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Densified biomass in Thailand: Potential, status and problems
Biomass 8 (1985) 255-266
Densified Biomass in Thailand: Potential, Status and Problems S.C. Bhattacharya, R. Bhatia, M.N. Islam and N. Shah Energy Technology Division, Asian Institute of Technology, Bangkok, Thailand (Received: 29 April, 1985) ABSTRA CT The potential o f the use of densifled rice husks and sawdust in Thailand is analysed from an energy viewpoint. A survey of densified fuel manufacturers and the market was conducted and a number of densification machines were found to be lying idle, chiefly due to lack of a market lbr the fuel. An economic analysis of briquette making from sawdust is presented and explanations for the partial commercial failure of this technology detailed. Key words: rice husk, sawdust, densification, briquettes, agricultural residues.
INTRODUCTION Fuelwood and charcoal are the predominant fuels for about 70% of the total population of about 50 million which reside in rural areas of Thailand and a m o u n t to more than 30% of the country's gross energy requirements. The destruction o f forests, used for fuelwood and charcoal, is not matched by reforestation. The cost of imported fuel is high. Hence, the application of densification technology to agricultural residues would appear to have an important role to play in Thailand and other developing countries in a similar situation. In Thailand there has been interest in producing densified fuels based on agro-industrial residues for usage as a substitute of wood fuel for the past 5 to 6 yr. Such fuel can be used in small scale industries and for cooking in households, as well as to produce charcoal. 255 Biomass 0144-4565/85/$03.30- © Elsevier Applied Science Publishers Ltd, England, 1985. Printed in Great Britain
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S. C. Bhattacharya, R. Bhatia, M. N. Islam, N. Shah
The advantages o f densification are: (i) the process produces a fuel which is uniform in size and quality; (ii) it increases the net calorific value o f the material per unit of volume; (iii) it creates an alternative to fuelwood and w o o d charcoal; (iv) the end product is far easier to transport and store than the loose biomass; (v) it helps in solving the problem o f disposal o f the agricultural residues. In the early 1980s several hundred commercial densification machines had been installed and the technology appeared to have established firm roots in Thailand. In the few years since then, the densified fuel market has suffered serious setback.
POTENTIAL RAW MATERIALS F O R DENSIFICATION Ligno-cellulose residues which can be converted into densified fuels (briquettes) include rice husk, sawdust, bagasse, groundnut shell, and coconut fibre. These amount to several million tonnes per year, as shown in Table 1. Approximately 4.2 million t of rice husks were produced in 1982. A saw mill processing 25 t o f round w o o d per day will generate 2-3 t of sawdust] Thailand produces about 2.3 million (1982) t o f wood, 2'4 yielding sawdust amounting to a b o u t 770 TJ yr -1 on a heat equivalence basis. The production of rice, sugarcane, and associated residues, for the crop year 1982-83 is given in Table 1. Although there is an apparent large energy potential in these residues, there are several constraints in their usage as fuel source. These include aspects of collection, transportation, the low energy density and other alternate traditional uses as non-energy and energy materials. However, the use of rice husk and sawdust would not present collection and transportation problems and hence they appear to be the more attractive raw materials.
DENSIFICATION PRACTICE IN T H A I L A N D Briquetting machines and their
suppliers
The three developers of densification machines in Thailand are located in the Bangkok district. They are:
Densifled biomass in Thailand: potential, status and problems
257
TABLE 1
Amount and Energy Content of Major Agricultural and Agro-industrial Residues in Thailand, for the Crop Year 1982/833 Residues
Residue amount (thous. t)
Residue yield (t ha-1)
Energy content (x 1015 J)
Cassava stalks Coconut husks Coconut shells Cotton stalks Groundnut stalks Maize stalks Mungbean stalks Rice straw Rice husks Sorghum stalks Soybean stalks Bagasse Sawdust and shavings
7 115.20 355.08 161.40 244.00 363.25 6 004.60 703.25 25 318-50 4 219.75 827.05 340.20 5 857.68 -
5.76 0.91 0.41 2.13 2.98 3.58 1.45 2.63 0.44 3.37 2.73 10-04 -
39.84 4.62 2.91 1.37 2.03 33.62 3.94 212-66 58.23 4-63 1.90 82.00 0.77
Total
448.52
(a) VS Machine: 90/20 Soi 1, Laprao Road, Bangkok 10900 (the largest supplier). (b) Thailand Institute of Scientific and Technological Research (TISTR): 196 Paholyotin Road, Bangkane, Bangkok. (c) S.P. Energy: 53 Moo 6, Ladkrabang, Bangkok 10520 (developing a machine). Technical details and cost o f machines All the densification machines supplied by different manufacturers in Thailand basically follow the same design pattern. The machines are extrusion devices using a screw to force the feedstock into a die forming large hollow cylindrical logs having an outside diameter of about 5 cm and an inside diameter of about 2-5 cm. The throughput is about 100 kg h -1. The design appears to have originated from Taiwan. The die is heated from the outside by electricity or briquette combustion to
258
S. c. Bhattacharya, R. Bhatia, M. iV. 1slam, N. Shah
cause lignin softening that is necessary for proper binding action. The cost o f machines made in Thailand compares very favourably with the cost o f similar machines available elsewhere in the world. Ref. 1 presents a comparison o f costs of briquetting machines available worldwide.
