Charcoal is used as a domestic fuel for cooking and heating in many developing countries. It is the most popular barbecue fuel throughout the world. Its advantages when used as a domestic fuel are that it: produces less smoke while burning, requires little or no preparation before actual use, has a higher energy content per unit mass, can be easily transported and stored, and reused when left over after cooking.
Introduction :
Charcoal production is done through a method called pyrolysis of biomass. Pyrolysis is defined as the irreversible chemical change brought about by heating the biomass in the absence of oxygen. During pyrolysis, biomass undergoes a sequence of changes and normally yields a black carbonaceous solid, called charcoal, along with a mixture of gases and vapors. Generally, charcoal production through pyrolysis is maximised in a process of low temperatures and slow heating rates, the so-called carbonisation.
Charcoal is used as a domestic fuel for cooking and heating in many developing countries. It is the most popular barbecue fuel throughout the world. Its advantages when used as a domestic fuel are that it: produces less smoke while burning, requires little or no preparation before actual use, has a higher energy content per unit mass, can be easily transported and stored, and reused when left over after cooking.
Until now, the primary raw material for charcoal production has been fuelwood. However, considering the fact that supplies of wood are often limited, a variety of agricultural and forestry residues that often remain unused appear to be potentially important raw materials for charcoal production.
Several successful projects in the efficient charcoal production have been reported so far. The Mafia Pilot Project in Tanzania on the use of Coconut Industry Waste for Energy production was started in 1985 (Bhattacharya and Abdul Salam, 2006). It was funded by the German development agency GTZ and implemented by the Ministry of Water, Energy and Minerals of Tanzania, with the following objectives:
- To produce high-quality charcoal from coconut shell and husk for local domestic and industrial use,
- To utilise gas produced in the process of shell/ husk carbonization for copra drying to replace 80,000 liters of fuel oil consumed annually by Mafia Coconut Ltd. in Mafia,
- To produce charcoal from coconut trunks that become available in the process of land clearing operations undertaken for the establishment of new plantations, and
- To investigate the possibility of substituting a diesel powered thermal power plant with a coconut waste fuelled power plant.
The carbonisation plant consisted of sixteen carbo-gas-retorts (made of iron plates), which were made locally. The carbo-gas retort technology can produce high quality charcoal and combustible carbonisation gas from coconut shell and husk. The technology was transferred to the local personnel towards the end of the project and a number of retorts were set up and operated by them without further external technical assistance.
The Malawi Charcoal Project funded by the World Bank and the Malawi Government was initiated in 1986 to produce charcoal from wood wastes generated on the forest plantations owned by the government (Bhattacharya and Abdul Salam, 2006). Following the pilot phase of the project between October 1986 and January 1988, a commercialisation phase extended through August 1989. The project also built two Beehive brick kilns with an effective capacity of 35 m3.
The total investment cost of a full size production centre of this project were USD 10,000 on average in 1988. By mid 1989, the estimated cost of lump charcoal (>10 mm) and charcoal fine (<10 mm) were USD 36 and 26, respectively. The selected mode of charcoal production proved to be cost-effective and appropriate to local conditions. The construction and operation of the kilns was done by the trained local labour and all the necessary inputs and materials were procured locally.
Another successful charcoal production project is Dandora Charcoal Plant which was established by the Kenya Planters Co-operative Union to produce charcoal briquettes from coffee husks (Bhattacharya and Abdul Salam, 2006).
Batch carbonisation of coffee husk is carried out in pit kilns to obtain charcoal dust. Maize starch is used as binder of briquetting the charcoal dust. The mass conversion efficiency of the kiln was 33%. The charcoal produced had a fixed carbon content of about 70% and a volatile matter content of about 10%.
In 1986, batch charcoal production from rice husk weighing 10 kg was performed in India, based on a concept developed at the Indian Institute of Technology. The best carbonisation sample had 33.9% ash, 22.5% volatile matter and 43.6% fixed carbon. In 1980, the design of a vertical packed bed, partial oxidation pyrolysis reactor was reported by Bhattacharya and Abdul Salam (2006). Different versions of this basic design that originated from Georgia Institute of Technology were developed and tested in Ghana, Thailand, Indonesia, Papua New Guinea, and the Philippines.
