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CLOSE THIS BOOKThe Economic and Technical Viability of Various Scales of Building Materials Production (HABITAT, 1989, 58 p.)
VIEW THE DOCUMENT(introduction...)
VIEW THE DOCUMENTFOREWORD
VIEW THE DOCUMENTINTRODUCTION
VIEW THE DOCUMENTI. SCALE OF TECHNOLOGY AS A STRATEGY FOR THE BUILDING-MATERIALS SECTOR
II. ANALYSIS OF CASE STUDIES ON TECHNICAL VIABILITY OF ALTERNATIVE SCALES OF PRODUCTION
III. ANALYSIS OF CASE STUDIES ON ECONOMIC VIABILITY OF ALTERNATIVE SCALES OF PRODUCTION
IV. FOCUS ON CEMENTITIOUS MATERIALS
VIEW THE DOCUMENTV. CONCLUSION
VIEW THE DOCUMENTREFERENCES
VIEW THE DOCUMENTANNEX - SUMMARIES OF COUNTRY CASE STUDIES
VIEW THE DOCUMENTBACK COVER

ANNEX - SUMMARIES OF COUNTRY CASE STUDIES

A. Egypt: production of burnt bricks

Egypt has a tradition of brickmaking by artisans which spans several centuries. Following the completion of the Aswan high dam in 1965 which deprived the traditional brick industry of its basic raw material, brickyard owners started to exploit the fertile top soil of surrounding agricultural land. The Government subsequently enacted a law prohibiting this practice in order to protect the country’s agricultural wealth. Current brick production in the small- and large-scale sectors is based on desert shale and clay deposits even though some bricks were still produced in traditional plants from Nile silt until 1987. In that year the traditional plants produced a total of 6267 million bricks compared with 160 million by modernized small-scale plants and 1286 million by large-scale plants. In 1988, the Government decided to close down completely all traditional brickyards and clamps and no permits for operation are given except to those who are prepared to modernize their production by installing production lines with mechanical devices suitable for the processing of desert shale and clay. This case study covered the operations of the modernized small-scale plants and large-scale plants only.

The production capacity of the small-scale plants ranges between 6 million and 15 million bricks per year. Simple processing techniques are employed in the preparation and processing of the clay. High-speed roller mills and single- or double-shaft mixers are used to ensure proper mixing of the raw materials. The extruded bricks are dried in the open under sheds. Firing of bricks is done in roofless Hoffmann kilns. Manual handling methods are used throughout the brickmaking process. The majority of small-scale producers do not operate quarries or have their own means of transport and, therefore, depend on private contractors to transport the selected raw materials to the production site.

The large-scale plants, with annual capacities ranging from 35 million to 60 million bricks, adopt mechanized processing techniques. Drying is artificial, in chamber or tunnel drlers. Firing is generally carried out in tunnel kilns with the exception of two cases which use a zig-zag Hoffmann kiln and a transverse Hoffmann kiln, respectively. Handling of the product between the various production stages ranges from mechanized to fully automated. Almost all the large-scale plants operate their own shale or clay quarries at a distance not exceeding 10 to 15 kilometres from the plant. Other raw materials, such as desert sands, are usually purchased from nearby quarries or exploited from sites near the shale quarries.

Small-scale brick plants operate at almost 100 per cent capacity. Large-scale plants, however, have had a record of low capacity-utilization rates. A survey of five large-scale brick plants showed that in 1987 the utilization of installed capacity ranged from 19 to 75 per cent. The two plants which recorded less than 20 per cent utilization rates were public sector plants. It is reported, however, that more recently, the large plants have achieved higher capacity-utilization rates because of the introduction of three-shift operations.

Small-scale plants consume less energy per ton of final product compared with large-scale plants. They consume 27 kilograms of furnace oil and 22 kWh electricity compared with 55 kilograms and 50kWh, respectively, for the large-scale plants.

