Charcoal Production
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Challenges and potentials to sustainable charcoal production
Charcoal is a prime source of energy in most African countries, and is a driving force in their economies. Worldwide charcoal production has increased, rising by an annual 3.7 percent from 1990 to reach 44 million tones in 2000: Forests_and_Energy.pdf . Surprisingly, policy makers pay little attention to the ways in which charcoal is produced and sold; whether wood used for charcoal burning is harvested in a sustainable fashion. Without coherent policies, almost all charcoal production, transportation and distribution remains informal and unregulated – leading to inefficient and risky production methods.
The common issues characterizing the charcoal production chain in many African countries comprise:
(i) unregulated/illegal resources
(ii) rampant and systemic corruption
(iii) inefficient conversion technologies
(iv) a perception that it is a poor man’s business considered ‘dirty’ and economically unattractive
(v) free access to wood resources, leading to deforestation and degradation
(vi) the charcoal business is dominated by a few powerful individuals.
Lessons from eastern Africa's non-sustainable charcoal trade are summarized in the publication: Lessons Learnt from Eastern Africa’s Unsustainable Charcoal Trade. World Agroforestry Centre (2006)
Despite the growing scarcity of wood, charcoal generally remains underpriced by more than 20% to 50%, relative to its economic cost as only the opportunity cost of labour and capital required for charcoal production and transport are reflected. The production price for the raw material wood is often not reflected when wood is exploited from unsustainably managed wooded areas (e.g. open access areas). In addition dues are ineffectively collected. Undervaluation translates into wasteful and inefficient production and consumption, and creates a formidable disincentive for forest management and tree growing (see box). A World Bank Publication from some years ago still correctly illustrates the problems of underpricing and provides methods for estimating adequate woodfuel stumpage values: Fuelwood Stumpage. Financing Renewable Energy for the World’s Other Half
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Impacts of underpricing charcoal As long as charcoal is not sold at a real market price, investments in improved production/conversion are economically not attractive.
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Problems arise at all stages of the charcoal value chain, so a precise understanding of the charcoal value chain provides an excellent entry-point for shaping sound policy frameworks. It offers an opportunity to the various stakeholders to add knowledge, innovation, capital, and technology at each step or link in the value chain. Sound policy can provide checks and balances, creating more balance within and between the sectors, and supporting the intended overarching goals, such as the Millennium Development Goals (MDGs).
Other papers highlighting the importance of adopting a value chain approach include: Analysis of charcoal value chains - general considerations; and Policy and Distributional Equity in Natural Resource Commodity Markets: Commodity-Chain Analysis as a Policy Tool
Furthermore, evidence-based analyses of the charcoal value chain provide the opportunity to demonstrate the regional added value of charcoal production and thus help to sensitise policy makers for a source of energy hitherto neglected & left to the informal sector. Examples of study projects, geared towards a comprehensive assessment and analysis of the charcoal production chain, include:
- the supra-regional Chaposa project (1998-2002) investigating the charcoal potential for Southern Africa: sei-international.org/mediamanager/documents/Publications/Climate/chaposa.pdfcoastalforests.tfcg.org/pubs/Char_Southern_Africa_CHAPOSA.pdf
- the National Charcoal Survey:Exploring the potential for a sustainable charcoal industry in Kenya(ESD 2005)
- the study initiated by the Forest Governance Learning Group (FGLG) for Malawi:pubs.iied.org/13544IIED.html
- a policy note prepared by Worldbank staff for decision makers in Tanzania summarizing the fundamental characteristics of charcoal use in the country and presenting policy options along the entire value chain of charcoal production and consumption (2010): siteresources.worldbank.org/EXTCC/Resources/PolicyNote_Charcoal_TZ_08-09.pdf.
Basics on charcoal
Carbonization or pyrolysis is defined as the irreversible thermo-chemical reaction that is initiated by heating a pile of wood under controlled conditions in a closed space such as a charcoal kiln with a very limited supply of air triggering endothermic and exothermic reactions. The biomass produces, as a result of the pyrolysis process under normal conditions, a mixture of gas, liquid and charcoal.