By the year 1996, five commercial Carbolisi Process Plants were installed in Europe. The capacities of these plants were in the range of 1500-6000 tonnes/year. Through the Carbolisi process, woody biomass such as stumps, coconut shell, vine prunings, branchlets, etc., can be converted into charcoal (Bhattacharya and Abdul Salam, 2006).
In 2003, the BOC Foundation awarded a grant of £ 26,175 to the UK-based environmental organization Bio Regional
Development Group to fund the development of regional charcoal production from UK woodlands. The BOC Foundation awards grants for projects proposing practical solutions to environmental problems in the UK. The project aims to prove that eco-products can deliver good returns whilst reducing pollution and helping biodiversity. With Bio Regional under operation, the CO2 emissions due to transporting the charcoal are 85% less than when charcoal is imported from, for example, South Africa or South America. Currently, BOC is acquired by the Linde group after supporting 140 environmental projects.
Between 1993 and 1997, the Asociación de Productores Forestales de Villa Mills (ASOPROFOR-Villa Mills Forestry Producers Association) developed a production and commercialisation system of vegetal charcoal in the Villa Mills, Piedra Alta, and Alto del Jaular communities of Pérez Zeledón, Costa Rica. The project was executed by producers, packers, and a local transporter who were seeking to commercialise charcoal produced in harmony with nature, using wood dead from natural causes or from sustainably managed forests. Traditional charcoal production techniques were investigated and improved techniques were proposed. It also created part-time employment possibilities for women, who traditionally lacked job opportunities until then.
Figure 1: Malawi Charcoal Project (Source: Global Envision)
Feasibility of technology and operational necessities :
Basically, the charcoal production has two technological routes for producing charcoal briquettes from waste biomass and residues:
i) the briquetting – carbonisation (B-C) option: the raw material is first densified and then carbonised to produce charcoal briquettes. Biomass densification can be regarded as an established technology and a wide range of techniques, raw material and capacity are available.
ii) the carbonisation – briquetting (C-B) option: the raw material is first carbonised and crushed if necessary to obtain powdered charcoal, which is then briquetted using a suitable binder.
Reactors used for biomass pyrolysis are most commonly classified depending on the way the solids move through the reactor. The reactors can be classified as follows:
In the Philippines, Approtech Asia, the country’s contact point of the Asia Regional Cookstove Programme (ARECOP), are involved in various programmes to improve the kiln construction for charcoal and briquette production. The Improved Cook Stove Programme of the Philippines (ICSP) promotes the use of ICS and improved fuel, such as quality charcoal, briquette from agri wastes and ‘wood vinegar’. This stimulates the rural industry and thus contributes to poverty alleviation. Approtech Asia, through ICSP, promotes the use of improved charcoal stove and quality charcoal and briquette from agricultural wastes available in the area. Local government units and co-operatives are encouraged to establish rural industries for high quality charcoal and briquette production using improved kiln technology. Surveys show that charcoal is still popular as cooking fuel, especially in roasting pigs and chicken in populated urban centres.
A process of carbonising sugarcane leaves has been developed in India. The process consists of packing sugarcane leaves tightly in stainless lidded cans. Heat for pyrolysis comes from burning cane trash on a grate below the cans; pyrolysis gases escaping from holes at the bottom of the stainless steel cans also contribute some heat for carbonisation. The results of thermogravimetric analysis and differential thermal analysis of bagasse, cane tops and leaves have been reported to yield lower volatiles and higher ash and char compared with wood (Deepchand, 1987).
Charcoal production of wood wastes has been studied by many researchers using different type of reactors. A conceptual design of a fluidised bed system for carbonising timber industry waste has been presented in Fung (1979). An economic analysis of the system showed that wood residues could be profitably utilised with a payback period of 5 years. Mass and energy balance on an experimental fluidised bed at 5000 C showed that the charcoal recovered could correspond to 11% of the energy input.