Tables 1 and 2 give data on labour requirements, skills and cost, and a comparative assessment of capital investments in small- and large-scale brick plants. Analysis of these data, as well as production cost data for the plants, reveals the following:

(a) The number of employees per unit of output is higher in small-scale plants compared with the large plants. However, since capacity utilization in the large-scale plants is around 60 per cent, the actual labour force per million bricks is 4 which is about the same as for the small plants;

(b) The ratio of skilled to unskilled labour is much higher in the large-scale plants compared with the small-scale plants;

(c) Labour cost per thousand bricks in the large-scale plants is about 25 per cent higher than the cost for the small-scale plants. This situation is reflected in the cost of production as well as in the break-even point since wages form an important item in production cost;

(d) The total production cost per ton of final product is

£E39.39 for the large-scale plant compared with £E22.36 and

£E17.96, respectively for the small-scale plant with imported equipment and the small-scale plant with local equipment. The production cost per thousand bricks ranges between £E65-97 for large-scale plants and £E38-46 for the smaller plants. The cost differential can be attributed to the high values of depreciation, energy cost, amortization and interest on capital paid by the large-scale plants. With the market price of bricks ranging between £E85 and £E100, the small-scale plants operate at very high profit levels whereas the large-scale plants operate near the break-even point. The urge for the traditional brickyard to modernize is therefore strong.

(e) The investment required for large-scale plants with an average design capacity of 50 million bricks per year is 15 to 24 times that required for modernization of small-scale plants with an average annual production capacity of 7.5 million to 9 million bricks. The ratio of investment per thousand bricks in large-scale relative to small-scale plants ranges from 2.2:1 to 2.7:1. At the same time, large-scale plants have a gestation period which is three to five times that for small plants. It should be noted that the small-scale plant with locally-produced equipment is advantageous over the one with imported equipment with respect to unit-investment cost.

Table 1. Labour requirements, skills and cost in small- and large-scale brick plants

Item

Production scale


Smalla

Largeb

Engineers and graduates (percentage)

-

13.1

Skilled labour (percentage)

29.6

67.2

Unskilled labour (percentage)

70.4

19.7

Ratio of skilled to unskilled labour

1:2.4

4:1

Labour/million bricks

3.1-3.73

2.44

Labour cost/1000 bricks (£E)

6.2-7.5

8.77

Notes:

a/7.5 million to 9 million bricks/yer.
b/50 million bricks/year.

Table 2. Comparative analysis of investments in small and large-scale brick plants

Production scale

Item

Large-scale

Small-scale

Imported equipment

Local equipment

Production capacity:

In million bricks/year

40-60

7.5-9

7.5-9

In tons final product/year

98280

19800

19800

Required investment (£E thousands):

Fixed assets

13980

876

519

Other assets

1162

103

54

Working capital

332

72

69

Total investment

15474

1051

643

Investment components (percentage):

Foreign

64.7

74.7

0

Local

35.3

25.3

100

Investment coefficients:

Investment/1000 bricks

387-258

140-117

86-72

Investment/tons final product

157

53

32

Investment/labour (£E thousands)

127

38

23

Required period for erection (in years)

2.5-3.5

0.5-1

0.5-1

Based on the foregoing techno-economic situation in the clay brick industry, the recent master plan emphasized the importance and, hence, the encouragement of private small-scale production ventures as against large-scale plants.

B. Egypt: production of concrete bricks and blocks

The scale of production of concrete bricks and blocks in Egypt ranges from small mobile activities that produce a few hundred bricks a day to large complexes capable of producing more that 300,000 bricks a day. The type of product also varies, from small solid bricks of standard dimensions, 25 × 12 × 6.5 cm to large hollow blocks, 40 × 20 × 20 cm with cavities exceeding 50 per cent. In the case study attention was focussed on the solid bricks.

The very-small-scale production units are usually informal, in the sense that they do not operate under official industrial permits. They operate on the premises of construction sites, in both urban and rural areas with particular emphasis on the latter. The activities may also exist in the form of small workshops in rural areas. Raw materials are mixed manually or with a small mechanical mixer. Shaping of bricks or blocks is accomplished using a stationary press which essentially shapes the mix through vibration and hand-pressing which serves also in demoulding. The output of presses ranges between 500 and 750 bricks or 200 and 300 hollow blocks a day.

