).

Vigorous mixing must be carried out in fermentation chambers to prevent the formation of a floating substance in the upper part of the layer. This greatly speeds up the fermentation process and the biogas yield. Without stirring, to obtain the same productivity, the volume of the reactors must be significantly increased. Hence, the consequence is high costs and an increase in the cost of installation.

Mixing is carried out:

• mechanical agitators of various shapes or submersible pumps driven by an electric motor,
• hydraulic nozzles due to the energy of the jet pumped by the fermented manure pump or recirculation,
• excess pressure of biogas passed through a bubbler or a tube located at the bottom of the reducer.

The residue resulting from the biogas production process contains a significant amount of nutrients and can be used as fertilizer. The composition of the residue obtained from the anaerobic processing of animal waste depends on the chemical composition of the feedstock loaded into the reactor. Under conditions favorable for anaerobic digestion, about 70% of organic matter is usually decomposed, and 30% is contained in the residue.

The main advantage of anaerobic digestion is that almost all of the nitrogen contained in the feedstock is retained in organic or ammonium form.

The method of anaerobic digestion is the most suitable for the processing of animal waste from the point of view of hygiene and environmental protection, as it provides the greatest decontamination of the residue and the elimination of pathogenic microorganisms.

The liquid phase of manure after anaerobic processing usually meets the requirements for wastewater quality by the environmental authorities. The spent liquid organic mass enters the fermented mass tank through the unloading chamber, and from there it is pumped into tanks, with the help of which ordinary manure mass is applied to the fields.

The amount of biogas that can be isolated from various agricultural wastes, residues and mixtures under optimal anaerobic processing conditions depends on the amount of substrate, process conditions, bacterial composition in the reactor, etc. Some data are shown in Table 4.

Table 4. Output of methane (biogas) during methane digestion of agricultural waste

To increase productivity, different wastes are mixed (table 5).

Table 5. Increase in biogas production when mixing different wastes

It is estimated that the annual need for biogas for heating a residential building is about 45 m2 per 1 m2 of living space, the daily consumption for heating water for 100 heads of cattle is 5-6 m2. The consumption of biogas when drying hay (1 ton) with a moisture content of 40% is 100 m2, 1 ton of grain - 15 m2, to obtain 1 kW. h of electricity - 0,7 + 0,8 m2.

In Ukraine, only large pig and poultry enterprises annually generate more than 3 million tons of organic waste in terms of dry matter, the processing of which will make it possible to obtain about 1 million tons of c.e. tons in the form of biogas, which is equivalent to 8 billion kW. h electricity. In addition, there are about 2 million non-gasified family farmsteads in Ukraine. The experience of countries that are not provided with natural gas (for example, China) shows that it is advisable to gasify remote rural areas with the help of small bio-installations operating on organic waste from family farmsteads. Thus, the introduction of 2 million installations in Ukraine would make it possible to obtain about 2 billion m2 of biogas per year. which is equivalent to 13 billion kWh. h of energy, and would provide family estates with organic fertilizers in the amount of 10 million tons per year.

According to 1990 data, the average annual number of pigs in collective farms, state farms and other farms in Ukraine amounted to almost 20 million heads; for cattle, this figure exceeded 25 million, for sheep and goats, respectively, about 9 million, for birds - about 85 million heads. The amount of manure and manure from such livestock per year: from pigs - 45 million tons, from cattle - more than 290 million tons, sheep and goats - 6 million tons, poultry - almost 4 million tons.

The experience of creating biogas plants shows that their design and technological features are determined by various factors and, first of all, raw materials, their properties and previous processing.

In many countries of the world, both small farm and large industrial plants for processing manure into biogas have been created, tested and successfully operated.

In Germany, there are 60 new biogas plants for the production of biogas from animal waste. Due to the fermentation of waste with a dry residue content of 5 to 15%, biogas is obtained with a calorific value of 5,6 to 6,7 kWh/m2. Biogas density - 1,22 g/m2. Its explosive concentration in the air is from 19 to 25%. Energy consumption for own needs is from 20 to 30% of the biogas produced. The payback period is 4,2 years.

