an integrated rural energy model for a village in bangladesh

bwgy Vol. 15. No. 2, pp. 131-139, 1990 03604442/90 $3.00 + 0.00 Rimed in Great Britain. Ail rights reserved Copyright @ 1990 Pergamon Press plc

AN INTEGRATED RURAL ENERGY MODEL FOR A VILLAGE IN BANGLADESH

M. S. ALAM,? A. M. Z. Hwo,S and B. K. BALA§ t Department of Electrical and Electronic Engineering, Bangladesh Institute of Technology, Rajshahi, $ Department of Electrical and Electronic Engineering, Bangladesh University of

Engineering and Technology, Dhaka and 5 Department of Farm Power and Machinery, Bangladesh Agricultural University, Mymensingh, Bangladesh

(Received 18 October 1988; received for publication 3 August 1989)

Abstract-We present Huq’s model of integrated rural energy systems in revised form. The model forms the basis for the development of a computer model based on the system dynamics methodology of Forrester for policy planning. The model has been constructed to integrate crop production, biogas production, and rural forest and agro-based industries with the aim of optimizing edible, saleable and inflammable outputs to improve the quality of life. We also present Huq’s revised mode1 for a village in Bangladesh and discuss the simulated results for policy changes and implications of the model.

INTRODUCTION

Rural energy resources in Bangladesh, as in many other developing countries, are mainly comprised of biomass, animal and human energy and, to a lesser extent, of natural gas and electricity. Energy is used to grow and prepare food, provide shelter, protect health, and improve the standard of living. Biomass energy is used up rapidly and is being exhausted. Cattle is still the main source of draft power for cultivation and is also in short supply. Animal waste in the form of cowdung is either burnt directly as a fuel for cooking or is applied directly in the field as an organic fertilizer for crop production. Inefficient burning (efficiency 40%) and application of untreated slurry are linked to the depletion of fuel wood resources. This depletion creates ecological imbalance. The production of biomass in anaerobic digestion promises to meet the demands for fertilizers while minimizing the destruction of rural forests since it provides an alternative to fuel wood.

An integrated approach is needed for the production of food and energy through the sagacious use of available resources. The integrated rural energy system is a complex system, which contains technological, economic and social elements. Its quantitative modelling is a formidable challenge.

Modelling of integrated rural energy systems in Bangladesh was initiated by Huq.’ Bala and Satteti developed a dynamic model for integrated energy systems for food production, based on Huq’s model; this model was used to simulate food and animal production, draft power and organic fertilizer supply to the year 2000. The model of Ref. 2 does not include biogas production. Here, we present an integrated rural energy model for food and energy production and illustrate the potential implications of the model by data from a village.

THE MODEL

The rural energy system consists of several closed loops. Feedback for these loops simulates the dynamic behaviour of a highly complex system. Huq’s revised model is shown in Fig. 1. This model is based on the system dynamics methodology of Forrester for the village Langulia and is shown in Fig. 2.

The crop-production system is mainly concerned with the production of food grain and straw. The straw is primarily used for cattle feed. The major inputs for crop production are draft power, irrigation, fertilizer, and human energy. Crop production can be increased either by increasing the cropped area or the yield. Since land is limited, crop production must be

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134 M. S. ALAM et al

increased by using high-yielding varieties in conjunction with irrigation and fertilizers. The

yield is influenced by draft power from the animal system. The animal system, in turn, is

influenced by crop production. Thus, crop production forms a closed loop with animal

production.

The animal-production system provides cowdung, which is supplied to the biogas system.

The biogas system is essentially a biogas digester for the production of biogas and treated slurry

by anaerobic digestion. The treated slurry replaces the use of inorganic fertilizer in crop

production. The straw from crop production is used as a cattle feed. Thus, crop, animal and biogas production form a closed loop.

The proposed biogas production system supplies biogas as a fuel for cooking and therefore reduces the pressure on rural forests and also diminishes pollution. This process, in turn, reduces the ecological imbalance.

The quality of life is used here as a measure of performance for integrated rural energy

systems. It is computed by multiplying the standard of life, food and crowding. The multipliers are chosen to be 1 for 1988.

The mechanics of our formulation are based on Forrester’s system dynamics approach and the model takes into account the inherent nonlinear, dynamic, feedback and time-lag characteristics of the system. The model has been programmed in BASIC.

DESCRIPTION OF THE VILLAGE

The village Langulia under the Muktagacha upazila of the Mymensingh district in Bangladesh was used as an example in the model. Its population is 1121, of whom 52.72% are male and 47.28% are female. The total cultivated land is 103 ha and the main cultivated crop is rice, which is grown twice a year. The number of cattle is 328 and production of manure per cow per day is assumed to be 10 kg. All of the available cowdung is composted by the farmers and later on applied directly in the field as organic fertilizer. Even landless farmers collect and compost the cowdung for sale to other farmers who apply these organic fertilizers. There is no biogas digester in the village to treat the slurry for the purpose of obtaining biogas in addition to treated slurry, without the loss of nutrients. Per capita energy consumption for cooking in this village is 4.21 GJ. This energy is mainly comprised of firewood, leaves and twigs. Cooking fuel is predominantly firewood and accounts for about 75% of the energy consumption for cooking. This firewood comes from the nearby Modhupur reserve forest.