Small-scale plants with outputs ranging from 2.4 million to 4.5 million bricks (or 300,000 to 900,000 blocks) per annum operate with a mechanical mixer and a stationary press or mobile “egg-laying” block machine. Medium-scale plants usually have a mechanical batching-and-mixing plant, and either a stationary press or a mobile block-laying machine. Production output of these plants varies from 10 million to 20 million standard bricks per year. Large-scale plants also are equipped with mechanical batching-and-mixing plant and stationary presses, and with facilities for automatic handling of the raw material mix and for the moulded product through the various processing stages. Production capacity is of the order of 33.6 million blocks or 275 million standard bricks per year.

The raw material mix usually includes cement, sand and coarse aggregate (natural or crushed). Pumice and expanded clay aggregate are used for the production of light-weight concrete blocks. Large-scale plants tend to be located near suitable limestone deposits and produce their own requirements of crushed rock aggregate. Occasional shortages in cement have a greater impact on small-scale producers. Open-air curing of bricks and blocks is practised in the small-scale plants and medium-scale plants using the “egg-laying” machine. In the large plants, curing is carried out in closed chambers.

Constraints faced by large-scale plants are related to the need for operational experience with the automatic handling systems, equipment maintenance, availability of essential spare parts which have to be imported, and proper technical and administrative management.

Small - and medium-scale plants are, in general, able to achieve a 100 per cent capacity-utilization rate in response to sustained demand. However, actual productivity tends to decrease as the degree of mechanization increases, a particularly if imported equipment is used. With the development of local spare parts manufacturing capacity, the majority of the required spare parts can now be obtained locally. The first large-scale plant started operations only in 1987; two others started in 1988. Information on capacity-utilization rates is not available but expected problems with operating and maintaining automatic control-and-handling systems and spare parts problems could lead to a 12-20 per cent reduction in capacity utilization.

The electrical energy consumed per ton of concrete bricks and blocks in the large-scale plants is about 1.5 times the consumption by the medium-scale plants, and 2.2 times and 9.2 times the consumption in the small- and very-small-scale plants, respectively. Another source of energy that is needed in medium- and large-scale plants is diesel fuel required for operating forklifts which is estimated at one litre per ton of final product.

Tables 3 and 4 present comparative data on labour and investment costs for the various production scales. Analysis of these data and other relevant data show that:

(a) Large-scale plants would require investments that amount to 1.64 to 2.22 times that required for medium-scale plants, 2.1 to 2.74 times that required for small-scale plants and 5.8 to 7.5 times the investment in very-small-scale plants. Besides, large-scale plants require about 66.4 per cent of total investment in foreign currency compared with 42.7 per cent in the case of medium-scale plants and no foreign financing in the case of the small-scale plants. Generally the required investment for large-scale plants can only be allocated by large investment companies or by the Government for public sector activities; investments for the other scales of production could be raised by the private sector.

(b) The investment per work place increases as the production scale increases; for large-scale plant the relative investment cost is 10.9 times that for small-scale plant and 73 times that for very-small-scale plant.

(c) The large-scale plants have the highest relative cost of production. This situation results from the relatively high values of the cost of depreciation, spare parts and maintenance and loan repayments. The next highest production cost is recorded by the very-small-scale plant. This is the result of the relatively high cost of labour per ton of product which amounts to 3.5 times that of the large-scale plant and 1.65 times that in the small-scale plant.

(d) The availability of suitable technical and administrative personnel, back-up services and spare parts is crucial for the successful operation of large-scale plants but has little consequence on the production efficiency of the small-scale plants.

(e) The staff of the large-scale plant is 16 per cent university graduates and 73 pr cent skilled labour. Very-small-scale plants employ about 75 per cent unskilled labour. At the same time, very-small-scale plants require 3.2 and 12.9 times the labour per unit production compared with small- and large-scale plants. This confirms the superior employment generation potential of the small-scale plants.

