Leeuwis, N. Sakyi-Dawson et al. The cases of Benin and Ghana. Vanlauwe, B. Tittonell, and J. Within-farm soil fertility gradients affect response of maize to fertilizer applications in western Kenya. Vermillion, D. Impacts of irrigation management transfer: A review of the evidence.
IWMI Res. IWMI, Colombo. Impacts of Colombia's current irrigation management transfer program. Samad, S. Pusposutardjo, S.
Arif, and S. An assessment of small-scale irrigation management turnover program in Indonesia. Transfer of irrigation management services, guidelines. FAO Irrig. Drainage Pap. Visser, C. Making intellectual property laws work for traditional knowledge. Finger and P. Schuler ed Poor people's knowledge: Promoting intellectual property in developing countries. Vorley, B. Global food chains — constraints and opportunities for smallholders. Agriculture and pro-poor growth team workshop.
OECD, Paris. Fearne and D. Regoverning markets: A place for small- scale producers in modern agri-food chains? Gower Publ. Wals, A. Social learning: Towards a sustainable world. Wageningen Acad. World database of protected areas. Online database. UNEP, Nairobi. Warren, D. Slikkeveer, and D.
Brokensha ed Indigenous knowledge systems: the cultural dimension of development. Kegan Paul Int. Watkins, K. Von Braun. Time to stop dumping on the world's poor.tematika2.relogika.ru/wp-content/montana/399.php
Development of the Technology for Combustion of Large Bales Using Local Biomass
Wei, A. Establishing linkages between globalization, developing country economic growth and agroindustrialization: The case of East Asia. Food Agribusiness Manage. Weiss, R. Tainted Chinese imports common. The Washington Post. May Wennink, B. Heemskerk ed Farmers' organisations and agricultural innovation. Prices of fossil fuels grow proportionally to the decreasing of fossil fuel reserves. Since available reserves of fossil fuels in Serbia, especially those of high quality, are relatively limited, this problem becomes even more emphasized [ 1 - 3 ]. On the other hand, it is necessary to harmonize the energy production legislation and practice in Serbia with the directives of the European Union, in the sense of intensifying the utilization of renewable energy sources and thus reducing pollution and greenhouse effect formation.
Biomass is one of key renewable energy sources [ 4 ]. This is the reason for the development of cheap thermal devices boilers and furnaces burning biomass from agricultural production as quite available and cheap energy source. These devices could be used primarily in villages, small towns and small businesses processing agricultural goods greenhouses, dairy farms, slaughterhouses etc.
The devices could also be used for heating schools, hospitals, prisons and other institutions. Annual energy consumption in the Republic of Serbia currently reaches 15 million tons oil equivalent Mtoe , out of which 7. According to the official date of Ministry of Infrastructure and Energy of Republic of Serbia [ 6 ], Serbia is in dispose of 4. Currently, only a small portion of waste biomass is being used in energy production mostly for heating not taking into account burning in the individual households, in small ovens , for several reasons: low electricity price and non-resolved problems in biomass gathering.
Also, there is no regulated biomass market, and no developed technologies for its utilization as fuel. Besides, small financial power of potential buyers have to be mentioned, as well as costly commercial credits and total absence of state subsidizing of biomass facilities. This biomass is a cheap and available fuel, but its utilization is linked to the problems of its collection, preparations for its transportation cutting, tying into haystacks, baling , transportation and storage [ 7 ]. The best way for utilizing residual agricultural biomass for energy production in industrial or district heating is to be used close to place of its gathering - in large agricultural companies.
That is the optimal solution, from energy, as well as economic point of view. Agricultural biomass is usually collected in form of bales, varying in size and shape, so it is most convenient to use it in that form. One of the most efficient ways, recommended by many institutions worldwide, is the combined heat and power electricity production — CHP [ 8 ], which use residual biomass as fuel, and have least as possible own power consumption.
Two technologies are currently used for the combustion of biomass bales. This technology was found to be very suitable for straw combustion and was deemed not to be associated with any process limitations. In the process of production of different crop residues that occur in some species exceed three times the amount of crops produced. These residues can be baled and still used. Today in Serbia the producers of baled biomass are mainly farmers who receive biomass in baled form as by-products of primary production. Advantages and disadvantages of specific types of bales are the following [ 9 ].