Densified fuel manufacturers in Thailand The precise number o f machines in operation for briquette making in Thailand is not known. It has been estimated that the number o f individuals owning the machines in Thailand was about 100 and that between them they possessed about 300 machines. On a heat equivalent basis, this would represent an installed capacity of about 1600 TJ yr -1. However, the location o f all the machine owners could not be established. In this study 27 briquette manufacturers were located. Fifteen manufacturers have the capability of making briquettes from rice husk, and nine 6 f them use sawdust. One manufacturer uses both raw materials. Another machine is at the Asian Institute of Technology and is used for experimental work.
Quality of briquette and charcoal The quality o f briquettes made from sawdust and rice husk is compared with mangrove fuelwood in Table 2. It is clear that the briquette made
TABLE 2 The Quality of Fuel from Sawdust and Rice Husk Briquettes, and Mangrove Fuelwood s Quality
Moisture (%) Carbon (%) Volatile matter (%) Ash (%) Calorific value (kcal kg-1) Density (kg m-3)
Sawdust briquettes
Rice husk briquettes
Mangrove fuelwood
5.7 24-9 72.5 2-6 4 820 1 257
5.9 20.4 62.1 17-5 3 900 1 325
8-0 22.8 73.3 3.9 4 390 626
Densified biomass in Thailand: potential, status and problems
259
TABLE 3 Quality of Charcoal from Sawdust and Rice Husk Briquettes, and Mangrove Fuelwoods Quality
Moisture (%) Carbon (%) Volatile matter (%) Ash (%) Calorific value (kcal kg-I) Density (kg m-3)
Charcoal Sawdust briquettes
Rice husk briquettes
Wood
3.5 83.6 10.6 6.2 7 530 875
2.2 59.8 6.3 33.9 4 820 885
9.4 84.6 10-0 5.4 7 450 705
from sawdust has similar qualitites to the mangrove fuelwood. Rice husk briquette is an inferior fuel in comparison because o f its high ash content. The ash content depends on the paddy variety and can be higher than the value given here. Table 3 compares the composition o f charcoal made from sawdust and rice husk briquettes with that produced from Mangrove wood. The charcoals from Mangrove wood and briquetted sawdust are similar. However, again the rice husk product has a higher ash content and a lower calorific value.
PROBLEMS ASSOCIATED WITH DENSIFIED FUELS IN THAILAND In order to find out details about the current operational status of the densification machines a number o f field visits were made. In addition, a small questionnaire was prepared. However, the responses to the questionnaire were very poor.
Survey of fuel producers Almost all of the densification machines visited have been installed during the past 4 to 5 yr. This was associated with an influx of
260
S. C. Bhattacharya, R. Bhatia, M. N. Islam, N. Shah
Kampuchean refugees into Thailand; the briquettes being provided to the refugees for use as fuel for cooking purposes. Fuel producers could be classified into three categories according to the source of raw material used for making briquettes: (i) rice mill owners with their own supply potential of rice husk; (ii) saw mill owners with their own supply potential of sawdust; (iii) fuel producers without their own source of raw material. Rice mill owners
The rice mills surveyed by the team ranged in capacities from 24 to 500 t day -1. At seven out of eight places the rice husks were being utilised for steam generation in the rice mills themselves, and at one place electricity from the grid was being used for the power requirements. The rice mill owners claimed from 20% to 30% o f paddy gets converted into rice husk, depending upon milling efficiency, rice varieties, etc. However, although there were on average four machines installed at each location there was no ongoing briquette production. A b o u t 4 to 5 yr ago, apparently, there was some demand for briquetted fuel to be used in Kampuchean refugee camps, b u t for the last 2 to 3 yr use of densified fuels in refugee camps appears to have ceased. At two locations the purchased machines were not installed and the predominant reason for this was the lack of market demand for the fuel. In general, the rice husks left over after steam generation were either disposed of free o f cost to villagers or sold to brick manufacturers where the price that could be commanded ranged from about 3.7 to 9.3 US$ t -1. One rice mill owner claimed that he not only utilised all o f the rice husk produced in milling, but he also sometimes bought additional quantities. Other alternative uses of rice husk indicated were as poultry litter and filling material in the form o f ashes, firing claybricks, as a packaging material for egg protection, etc. However, in spite of all the uses, there were indications that disposal of b o t h rice husk ash and rice husk itself was a problem in some regions. An interesting case is that of a Saraburi rice mill owner. In the period 1980-81, he had invested about U S $ 1 5 0 000 to set up 15 densification machines in his rice mill. Initially he could sell his product to the refugee camps, at prices of about 45 US$ t -1 ofdensified fuel, but for the past 2 yr he has dismantled his installation due to lack of demand for
