biogas energy technology in sudan

Renewable Energy 28 (2003) 499–507www.elsevier.com/locate/renene

Technical note

Biogas energy technology in Sudan

A. M. Omer∗, Y. FadallaNCMWE, P.O. BOX 15007, Khartoum 12217, Sudan

Received 3 January 2001; accepted 14 March 2002

Abstract

Biogas from biomass appears to have potential as an alternative energy in Sudan, which ispotentially rich in biomass resources. This is an overview of some salient points and perspec-tives of biogas technology in Sudan. The current literature is reviewed regarding the ecological,social, cultural and economic impacts of biogas technology. Sudan is blessed with abundantsolar, wind, hydro, and biomass resources. Results suggest that biogas technology must beencouraged, promoted, invested, implemented, and demonstrated, but especially for remoterural areas. 2002 Elsevier Science Ltd. All rights reserved.

1. Introduction

Sudan is the largest country in the African continent, with an area of approximatelyone million square miles (2.5 million square kilometers). Sudan is viewed as one ofthe potentially richest nations especially in livestock beside water and land with 30million head of cattle, 70 million head of sheep and goats, and 3 million head ofcamels [1]. Besides that, Sudan has a great wealth of the wild life, birds, reptiles,and fish wealth, which are estimated to give 200,000 tons of food annually. Sudanhas a total population of about 30 million people, which is growing at an annualrate of about 2.8%. About 70% of the population live in rural areas. About 62% ofthe population are employed in agriculture [2]. Agriculture contributes about 33%of the gross national product (GNP), and 95% of all earnings.

Energy is an essential factor in development since it stimulates and supports econ-

∗ Corresponding author. Present address: School of Built Environment, University of Nottingham, Uni-versity Park, Nottingham NG7 2RD, UK Tel.:+44-115-9513163; fax:+44-115-9513159.

E-mail address: [email protected] (A.M. Omer).

0960-1481/03/$ - see front matter 2002 Elsevier Science Ltd. All rights reserved.PII: S0960 -1481(02 )00053-8

500 A.M. Omer, Y. Fadalla / Renewable Energy 28 (2003) 499–507

omic growth and development. Fossil fuels, especially oil and natural gas, are finitein extent, and should be regarded as depleting assets, and efforts are oriented tosearch for new sources of energy. The clamour all over the world for the need toconserve energy and the environment has intensified as traditional energy resourcescontinue to dwindle whilst the environment becomes increasingly degraded. Biomassenergy supply in Sudan has contributed 87% of the total energy supply since the1980s [6]. The basic form of biomass comes mainly from firewood, charcoal andcrop residues. Out of total fuel wood and charcoal supplies 92% was consumed inthe household sector with most of the firewood consumption in the rural areas.

The total area of the land of Sudan is 600 million Feddans (Feddans=1.038acres=0.420 hectares). The land use in the country is classified into four main categ-ories. There are arable land (8.4 million hectares), pasture (29.94 million hectares),forest (108.3 million hectares), and about 38.22 million hectares used for other pur-poses [9]. Agricultural residues consist mainly of cotton stalks, groundnut shells, andbagasse, with estimates of more than 15 million metric tons [2]. Also, considerableamounts of non-woody biomass is available as animal dung, which is estimated at300 million metric tons annually [4].

Biogas technology was introduced to Sudan in the mid-seventies when GTZdesigned a unit as part of a project for water hyacinth control in central Sudan.During the last fifteen years about 200 biogas units have been built in Sudan indifferent areas, producing methane, CH4, for cooking, water pumping and electricitygeneration. In order not to repeat this successful technology to excess on local con-ditions, conscientious planning is urged [6]. The goals should be achieved through:

� Review and exchange of information on computer models and manuals useful foreconomic evaluation of biogas from biomass energy.

� Exchange and compilation of information on methodologies for economic analysisand results from different types.

� Investigation of the constraints on the implementation of the commercial supplyof biogas energy.

