Malawi - Technical assistance package to improve the efficiency of fuelwood use in the tobacco industry

Joint UNDP/World Bank Energy Sector Management Program Activity Completion Report No. 009/83 Country: MALW Activity: TECHNICAL ASSISTANCE PACKAGE TO IMPROVE THE EF1ICIEICY OP FUELWOOD USE IN THE TOBACOO INDUSTRY November 1983 Report of the Joint UNDP/World Bank Energy Sector Management Pram This document has a restricted distribution. Its cor,tents may not be disdosed without authofization from the Govemment. the UNDP or the World Bank.  Energy Sector Management Program The Joint UNDP/World Bank Energy Sector Management Program is designed to provide a rapid and flexible response to governments ,:o request assistance in implementing the policy, planning and institutional recomendations of the Energy Assessment Reports produced under anott.er Joint UNDP/World Bank Program, or in carrying out prefeasibility studies for energy investments identified in these reports. The Energy Sector Management Program can provide the following types of assiscance for countries which have had assessments: o assistance to improve a government's ability to manage its energy sector, for example by defining staffing and work programs, evaluating management information needs, identifying sources of public and private finance, developing a medium-term investment plan; o prefeasibility work on priority investment plans, especially those which will improve the efficiency of energy use, bring about economic fuel substitution, or provide enough affordable energy to rural areas; o specific short-term assistance in institutional and manpower development, both at the sectoral and agency levels. The Program aims to supplement, advance and strengthen the impact of bilateral or multilateral resources already available for technical assistance in the energy sector. Funding of tbe Program The Program is a major international effort and, while the core finance has been provided joint y by the UNDP and the World Bank, important financial contributions to the Program have been made by the Governments of the United Kingdom, the Netherlands, Denmark, Finland, Norway, Sweden, Australia and New Zealand.  HALAWI Technical Assistance Package to Improve the Efficiency of Fuelwood Use in the Tobacco Industry. November, 1983  ACRONYMS ADD Agriculture Development Division AHL Auction Holdings Limited ALO Agricultural Liaison Officer CBM Commercial Bank of Malawi Limited DA Development Area DAD Department of Agricultural Development EPA Extension Planning Officer ETA Extension Technical Assistants ETO Extension Technical Officers FAO Food and Agricultural Organization of the United States FCV Flue-Cured Virginia Tobacco KFCTA Kasungu Fl"e-Cured Tobacco Authority MA Ministry of Agriculture MATSS Ministry of Agriculture Tobacco Sector Study MDF Malawi Division of Forestry NBK National Bank of Malawi Limited NDDF Norchern Division Dark Fire-Cured Tobacco SDDF Southern Division Dark Fire-Cured Tobacco TPI Tropical Products Institute TRA Tobacco Research Authority WEP Wood Energy Project USAID United States Agency for Internatioral Development WEIGHTS AND MEASUREMENTS 1 kilogram (kg) 8 2.204 pounds I metric ton a 1000 kg 3 2,204 pounds 0.948 long ton - 1.102 short ton 1 centimeter (cm) - 2.54 inches 1 meter (m) a 3.28 feet 1 square meter (m2) - 10.76 square feet (ft2) 1 square centimeter (cm2) . 0.155 square inches (in2) 1 liter (1) - 0.2642 US gallons (gal.) 1 cubic centimeter (cm3) 0.06102 cubic inches (in3) 1 cubic meter (m3) - 35.3 cubic feet (ft3) degrees Celsius (oC) - Fahrenheit (OF) - 32 1.8 EXCHAGE RATE June - July 1983: Malawi Kwacha (M1K) Tambola (t) MlK 1 - US$O.8917  Table of Contents Page No. I. INRDCIN................................. .................... ... .. 1 Background of .......................... . ...0. 1 Objectives of Study, *.......... ....................... 1 Conduct of the Work .,........ 2 II. FUEL SOURCES AND USE..................................... 3 Alternative Energy Sources... ................... 3 Wood as an Energy Source .............................. 5 Factors Contributing to Inefficient Wood Use......,... 7 Potential for Saving Fuelvood in the C'uring Process .......................) 12 III. TECHNICAL PACRAGES TO IMPROVE CURING STSTEMS...*......... 14 Improving Existing Barns and Management.,.,.,,,,,ent, 14 Installing Continuous Tunnel Curing System (New Barn)............ 19 Bulk Curing System (New Barn).................,....... 