Densified biomass in Thailand: potential, status and problems
261
the product. Since then he has sold some of his densification machines to other users or scrapped them. None o f the past fuel manufacturers complained of any major technical problems with the densification machines. They said that the technology was simple and reliable. S a w mill o w n e r s
Two saw mills were visited during the period of study. At one location machines bought in 1980 are currently out of operation. The sawdust is disposed of at a negligible price (or even cost free) to anyone who comes and collects it. The machines were not being used due to lack of demand for densified fuels and excessive electricity consumption by the machines. At the second location the machines were installed in January, 1984 and have been used since then for 8 h day -1 on alternate days in a week. The owner indicated that about 10% w / w of the logs becomes sawdust. Also, the a m o u n t o f sawdust obtained from s o f t w o o d species is larger than that obtained from hardwood species, as s o f t w o o d is often sawn into finer sizes than hardwood. The owner claims to have sold briquettes in the past, to the refugee camps, at a price of about 46 US$ t -1. Alternatively, he could sell sawdust at about 5.2 US$ t -1. Again there was an absence of a market demand for the briquettes, but there was no technical problem in manufacturing briquettes. M a n u f a c t u r e r s w i t h no raw material o f their o w n
Three producers of this kind, who b u y the raw materials, rice husk or sawdust from various mills, were visited. Out of these three, one using rice husk as raw material had gone out of operation. Before this he was selling briquettes to refugee camps at a price of about 44 US$ t -a. At two other places sawdust is used as raw material and both these producers are apparently doing good business. At one location the entire production of briquettes is pyrolised and briquetted charcoal (or 'tube' charcoal, as it is locally termed) is then sold in the open market. The daily production is estimated to be about 2.1 t of briquetted charcoal, sold at an ex-factory price of 0.41 US$ bag -1, each bag being 3 kg. At the second place the sawdust costs about 11 US$ t -1, and 70% of the o u t p u t is converted into charcoal and sold at 0.41 US$ bag -a, each being 3 kg. The remaining 30% is sold in uncarbonised form, presum-
262
s. c. Bhattacharya, R. Bhatia, M. N. Islam, N. Shah
ably to refugee camps, at a price of US$52 t -1. The facilities contain several sheet metal charcoal kilns for charcoal production from the briquetted logs. This operation has now been running for a year. Survey o f the market Briquetted sawdust charcoal is supplied to the (Rangsit) market by the local producer. The producer sells the charcoal at the price of 0.41 US$ bag -1 (3 kg) to the distributor, who carries it to the market, and sells each bag to the retailers and the consumers at 0.44 US$ bag -1. The market is located at a distance o f a b o u t 2-3 km from the producer. The retailer sells the charcoal at 0.48 US$ bag -1. Consumers felt that briquetted charcoal is preferable to woodfuel charcoal as it does not give o f f sparks when burned. They also feel that it has a higher calorific value than w o o d charcoal, a fact which we know to be correct. The entire production o f one producer, i.e. more than 2 t o f charcoal per day is sold in this manner. It appears that there exists no consumer market for the uncarbonised densified briquettes. The fuel can be used with the Thai bucket-type stoves without any problem.
ECONOMIC ANALYSIS OF SAWDUST B R I Q U E T T E MAKING The following economic analysis has been done based on an installation o f four extrusion type densification machines with a rotary drier and other ancillary distribution arrangements. It is assumed that a densification machine produces 800 kg of briquettes in 8 h o f operation. 1. Costs: A . Initial i n v e s t m e n t costs."
(i) Cost o f four extrusion machines + installation (ii) Cost o f rotary drier + cyclone + distribution system + installation cost (iii) Civil works (iv) Miscellaneous Total
US$ 14 800 13 700 1 850 1 850 32 200
Densified biomass in Thailand: potential, status and problems B. Annual expenses: Assuming that machines are operated for 300 days yr -1 (i) Labour cost: @ $2.6 day -1 of 8 h, and assuming that labour is paid for the whole year for six persons 6 × 2.6 X 365 (ii) Electricity: 0.17 kWh per briquetted log of 1.3 kg (0.17)/(1.3) × 800 kg day -~ × 300 days yr -~ X $0.056 kWh -1 × 4 machines (iii) Maintenance: replacement of screw 15 times year -1 machine -1 + other expenditure: $22 (screw cost) X 15 × 4 machines = 1330 + 520 (iv) Raw material: assuming a 30% process loss during the entire process (800)/(0.7) X 300 days yr -1 × $0.011 kg -1 × 4 machines (v) Land rent: @ $370 month -1 (vi) Miscellaneous
Total
263
US$
5 680
6 970
1 850
15 240 4 440 1 850 36 030
2. Benefits. The benefits could either be by sale of briquettes or by sale of briquetted charcoal. However, there is no evidence of sale of uncarbonised briquettes (see section on Survey of the Market).