� Investigation of the relations between supplies and demand for the feedstock fromdifferent industries.

� Documentation of the methods and principles for evaluation of indirect conse-quences such as the effects on growth, silvicultural treatment, and employment.

2. Biomass energy

Agriculture is the backbone of economic and social development in Sudan.Biomass resources play a significant role in energy supply in Sudan as in manycountries as shown in Table 1 and Table 2.

Cooking is largely done with firewood (45%) and charcoal (30%). Hence, 75%of total energy per annum, represented by roughly 3 million metric tons of forestreserves and agricultural residues, which come mainly from cotton stalks, groundnutshells and bagasse which are estimated at more than 15 million metric tons. Also,

501A.M. Omer, Y. Fadalla / Renewable Energy 28 (2003) 499–507

Table 1Sources of biomass energy available in Sudan, Million tons of equivalent (TOE) [3]

Item Source 106 TOE

1. Natural and cultivated forests 2.902. Agricultural residues 6.203. Animal wastes 1.054. Water hyacinth 3.16

Total 13.31

Table 2Biomass energy consumption in Sudan, 1000 Tons of equivalent (TOE) [7]

Item Sector 103 TOE (%)

1. Residential 4549 92.02. Industrial 169 3.43. Othersa 209 4.6

Total 4927 100.0

a Others are commercial, construction, and Quranic schools.

a considerable amount of non-woody biomass is available as animal dung, estimatedat 17 million tons as shown in Table 3. Water hyacinth and aquatic weeds are esti-mated at 9000 and 3000 tons per annum, respectively.

Biogas technology has been known for a long time, but the interest in it hasrecently increased very considerably—mainly because of the higher costs and therapid depletion of local traditional fuel sources and fossil fuels. In developing coun-tries the interest in biogas technology has been further stimulated by the promotionalefforts of various international organizations and foreign aid agencies through theirpublications, meetings, and visits.

Table 3Biomass energy potential from animal dung in different states of Sudan [10]

Item States Animal dung available (1000 Tons) Energy (TOE)

1. Northern states 102.4 15432. Eastern states 1222.9 184313. Khartoum state 104.3 15724. Central states 4223.7 636585. Darfur states 5062.5 363016. Kordofan states 2596.9 791407. Southern states 4545.2 68505

Total 17857.9 269150


Table 4Anaerobic degradation of organic matter [5]

Level Substance Molecule Bacteria

Initial Manure, vegetable, wastes Cellulose, proteins Cellulolytic,proteolytic

Intermediate Acids, gases, oxidized, inorganic salts CH3COOH, Acidogenic,CHOOH, SO4, hydrogenic, sulfateCO2, H2, NO3 reducing

Final Biogas, reduced inorganic compounds CH4, CO2, H2S, Methane formersNH3, NH4

3. Technical description

Bacteria form biogas during anaerobic fermentation of organic matters. The degra-dation is a very complex process and requires certain environmental conditions aswell as different bacteria populations. The complete anaerobic fermentation processis briefly described below as shown in Table 4, and Fig. 1.

Biogas is a relatively high-value fuel that is formed during anaerobic degradationof organic matter. The process has been known, and put to work in a number ofdifferent applications, during the past 30 years, for rural needs such as described in[8]: food security, water supply, health care, education, communications.

4. Biogas digester designs

There are in practice two main types of biogas plant that have been developed inSudan; the fixed-dome digester, which is commonly called the Chinese digester, and

Fig. 1. Biogas production process.