A research project on the viability of charcoal production from wood wastes generated on government forest plantation in Sub-Sahara Africa successfully implemented a charcoal plant with a capacity of 9.5 ktonnes per year (Teplitz-Sembitzky and Zieroth, 1990).
A feasibility study on pyrolysis gas utilisation in the Philippines was conducted in 1991 (Apale et al., 1991), which showed that coconut shells could be converted to charcoal without wasting the resulting pyrolytic gases. Similarly, production of charcoal from coconut shell in various types of kilns was studied in Estudillo et al. (1977), which showed that modified drum kiln deliver a charcoal yield in the range 27-35%. A continuous retort designed by the Forest Product Research and Industries Development Commission was found to give better results than the masonry and earthen kilns (Estudillo et al., 1977).
The Thai programme of rice husk pyrolysis using vertical packed bed reactors was carried out at the Thailand Institute of Scientific and Technological Research (TISTR) in the early 1980s (TISTR, 1984). A demonstration plant installed in the framework of the programme at a rice mill showed that the charcoal yield was about 45% of the feedstock. On a dry basis, the fixed carbon content of the char was 34.7-59.8% (volatile matter 5.2-9.8%, and ash 33.9-58.6%).
i) the briquetting – carbonisation (B-C) option: the raw material is first densified and then carbonised to produce charcoal briquettes. Biomass densification can be regarded as an established technology and a wide range of techniques, raw material and capacity are available.
ii) the carbonisation – briquetting (C-B) option: the raw material is first carbonised and crushed if necessary to obtain powdered charcoal, which is then briquetted using a suitable binder.
Reactors used for biomass pyrolysis are most commonly classified depending on the way the solids move through the reactor. The reactors can be classified as follows:
- Type A: No solid movement through the reactor during pyrolysis (batch reactors),
- Type B: Moving bed (shaft furnaces),
- Type C: Movement caused by mechanical forces (e.g., rotary kiln, rotating screw, etc.), and
- Type D: Movement caused by fluid flow (e.g, fluidized bed, spouted bed, entrained bed, etc.).
In the Philippines, Approtech Asia, the country’s contact point of the Asia Regional Cookstove Programme (ARECOP), are involved in various programmes to improve the kiln construction for charcoal and briquette production. The Improved Cook Stove Programme of the Philippines (ICSP) promotes the use of ICS and improved fuel, such as quality charcoal, briquette from agri wastes and ‘wood vinegar’. This stimulates the rural industry and thus contributes to poverty alleviation. Approtech Asia, through ICSP, promotes the use of improved charcoal stove and quality charcoal and briquette from agricultural wastes available in the area. Local government units and co-operatives are encouraged to establish rural industries for high quality charcoal and briquette production using improved kiln technology. Surveys show that charcoal is still popular as cooking fuel, especially in roasting pigs and chicken in populated urban centres.
A process of carbonising sugarcane leaves has been developed in India. The process consists of packing sugarcane leaves tightly in stainless lidded cans. Heat for pyrolysis comes from burning cane trash on a grate below the cans; pyrolysis gases escaping from holes at the bottom of the stainless steel cans also contribute some heat for carbonisation. The results of thermogravimetric analysis and differential thermal analysis of bagasse, cane tops and leaves have been reported to yield lower volatiles and higher ash and char compared with wood (Deepchand, 1987).
Charcoal production of wood wastes has been studied by many researchers using different type of reactors. A conceptual design of a fluidised bed system for carbonising timber industry waste has been presented in Fung (1979). An economic analysis of the system showed that wood residues could be profitably utilised with a payback period of 5 years. Mass and energy balance on an experimental fluidised bed at 5000 C showed that the charcoal recovered could correspond to 11% of the energy input.
A research project on the viability of charcoal production from wood wastes generated on government forest plantation in Sub-Sahara Africa successfully implemented a charcoal plant with a capacity of 9.5 ktonnes per year (Teplitz-Sembitzky and Zieroth, 1990).