Sale of carbonised fuel: @ $0-407 bag -1 of 3 kg and assuming a conversion efficiency by weight of 25%: 800 × 0.25 × 0-407/3 × 300 days X 4 machines 32 600 3. Economic life." The economic life of the unit has been taken as 10 and 7 years for 8 and 16 h day -x o f operation, respectively. 4. Salvage value: Salvage value of the whole unit at the end of economic operation has been taken as US$3700.
For the purposes of financial calculation, the carbonisation costs of the briquetted fuel blocks, being very small, have been neglected. A sensitivity study was carried out using the following parameters: char-
264
S. c. Bhattacharya, R. Bhatia, M. iV. 1slam, iV. Shah
coal sale price from 8 to 14 Bahts bag -1 of 3 kg (note that 27 ]~ = 1US$); charcoal conversion efficiencies by weight from 20% to 30%; and raw material process loss from 10% to 30%. The internal rate of return was calculated in each case and the calculations repeated for a 16 h day -~ (two shifts) operation. The results of the analysis are expressed in graphical form in Figs 1 and 2. As was mentioned in the section on Survey of the Market, the briquetted charcoal selling price presently stands at 11 Bahts bag -] of 3 kg. At this price, even when considering the ideal case with process loss 10% and a charcoal yield o f 30% (by weight), the rates o f return are very low and even a slight decrease in any one o f the parameters can cause the operation to be uneconomical. The situation changes radically in Fig. 2 when the plant is operated in two shifts, and this results in better financial returns. The results clearly reveal the high sensitivity o f the briquetting process to the selling price o f charcoal and the charcoal yield by weight. As is seen from the figures, if charcoal yields are at around 20%, there exists no way in which the process can be economical. Above all, small changes in selling price can shift the rates of return dramatically.
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Kg.
IRR vs selling price of charcoal for different charcoal yields and process losses - for 8 h day-1 operation.
265
Densified biomass in Thailand." potential, status and problems Charcoal
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IRR vs selling price of charcoal for different charcoal yields and process losses - for 16 h day-1 operation.
REMARKS AND CONCLUSIONS (i) Densification of agricultural-residues, especially rice husk and sawdust, is technically well established in Thailand. (ii) Some, indigenous, extrusion type densification machine suppliers (manufacturers) are available in Thailand. (iii) A number of densification machines have been installed in Thailand. However, many of the machines that were actually visited during the course of this study were not being operated. A number o f reasons have been found for this. Amongst these are : (a) Lack of market for the briquetted fuel blocks. (b) The economics of briquette making does not compare favourably with prices at which traditional fuels can be bought. (iv) The utilisation of rice husk for briquetting appears to be limited by the fact that many of the larger capacity rice mills (as far as could be observed during the field visits) are utilising the husk to meet their own energy requirements.
266
S. c. Bhattacharya, R. Bhatia, M. iV. Islam, N. Shah
(v) The usage o f sawdust appears to be more promising for briquetting. Sawdust has no real alternative use apart from being used as a fuel. (vi) The Thai traditional fuels - w o o d and charcoal - are relatively very cheap thus far underpricing the levels at which briquettes can be sold.
ACKNOWLEDGEMENT We are grateful for the support received during the course o f this study from the European Economic C o m m u n i t y (Directorate General for Development).
REFERENCES 1. Smith, A. E., Flynn, G. & Breag, G. R. (1983). A profile of the briquettingof agricultural and forestry residues, London, Tropical Development and Research Institute. 2. Forest Statistics Section (1982). Forestry statistics, 1982, Bangkok, Royal Forest Department. 3. Center for Agricultural Statistics Office of Agricultural Economics (1982). Agricultural statistics o f Thailand crop year 1982/83, Agricultural Statistics No. 202, Bangkok, Ministry of Agriculture and Cooperatives. 4. Asian Institute of Technology (I 983). Evaluation and selection of ligno-cellulose wastes which can be converted into substitute fuels, Bangkok, Division of Energy Technology, Asian Institute of Technology. 5. Phithakannoph, N. (1984). The densifiedfuelfrom residue, Thailand Institute of Scientific and Technological Research, Thailand.