Table 5Optimum condition for biogas production

Parameter Optimum value

Temperature °C 30 –35pH 6.8–7.5Carbon/nitrogen ratio 20–30Solid content (%) 7–9Retention time (days) 20–40

Table 6Average daily gas production based on head count

Source of waste Waste production (kg d�1) Gas production (m3 d�1)

1 cow 10 0.25–0.4010 chicken – 0.02–0.041 latrine user 1 0.02–0.031 sheep/goat – 0.02–0.04

the type with a floating gas holder known as the Indian digester. The optimum rangein Table 5 is for ambient temperatures during hot seasons of Sudan’s tropical climate.The potential gas volumes produced from wastes vary depending on many factors,and can be expressed based on head count as shown in Table 6, or on a fixed weightas shown in Table 7. A list of the potential gas production from a number of materialsis presented in Table 8. The requirements for gas for various purposes, and a com-parison between biogas and various commercial fuels in terms of calorific value andthermal efficiency, are presented successively in Table 9 and Table 10. The amountof biogas actually produced from a specific digester depends on the following factors:(1) the amount of material fed, (2) the type of material, (3) the carbon/nitrogen ratio,and (4) digestion time and temperature.

Table 7Average gas production based on waste amount

Source of waste Gas production m3/103 kg animal Gas production m3/103 kg waste

Dairy cattle 2.53 –Beef cattle 2.47 –Poultry 6.92 65.5-115Pretreated crop waste – 30–40Water hyacinth – 40–50


Table 8Ultimate gas yields for some different materials

Materials Yield (m3/kg day solids)Manure:� Cow 0.34� Poultry 0.48� Human 0.40Vegetable matter:� Straw 0.17� Grass 0.43� Leaves 0.30� Water hyacinth 0.40

Table 9Comparison of various fuels

Fuel Calorific value (kcal) Burning mode Thermal efficiency (%)

Electricity, kWh 880 Hot plate 70Coal gas, kg 4004 Standard burner 60Biogas, m3 5373 Standard burner 60Kerosene, l 9122 Pressure stove 50Charcoal, kg 6930 Open stove 28Soft coke, kg 6292 Open stove 28Firewood, kg 3821 Open stove 17Cow dung, kg 2092 Open stove 11

Table 10Biogas requirements for various purposes

Purpose Specifications Gas required (m3)

Cooking per person 0.425/daystove 10 cm dia. 0.47

Lighting 200-candle power 0.140-watt bulb 0.132-mantle 0.14

Gasoline engine Per HP 0.43Diesel engine Per HP 0.45Refrigerator Per m3 1.2Incubator Per m3 0.6Table fan (indirectly) 30 cm diameter 0.17Space heater 30 cm diameter 0.16


5. Economic Aspects

In Sudan, people are requested to construct biogas plants by themselves in orderto reduce costs. In remote areas, the costs for materials increase by about 15–20%due to transportation. The costs of construction of the fixed digester are given inTable 11.

In an economic analysis, many factors have to be considered, as outlined in Table12. It is clear that many factors listed cannot be expressed in monetary terms. Thebasis of evaluation of the gas produced is of significance. For example, in placeswhere people use waste, but not kerosene, as fuel valuing the gas at the market priceof kerosene equivalent is not correct, since this over-estimates the benefits. It hasbeen observed that some of the present evaluations on biogas systems, while compar-ing the benefits with respect to existing practices, make the error of double account-ing. For example, if the dung, which is already used as manure, is fed to a digester,only its incremental value can be taken into account. Due to the lack of knowledgeand awareness, villagers cannot be expected to understand the benefits of defores-tation control, nutrient conservation, or health improvement. A poor rural peasant isvery hesitant to enter a new venture. The negative attitude towards the use ofnightsoil varies from place to place, but when it occurs, it is a major obstacle to theimplementation of biogas technology.