Charcoal is first of all characterized by its density which can vary between 0.2 and 0.6 t/m3 depending on the density of wood used as raw material. Charcoal produced from hardwood is heavy and strong, whereas produced from softwood is soft and light. The coefficient of transformation is about half (example: eucalyptus with a density of about 0.6 gives charcoal with a density of around 0.25 to 0.35).
The bulk density of charcoal does not only depend on the apparent density but also on the size distribution, and is in the range of 180-220 kg/m3.
Charcoal has a relatively low moisture content of around3 to 10%. The gross calorific value of charcoal is linked to the amount of fixed carbon and depends strongly on the carbonization temperature varying from 27 to 33 MJ/kg. Low carbonization temperatures give a higher yield of charcoal but this charcoal is low grade, is corrosive due to its content of acidic tars, and does not burn with a clean smoke-free flame. Good commercial charcoal should have a fixed carbon content of about 75% and calling for a final carbonization temperature of around 500°C.
Technological Aspects
For conversion of wood into charcoal people use "kilns". The most common types of traditional kilns are earth pit or mound kilns with efficiencies ranging between 8% and 12 % (Table 7). Because parameters like the humidity of the wood used, kiln size, and process control, play an important role, the relative gain of an improved technology ranges between 5% to 50%. See: http://www.fao.org/docrep/X5555E/X5555E00.htm
| Table 7: Efficiencies of various types of kiln | ||
| Production of 1 kg of charcoal from | Kiln efficiency | |
| Traditional Kilns | 8- 12 kg wood | 8 – 12% |
| Improved traditional kilns | 6 – 8 kg wood | 12 - 17% |
| Industrial production technologies | 5 – 7 kg wood | 20 – 14% |
| New high-yield, low-emission systems | 3 – 4 Kg wood | 25 - 33% |
Part of the energy losses during charcoal making are compensated for during end use, as charcoal stoves have higher efficiencies than wood stoves (30% - charcoal stoves versus 10%-15% untended open fire or tripod).The following table gives information on the amount of energy loss in % when introducing improved kilns and/or improved stoves in comparison to the usage of firewood (e.g. there is an energy loss of 73% when charcoal is converted by traditional kilns (efficiency of only 8%) and consumer use stoves with an efficiency of 20%).
| Table 8: Energy losses converting woodfuel to charcoal for various stoves | |||||
| Stove efficiency | |||||
| Traditional | Improved | ||||
| 24% | 30% | 35% | |||
| Traditional Kilns | 8% | 73% | 68% | 60% | 53% |
| 12% | 60% | 52% | 40% | 30% | |
| Improved Kilns | 14% | 53% | 44% | 30% | 18% |
| 18% | 40% | 28% | 10% | -5% | |
Publications:
Impacts of Greenhouse Gas and Particulate Emissions from Woodfuel Production and End-Use in Sub-Saharan Africa: http://rael.berkeley.edu/old-site/OA5.1.pdf
Traditional Kilns
Aus Seidel 2008
Earth Pit Kilns
Earth pit kilns are the traditional way of making charcoal in many parts of the world and may represent the simplest technology for charcoal production. In brief, wood is stacked in a pit, sealed with a layer of grass and soil and carbonization is started by igniting the wood at one end. Pit kilns can also be built in small size and thus they are suitable for families and even individuals. In pit kilns also large pieces of wood can be used. However, ventilation may be difficult to control and frequently carbonization is incomplete, producing only low quality charcoal. Further, efficiency is lower than in earth mound kilns. To improve efficiency, pit kilns can be equipped with a chimney which allows the use of biomass other than wood such as coconut shells. Nevertheless, even the improved pit kiln is less efficient than a well-managed earth mound kiln. In addition, pit kilns are labor intensive since a pit must be dug into the ground.
Earth Mound Kiln
This is also a common kiln used for charcoal production. It can be constructed from locally available material. In brief, wood is collected and stacked in the polygonal shape of kiln. The wood is then covered with a layer of grass and the construction is sealed with soil. A small opening allows the control and monitoring of the process. When the kiln has been lit, it requires continuous attention for 3 to 15 days depending on the size. After the kiln has cooled down charcoal can be harvested. The main advantage of this type of kiln is that it can be constructed easily without cost at the harvest site. However, carbonization takes rather long and the process requires continuous attention. In addition, charcoal quality is rather low and efficiency is only between 8 and 15 %. Therefore charcoal production using traditional kilns is associated with high consumption of wood.