19 Preliminary Economic Analysis..a l y s is................ 20 Establishing Fuelvood Cost..................,......... 22 Tobacco Quality as Affected by Curiag Facilities,..... 22 IV. INTRODUCING NEW TECHNOLOGY......................OLO...... 25 Existing Extension Services.ri....s.o............. . 25 Constraints to Adopting Recommended Technology..o..... 27 Proposed Extension Program 29 Program of Ac.i o n 31 Estimated Cost of Extension Progra*,............*...... 33 V. RESEARCH AND DEVELOPMENT ....................34 Inrdcin......... *.................... ............. ....... 34 TRA Research Expansion Needs.......................... 35 Estimated Cost of Research Program.................... 36 VI. FUELWOOD USE IN DARK FIRE-CURED TOBACCO.................. 38 Introduction .. .0.0.......... .................. ........ 38 Fuel,wood Requlzeent .... 39 Extension Services 40 Constraints to Adopting Technology..,......... .... 40 Proposed Extension Program o g r sm... o.*.......... 41  Page No. ANNEXES A, List of Persons Met,.....................................* 43 Be The Tobacco Curing Process..,........ ............. 45 C; Description of Existing Curing Sts tems 51 D. Wood Use and Cost - Response of Selected Producers..,.*. 55 E. Sketches of Alternative Curing Facilities and Improve57ents............. .,. , , 57 FIGURES 1. Typical ventilator and furnace construction 63 2, A furnace and flue layout,...................... 64 3. Typical fam construction top ventilator for tobacco barns, * 65 4. Construction instructions for tobacco barn roof ventilatorn... t i l at. ............... or............. 66 5. Section of ventilator showing ground level control from barn outside..........,.................... 67 6. Commercial type tebacco barn top ventilators*.*......... 68 7. Section of cascade continuous curing systemo............. 69 8. Section of typical conventional estate battery barn.....,........,..,.,.......,,,,,...........,.,,.,.., 70 9. Cascade continuous curing system with fan for each chamber as proposed by J. S Redmile, Zimbabwe.....o..... 71 10. Plan views of two tobacco curing tunnels 72  SUMMARY The purpose of this study was to compile and evaluate the various technical options that may be used to improve the efficiency of fuelvood use in the tobacco industry in Malawi and to recomwend an appropriate program of action. The principal findings of the study are: (M) A whole range of technical options -- of virying degress of readiness, sophistication, costs and benefits - can be used to improve the efficiency of wood use in the tobacco industry in Malawi. In the longer run it is feasible that wood used for tobacco curing (40% of the country's total wood use) could be reduced by as much as one-half. (i) The highest returns and quickest paybacks are associated with two relatively low cost measures - installing doors and grates on furnaces and installing controllable ventilators - in the least efficient barns at a cost of about MK 400 per barn. Thetse investments would be paid back in less than two years. (iii) The more efficient barns would require more sophisticated and capital intensive improvements which are also likely to be economically profitable but which require further demonstration and testing. (iv) The principal constraint to embarking on a large scale program to iTprove the tobacco industry's energy efficiency is the absence of an effective and adequate extension mechanism to disseminate the potential savings from these improvements. Other constraints include the short horizon of barn managers, the non-availability of long term financing, the unclear demarcation of institutional respon- sibilities, and uncertainty about the actual existing conditions regarding wood use, efficiency and the cost of wood in different areas. To tackle these problems, this study recommends a two-phase program to improve the efficiency of energy use in the tobacco industry. The first phase would compri'se the following elements: (i) A pilot project to install doors, grates and ventilators in forty low efficiency barns at five different sites and to monitor and evaluate the savings that accrue from these improvements over a two-year period. The Tobacco Research Authority (TRA) would be the coordinating agency for this project.  - ii - (ii) The setting up of an effective extension, monitoring and evaluaticn capability both for the pilot project and for a larger program in the subsequent phase. This task would involve the Tobacco Research Authority, the Ministry of Agriculture and the Ministry of Forestry and Natural Resources. (iii) An extensive survey of tobacco curing facilities to define existing conditions and to evaluate the economic attrac- tiveness and investment and human resource requirements of a full-scale program to improve energy efficiency in tobacco curing. The Energy Studies Unit in the Ministry of Forestry and Natural Resources is currently developing such a survey. However, the survey proposal needs to be reviewed and support for its implementation may be required from the TRA and from the extension staff of the Ministry of Agriculture. (iv) Support for further testing and research by the TRA of the more sophisticated technical improvement packages, some of which could be deployed in Phase II. This first phase would be implemented over a two-year period and wouild cost about MK 316,000 as shown below. However, it is important to note that this costing is not based on detailed engineering and therefore should be treated as indicative only. Item Cost (M1K) Equipment for pilot project barn improvements 36,000 Technical experts, monitoring and evaluation for pilot project; Development of extension network for subsequent phase 190,000 Research and Development Program 90,000 TOTAL 316,000 At the end of the two-year implementation period for the first phase summarized above, a full scale program of tobacco industry effi- ciency improvements could be launched. It is difficult at this time to estimate the investments and benefits associated with such a program because the mix of the various measures required still has to be deter- mined. However, such a program is likely to entail investments in excess of MK 10 million and would take five to seven years to implement. The expected benefits are also difficult to quantify with precision but if they result in savings of a quarter of the current wood used for tobacco curing - which is a conservative estimate - then, at an estimated cost of MK 6 per cubic meter of wood (again a conservative estimate) - the anuual value of savings would amount to MK 5 million.  - iii - Background Fuelwood is Malawi's main source of energy, supplying some 90% of the country's primary energy requirements. As in most other countries which rely heavily on wood energy, fuelwood consumption in Malawi exceeds the incremental production of this resource and is a contributor to the country's depleting forest cover. The government is concerned about this both for environmental reasons and because the increasing difficulty in obtaining wood -- either purchased or collected -- directly affects the quality of life for Malawi's population, 90% of whom rely almost exclusively on wood for their energy needs. To tackle this problem the Government has embarked upon a reforestation program but its scope is constrained by resource limitations and the need to mobilize community support. A complementary program to improve the efficiency of wood use through better cook stoves in the household sectot also has been started but is again held back by the pace of consumer acceptance and the need to reach a large number of individual households. Tobacco curing accounts for an estimated 40% of Malawi's fuelvood consumption. Of this, some 400 flue-cured tobacco growers use 75% of the wood, and 42,600 fire-cured growers use the remaining 25%. While enerly savings are possible in both fire-cured and flue-cured tobacco production, the immediate potential appears to lie with the former, where considerable preparatory work has been done in the country and where improved practices in other countries can most easily be applied. Therefcres, this report focuses primarily on flue-cured tobacco facilities. The Tobacco Research Authority in Malawi estimates that the amount of wood consumed per kilogram of flue-cured tobacco ranges from 0.02 m3 on the most efficient estates to 0.13 m3 on the least efficient ones - a range of almost seven to one. Furthermore, the most efficient barns use about three to four times more energy than current best prac- tices in industrialized countries such as the United States. Thus, economically profitable energy efficiency improvements could probably be maue in all barns. However, given implementation constraints, a phased program would be more appropriate. Initially, the emphasis should be on low cost, well-tested measures, where the primary objective is to bring the efficiency of below average barns up to the level of the more efficient ones. More fundamental design and technology changes to improve even the most efficient barns could be contemplated as a second phase, particularly as some technical and economic uncertainties associated with them still need to be resolved. This study therefore concentrates on the first phase, and on further work required to resolve some of the uncertainties associated with the more sophisticated measures.  - iv - Low Cost Improvements The study has identified two low cost. technical improvements w lch may be easily adopted to reduce fuelwood use In existing low efficiency flue-cured tobacco barns: (i) rebuilding furnaces, adding grates an$ doors; and (ii) installing controllable top and bottom ventilators. Preliminary estimates by TRA suggest that the former could result in a 25% fuelwood savings, and the latter a further 15% savings. TRA has indicated that a typical "inefficient' barn msv consume 20 m3 of fuelwood per 500 kg cure of tobacco; this translates into a wood savings of 5 m3 and 3 m3, respectively, for the two improvements. Based on six cures (of 500 kg each) per annum and an average cost of HR 6 per m3 of wood, this infers an annual savings of MK 180 and 1K 108, respectively. Investment costs for the two measures are MK 250 and MK 160; therefore, assuming that incremental labor costs and O&M costs are small, in both cases the payback period is less than two years. This preliminary analysis suggests that both measures are highly cost effective. However, it is recommended that a 24-month pilot project be conducted to verify these savings in field conditions before proceeding on a full-scale program of implementation in Malawi. The Pilot Project The study recommends a pilot project in which 40 low efficiency barns in five main growing regions are upgraded. To carry out a controlled experiment, eight other low efficiency, unimproved barns in each region need to be identified and monitored at the same. time. A techuical assistant is required for each regional experiment to monitor fuelwood consumption, train barn-tending labor, and evaluate the amount and quality of cured tobacco. Resources will also be required to set up an effective extension, monitoring and evaluation capability at the TRA both for the pilot project and for the subsequent larger scale improve- ment program. To assess the incremental savings associated with imple- menting the two measures in improved barns, it is recommended that only one option be installed in some of the barns and that both options be installed in others. The pilot program would be scheduled over a two- year period encompassing two curing seasons. As the curing season is only six weeks long, and allowing another four weeks for data analysis and report writing, there should be ample time available for the additional TRA staff and the five technical asslstants to be involved in the other related activities recommended in this report. Survey of Tobacco Barns Assuming that the attractive economics of these improvements are verified by the pilot project, the next step would be to establish a similar program for all low efficiency barns. However, before this can be done several issues associated with fuelwood use in the tobacco  -v - industry need to be resolved. In particular, a great deal of uncertainty exists in the following areas: (M) the number of barns operating at the various levels of energy efficiency; (ii) the total amount of fuelwood used for tobacco curing in Malawi, and.how this is distributed among small and large producers and energy efficient and inefficient producers; and (iii) the variation in present costs of fuelwood to producers in different regions and how these costs may change in the future. A detailed survey of all (approximately 400) flue-cured tobacco producers would help eliminate much of this uncertainty, and this study recommends that in parallel with the pilot project, such a survey be carried out by the Energy Studies Unit in the Ministry of Forestry and Natural Resources. A suitably experienced engineer (possibly expatriate) should be made responsible for this operation, and support for this work should be provided by TRA and the extension staff of the Ministry of Agriculture. Further Research and Development Work The study identified a number of other technical improvements which may lead to further reductions in fuelvood use, but at a higher investment cost. These include: - efficient flues and chimneys; - forced draft flue systems; - cascade continuous curing; - tunnel continuous curing; and - bulk curing with a centralized heating plant An ongoing research program at TRA is evaluating the savings associated with some of these options. This program reeds to be strengthened with funds for additional supplies and equipment. The TRA and other interested parties should also consider addressing issues unresolved by this study. In particular, the following need to be addressed: (i) alternative means of financing a full-scale implementation program, and (ii) the impact of improved energy efficiency and controlled environment on the quality of tobacco produced, and hence its marketable value.  - vi - Fire-Cured Tobacco The Ministry of Forestry and Natural Resources is currently investigating fuelvood sse for fire-cured tobacco. This work could identify possible improvements in fuelwood efficiency and future technical assistance requirements in this subsector.  I: INTRODUCTION Background to the Study 1.1 Malawi's climate is ideally suited for tobacco growing. This fact, coupled with the availability of suitable soils, has allowed the development of an industry that currently provides 40-502 of Malawi's foreign exchange earnings. 1/ 1.2 The curing of flue-cured and dark fired-cured tobacco requires an adequate supply of fuelvood. At present, most of this fuelwood is obtained from natural woodland. It has been stated that one hectare of flue-cured tobacco requires 41.7 hectares of natural woodland to sustain production indefinitely. 2/ 1.3 Assuming an increase of 3.5% a year ',In the demand for fuelwood from all sources, the supply of indigenous natural timber would be exhausted by the 1990s. Much of the available natural woodland has already been removed from large tracts of the Central and Southern Regions. 3/ 1.4 Much evidence indicates that the amount of wood consumed by the tobacco industry could be reduced considerably through measures to improve the efficiency with which wood is burned, While energy savings are possible in both flue-cured and dark fire-cured production, the immedlate potential appears to be in the former, where considerable preparatory work already has been done in Malawi and where improved practices from neighboring countries can be most easily applied. Moreover, there is a far greater concentration of wood use in the flue cured sector which makes it easier and more profitable to concentrate first on this group: Some 400 growers of flue-cured tobacco account for 75% of the tobacco industry's wood consumption, with the remaining 25% being used by over 42,000 growers of fire-cured tobacco. Estimates of the potential savings in wood consumed by flue-cured tobacco that could be realized through relatively low cost investments and better curing techniques range from 30% to 50%. Potential savings in dark fire-cured production have not been thoroughly explored. 1/ Government of Malawi, Ministry of Agriculture, MW007/3 10.82 Tobacco Sector Study, Vol. I, pg. 47. 2/ IBID. 3/ IBID.  -2- Objectives of the Study 1.5 The objectives of the study were as follows: (i) To prepare a comprehensive inventory of the various technical packages that could be used to improve the efficiency of energy use in the Malawi tobacco industry. (ii) To compare these alternatives in terms of investment cost, likely savings, lead time for implementation, ease of administration, degree of commercial readiness, etc. (iii) To recommend a costed and scheduled program of action based on the above. This should include the pre-investment work required to achieve these savings and any experimental or pilot projects needed to further evaluate specific technical options not yet fully tested. (iv) To recommend training and extension measures necessary to ensure the acceptance and successful implementation of the program in the tobacco sector. (v) To suggest the agencies which would be responsible for co- ordinating and implementing the project. Conduct of the Work 1.6 The work was carried out in Malawi by an engineer experienced in tobacco curing and a tobacco extension specialist between June 13 and July 9, 1983. Field visits were made to estates, small holdings, research centers, and discussions were held with tobacco growers, extension workers, researchers and a number of officials concerned with providing services to the tobacco sector.  -3- II. FUEL SOURCES AND USE Alternative Energy Sources 2.1 Many fuels are used to cure flue-cured tobacco (FCV) around the world. However, Malawi may be one of the few that uses fuel wood almost exclusively. 