A feasibility study on pyrolysis gas utilisation in the Philippines was conducted in 1991 (Apale et al., 1991), which showed that coconut shells could be converted to charcoal without wasting the resulting pyrolytic gases. Similarly, production of charcoal from coconut shell in various types of kilns was studied in Estudillo et al. (1977), which showed that modified drum kiln deliver a charcoal yield in the range 27-35%. A continuous retort designed by the Forest Product Research and Industries Development Commission was found to give better results than the masonry and earthen kilns (Estudillo et al., 1977).
The Thai programme of rice husk pyrolysis using vertical packed bed reactors was carried out at the Thailand Institute of Scientific and Technological Research (TISTR) in the early 1980s (TISTR, 1984). A demonstration plant installed in the framework of the programme at a rice mill showed that the charcoal yield was about 45% of the feedstock. On a dry basis, the fixed carbon content of the char was 34.7-59.8% (volatile matter 5.2-9.8%, and ash 33.9-58.6%).
Figure 2: Carbonized Rice Husk (Source: Rice Knowledge Bank)
Factors that could affect commercial charcoal production and trade include: scarcity of wood for charcoal making; inadequacy or flaws in government regulations; lack of understanding of local wood fuel systems which often tend to adapt themselves to changing situations; informal nature of operations and the market; variations in the systems to match specific site conditions.
Several barriers on the policy issues have been reported in various nations (Evans, 2002). In most developing countries, there is a greater need for official recognition of charcoal production and marketing by national energy policies. For instance, although energy policy in Kenya favours development and promotion of improved charcoal cook stoves and sustainable farm forestry for fuel wood, charcoal making remains illegal in the country. Only official policy recognition can realise community development initiatives, including capacity building in farm forestry methods, charcoal-making and stove fabrication, charcoal trade and entrepreneurship. Similarly, national energy and technology policies need to be harmonised to allow for cross border technology transfer and capacity building. Personnel exchanges among collaborating institutional entities would be promoted through such schemes. The land tenure policy in many countries in sub-Saharan Africa requires streamlining and is presently a source of conflict. But when a household has rights over a given land area, it can confidently develop it further through activities including modern farm forestry methods.
Status of the technology and its future market potential :
In many developing countries, e.g. Indonesia, the Philippines, and Thailand, among the commonly used biomass fuels, charcoal has occupied a specific place specifically for cooking purpose. Some developed countries in Asia buy charcoal and charcoal briquettes from other countries in the region. Considering the specific requirements mentioned above, it can be concluded that there is a continued need for improvement in efficiency of production, unhindered, open and competitive trade, and optimal utilisation through technological innovations in the coming years.
In view of the shortage of fuel wood in most developing countries, biomass residues and wastes appear to be potentially important raw materials for charcoal making. Charcoal production from different biomass residues and wastes has been studied quite extensively. Also, a wide range of equipment is available for industrial charcoal making from these materials. Charcoal production from biomass briquettes to produce briquetted charcoal is commercially established in a number of Southeast Asian countries. Some important developments have taken place regarding charcoal making recently, which include torrefaction, carbonisation under pressure, and fluidised bed charcoal making.
Figure 3: Charcoal Briquette (Source: Wikipedia)
In view of the shortage of fuel wood in most developing countries, biomass residues and wastes appear to be potentially important raw materials for charcoal making. Charcoal production from different biomass residues and wastes has been studied quite extensively. Also, a wide range of equipment is available for industrial charcoal making from these materials. Charcoal production from biomass briquettes to produce briquetted charcoal is commercially established in a number of Southeast Asian countries. Some important developments have taken place regarding charcoal making recently, which include torrefaction, carbonisation under pressure, and fluidised bed charcoal making.