Improved kilns
Casamance Kiln
The Casamance kiln was developed in Senegal and is an earth mound kiln equipped with a chimney. This chimney, which can be made of oil drums, allows a better control of air flow. In addition, the hot flues do not escape completely but are partly redirected into the kiln, which enhances pyrolysis. Due to this reverse draft carbonization is faster and more uniform giving a higher quality of charcoal and efficiency up to 30 %. Disadvantages of this kiln type are that it requires some capital investment for the chimney and it is more difficult to construct. Comparative tests of the casamance kiln and traditional mound kilns confirmed the advantages in terms of efficiency and shorter carbonization times due to the enhanced hot flue circulation Meule_casamancaise_PERACOD_Mundhenk.pdf.
Brick Kiln
The brick kiln is stationary, unlike to the Casamance or traditional kilns. They have an efficiency of up to 30 % and are suitable for semi-industrial production of charcoal. One type is the truncated pyramid kiln, which is used in Chad mainly in the informal sectors. However, it has a lower efficiency than other brick kilns. The most notable type is the Argentine half orange Kiln, which has been adopted by the Malawi Charcoal Project. It is made entirely out of brick and mud as mortar. Loading and unloading is performed through two opposite doors, which are sealed before the kiln is ignited. The carbonisation cycle is much quicker and allows harvesting of charcoal after 13 – 14 days. Using a kiln of about 6 m diameter up to 15 t of high quality charcoal can be produced per month. However, as brick kilns are stationary once built, they can only be used in areas with easy supply of wood. Furthermore, the wood has to be cut with some precision and water supply is required for preparation of mortar. Kilns can also be produced using concrete instead of bricks; however, as their construction is very cost-intensive they have not succeeded in Africa.
Steel Kiln
A large number of different types of steel kilns have been developed which are considered as one basis of modern charcoal production. They are capable to carbonize even poor quality wood and can easily be transported when necessary. However as the annual output of a typical demountable steel kiln is about 100 – 150 t, they are not suitable for high-volume production. Furthermore, the investment costs may be as high as 1.000 US$, which limits the use of steel kilns considerably. Nevertheless, since efficiency is high (27 – 35 %) and carbonization is very quick (16 to 24 hours after ignition) steel kilns have been promoted as community kilns in Kenya.
Charcoal Retorts
Adam retort
The Improved Charcoal Production System (ICPS), also called Adam-Retort, may be presented as an example of retort technology. The kiln returns the wood gases back to the carbonisation chamber, burns the volatile a higher proportion of the tar components almost completely and uses the heat for the carbonisation process. Efficiency can be as high as 40 % and noxious emission are reduced by 70 %. In addition the production cycle is completed within 24 to 30 hours. The retort is suitable for semi-industrial production. However, it’s a stationary kiln, investment costs exceed 1.200 US$ and special skills are required for construction. Nevertheless the Adam-retort has been introduced in several countries (Senegal, Madagascar, Peru etc.) on a pilot basis. Currently, the method is further refined for up-scaling.
Charcoal Briquetting
Residues from agriculture and forestry are a valuable source of raw material for the production of domestic fuel e.g. bagasse, coffee husks, saw-dust and charcoal fines, coconut husks and lump wood waste etc.. This presents opportunities for improved waste management strategies.
After collection, the wood or agro-industrial waste is dried before it is converted to charcoal in a charring kiln. The carbonised biomass is then mixed with water and locally-available binders such as starch, gum arabic, molasses, clay and others. Finally, the mixture (powdered charcoal + binder mixture) is pressed into briquettes. Piston and screw presses are the most widely used technologies where as in the developed countries roll presses are more common. The production capacity of screw presses is around 40 to 70 kg per hour. After a subsequent drying step the briquettes will develop the required strength and stability.
Forest and agricultural waste charcoal briquettes, with about 20% of clay, produce about 12 MJ/kg depending on the composition of charcoal.
