ЭНЕРГИЯ БИОМАССЫ
ENERGY OF BIOMASS
Статья поступила в редакцию 17.04.11. Ред. рег. № 964 The article has entered in publishing office 17.04.11. Ed. reg. No. 964
УДК 504.05
ЭНЕРГИЯ БИОМАССЫ: НАПРАВЛЕНИЯ ИСПОЛЬЗОВАНИЯ И ЭКОЛОГИЧЕСКИЕ ПРОБЛЕМЫ
С.М. Говорушко
Тихоокеанский институт географии ДВО РАН 690041 Владивосток, ул. Радио, д. 7 Тел./факс: 8(4232)311653, e-mail: sgovor@tig.dvo.ru
Заключение совета рецензентов: 27.04.11 Заключение совета экспертов: 28.04.11 Принято к публикации: 30.04.11
Рассмотрены различные аспекты биомассы (понятие, пути преобразования биомассы, количественные характеристики в глобальном масштабе). Дана характеристика основных направлений использования биомассы, обсуждены вопросы производства электроэнергии из биогаза и спиртов, описаны экологические проблемы, связанные с использованием энергии биомассы.
Ключевые слова: биомасса, биогаз, спирты, экологические последствия, органические отходы, бактерии, анаэробное сбраживание, свалочный газ, производство электроэнергии.
BIOMASS ENERGY: DIRECTIONS OF USE AND ENVIRONMENTAL ISSUES
S.M. Govorushko
Pacific Geographical Institute FEB RAS 7 Radio str., Vladivostok, 690041, Russia Tel./fax: 8(4232)311653, e-mail: sgovor@tig.dvo.ru
Referred: 27.04.11 Expertise: 28.04.11 Accepted: 30.04.11
Different aspects of biomass (the essence, ways of biomass transformation, the global quantitative parameters). Characteristics of the main directions of biomass using are given, the production of electricity from biogas and alcohols is discussed, the environmental problems associated with the use of biomass energy are described.
Keywords: biomass, environmental consequences, landfill gas, biogas, spirits, generation of electric energy, bacteria, organic wastes, anaerobic fermentation.
Biomass
Biomass is organic matter that retains the energy of the Sun owing to the process of photosynthesis. Its initial form is plants. Further along the food chain, biomass can be transferred to herbivorous animals, and then to carnivores when the herbivorous animals are eaten. In turn, humans also eat plants and animals.
The further transformation of biomass occurs in many ways. Finally, it can be present in the form of manure (Fig. 1), bird droppings, faecal deposits, and domestic waste. Industrial biomass can be grown from numerous types of plants, including miscanthus, switchgrass, hemp, corn, poplar, willow, sorghum, and sugar cane [1]. According to data from different sources, biomass reserves are equivalent to 1.0 [2] to 1.2 billion tons of petroleum [3].
International Scientific Journal for Alternative Energy and Ecology № 4 (96) 2011
© Scientific Technical Centre «TATA», 2011
Рис. 1. Одним из наиболее типичных результатов преобразования биомассы является навоз. Во многих развивающихся странах он используется для получения тепловой энергии. На снимке - высушенные коровьи лепешки, продаваемые в качестве топлива в штате Раджастан, Индия. Фото: С.М. Говорушко, 01.11.2007 Fig. 1. One of the most typical rezults of biomass transformation
is manure. In many developing countries it is used for generation of thermal energy. Dried cow cakes put up for sale as a fuel in Rajasthan State (India) are shown.
Photo credit: S.M. Govorushko, 01.11. 2007
Directions of biomass use
So far, biomass is mainly used for production of heat energy by three basic processes: (1) direct combustion; (2) biomass fermentation; and (3) use of energy carriers produced in the course of biomass transformation (biogas, spirits, etc.) [4].
In the first process, biomass is directly used as a fuel. For example, approximately 2.5 billion people in the world use firewood for heating and cooking (Fig. 2). Firewood accounts for 15% of the world's energy supply and up to 35% of the supply in the developing countries [5]. Share of wood fuels in national energy consumption is shown on Fig. 3.
Рис. 2. Древесина и древесный уголь являются источником
12% всей получаемой энергии. Эти материалы используются, главным образом, в развивающихся странах. Показан рынок топливной древесины в Дарфуре, Судан.
Фото: ЮНЕП, 15 июня 2006 г. Fig. 2. Firewood and woody coal provide 12% of the world's energy; these materials are used largely in the developing countries. The photo shows a fuel wood market in Darfur, Sudan. Photo: UNEP, 15 June 2006
Международный научный журнал «Альтернативная энергетика и экология» № 4 (96) 2011 © Научно-технический центр «TATA», 2011
Энергия биомассы
In the second process, heat released in the course of fermentation by organic waste (manure, droppings, sawdust, etc.) is harnessed. This heat is most often used for heating greenhouses, hotbeds, and other structures. In the third process, such energy carriers as biogas and spirits are extracted from biomass. The generation of electric energy from biomass is possible with the use of the third process.