Figure 3: Charcoal Briquette (Source: Wikipedia)
Currently, large fractions of biomass residues and waste generated annually remain unused and simply decay to release their carbon content as as GHG to the atmosphere. When these residues, including charcoal produced from them, are used for energy generation instead of fossil fuels, GHG emissions could be reduced. Also, the charcoal could be suitably stored, e.g. in soil, to sequester carbon from the atmosphere. These applications are likely to promote charcoal making from planted trees and herbaceous crops as well as residues and wastes in the years to come.
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How the technology could contribute to socio-economic development and environmental protection :
There are several environmental and socioeconomic benefits associated with each stage (extraction, processing, use, and disposal) in the process of efficient charcoal production. With sustainable fuelwood production, there will be increased carbon sink and moisture reservoir, enhanced household energy security and greater entrepreneurial opportunities created through sales of poles and firewood. The efficient biomass harvesting helps to reduce wood residues and wastes on the one hand, and increases the sales of residues as firewood and wood chips on the other hand. Improved efficiency pyrolysis will reduce CH4 emissions. The carbon sink potential of forests is preserved by avoiding tree cutting and less amount of wood is required to yield the same amount of charcoal.
Contribution of the technology to economic development (including energy market support) :
Due to increased on-farm availability of fuelwood, the time spent daily on gathering fuelwood is saved for use in more productive activities and higher incomes, which in itself could further improve livelihoods. Furthermore, the capacities of the locals to initiate and sustain biomass husbandry projects, charcoal production and stove fabrication would be strengthened. Other skills gained would include small business management and marketing. This life-cycle focused strategy is designed to minimise the loss of material and energy at the various life-cycle stages and this could supply extra wood for competing demands. It has the potential for application in the entire sub-Saharan Africa region with a wide array of social, economic and environmental gains. If well designed and implemented, the approach is potentially cost-effective with high chances of success due to local community participation.
Contribution of the technology to protection of the environment :
This technology will significantly reduce toxic indoor air pollutants which will result in improved health conditions, in particular for women and children. Acute respiratory infections rank fourth in the list of diseases in sub-Saharan Africa and cause reduced productivity and lower life expectancy. According to Domac and Trossero (2008), a small scale charcoal production unit can emit quantities of particulate matter (PM), carbon monoxide (CO), nitrate oxides (NOx) and sulphate dioxide (SO2), hydrogen fluoride (HF), hydrogen chlorine (HCl), formaldehyde, phenol, acetic acid, xylene and toluene. There are still various technologies, which permit a cleaner production of charcoal, such as the Social for Profit project whose products can acquire Eco-label and Fair-trade labels.
Improved charcoal use will thus contribute to CO2 emission reduction and fuel saving. For calculation of GHG emission reductions (mainly methane), it is recommended to apply the approved methodology for mitigation of methane emissions in the wood carbonization activity for charcoal production project (large scale activities) which has been developed under the Clean Development Mechanism of the UNFCCC Kyoto Protocol (CDM). This methodology helps to determine a baseline for GHG emissions in the absence of the project (i.e. business-as-usual circumstances), how emission reductions below this baseline can be calculated, and how these reductions can be monitored. General information about how to apply CDM methodologies for GHG accounting can be found at: http://cdm.unfccc.int/methodologies/PAmethodologies/approved.html.
Financial requirements and costs :
For the general cost assessment of the charcoal production process, an example is taken from operations in the Chaco forests of South America where charcoal is made on a large scale in a well organised manner. The unit operations include road construction, water supply, cutting underbrush, cross cutting with axes, primary extraction of mules, loading trailers, secondary transportation with tractor/ trailers, discharging trailers, loading kilns, carbonisation, unloading kilns to stockpile, loading trucks, transport to rail, unloading trucks, loading on rail, and rail transport to user.