Further information on biomass charcoal briquetting for energy based income generation in rural areas can be found in www.amm-mcrc.org/publications/BiomassCharcoalBriquetting_English.pdf
The GIZ Program to promote rural electrification and a sustainable supply of domestic fuel (PERACOD) in Senegal documented their experience at the following website:www.peracod.sn
Transport and Marketing
The trade of charcoal in many African countries is primarily informal and it is characterized by a high turnover rate. There is no significant warehousing. All stocks produced are promptly consumed. Abundant evidence of the charcoal trade is visible throughout the cities and surrounding regions. Roads are lined with charcoal bags for sale in the center of the cities, both on the city outskirts as in the proximity of the production areas.
Charcoal trading is a key segment in the supply/demand chain, and the dealers are the key actors in this regard. Often transporters function as middlemen and wholesalers.
Lorries and pickups are the most popular kind of motorized transport due to their carrying capacity. Charcoal is not a heavy commodity but it is bulky. Bicycles are the most common non-motorised form of transport. Some carry up to five bags of charcoal. Furthermore the use of donkey carts is a notable form of transportation. Human transport is also used, but only for short distances especially in areas inaccessible by other forms of transport.
Transport costs are a critical component not only of urban woodfuel prices but of the area from which woodfuels can be supplied at competitive prices.
Profits are usually concentrated in the hands of a few intermediaries, engaged as transport agents or wholesalers. Instead of equitable revenue-sharing along the entire value chain, revenue circulates in a loop between traders and consumers reaping off up to 80% of the value chain profits. Marginal profits (20-30%) go to the charcoal producers– and virtually none to those communities, whose forest areas are being depleted in the process.
Social, Economic and Environmental Impacts
Charcoal consumption is a very controversial issue, as the transformation process from wood to charcoal results in considerable energy loss, requiring significantly more forest resources to produce the same amount of energy. This has led to many countries imposing bans (Kenya, Tanzania, Gambia etc), but with little success, and charcoal use continues to increase with the pressures of growing urbanisation. Charcoal burns more cleanly than wood or dried biomass, producing higher temperatures and it is cheaper to transport and store. For these reasons, interest in charcoal as a fuel is reviving, and steps need to be taken to promote improved charcoal-making technologies and thus reduce the amount of raw biomass required.
Charcoal production is a labour-intensive process, employing a large number of people at different phases of the process and distribution. It is estimated that charcoal production generates between 200-350 person days of employment per Terajoule of energy, compared to 10 person days per Terajoule for kerosene. Sustainable production of wood-based fuels (particularly charcoal) can support rural development through; locally available, affordable and renewable resources, decentralised processing & production, short transport distances with low risks, potential for short-term efficiency improvements (improved stoves, kilns etc.), it can yield a health-dividend, due to reduced levels of smoke, cleaner combustion and easy handling. To be environmentally beneficial, highly efficient kilns and renewably-sourced fuels are required.
To this end, woodfuel policies need to be designed within the context of a sustainable (rural) development approach, and principles of local control and participation adhered to in the planning process. Comparative advantages of locally produced/managed energy sources must be fully exploited to stimulate regional economic growth. Further ways to shape charcoal policies are described in the following paper: "Shaping charcoal policies: context, process, and instruments as exemplified by country cases".
Further information
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Manual for Charcoal Production in Earth Kilns in Zambia |
http://www.bioquest.se/reports/Pdf%20summaries/Cprodman%20SUMMARY.pdf |
| Review of Technologies for the Production and Use of Charcoal |
http://rael.berkeley.edu/files/2005/Kammen-Lew-Charcoal-2005.pdf |
| Overview on charcoal in Africa-Importance, Problems and Possible Solution Strategies | Charcoal-in-africa-gtz_2008-eng.pdf |
| Founded in 2009, the Charcoal Project is supported by a global network of volunteer specialists that include scientists, conservationists, marketing, web, social development, and business experts. Their mission is to promote, facilitate, and advocate for the widespread adoption of clean burning technologies, sustainable fuel alternatives, and policies that support energy-poverty alleviation for those who depend on biomass as their primary fuel around the world. |
http://www.charcoalproject.org/ |
| The FAO supported project in Croatia to enhance the development of a sustainable charcoal industry provides several useful reports on the ecological and economical impacts of charcoaling |
www.drveniugljen.hr/75.html |