2.2 In the United States, for example, LPG and fuel oil are primarily used for curing FCV, and hardwood is used for curing dark fire- cured tobacco. Zimbabwe has been using coal for nearly a decade for curing FCV since wood became less available and oil escalated in price. Their producers expressed doubt some ten years ago that they could change to coal (mined within the country) and remain competitive in tobacco production. 2.3 Malawian producers may have a more critical decision to make on the choice of fuel if wood becomes unavailable, Low grade coal is available in the northern part of the country, but the transportation cost appears prohibitive. Other internally available sources of energy such as solar, biomass or field residue, and hydro-generated electric power also have limitations in application and cost. 2.4 Fuels that might be Imported include coal, fuel oil, and LPG. The present cost of coal delivered to Blantrye from Mozambique by rail is MK 70 per ton or MK 140 if delivered by truck. The coal still must be delivered to the point of use. Fuel oil is now nearly MK 1 per liter. Any switch to a fuel other than coal would require a large investment in. equipment and facilities to enforce. 2.5 Table 2.1 compares the cost of three fuels in poor barns with improved barns equipped with controllable bottom and top ventilators. Puel oil is not competitive with coal or wood for use in conventional barns, Coal may be competitive with wood at MK 6.50 per m3 if trans- ported by rail and farm delivery is close to the railhead.  - 4 - Table 2.1 Fuel Cost to Cure 500 Kg of Tobacco Fuel Oil Coal Wood MK 0.96 MK 70 MK 140 MK 6.50 MK 11 Kind of Barn Per L Per t Per t Per m3 Per m3 Poor Barn Fuel Oil, 870 L a/ 634 Coal 2250 kg b/ 160 320 Wood 20 m3 130 220 Improved Barn with Controllable Ventilators Fuel Oil 582 L c/ 559 Coal 778 kg d/ 55 110 Wood 12 m3 e4T 78 132 Study estimate b/ R.W.Jo Ashburner and P.M. Foot, Zimbabwe Tobacco Association and Wankie Colliery Company, respectively. Rupert W. Watkins and W,D, Toussa4nt. 1965 Tobacco Curing Tests Using LP Gas and No. 2 Fuel Oil. Information Circular No. 17. N.C. State University, Raleigh, N.C. d/ E.M. Matthews, M.H. McVickar, and LB. Davis, Jr. 1946. Curing Bright Tobacco with Coal and Oil, Bulletin 396. Virginia Agri- cultural Experiment Station, Virginia Polytechnic Institute, Blacksburg, VA. See discussion of Potential for Saving Fuelwood in the Curing Process, also Appendix E, Wood Use and Cost.  Wood as an Energy Source 2.6 A review of previous reports indicates considerable variation in wood energy values and in the measurement of wood. Table 2.2 gives the density and calorific values, both solid and stacked, for the most common species of wood. The density and calorific values for solid wood seem to be accepted as authentic. 1 2/ However, the density and calorific values of stacked wood are quite uncertain based on reports by the Malawi Division of Forestry (MDF) and the Tropical Products Institute (TPI). 2.7 Measuring wood is further complicated by the absence of a true definition of a cord as described by farmers. A standard cord is generally defined as 1.22 m x 1.33 m x 2.44 m or 3.96 m3. A stacked cord of wood was described by farmers as either 0.91 x 1.22 m x 1.83 m or 2m3, or 0.91 m x 1.52 m x 1.22 m or 2.53 m3. Therefore, a cord as described by farmers is somewhere between 2 to 2.5 m3. 2,8 NDF has used a stacked dry wood factor of 0.67, or two-thirds of the solid weight of an equal volume. TPI found a stacked density of 259 to 267 kg per m3 from trials in two different years (TPI Report R735). A stacked density of 267 kg per m3 and a solid volume density of 570 kg per .a3 gives a ratio of 0.469. Using this factor, the average stacked weight ft.r the several species is 317 kg per m3. For purposes of this report, the stacked density of 325 kg per m3 as suggested in the Tobacco Sector Study, Voltme IV, is used. 2.9 The basic calorific value of wood has been given as 18.7 NJ per kg, dry basis, and 14.3 MJ per kg at 25% moisture, wet basis, air dried. This agrees closely with a value of 19.3 MJ per kg on a dry weight basis as indicated by the East African Agriculture and Forestry Research Organization. Other information (Malawi Department of Forestry and Game, S.P.RO., Zomba, 1978) showed the basic calorific value of wood at 25% moisture content to be 18.7 MJ per kg. A study within Malawi (TPI Report R-735, 1978) gave 18.48 MJ per kg for wood at 25% moisture content, wet basis. The value of 18.7 MJ per kg, dry basis, agrees approximately with many textbook definitions of the basic calorific value of wood. 1/ W.G. Dyson, Tree Breeder, East African Agriculture and Forestry Research Organization, Nairobi, Kenya, letter to Malawi Director of Forestry axnd Game, Ministry of Natural Resources, Zomba, Malawi, July 4, 1)72. 