Densified Biomass in Thailand: Potential, Status and Problems S.C. Bhattacharya, R. Bhatia, M.N. Islam and N. Shah Energy Technology Division, Asian Institute of Technology, Bangkok, Thailand (Received: 29 April, 1985) ABSTRA CT The potential o f the use of densifled rice husks and sawdust in Thailand is analysed from an energy viewpoint. A survey of densified fuel manufacturers and the market was conducted and a number of densification machines were found to be lying idle, chiefly due to lack of a market lbr the fuel. An economic analysis of briquette making from sawdust is presented and explanations for the partial commercial failure of this technology detailed. Key words: rice husk, sawdust, densification, briquettes, agricultural residues.
INTRODUCTION Fuelwood and charcoal are the predominant fuels for about 70% of the total population of about 50 million which reside in rural areas of Thailand and a m o u n t to more than 30% of the country's gross energy requirements. The destruction o f forests, used for fuelwood and charcoal, is not matched by reforestation. The cost of imported fuel is high. Hence, the application of densification technology to agricultural residues would appear to have an important role to play in Thailand and other developing countries in a similar situation. In Thailand there has been interest in producing densified fuels based on agro-industrial residues for usage as a substitute of wood fuel for the past 5 to 6 yr. Such fuel can be used in small scale industries and for cooking in households, as well as to produce charcoal. 255 Biomass 0144-4565/85/$03.30- © Elsevier Applied Science Publishers Ltd, England, 1985. Printed in Great Britain
256
S. C. Bhattacharya, R. Bhatia, M. N. Islam, N. Shah
The advantages o f densification are: (i) the process produces a fuel which is uniform in size and quality; (ii) it increases the net calorific value o f the material per unit of volume; (iii) it creates an alternative to fuelwood and w o o d charcoal; (iv) the end product is far easier to transport and store than the loose biomass; (v) it helps in solving the problem o f disposal o f the agricultural residues. In the early 1980s several hundred commercial densification machines had been installed and the technology appeared to have established firm roots in Thailand. In the few years since then, the densified fuel market has suffered serious setback.
POTENTIAL RAW MATERIALS F O R DENSIFICATION Ligno-cellulose residues which can be converted into densified fuels (briquettes) include rice husk, sawdust, bagasse, groundnut shell, and coconut fibre. These amount to several million tonnes per year, as shown in Table 1. Approximately 4.2 million t of rice husks were produced in 1982. A saw mill processing 25 t o f round w o o d per day will generate 2-3 t of sawdust] Thailand produces about 2.3 million (1982) t o f wood, 2'4 yielding sawdust amounting to a b o u t 770 TJ yr -1 on a heat equivalence basis. The production of rice, sugarcane, and associated residues, for the crop year 1982-83 is given in Table 1. Although there is an apparent large energy potential in these residues, there are several constraints in their usage as fuel source. These include aspects of collection, transportation, the low energy density and other alternate traditional uses as non-energy and energy materials. However, the use of rice husk and sawdust would not present collection and transportation problems and hence they appear to be the more attractive raw materials.
DENSIFICATION PRACTICE IN T H A I L A N D Briquetting machines and their
suppliers
The three developers of densification machines in Thailand are located in the Bangkok district. They are:
Densifled biomass in Thailand: potential, status and problems
257
TABLE 1
Amount and Energy Content of Major Agricultural and Agro-industrial Residues in Thailand, for the Crop Year 1982/833 Residues
Residue amount (thous. t)
Residue yield (t ha-1)
Energy content (x 1015 J)
Cassava stalks Coconut husks Coconut shells Cotton stalks Groundnut stalks Maize stalks Mungbean stalks Rice straw Rice husks Sorghum stalks Soybean stalks Bagasse Sawdust and shavings
7 115.20 355.08 161.40 244.00 363.25 6 004.60 703.25 25 318-50 4 219.75 827.05 340.20 5 857.68 -
5.76 0.91 0.41 2.13 2.98 3.58 1.45 2.63 0.44 3.37 2.73 10-04 -
39.84 4.62 2.91 1.37 2.03 33.62 3.94 212-66 58.23 4-63 1.90 82.00 0.77
Total
448.52
(a) VS Machine: 90/20 Soi 1, Laprao Road, Bangkok 10900 (the largest supplier). (b) Thailand Institute of Scientific and Technological Research (TISTR): 196 Paholyotin Road, Bangkane, Bangkok. (c) S.P. Energy: 53 Moo 6, Ladkrabang, Bangkok 10520 (developing a machine). Technical details and cost o f machines All the densification machines supplied by different manufacturers in Thailand basically follow the same design pattern. The machines are extrusion devices using a screw to force the feedstock into a die forming large hollow cylindrical logs having an outside diameter of about 5 cm and an inside diameter of about 2-5 cm. The throughput is about 100 kg h -1. The design appears to have originated from Taiwan. The die is heated from the outside by electricity or briquette combustion to
258
S. c. Bhattacharya, R. Bhatia, M. iV. 1slam, N. Shah
cause lignin softening that is necessary for proper binding action. The cost o f machines made in Thailand compares very favourably with the cost o f similar machines available elsewhere in the world. Ref. 1 presents a comparison o f costs of briquetting machines available worldwide.