Small conventional bales have many advantages: low cost of presses, binders moderate prices, the need for a smaller tractor, good storage, a favorable agreement on means of transport, simple disintegration and chopping by means of lower prices, the possibility of firing the entire bales and others.
Deficiencies are inevitable manual operation, by hand using auxiliary storage means, a relatively high usage of the binder, the lower reliability than other presses etc. The advantages of large cylindrical bales are moderate presses price, simple and fully mechanized manipulation, in the case of unwinding a simple and inexpensive device, conveniently storing for own needs on medium farms, the opportunity to work with medium power tractors etc.
The disadvantages of this bundle are: the highest consumption of binder, the lower performance because of the need to halt the bale tying and ejection from the workspace, the sensitivity of trusses on the quality of the binder, the deformation under the bonding quality, lower transportability because the empty space, need more storage space etc.
Large square bales have the following advantages: high pressure compression, high performance, low consumption of binder, best transportability, good storage conditions, the whole mechanization and the lowest price of manipulation, the lowest consumption of binder etc.
- Biomass and Liquid Biofuel (Technical Brief).
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The disadvantages are reflected in the following: high initial cost of machinery, required a large tractor, requires special means for manipulation, machinery sensitive to the application of low-quality binders, need of special funds for the disintegration etc. Furnaces and boilers that would use baled biomass from agricultural production can be a wide power range from 0. Baled biomass as a fuel does not require big investments in preparation because balers have nearly every farmer. These are not expensive and complicated machines and do not require high energy consumption per kg of baled biomass.
On the other hand, neither of which would be the biomass used as fuel, not far from the place of origin nor transport is not a major problem. Storage can be a problem, but as there is plenty of farmland damage caused by his occupation is insignificant, and increased investment costs to build a warehouse to quickly pay the difference in price between the liquid or gaseous fuels and biomass.
In addition, profit get from the green credits - benefits that are obtained in the case of renewable energy usage are paid this facilities only through the benefits in a very short period of time. In the Laboratory for Thermal Engineering and Energy of the "Vinca" Institute in Belgrade, efforts have been made to develop a clean technology for utilizing baled biomass for energy production.
The initial set of analyses carried out in the research investigation conducted focused on the combustion of small, 40x50x80 cm straw bales in cigar burners. For the said purpose, an experimental, 75 kWth hot water boiler was designed and constructed [ 9 ]. The furnace was built entirely out of an insulating material providing favorable biomass combustion conditions. Appropriate boiler tests were conducted in order to properly determine required design parameters.
Although the boiler assembly examined was a small-scale facility intended to be used by individual farm owners and utilized for space heating, it provided a good basis for development of large, industrial scale straw-fired facilities. In order to assess the combustion quality and obtain data needed for proper design of the straw-fired hot water boiler, a 1 MWth demonstration furnace was designed, constructed and tested [ 10 ]. As a result of the specified investigation efforts, a pilot plant capable of burning large, 0. The boiler house was built in the immediate vicinity of the greenhouse complex.
Technologies enabling biomass use for energy generation are mainly dependant on biomass characteristics. Different biomass conversion technologies available on the market include: fixed-bed combustion, combustion on the grate, combustion in dust burners, fluidized bed combustion and gasification [ 12 ]. Utilization of agricultural biomass faces a lot of challenges. One of the main disadvantages associated with combustion of agricultural biomass is a tendency of biomass ash to melt [ 13 ]. Cigar burner technology was found to be very suitable for straw combustion and was deemed not to be associated with any process limitations.
The research investigation described herein was focused on developing a cigar burner combustion system suitable for the combustion of bales of various sizes and shapes and their utilization for energy production. The experimental boiler burning small soya, corn, rape seed or wheat straw bales, with 0. The combustion has been organized on the principles of cigarette burning [ 17 ]. Thermal power of the boiler is around 75 kW. In Figure 1 , the scheme of the experimental boiler is shown. Baled straw is introduced through the inlet 3 into the combustion zone 7. The inlet is supplied by devices for continuous bale feedings and provides stable combustion conditions Figures 2 and 3.