2/ E.D. May, P.A.C.P., for Director of Forestry and Game. Working Pape rs.  Table 2.2: Density and Calorific Value of Wood 1/ Density Calorific value stacked drywood Calorific Stacked Drywood using 0.469 factor value Solid Applying solid 0.67 0.469 BTU/ft3 factor factor 2/ (dry weight lb/ft3 lblft3 lb/ft3 BTU/ft3 kcal/m3 kJ/m3 Species basts) Brachestegia spici formis 393,500 49 32.8 23.0 184,704 1,538,528 6,881,510 Isoberlinia scheffleri 393,500 49 32.8 23.0 184,704 1,538,528 6,881,510 Jalbernardi globiflora 449,700 56 37.5 26.3 211,198 1,897,382 7,868,597 Gmelina arborea 224,800 28 18.8 13.1 105,174 958,810 3,918,464 Pinus patula 274,000 34 22.8 15.9 128,135 1,145,271 4,795,021 Eucalyptus grandis 289,100 36 24.1 16.9 135,546 1,206,180 5,050,033 Melia azedirach 305,100 38 25.5 17.8 142,915 1,271,754 5,324,580 Cassia siamea 345,300 43 28.8 20.2 162,211 1,443,463 6,043,490 Eucalyptus camaldulensis 345,300 43 28.8 20,2 162,211 1,443,4b3 6,043,490 Eucalyptus tereticornis 345,300 43 28.8 20.2 162,211 1,433,463 6,043,490 Azedirachta indica 361,400 45 30.2 21.1 169,456 1,507,933 6,313,416 Average (arithmetic) 42.2 28.3 19.8 159,004 1,414,915 5,923,964 1/ Information supplied by Malawi Department of Forestry, Dr. E.D. May. TI TPI Report R735, In trials on density of stacked wood 16.2 to 16.7 lb/ft3 was determined and solid volume density 35.6 lb/ft3.  -7- Factors Contributing to Inefficient Wood Use 2.10 Tobacco curing as it is practiced in Malawi comes from experi- ence with facilities constructed of locally available materials and until recently, a reasonably ample supply of wood. The curing process that has been used works with a minimum of knowledge of the process and possible errors by the operators. This chapter will discuss how this process works and how it leads to inefficiencies in wood use. The four major components of the process are (1) the curing structure; (2) furnaces; (3) flues and chinneys; and (4) ventilation. Management and barn packing (loading) also influence fuel use but they are difficult to evaluate because they were not observed at the time of this investigation. Barn Structure 2.11 Most of the buildings used for tobacco curing are constructed of brick, mud, poles, and metal or thatched grass roofs. Locally made labrite brick is a reasonably good construction material. However, has a relatively poor insulation value when used in solid walls. Consequently, there is a relatively large conductive heat loss through brick walls. Also, the mud used for mortar is -jade from soil mixed with water, with no cement or binder added. This serves the intended purpose where it is kept dry but is a pdor material for foundations and for surfaces eo osed to the weather. Occasional failures of barns were reported to be due mainly to foundation collapse. In some instances, the mortar joints had deteriorated to a point where air could freely pass through the walls. The use of cavity walls to provide a dead air space for insulation was observed at research and demonstration sites. 2.12 Wood poles and lumber used in barns are subject to early failure, mainly because of termite damage. At some locations it ws noted that tier poles were supported independently of the wall structure so that they could be replaced without interfering with the walls. There was no evidence of the use of metal termite shields, especially to pro- tect the roof structure. 2.13 The roof covering materials used on barns have relatively little insulating value. This Is not a critical factor except in the leaf and stem drying phases of the curing process, and then only where there is no sunlight. Furnaces 2.14 Furnaces are generally made of brick and mud or mortar cement, in some cases with metal reinforcing to support the top. Furnaces are built on site in several configurations to match the barn and flue layout. Over half of the barns are estimated to have open hearth (h.ull 1/ Low density, 1890 kg per m3, conductivity (K) = 11 W per m2. OC per cm thickness. For wood K - 1.8.  -8- type) furnaces which are simply a shell with an opentdng in one end for inserting wood, Open hearth furnaces are inherently inefficient as there is no control over air supply and the burning rate except through wood supply. 