All of the information needed for energy calculations was collected through questionnaires. me energy expenditures by men and animals on field work were taken to be 628 and 1674 kJ/hr, respectively. 3*4 The energy embodied in the fertilizer input is 77.4 x ld W/kg of N, 13.8 x l@kJ/kg of P ‘and 9.6 x 103kJ/kg of K.’ The energy requirements for irrigation equipment are 86.7 x 103 kJ/kg of equipment. 6 The energy requirement to produce 1 kg of pesticide is assumed to be 101.3 X lo3 kJ. The energy from 1 kg of seed is 19,491.g kJ/kg.’ The energy value of firewood or of twigs and leaves is 15,160 kJ/kg. The energy available from 1 kg of rice is 14,527.36 kJ.* The average incident solar radiation is 5.02 x 10” M/ha-yr.’

RESULTS AND DISCUSSION

Rice is the main food grain in Bangladesh and it is the only food grain cultivated in the village Langulia. Major inputs and outputs of the crop-production system are shown in Table 1. Energy inputs are in the form of fertilizers (both organic and inorganic), irrigation, interculture operations, and land preparation. The annual outputs of edible energy and protein per hectare from food grain rice are 65.0 GJ and 378.45 kg, respectively. The biological efficiency of rice for food utilization in the human system is 68%. lo Hence, the net availability of energy and protein from 1 ha of land with rice crop become 44.2 GJ and 257.37 kg/yr, respectively. The annual energy and protein per ha from rice straw are 73.08 GJ and 62.64 kg, respectively. The rice straw is used as a source of nutrient to feed the cattle in the village. In the animal system,

Integrated rural energy model for a Bangladeshi village 135

Table 1. Energy inputs and outputs of the crop production system.

Source/operation Input ( 1~10~ kJ/hr ) Output ( x~O-~ kJ/ha 1

Tillage

Sowing

Weeding

Plant protection

Irrigation

Fertilizer

Harvesting

Threshing

Seed

Rice grain

Rice straw

56.65

38.00

76.40

50.18

167.54

1822.38

38.10

29.77

131.00

65.00

73.00

the efficiency of protein utilization of rice straw tends to be zero whereas the energy utilization of rice straw in the animal system is 40-60%.” The deficiency of protein in the animal rations is made up from the road side and from homestead garden fodder and concentrates.‘*

The animal system consists mainly of cattle and it is the only source of draft power for crop production in Langulia. The inputs and outputs of the animal-production system are shown in Table 2. Energy inputs in the form of draft power used for crop production in 1988 were 727 MJ/ha; thus, the available draft power per hectare was 0.53 kW. The availability of draft power is greater than the minimum requirement of 0.373 kW/ha. Inputs into the animal- production system are in the form of rice straw, green fodder and concentrates. The animal system supplies energy and protein through meat and milk to the human system.

The proposed biogas production system accepts cowdung as inputs and provides treated slurry and biogas. The input and output potentials of the biogas production system are shown in Table 3. The biogas system has a potential of 875.7 GJ of energy per year as cooking fuel, which is equivalent to 57.92 tonnes of firewood. This energy may be recovered without loss of nutrient to the residual organic fertilizers if the facilities of anaerobic digestion to the available

Table 2. Inputs and outputs of the animal-production systems.

Source I Input Dry rater

I (Xl I (tonnes&r)

Output

(kg/~) (kW/ha)

Green roughage f 63 2185

Dry roughage 31 1075

Concentrate t 6 208

Draft power

Cowdung

0.53

11.972x10s

t Rote : Green roughage and concentrates are estimated by using the national average values.12


Table 3. inputs and outputs of the biogas production systems.

Input output Source

(kg/w) (kg/v) (GJ/yr)

Cowdung 11 .972x10s

Organic fertilieer

N 3591.6

pzos 2394.4

KZC 1197.2

Biogam 676.70

cowdung exist. The digested slurry has the potential of 3591.6 kg of N, 2394.4 kg of PzOs and 1197.2 kg of K,O.

The traditional earthen stoves are mainly used for cooking and their efficiency is GO%. Workers at the Fuel Research Institute have developed improved earthen stoves for cooking and their efficiency is claimed to be double that of traditional stoves. These stoves have not yet been introduced. l3

Eusuf14 developed an equation involving the cost-benefit ratio (BCR) for economic evaluation of family-size biogas digesters and showed that if the substituted fuels are firewood with a price of OSTaka/kg (1 U.S. Dollar = 30.00 Taka), the BCR value is 2.25 at 15% interest rate. This result shows that biogas in Bangladesh is economically acceptable. Adverse effects of forest depletion and pollution of the environment are now being realiied in Bangladesh. Considerations of the economy and of threats to the ecological balance justify the installation of biogas digesters. But the question remains how it should be implemented. When interviewed, some of the farmers with medium and large farms showed interest in the installation of biogas digesters provided the technology is demonstrated and the costs of the digesters are subsidized.