Furnace walls 4 have been made of refractory material — chamotte, with thermal insulation 5. Under the original solution fresh air is injected through two channels, the primary air through channel 8 , and secondary air through channel 9 , and they are divided using compartment The tertiary air is supplied through the inlet 12 , and is previously heated by flowing inside the walls In the zone 14 is carried out the process of final combustion of the bale. After the first examination of the boiler some changes were carried out in the distribution of air so that after this change the air for combustion is inserted into the space through the distributor 26 which is connected to a fan of fresh air By changing the position of the air distributor can be regulated the part of the bale involved in combustion and thus indirectly is regulated the heat output of the boiler.
The heat produced by combustion of biomass is transferred by the gas-to-water heat exchanger After passing through the channels 16 to the flue gases collector 17 , the flue gases leave the boiler through the smokestack 18 , equipped with the valve 19 and flue gas fan 28 , and through the cyclone-type particle precipitator Ash is collected in ash collectors 20, 21, and A mobile tube for ash removal 23 has been placed inside the furnace, as well as a tube for pneumatic transport of ash The boiler has a revision opening 25 for manual ash removal.
In order to obtain to plant work at nominal power, heat accumulator thermal reservoir, with volume of 5 m 3 has been installed Figure 2. In this way it is ensured that no matter what the current needs for heating buildings are, boiler always works with the nominal power. Thermal scheme of distribution facilities is shown in Figure 4. From it can be seen following thermal circles: a Hot water from the boiler goes directly into a building that is heated, b Hot water from the boiler goes into heat only tank, c Hot water from the boiler going at the same time in the building and heat reservoir, d Hot water tank from the heat goes into the building.
Also, the boiler is equipped with appropriate management and control system Figure 5. The thermal power of the boiler has been regulated with: the amount of straw engaged in the combustion process, the air excess and the fuel feeding rate. This experimental boiler could be scaled, since it satisfies the similarity requirements in: geometry, flow patterns, thermal load, thermal flux, adiabatic temperature, average temperature and flue gases content.
In order to assess the combustion quality and to obtain data for the design of a soya straw-fired hot water boiler, a demo furnace with thermal power of 1 MW has been designed and built [ 10 , 18 , 19 ]. The appearance of the furnace, with the thermocouple probes, the primary air fan and channel, and the fuel feeding channel is shown in Figure 6.
This furnace has been adopted for cylindrical bales, with 1. The cross is clearly visible on Figure 7 where the scheme of the experimental demonstration unit for burning large rolled soy straw bales was presented. There can be also clearly distinguish three characteristics combustion zones in the cigar burner: drying zone 6 , zone of devolatilization 5 and zone of char burning The proximate analysis of soya straw used in testing is given in Table 1.
Modern Biomass Conversion Technologies | SpringerLink
The sum of five tests was done. A summary of main test parameters is given in Table 2. During all tests, three gas temperatures in the combustion zone were measured, with shielded type K thermocouple probes. Gas sampling was done with a probe placed near the furnace exit. Gas samples were continuously analyzed with two analyzers, collected every 5 seconds and stored on-line. It should be noted that secondary air supply through the movable cross was not present in the first version of the demo furnace, which was examined in tests 1 and 2.
The results from these tests stressed the need to introduce secondary air in the combustion zone, at the bale forehead, and the furnace with secondary air supply through the cross was examined in tests 3, 4 and 5. Test 1 was conducted with one bale of straw placed in the feeding channel. Only temperature measurements were done, and the results showed that the temperature in the combustion zone, in steady conditions, was quite stable o C, Figure 8 for a reasonable period of time 40 minutes.
It was noted that the amount of tertiary air did not contribute much to overall combustion conditions, and that in fact this air over-cooled the flue gases in the combustion zone. In test 2, along with temperatures, gas composition was continuously measured. Less air was supplied as tertiary than in test 1. In the initial, start-up period Figure 9 , gas samples were taken directly from the combustion zone, and very high levels of CO in the flue gases were noted. After the choking of the gas sampling probe and its cleaning, and also in all following tests, gas samples were taken only from the top of the furnace.