Caterpillar manufactures stand-alone ES (power systems) equipped with spark ignition engines that can use biogas generated from the decomposition of waste in landfills. In Norway, the first of two such power plants with a capacity of 360 kW has been installed. The ES is fully automated, the switching equipment is able to synchronize the operation of the ES with the local power grid. Gas is supplied from 36 wells, 14m deep, penetrating to the waste layer of twenty years ago. This provides a biogas flow rate of 300 m3/hour. The content of methane in biogas is 48-57%. In the south east of England, two biogas power plants provide a combined capacity of 1000 kW for a hydroprocessing plant, of which only 360 kW is used for plant needs, with the remaining 650 kW fed into the national grid.

Blue Cirkle (UK) plans to generate 7,5 MW of electrical power using biogas from 3 landfills in southern England.

In the countries of Western Europe, serial production of flow-type biogas plants has been launched. One such plant processes bird droppings from 10 thousand laying hens, providing an average daily production of 100 m3 of biogas (60% methane), and pays off in 1,9 years when fermented slag is used as organic fertilizer.

In Switzerland, a biogas plant with an average capacity of 100 m3 per day processes the manure of 30 cows fed into an 80 m3 buried sump. A cylindrical tank with a capacity of 540 m3, covered with a polymer film, is used for manure fermentation and biogas storage. Biogas is used to generate electricity in a water heating plant.

A biogas plant is also operated there, all units of which are located directly under the pig farm. The biogas is stored in a tank and used in the heating system. The productivity of a biogas plant with grazing livestock in summer is twice as low as in winter. At the same time, about a third of the biogas is used for its own technological needs, and the rest is used to heat water and heat the farm. 1 m3 of biogas is equivalent to 0,7 l of fuel oil.

Biogas has high anti-knock properties and can serve as an excellent fuel for internal combustion engines with forced ignition and for diesel engines, without requiring their additional re-equipment (only the adjustment of the power system is necessary).

Comparative tests have shown that the specific consumption of diesel fuel is 220 g/kWh of rated power, and that of biogas is 0,4 m3/kWh. This requires about 300 g / kWh (m. b. - 300 g) of starting fuel (diesel fuel used as a "fuel" for biogas). As a result, diesel fuel savings amounted to 86%. At 40% engine load and engine speed of 1400 rpm (average tractor load in Switzerland), diesel fuel consumption is 250 g/kWh, with biogas it is 80 g/kWh, plus biogas consumption 9,6, 3 m70/kWh, which corresponds to almost XNUMX% savings in diesel fuel.

In Wippachdelhausen (Germany), a universal type biogas plant was put into operation, designed for the fermentation of slurry and the processing of cattle, pig and chicken manure. The biogas reactor operates at a temperature of 35°C and a pressure of 2,0-5,0 kPa in both continuous and batch modes.

In Ukraine, in Zaporozhye KTISM, a set of equipment of the "Cobos" type for anaerobic digestion of manure has been developed. Such an installation with a volume of 250 m3 operates in the village. Grebinki Kyiv region. The unit with a manure capacity of 10 m3/day was tested at the Rassvet state farm in the Zaporozhye region - UkrNIIAgroproekt has pilot plants: at the Kiev poultry farm - with a periodic operation of 20 m3, at the Rossiya state farm of the Cherkassy region - with a volume of 200 m3. In the subsidiary farm of the Sumy MNPO them. Frunze for 3000 heads of pigs there is a plant for processing wastewater with a volume of 300 m3.

Technical, economic and operational characteristics of some biogas plants are presented in table 7.

For the development of bioenergy in Ukraine in order to obtain biogas and high-quality fertilizers, it is necessary to create an economic mechanism that stimulates scientific and technical work in this area, the production and implementation of appropriate equipment.

Table 7. Technical, economic and operational indicators of biogas plants

Now we already know that the most common organic waste from a rural farmstead - animal manure, garden tops, weeds and other "organics" - under certain conditions can become a source of much-needed combustible gas in the household, which is suitable for cooking, heating a room and obtaining hot water. Let's call it biogas.