Densified fuel manufacturers in Thailand The precise number o f machines in operation for briquette making in Thailand is not known. It has been estimated that the number o f individuals owning the machines in Thailand was about 100 and that between them they possessed about 300 machines. On a heat equivalent basis, this would represent an installed capacity of about 1600 TJ yr -1. However, the location o f all the machine owners could not be established. In this study 27 briquette manufacturers were located. Fifteen manufacturers have the capability of making briquettes from rice husk, and nine 6 f them use sawdust. One manufacturer uses both raw materials. Another machine is at the Asian Institute of Technology and is used for experimental work.
Quality of briquette and charcoal The quality o f briquettes made from sawdust and rice husk is compared with mangrove fuelwood in Table 2. It is clear that the briquette made
TABLE 2 The Quality of Fuel from Sawdust and Rice Husk Briquettes, and Mangrove Fuelwood s Quality
Moisture (%) Carbon (%) Volatile matter (%) Ash (%) Calorific value (kcal kg-1) Density (kg m-3)
Sawdust briquettes
Rice husk briquettes
Mangrove fuelwood
5.7 24-9 72.5 2-6 4 820 1 257
5.9 20.4 62.1 17-5 3 900 1 325
8-0 22.8 73.3 3.9 4 390 626
Densified biomass in Thailand: potential, status and problems
259
TABLE 3 Quality of Charcoal from Sawdust and Rice Husk Briquettes, and Mangrove Fuelwoods Quality
Moisture (%) Carbon (%) Volatile matter (%) Ash (%) Calorific value (kcal kg-I) Density (kg m-3)
Charcoal Sawdust briquettes
Rice husk briquettes
Wood
3.5 83.6 10.6 6.2 7 530 875
2.2 59.8 6.3 33.9 4 820 885
9.4 84.6 10-0 5.4 7 450 705
from sawdust has similar qualitites to the mangrove fuelwood. Rice husk briquette is an inferior fuel in comparison because o f its high ash content. The ash content depends on the paddy variety and can be higher than the value given here. Table 3 compares the composition o f charcoal made from sawdust and rice husk briquettes with that produced from Mangrove wood. The charcoals from Mangrove wood and briquetted sawdust are similar. However, again the rice husk product has a higher ash content and a lower calorific value.
PROBLEMS ASSOCIATED WITH DENSIFIED FUELS IN THAILAND In order to find out details about the current operational status of the densification machines a number o f field visits were made. In addition, a small questionnaire was prepared. However, the responses to the questionnaire were very poor.
Survey of fuel producers Almost all of the densification machines visited have been installed during the past 4 to 5 yr. This was associated with an influx of
260
S. C. Bhattacharya, R. Bhatia, M. N. Islam, N. Shah
Kampuchean refugees into Thailand; the briquettes being provided to the refugees for use as fuel for cooking purposes. Fuel producers could be classified into three categories according to the source of raw material used for making briquettes: (i) rice mill owners with their own supply potential of rice husk; (ii) saw mill owners with their own supply potential of sawdust; (iii) fuel producers without their own source of raw material. Rice mill owners
The rice mills surveyed by the team ranged in capacities from 24 to 500 t day -1. At seven out of eight places the rice husks were being utilised for steam generation in the rice mills themselves, and at one place electricity from the grid was being used for the power requirements. The rice mill owners claimed from 20% to 30% o f paddy gets converted into rice husk, depending upon milling efficiency, rice varieties, etc. However, although there were on average four machines installed at each location there was no ongoing briquette production. A b o u t 4 to 5 yr ago, apparently, there was some demand for briquetted fuel to be used in Kampuchean refugee camps, b u t for the last 2 to 3 yr use of densified fuels in refugee camps appears to have ceased. At two locations the purchased machines were not installed and the predominant reason for this was the lack of market demand for the fuel. In general, the rice husks left over after steam generation were either disposed of free o f cost to villagers or sold to brick manufacturers where the price that could be commanded ranged from about 3.7 to 9.3 US$ t -1. One rice mill owner claimed that he not only utilised all o f the rice husk produced in milling, but he also sometimes bought additional quantities. Other alternative uses of rice husk indicated were as poultry litter and filling material in the form o f ashes, firing claybricks, as a packaging material for egg protection, etc. However, in spite of all the uses, there were indications that disposal of b o t h rice husk ash and rice husk itself was a problem in some regions. An interesting case is that of a Saraburi rice mill owner. In the period 1980-81, he had invested about U S $ 1 5 0 000 to set up 15 densification machines in his rice mill. Initially he could sell his product to the refugee camps, at prices of about 45 US$ t -1 ofdensified fuel, but for the past 2 yr he has dismantled his installation due to lack of demand for
Densified biomass in Thailand: potential, status and problems