6. Recommendations

1. The introduction of biogas technology on a wide scale has implications for macroplanning, such as the allocation of government investment and its effects on thebalance of payments. Factors that determine the rate of acceptance of biogasplants, such as credit facilities and technical backup services, are likely to have

Table 11Cost of construction materials for a 7 cubic meters fixed dome digester in Sudanese Dinars (D.S) (July2000)

Construction material Cost (D.S)

1. Cement, 23 bags (1 bag=2500 Dinars) 575002. Sand, 3 m3 (1 m3=2000 Dinars) 60003. Gravel, 3 m3 (1 m3=2500 Dinars) 75004. Construction steel, 1 m3=9000 Dinars 900005. Pipe, 6’’ ×3 m 230006. Pipe, 8’’ ×2 m 230007. Steel wire (1 kg=400 Dinars) 4008. Gas valve, 2 pieces (1 piece=3500 Dinars) 70009. Rubber pipe, 20–30 m (1 m=150 Dinars) 450010. Burner 51250Total 270150


Table 12Factors to be considered in economic analysis

Economic Factors� Interest on loan� Current/future cost of alternative fuels� Current/future cost of chemical fertilizer� Current/future cost of construction materials� Saving of foreign currency� Current/future labor cost� Inflation rate� Costs of transport of feeding materials and effluentsSocial factors� Employment created� Better lighting: more educational/cultural activities� Less time consumed for fetching firewood and for cooking� Improved facilities in villages; thus less migration to cities� Less expense for buying alternative fuels� More time for additional income earning activitiesTechnical factors� Construction, maintenance and repairs of biogas plants� Availability of materials and land required� Suitability of local materialsEcological/health factors� Improved health� Forest conservation (positive or negative)� Environment pollution abatement� Improvement in yields of agricultural products

to be planned as part of general macro-policy, as do the allocation of researchand development funds.

2. In some rural communities, cultural beliefs regarding handling animal dung areprevalent and will influence the acceptability of biogas technology.

3. Co-ordination of production and use of biogas, fertilizer and pollution control canoptimize the promotion and development of agricultural and animal husbandry inrural areas.

7. Conclusions

1. Biogas technology cannot only provide fuel, but is also important for comprehen-sive utilization of biomass forestry, animal husbandry, fishery, evolution of theagricultural economy, protecting the environment, realizing agricultural recycling,as well as improving the sanitary conditions in rural areas.

2. Biomass energy is one of the important options which might gradually replaceoil, which is facing increasing demand and may be exhausted early in this century.Sudan can depend on the biomass energy to satisfy part of local consumption.

3. Development of biogas technology is a vital component of the alternative rural


energy program in Sudan, the potential of which is yet to be exploited. A con-certed effort is required by all if this is to be realized. The technology will findready use in domestic, farming, and small-scale industrial applications.

4. Support for biomass research and exchange of experiences with countries that areadvanced in this field is necessary. In the meantime, the biomass energy can helpto save exhausting the oil wealth.

5. The diminishing of agricultural land may hamper biogas energy development, butappropriate technological and resource management techniques will offset theeffects.

References

[1] Omer AM. Biogas technology and the environment. Regional Energy News, vol. 2, no. 4, Nairobi,Kenya, November, 1996.

[2] Omer AM. Sudan energy background; an overview. Renewable Energy Journal 1998;14(1–4):467–72.

[3] Omer AM. Renewable energy potential and future prospect in Sudan. Agriculture and Developmentin Arab World 1996;3:4–13.

[4] Omer AM. Biomass energy potential and future prospect in Sudan. Khartoum, Sudan, 1999.[5] Anonymous. Chinese or Indian: a comparison. Biogas Newsletter, Nepal, Vol.7, 1979.[6] National Energy Administration (NEA). The National Energy Plan 1985–2000. Khartoum, Sudan,

January, 1985.[7] Omer AM. Sudan: experience with renewables technology. Renewable Energy World, vol. 2, no.

2, James & James Science Publishers Ltd, UK, March, 1999.[8] Energy Research Institute (ERI). Renewable energy resource potential in Sudan. Khartoum, Sudan,

January, 1985.[9] Abdalla AA. Agriculture, globalization and information. Ministry of Finance and Economic Plan-

ning—Sudan, December, 1997.[10] Ali GE, Ali SS. Sudan biomass energy issues and options. Energy Research Institute (ERI), Khar-

toum, Sudan, April, 1993.

biogas energy technology in sudan

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