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0 I I I I 0 1990 1992 1994 - 1996 1996 2000

Year

Fig. 3. Population, food energy and per capita food consumption during the period 1990-2000 (-, basic mode; --- policy mode).


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Fig. 4. Cattle and draft power/ha during the period 1990_2OC@ (-, basic mode; ---, policy mode).

To illustrate the use of the model as a tool for policy planning, the model was simulated for both the basic mode and the policy-planning mode. The basic mode corresponds to existing conditions and the policy-planning mode corresponds to conditions for the policy options being tested. The simulated results of the model for both the basic mode and policy mode are shown in Figs. 3-7. The policy mode in this study involves birth-control measures (2.152.0% from 1988 to 2000) and improvement of cropping intensity (2000-300% from 1988 to 2000). The solid lines in the figures indicate results for the basic mode, while the dashed lines indicate results for the policy mode. Figure 3 shows population, food energy and per capita food use in both the basic and policy modes. The population of the village in the basic mode increases from

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Year

Fig. 5. N, P,O, and K,O during the period 1990-2000 (-, basic mode; and --, policy mode).


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1990 1992 1994 1996 1996 2coo

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Fig. 6. Biogas potential and biogas production during the period 1990-2l’KKl (- basic mode; ---, policy mode).

1121 to 1511 from 1988 to 2000, whereas in the policy mode the population slowly increases from I121 to 1456 by 2000. The energy availability from rice in the basic mode is almost constant at a level of 13,432 GJ during the period 1988-2Ml0, whereas in policy mode the food-energy supply increases as a result of the increase in cropping intensity. The improvement is quite significant. As a result, the per capita food use increases from an almost constant value of 34,323.79 kJ/day to a peak value of 39,890.49kJ/day in 1994 and then decreases to 37,854.86 kJ/day in the year 2000.

Figure 4 shows the cattle population and draft power/ha in both the basic and policy modes while Fig. 5 shows N, Pz05 and KSO. The cattle population is almost at a constant level of 324 during the period from 1988 to 2000. As a result, the draft power per hectare, N, P,05, K20, and biogas potentials are almost constant. In the policy mode, the cattle population is slighly increased from 328 in 1988 to 387 in 2000. The draft power/ha, N, PzOs, K,O, and the biogas potentials are thus improved. The effect of installation of biogas digesters at a rate of 30% of the difference between the biogas potential and the actual level of biogas production, for both the basic and policy modes, is illustrated in Fig. 6. The situation is improved in the policy mode.

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1994 1996 199.9 2000

Year

Fig. 7. Quality of life during the period 1990-2000 (-, basic mode; ---, policy mode).


The quality of life is assumed to be the product of food and crowding.15 In the basic mode, the quality of life will be reduced to 0.6341 in 2000 from 1 in 1988. In the policy mode, the quality of life is improved and is always >l (Fig. 7). This result implies that adoption of the policy would provide better conditions in terms of food and crowding.

Model implementation requires a continuing survey of the system parameters. Parameters sensitivities must be analysed to identify priorities for data collection and determination of policy-entry points. The model must be recalibrated to maintain it up to date.

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2.

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REFERENCES

A. M. Z. Huq, “Modelling for Agricultural Units in Bangladesh,” Proceedings of the Seminar on Integrated Rural Development, Inst. of Engineers, Bangladesh (1975). B. K. Bala and M. A. Satter, “Modelling of Integrated Energy Systems for Food Production in Developing Countries,” Proc. 2nd Znt. Conf Energiu and Agricultra, Sirmione/Brescia 3, 306 (19%). J. N. Black, Proc. A&. Biol. 67, 272 (1971). S. Chandra, AMA 9, 19 (1979). G. Leach and M. Slesser, “Energy Equivalents of New Work Inputs to Food Producing Processes,” Strathclyde University, Glasgow (1973). B. A. Stout and G. A. Meyers, AMA 9, 11 (1978). D. Pimental and M. Pimental, Food, Energy and Society, Edward Arnold, London (1979). Bangladesh Bureau of Statistics, “Statistical Pocket Book of Bangladesh 1984-85,” Dhaka (August 1985). M. S. U. Talukder, J. Inst. Engrs, Bangladesh 15, 17 (1987). C. Gopalan, B. V. R. Sastri, and Balasubramanian, “Nutritive Value of Indian Foods,” in Handbook of the National Institute of Nutrition, Vol. 10, p. 1, Hyderabad, India (1984). R. K. Mehla, A. Srivastava., R. S. Manik, and V. D. Mudgal, Agric. Systems 21, 159 (19%). J. R. Dickey and Q. M. Emdadul Huque, “Status of the Bangladesh Livestock Industries in Relation to Fodder Supply and to Consumption of Animal Products,” Bangladesh Agricultural Research Council, Dhaka (March 1986). “Improved Stoves, in Bengali” Fuel Research Institute, Dhaka (1988). M. Eusuf, “An Approach to the Economic Evaluation of Family Size Biogas Plants,” Bangladesh .Z. Sci. Znd. Res. 19, 220 (1984). J. W. Forrester, World Dynamics, Wright Allen Press, Boston, MA (1971).

an integrated rural energy model for a village in bangladesh

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