For each unit, costs can be calculated, e.g. per ton of charcoal at the side of the kiln; total production cost is the sum of all unit costs. For example, the total costs per tonne saleable charcoal related to harvesting and delivering wood to the roadside would amount to USD 36.50 (see http://www.fao.org/documents/show_cdr.asp?url_file=/docrep/x5555e/x5555e08.htm). This process must be repeated for all unit costs in order to determine their overall effect on production cost. It requires technical knowledge of the process and accounting skills. According to FAO, Where traditional clay brick kilns and a savannah forest yielding about 40 m³ of wood per ha are used, the following unit costs apply (expressed as a percentage of the cost of delivered charcoal): cost of wood of at kiln 60%, kiln labour costs 9%, working capital costs 3.5%, fixed investment costs 1.5%, transport costs of charcoal 26%.
The UN Foundation and the UNEP have undertaken an USD 8.6 million effort to help local entrepreneurs in Brazil, China and five African countries to create clean energy enterprises that deliver clean, affordable energy services to the rural and peri-urban poor. The Rural Energy Enterprise Development (REED) initiative with projects in Africa, Brazil and China is based on an enterprise development model pioneered by E&Co, a non-profit clean energy investor, and is being advanced at the country level in partnership with a diverse group of local NGOs (REED, 2003). The REED approach combines small amounts of start-up capital with extensive enterprise development services to help entrepreneurs create viable energy service enterprises, which offer a range of services and products including energy efficient cookstoves, solar dryers for food preservation, solar irrigation systems, wind pump repair services, the supply and service of solar home systems, LPG retail services, environmentally friendly charcoal production, etc.
In Africa, the African REED programmes promotes investment in charcoal cook stoves, LPG and biofuel. In China’s Yunnan Province, the Chinese REED programme is focused on financing fuel substitution enterprises, specifically those that help preserve the region’s rich biodiversity (REED, 2003). The Grande Caraj’s Programme in Brazil offers incentives to charcoal production for use in pig-iron mills; the first became operational on 8 January 1988. So far, incentives have been granted for eleven industries planned to function with charcoal. The contribution of charcoal to the energy demand in Europe is modest. Most of the charcoal produced is for private use (as fuel for barbecues) and for the production of active carbon (not for energy purposes).
Figure 4: BioCharcoal production (Source: Terra Preta)
For each unit, costs can be calculated, e.g. per ton of charcoal at the side of the kiln; total production cost is the sum of all unit costs. For example, the total costs per tonne saleable charcoal related to harvesting and delivering wood to the roadside would amount to USD 36.50 (see http://www.fao.org/documents/show_cdr.asp?url_file=/docrep/x5555e/x5555e08.htm). This process must be repeated for all unit costs in order to determine their overall effect on production cost. It requires technical knowledge of the process and accounting skills. According to FAO, Where traditional clay brick kilns and a savannah forest yielding about 40 m³ of wood per ha are used, the following unit costs apply (expressed as a percentage of the cost of delivered charcoal): cost of wood of at kiln 60%, kiln labour costs 9%, working capital costs 3.5%, fixed investment costs 1.5%, transport costs of charcoal 26%.
The UN Foundation and the UNEP have undertaken an USD 8.6 million effort to help local entrepreneurs in Brazil, China and five African countries to create clean energy enterprises that deliver clean, affordable energy services to the rural and peri-urban poor. The Rural Energy Enterprise Development (REED) initiative with projects in Africa, Brazil and China is based on an enterprise development model pioneered by E&Co, a non-profit clean energy investor, and is being advanced at the country level in partnership with a diverse group of local NGOs (REED, 2003). The REED approach combines small amounts of start-up capital with extensive enterprise development services to help entrepreneurs create viable energy service enterprises, which offer a range of services and products including energy efficient cookstoves, solar dryers for food preservation, solar irrigation systems, wind pump repair services, the supply and service of solar home systems, LPG retail services, environmentally friendly charcoal production, etc.
In Africa, the African REED programmes promotes investment in charcoal cook stoves, LPG and biofuel. In China’s Yunnan Province, the Chinese REED programme is focused on financing fuel substitution enterprises, specifically those that help preserve the region’s rich biodiversity (REED, 2003). The Grande Caraj’s Programme in Brazil offers incentives to charcoal production for use in pig-iron mills; the first became operational on 8 January 1988. So far, incentives have been granted for eleven industries planned to function with charcoal. The contribution of charcoal to the energy demand in Europe is modest. Most of the charcoal produced is for private use (as fuel for barbecues) and for the production of active carbon (not for energy purposes).