Biogas, if not completely, then at least partially, can meet the needs of rural residents, owners of summer cottages and garden plots for fuel. In addition, in the production of biogas, waste is completely used, as a result, not only the sanitary condition of the territory improves, pathogens of infectious diseases are destroyed, the unpleasant halls of rotting plants disappear, weed seeds die, but also the most valuable high-quality organic fertilizers with an increased humus potential are formed. .

But in order for everyone to be able to build the simplest biogas plant in their backyard with their own hands, it is useful to have an idea about the main features of the technology for producing biogas from organic waste, as well as the factors affecting the performance of biogas plants, and the designs of these plants.

Author: Shomin A.A.

See other articles Section Alternative energy sources.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Alcohol content of warm beer 07.05.2024

Beer, as one of the most common alcoholic drinks, has its own unique taste, which can change depending on the temperature of consumption. A new study by an international team of scientists has found that beer temperature has a significant impact on the perception of alcoholic taste. The study, led by materials scientist Lei Jiang, found that at different temperatures, ethanol and water molecules form different types of clusters, which affects the perception of alcoholic taste. At low temperatures, more pyramid-like clusters form, which reduces the pungency of the "ethanol" taste and makes the drink taste less alcoholic. On the contrary, as the temperature increases, the clusters become more chain-like, resulting in a more pronounced alcoholic taste. This explains why the taste of some alcoholic drinks, such as baijiu, can change depending on temperature. The data obtained opens up new prospects for beverage manufacturers, ... >>

Major risk factor for gambling addiction 07.05.2024

Computer games are becoming an increasingly popular form of entertainment among teenagers, but the associated risk of gaming addiction remains a significant problem. American scientists conducted a study to determine the main factors contributing to this addiction and offer recommendations for its prevention. Over the course of six years, 385 teenagers were followed to find out what factors may predispose them to gambling addiction. The results showed that 90% of study participants were not at risk of addiction, while 10% became gambling addicts. It turned out that the key factor in the onset of gambling addiction is a low level of prosocial behavior. Teenagers with a low level of prosocial behavior do not show interest in the help and support of others, which can lead to a loss of contact with the real world and a deepening dependence on virtual reality offered by computer games. Based on these results, scientists ... >>

Traffic noise delays the growth of chicks 06.05.2024

The sounds that surround us in modern cities are becoming increasingly piercing. However, few people think about how this noise affects the animal world, especially such delicate creatures as chicks that have not yet hatched from their eggs. Recent research is shedding light on this issue, indicating serious consequences for their development and survival. Scientists have found that exposure of zebra diamondback chicks to traffic noise can cause serious disruption to their development. Experiments have shown that noise pollution can significantly delay their hatching, and those chicks that do emerge face a number of health-promoting problems. The researchers also found that the negative effects of noise pollution extend into the adult birds. Reduced chances of reproduction and decreased fertility indicate the long-term effects that traffic noise has on wildlife. The study results highlight the need ... >>

Random news from the Archive Solar power plant on a roll 03.02.2005 In one of the works of the now forgotten Soviet science fiction writer Vladimir Nemtsov, a "solar fabric" appeared - a flexible solar battery made of semiconductor filaments that could be folded, cut, cut and sewn together. Something similar is already produced by the American company "IOP Technologies". These are flexible, rollable solar panels of different power - from 5 to 40 watts, they all give a voltage of 16,5 volts and are designed to charge batteries of various portable electronics - from a mobile phone to a laptop or a small TV. The most powerful of the batteries weighs about 1700 grams.

Other interesting news:

▪ The chances of meeting aliens are almost zero

▪ Dell Inspiron Zino HD

▪ The effect of coffee on memory

▪ Jet engine puts out fires

▪ Molecular electronic chip

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Batteries, chargers. Article selection

▪ article Requirements for lighting of premises and workplaces. Basics of safe life

▪ article What is the largest flying bird? Detailed answer

▪ article Layout designer. Job description

▪ article Regulator-stabilizer of the frequency of rotation of the collector engine. Encyclopedia of radio electronics and electrical engineering

▪ article The spectator holds some cards, but they become different. Focus Secret

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua
2000-2024