261
the product. Since then he has sold some of his densification machines to other users or scrapped them. None o f the past fuel manufacturers complained of any major technical problems with the densification machines. They said that the technology was simple and reliable. S a w mill o w n e r s
Two saw mills were visited during the period of study. At one location machines bought in 1980 are currently out of operation. The sawdust is disposed of at a negligible price (or even cost free) to anyone who comes and collects it. The machines were not being used due to lack of demand for densified fuels and excessive electricity consumption by the machines. At the second location the machines were installed in January, 1984 and have been used since then for 8 h day -1 on alternate days in a week. The owner indicated that about 10% w / w of the logs becomes sawdust. Also, the a m o u n t o f sawdust obtained from s o f t w o o d species is larger than that obtained from hardwood species, as s o f t w o o d is often sawn into finer sizes than hardwood. The owner claims to have sold briquettes in the past, to the refugee camps, at a price of about 46 US$ t -1. Alternatively, he could sell sawdust at about 5.2 US$ t -1. Again there was an absence of a market demand for the briquettes, but there was no technical problem in manufacturing briquettes. M a n u f a c t u r e r s w i t h no raw material o f their o w n
Three producers of this kind, who b u y the raw materials, rice husk or sawdust from various mills, were visited. Out of these three, one using rice husk as raw material had gone out of operation. Before this he was selling briquettes to refugee camps at a price of about 44 US$ t -a. At two other places sawdust is used as raw material and both these producers are apparently doing good business. At one location the entire production of briquettes is pyrolised and briquetted charcoal (or 'tube' charcoal, as it is locally termed) is then sold in the open market. The daily production is estimated to be about 2.1 t of briquetted charcoal, sold at an ex-factory price of 0.41 US$ bag -1, each bag being 3 kg. At the second place the sawdust costs about 11 US$ t -1, and 70% of the o u t p u t is converted into charcoal and sold at 0.41 US$ bag -a, each being 3 kg. The remaining 30% is sold in uncarbonised form, presum-
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s. c. Bhattacharya, R. Bhatia, M. N. Islam, N. Shah
ably to refugee camps, at a price of US$52 t -1. The facilities contain several sheet metal charcoal kilns for charcoal production from the briquetted logs. This operation has now been running for a year. Survey o f the market Briquetted sawdust charcoal is supplied to the (Rangsit) market by the local producer. The producer sells the charcoal at the price of 0.41 US$ bag -1 (3 kg) to the distributor, who carries it to the market, and sells each bag to the retailers and the consumers at 0.44 US$ bag -1. The market is located at a distance o f a b o u t 2-3 km from the producer. The retailer sells the charcoal at 0.48 US$ bag -1. Consumers felt that briquetted charcoal is preferable to woodfuel charcoal as it does not give o f f sparks when burned. They also feel that it has a higher calorific value than w o o d charcoal, a fact which we know to be correct. The entire production o f one producer, i.e. more than 2 t o f charcoal per day is sold in this manner. It appears that there exists no consumer market for the uncarbonised densified briquettes. The fuel can be used with the Thai bucket-type stoves without any problem.
ECONOMIC ANALYSIS OF SAWDUST B R I Q U E T T E MAKING The following economic analysis has been done based on an installation o f four extrusion type densification machines with a rotary drier and other ancillary distribution arrangements. It is assumed that a densification machine produces 800 kg of briquettes in 8 h o f operation. 1. Costs: A . Initial i n v e s t m e n t costs."
(i) Cost o f four extrusion machines + installation (ii) Cost o f rotary drier + cyclone + distribution system + installation cost (iii) Civil works (iv) Miscellaneous Total
US$ 14 800 13 700 1 850 1 850 32 200
Densified biomass in Thailand: potential, status and problems B. Annual expenses: Assuming that machines are operated for 300 days yr -1 (i) Labour cost: @ $2.6 day -1 of 8 h, and assuming that labour is paid for the whole year for six persons 6 × 2.6 X 365 (ii) Electricity: 0.17 kWh per briquetted log of 1.3 kg (0.17)/(1.3) × 800 kg day -~ × 300 days yr -~ X $0.056 kWh -1 × 4 machines (iii) Maintenance: replacement of screw 15 times year -1 machine -1 + other expenditure: $22 (screw cost) X 15 × 4 machines = 1330 + 520 (iv) Raw material: assuming a 30% process loss during the entire process (800)/(0.7) X 300 days yr -1 × $0.011 kg -1 × 4 machines (v) Land rent: @ $370 month -1 (vi) Miscellaneous
Total
263
US$
5 680
6 970
1 850
15 240 4 440 1 850 36 030
2. Benefits. The benefits could either be by sale of briquettes or by sale of briquetted charcoal. However, there is no evidence of sale of uncarbonised briquettes (see section on Survey of the Market).