Electricity generation from biogas and spirits
Biogas, which is produced by the fermentation of biomass, consists of methane, carbon dioxide, and small amounts of other gases such as hydrogen sulphide. Different organic wastes are suitable for this process, such as the following: waste of fish and slaughtering workshops (blood, fat, guts); wastes of starch and treacle production (fibre and syrup, wastes of potato processing and production of chips - peelings, rinds, rotten tubers); wastes of juice manufacturing (fruit, berry, vegetable marc, grape refuse); waste of milk plants (lactoserum as well as manure); and bird droppings and faeces [6].
Decomposition of biomass occurs under the influence of three kinds of bacteria. In the food chain, the subsequent bacteria are supplied with products of the vital functions of the preceding ones. The first kind is hydrolytic, the second is acid-forming, and the third is methane-forming bacteria.
At present, about 60 technologies of biogas production are used or are being developed. The most routine method is the anaerobic fermentation in metatanks or anaerobic columns [7].
Рис. 4. Одним из способов извлечения энергии из биомассы является газификация - процесс превращения органической массы в окись углерода и водород. Показан завод по газификации древесной стружки в г. Гюссинг (Gussing), Австрия. Его мощность составляет 2 МВт электро- и 4 МВт тепловой энергии. Фото: http://en.wikipedia.org/wiki/Biomass_gasification, 2006 г.
Fig. 4. One way of extracting energy from biomass is gasification, the process of turning organic matter into carbon monoxide and hydrogen. The plant for gasification of wood chips in Gussing, Austria is shown. Its capacity is 2 MW of electricity and 4 MW of thermal energy. Photo: http://en.wikipedia.org/wiki/Biomass_gasification
Biogas consists of 55-75% methane and 25-45% carbon dioxide. Gas yield depends on the content of dry substance and the kind of raw materials used. One ton of cattle manure may provide 50-65 cubic metres of biogas with a methane content of 60%. By using different kinds of plants, one can produce 150-500 cubic metres of biogas with methane contents of up to 70%. The maximal quantity of biogas (1,300 cubic metres), with methane contents of up to 87%, can be obtained from fat. The plant for gasification of wood chips is shown on Fig. 4.
One kind of biogas is landfill gas. It is obtained in the dumps of municipal domestic waste. In 2002, 350 landfill gas production plants in the United States and 750 plants in Europe were in operation. The total number of such plants in the world is 1,152, and the total energy generated is 3,929 megawatts, while the amount of waste treated is 4,548 million tons [6]. The plant for landfill gas production and one of technological stage are shown on Fig. 5 and 6.
Рис. 5. Завод по производству лэндфилл-газа в Тель-Авиве, Израиль. Он перерабатывает 150 т бытовых отходов в сутки. Фото: В. Кантор, Гринпис, Россия Fig. 5. A plant for landfill gas production in Tel Aviv, Israel, is shown. It was rated at processing 150 tons of waste a day. Photo credit: V. Kantor, Greenpeace, Russia
Рис. 6. Твердые бытовые отходы являются вторым по важности источником биогаза после отходов лесного и сельского хозяйства. С 1 кубометра биогаза можно получить от 2 до 3 киловатт-часов электроэнергии. Показаны муниципальные бытовые отходы на заводе по производству биогаза в Тель-Авиве, Израиль Фото: В. Кантор, Гринпис, Россия Fig. 6. Solid municipal wastes as a source of biogas are second in importance to wastes of forestry and agriculture. From 1 cubic metre of biogas, one can obtain from 2 to 3 kilowatt-hours of electric power. Delivered municipal household wastes in the plant for landfill gas production in Tel Aviv, Israel, are shown. Photo credit: V. Kantor, Greenpeace, Russia
International Scientific Journal for Alternative Energy and Ecology № 4 (96) 2011
© Scientific Technical Centre «TATA», 2011
From 1 cubic metre of biogas, one can obtain from 2 to 3 kilowatt-hours of electric power. There are several techniques for generating electric power from biomass through its gasification. For electric power generation, the following equipment can be used: gas turbine units, steam turbine plants, gas-diesel plants, or internal combustion engines with spark ignition [8].
In 2002, 9,733 megawatts of generating facilities operating on biomass were installed in the United States. Of this amount, 5,886 megawatts ran on waste of forestry and agriculture, 3,308 megawatts were produced from solid municipal waste, and 539 megawatts relied on other sources. In 2003, 4% of the total energy in the United States was generated from biomass. In 2004, a total output of 35,000 megawatts was produced from biomass.
Power generation from spirits is also possible. The spirits are obtained by way of fermentation of sugar-containing and starch-containing products (cereals, potatoes, sugar beets, and sugar cane). For example, the extraction of ethanol from sugar cane bagasse is extensively used in Brazil. Presently, it is economically viable to extract about 2
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