Soon after that, stable conditions were obtained Figures 9 and 10 , primarily by adjusting bale feeding.
It was also noted that tertiary air flow rate should be decreased, and therefore secondary air was introduced to the detriment of tertiary air. This change in design was examined in test 3, with two bales placed in the feeding channel. The supply of the secondary air through the cross provided excellent conditions for combustion Figure 11 — the concentration of CO was equal to zero for most of the time during the test.
On the other hand, the stability of the thermal output was found to depend largely on the active length of the bale immersed into the furnace. Therefore, it is of great importance to feed the bale uniformly in accordance with the combustion process, and to maintain this length as stable as possible, by moving the cross accordingly. The temperature instabilities from the minute 45 further on, Figure 11 during this test are a consequence of changes of this length.
The only peak in CO concentration coincided expectedly with low temperatures during this period. The principal aim of test 4 was to assess the possibility of longer furnace operation, with three bales placed inside the feeding channel. The bales prepared for this test were approximately 1. Problems with feeding undersized bales caused instabilities in the first hour of the test.
In the period shown in Figures 1 3 and 14 , the temperature was in the desired range, and CO concentration was acceptable for most of the period up to ppm , the only rise in CO occurring at the time of the temperature downfall minutes It was spotted by visual inspection, through the inspection openings, that the bale was not inside the furnace at the time of the downfall, due to the problems with manual bale feeding and cross positioning — the bale forehead remained inside the tube. This caused the flame to enter the tube at the time, which also occurred during test 5.
The aim of test 5 was to assess the influence of air flow rate control, with variable speed drives, on furnace performance. During a chosen period of 40 minutes Figures 1 5 and 16 , optimal air flow rates were obtained and bale feeding was kept stable. The use of renewable energy sources is becoming more and more important, mainly due to continuously increasing prices of fossil fuels, resource depletion and global attempts to achieve maximum feasible CO 2 emission reduction.
Researches in this area are very complex and in order to obtain reliable data it is necessary to carry out theoretical and experimental research of the process. For this purpose, a 1. The boiler is based on waste baled soybean and other types of straw combustion, and it is used for heating 1 ha m 2 of greenhouses.
Combustion in the boiler carried on so-called "cigarette" principle [ 11 ], where 0. In the developing world, gasifiers can provide something that the grid cannot — reliable electricity for industry. Biomass gasification reactors are simply steel vessels filled with wood chips. With one or more small openings to permit some air to enter, they are connected directly to an engine, and the engine suction pulls the gas through. They need no external water, electricity or gas, as they self-sustain their internal temperature. Reactor designs have changed little since the s, and are based around three main types: updraft, downdraft, and cross-draft.
There are also fixed and fluidised bed gasifiers air or steam gasification , but these are industrial-scale systems. Downdraft, fixed-bed gasifiers are the most widely used, as they produce high-purity gas with relatively low quantities of tar. For anyone with basic fabrication skills, small biomass gasifiers can be self-built, and full details of sizings and components can be found in our publication, Gasification: Succeeding with Small-scale systems.
Made from sturdy basic components, gasifiers are at present much like a classic car, which needs routine maintenance to ensure reliability, but which could last a lifetime. Specialist biomass gasification consultants are rare. In particular, before buying a system, look for the small print about what the feedstock requirements are, since some but not all systems will stipulate wood chip moisture levels below that which can be achieved naturally. Fines content can also be a problem. Outside of design specification feedstock range, temperature in the reactor varies and tar comes through in the gas, which can clog engine pipework.
Some systems use water scrubbing to clean tar from the gas, which can result in high disposal costs throughout the lifetime of the system. Others use basic wood chip filters, which work effectively. It burns with a distinctive blue flame. However, considering that oil and petrol are highly flammable, carcinogenic liquids, producer gas just poses a different hazard.
The gasifier reactor is silent when operating, but the engine will be noisy. In the UK, they are presently not eligible for feed-in tariffs, but system owners can get credits from ROCs and income from the Renewable Heat Incentive, although there are caveats. And finally — remember Wacky Races? Bridgewater, A. Renewable fuels and chemicals by thermal processing of biomass, Chemical Engineering Journal, 91, pp.