Sale of carbonised fuel: @ $0-407 bag -1 of 3 kg and assuming a conversion efficiency by weight of 25%: 800 × 0.25 × 0-407/3 × 300 days X 4 machines 32 600 3. Economic life." The economic life of the unit has been taken as 10 and 7 years for 8 and 16 h day -x o f operation, respectively. 4. Salvage value: Salvage value of the whole unit at the end of economic operation has been taken as US$3700.
For the purposes of financial calculation, the carbonisation costs of the briquetted fuel blocks, being very small, have been neglected. A sensitivity study was carried out using the following parameters: char-
264
S. c. Bhattacharya, R. Bhatia, M. iV. 1slam, iV. Shah
coal sale price from 8 to 14 Bahts bag -1 of 3 kg (note that 27 ]~ = 1US$); charcoal conversion efficiencies by weight from 20% to 30%; and raw material process loss from 10% to 30%. The internal rate of return was calculated in each case and the calculations repeated for a 16 h day -~ (two shifts) operation. The results of the analysis are expressed in graphical form in Figs 1 and 2. As was mentioned in the section on Survey of the Market, the briquetted charcoal selling price presently stands at 11 Bahts bag -] of 3 kg. At this price, even when considering the ideal case with process loss 10% and a charcoal yield o f 30% (by weight), the rates o f return are very low and even a slight decrease in any one o f the parameters can cause the operation to be uneconomical. The situation changes radically in Fig. 2 when the plant is operated in two shifts, and this results in better financial returns. The results clearly reveal the high sensitivity o f the briquetting process to the selling price o f charcoal and the charcoal yield by weight. As is seen from the figures, if charcoal yields are at around 20%, there exists no way in which the process can be economical. Above all, small changes in selling price can shift the rates of return dramatically.
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IRR vs selling price of charcoal for different charcoal yields and process losses - for 8 h day-1 operation.
265
Densified biomass in Thailand." potential, status and problems Charcoal
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IRR vs selling price of charcoal for different charcoal yields and process losses - for 16 h day-1 operation.
REMARKS AND CONCLUSIONS (i) Densification of agricultural-residues, especially rice husk and sawdust, is technically well established in Thailand. (ii) Some, indigenous, extrusion type densification machine suppliers (manufacturers) are available in Thailand. (iii) A number of densification machines have been installed in Thailand. However, many of the machines that were actually visited during the course of this study were not being operated. A number o f reasons have been found for this. Amongst these are : (a) Lack of market for the briquetted fuel blocks. (b) The economics of briquette making does not compare favourably with prices at which traditional fuels can be bought. (iv) The utilisation of rice husk for briquetting appears to be limited by the fact that many of the larger capacity rice mills (as far as could be observed during the field visits) are utilising the husk to meet their own energy requirements.
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S. c. Bhattacharya, R. Bhatia, M. iV. Islam, N. Shah
(v) The usage o f sawdust appears to be more promising for briquetting. Sawdust has no real alternative use apart from being used as a fuel. (vi) The Thai traditional fuels - w o o d and charcoal - are relatively very cheap thus far underpricing the levels at which briquettes can be sold.
ACKNOWLEDGEMENT We are grateful for the support received during the course o f this study from the European Economic C o m m u n i t y (Directorate General for Development).
REFERENCES 1. Smith, A. E., Flynn, G. & Breag, G. R. (1983). A profile of the briquettingof agricultural and forestry residues, London, Tropical Development and Research Institute. 2. Forest Statistics Section (1982). Forestry statistics, 1982, Bangkok, Royal Forest Department. 3. Center for Agricultural Statistics Office of Agricultural Economics (1982). Agricultural statistics o f Thailand crop year 1982/83, Agricultural Statistics No. 202, Bangkok, Ministry of Agriculture and Cooperatives. 4. Asian Institute of Technology (I 983). Evaluation and selection of ligno-cellulose wastes which can be converted into substitute fuels, Bangkok, Division of Energy Technology, Asian Institute of Technology. 5. Phithakannoph, N. (1984). The densifiedfuelfrom residue, Thailand Institute of Scientific and Technological Research, Thailand.