2.15 Some furnaces are constructed using both grate and doors for feeding wood and cleaning out ashes; although the design is satisfactory, problems have been sited with operation. Among them: doors are frequently left open, wood lengths are too long to close the door, the back of the furnace or firewall can be knocked out when wood is thrown in, heavy logs may cause the grate to buckle, and grate bars are spaced_ too far apart -- allowing unburned wood and charcoal to fall through. 2.16 It appears that most furnaces are reconstructed after one or two seasons. The idea is to invest as little as possible in furnace material without regard for labor cost as it is relatively inexpensive. Flues and Chimney 2.17 The most commonly used flues are made of sheet iron in pipe sizes of 28 cm and 35.5 cm diameter by 0.6 m to 2.4 m long. The flues extend out from the furnace at a central end point or fron two sides, depending on the flue layout. The first section of the flue pipe gene- rally overheats and warps and must be replaced two or three times per season, The other portion of the flue pipe should last several years before it deteriorates from rust. There was some evidence of poorly made joints which would affect the draft generated in the flue system. In general, flue pipes were fc-nd to rise slightly, 1 cm to 10 cm, in length from the furnace exit to the chimney outlet. 2.18 At some locations, there was a problem with non-uniform curing which may be caused by unequal heat distribution, This may result from improperly located bottom vents or insufficient flue surface for heat convection. In some of the larger 6 m x 12 m barns, metal drums were located in corners opposite the furnace to Increase heat convection at these locations. At some locations on the lower tier, there were reports that too much heat caused the tobacco to dry too quickly. This may have resulted from heat radiating from the flue pipe at the hottest points. The solutions are to separate the tobacco further from the flues, install a heat shield baffle to record radiant heat or to improve the flue design and layout for more uniform heat distribution. 2.19 In a study for the Kasungu Flue Cured Tobacco Authority (KFCrA), TPI (TPI-R653) recommended that a 35.5 cm diameter flue pipe be replaced with a 28 cm pipe which was said to increase the heat transfer efficiency by 20 percent. TRA has confirmed an improvement in fuel efficiency using 28 cm diameter flues in conjunction with a 35.5 cm diameter chimney. The theory is that a smaller pipe results in greater flue gas velocity, more friction, and greater turbulence which results in better heat transfer. The assumption is that the chimney height and differential temperature is sufficient to generate the necessary draft. Before many farmers scrap useable 35.5 cm diameter flue pipe, it might be advisable to try other  -9- alternatives such as changes in chimney damper, size and height, flue baffles and draft control on the furnace to accomplish the savings. Increasing the velocity of flue gas by reducing pipe size increases heat output but also increases friction in the pipe which must be compensated for by increasing stack height and effectiveness. 2.20 To carry the reduction in flue pipe size even further, a few producers were using a 22.8 cm diameter pipe, Among the advantages cited were efficient wood use (10 m3 per 500 kg of tobacco) and 36X less material than in the 35.5 cm diameter pipe. The disadvantages mentioned were quick burnout of the flue near the exit from the furnace, the necessity of cleaning flues after every cure, and an extension of curing by one day as mentioned by one producer. 2.21 In an effort to improve flue design, TRA has tested a flue of rectangular cross section which shows savings of up to 40% in trials on several estates. The rectangular flue has a greater surfacm area, a smaller hydraulic diameter, and less horizontal surface exposure for upward radiant heat, but it is expected to cost twice as much to construct as the 28-cm round flue oipe. However, the rectangular flue has not been fully evaluated by TRA. 2.22 In general, it is difficult to evaluate flue design indepen- dently of chimney design. Many different chimney arrangements exist - from no chimney to brick chimneys which extend above the roof line. Most barns have only one chimney although 6 m x 12 m barns frequently have two chimneys. The flue pipe often will extend through the barn wall and turn upward with a 90