Figure 4: BioCharcoal production (Source: Terra Preta)
References :
Apale, A.Y., Payawan, J.M. and Pelismino, D.G., 1991. Pre-Feasibility Study of Pyrolysis Gases Utilization from Coconut Shell Carbonization, Philippine Coconut Authority, Philippines (EC- ASEAN COGEN Programme through AIT, Bangkok).
Bhattacharya, S.C. and Salam, A.P., 2006. A Review of Selected Biomass Energy Technologies: Gasification, Combustion, Carbonization and Densification. A publication of Asian Regional Research Programme in Energy, Environment and Climate (ARRPEEC).
Deepchand, K., 1987. A Note on the Pyrolysis Behaviour of Sugar Cane Fibrous Products, Biological Wastes, 20, pp. 203-208.
Domac, J. and Trossero, M., 2008. Options for improved charcoal production in Belisce. North West Croatia Regional Energy Agency.
Estudillo, C.P., San Luis, J.M. , Amino, E.C. and Tamolong, F.N., 1977. Charcoal Production and Utilization of Coconut Shells and Trunk in the Philippines. NSDB Technology Journal, January- March 1977, pp. 35-46.
Evans K., 2002. Towards Sustainable Charcoal Production and Use: a Systems Approach, African Centre for Technology Studies, Nairobi.
Fung, P.Y.H., 1979. Carbonization of Timber Industry Waste and Heat Recovery in Fluidized Bed, in: Proceedings of Seventh Australian Conference on Chemical Engineering, pp. 130-134.
REED, 2003. A Focus on Household Energy, Rural Energy Enterprise Development, The REED Report.
Teplitz-Sembitzky, W. and Zieroth, G., 1990. The Malawi Charcoal Project Experience and Lessons, The World Bank Industry and Energy Department Working Paper, Energy Series Paper No.20.
TISTR, 1984. Feasibility Study on Rice Husk Pyrolysis Technology for Rice Mill Applications in Thailand, TISTR, Ministry of Science, Thailand.
Resouce: http://climatetechwiki.org/technology/charcoal-heating-and-cooking
Bhattacharya, S.C. and Salam, A.P., 2006. A Review of Selected Biomass Energy Technologies: Gasification, Combustion, Carbonization and Densification. A publication of Asian Regional Research Programme in Energy, Environment and Climate (ARRPEEC).
Deepchand, K., 1987. A Note on the Pyrolysis Behaviour of Sugar Cane Fibrous Products, Biological Wastes, 20, pp. 203-208.
Domac, J. and Trossero, M., 2008. Options for improved charcoal production in Belisce. North West Croatia Regional Energy Agency.
Estudillo, C.P., San Luis, J.M. , Amino, E.C. and Tamolong, F.N., 1977. Charcoal Production and Utilization of Coconut Shells and Trunk in the Philippines. NSDB Technology Journal, January- March 1977, pp. 35-46.
Evans K., 2002. Towards Sustainable Charcoal Production and Use: a Systems Approach, African Centre for Technology Studies, Nairobi.
Fung, P.Y.H., 1979. Carbonization of Timber Industry Waste and Heat Recovery in Fluidized Bed, in: Proceedings of Seventh Australian Conference on Chemical Engineering, pp. 130-134.
REED, 2003. A Focus on Household Energy, Rural Energy Enterprise Development, The REED Report.
Teplitz-Sembitzky, W. and Zieroth, G., 1990. The Malawi Charcoal Project Experience and Lessons, The World Bank Industry and Energy Department Working Paper, Energy Series Paper No.20.
TISTR, 1984. Feasibility Study on Rice Husk Pyrolysis Technology for Rice Mill Applications in Thailand, TISTR, Ministry of Science, Thailand.
Resouce: http://climatetechwiki.org/technology/charcoal-heating-and-cooking
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