(f) Whereas very-small- and small-scale, and to a lesser extent medium-scale, production units are generally located near consumption centres, large-scale units tend to be established in close proximity to raw materials sources. Consequently, transport costs and damage to finished product are less for the small-scale plants than to the large-scale plant. However, this deficiency is partially compensated for by the cost of transporting raw materials and the quality of the product.

(g) The survey of product quality shows the relative inferior strength properties of products of very-small- and small-scale plants, particularly those utilizing the “egg-laying” block machines. This situation provides other production scales, for example, medium-scale plants with stationary moulding presses and large-scale plants, to compete on the basis of the relatively better quality of their products. There is an apparent need for research and development into the current processing technologies in the very-small-to medium-scale plants in order to upgrade their product quality, changing the current investment or cost of production as little as possible.

The study demonstrates the relative advantages of small- and medium-scale plants over large-scale plants. Consequently, small-scale concrete brick and block plants are being encouraged within the framework of the Government’s master plan for the industry.

Table 3. Labour requirements, skills and cost in various scales of production in cement brick industry


Production scale

Item

Very Small

Small

Medium

Large

Engineers and graduates (percentage)

-

-

10.5

16.4

Skilled labour (percentage)

25

36.4

57.9

73

Unskilled labour (percentage)

75

63.6

31.6

10.6

Ratios of skilled to unskilled labour

1:3

1:1.75

1:0.55

1:0.15

Labour/1000 ton product

4.5-3.6

1.5

0.62

0.38

Labour cost/ton product (£E)

8.6-7.8

3.47

2.62

1.6

Table 4. Capital investment in various scales of cement brick production

Production scale

Item

Very Small

Small

Medium

Large

Production capacity:

In tons/year

1100

7530

30625

404250

In million bricks/year

0.225

1.2

3.6

108

In million blocks/year

0.09

0.6

2.5

33

In million equivalent bricks/ year

0.74

4.9

20.5

271

Required investment (£E thousands):

Fixed assets

5.1

124

638

21292

Other assets

0.4

5

54

1496

Working capital

3.3

33

137

1598

Total investment

8.8

162

829

24386

Investment components (percentage):

Foreign

-

-

42.7

66.4

Local

100

100

57.3

33.6

Investment coefficients

Investment/1000 bricks

39

108

138

226

Investment/1000 blocks

98

270

332

739

Investment/1000 equivalent bricks

12

33

40.4

90

Investment/ton of final product

8

21.5

27

60.3

Investment/labour (£E thousands)

2.2

14.73

43.63

160.4

Required period for erection (in years)

Up to 0.3

0.25-0.5

0.5-0.75

2-3

C. Ghana: production of burnt bricks

Nine brick factories were selected for the study. These included one large-scale, fully-mechanized plant, five medium-scale, semi-mechanized plants, and three small-scale, labour-intensive plants. The discussion is limited to three plants representative of the three scales of operation. Special features of the other plants are mentioned, where necessary, to give a clearer picture of production activities in a particular scale of operation.

The large-scale plant with a design capacity of 30,000 bricks per day (single-shift) is fully automated from clay mining through clay preparation and shaping to brick burning. The plant is equipped with an artificial drier and a tunnel kiln. A mixture of diesel oil and residual oil is used for firing the bricks. All the machinery and equipment were imported.

The medium-scale plant has a capacity of 16,000 bricks per day and is semi-mechanized; clay is won through the periodic use of rented excavators and conveyed to a storage shed by tipper trucks. Clay preparation and shaping is mechanized using an extrusion machine. Green bricks are dried naturally in racks under an open shed. The bricks are fired in a rectangular Hoffmann kiln using firewood and sawdust briquettes.

The small-scale plant chosen is really a cottage-level production unit with a design daily output of 3000 bricks. The production process is fully manual and the bricks are burnt in an intermittent kiln using firewood.

The study showed that the small-scale plant achieved a relatively high capacity-utilization rate of 67 per cent compared with 27 per cent and 46 per cent achieved by the large- and medium-scale plants, respectively. Frequent breakdown of mechanized equipment in the large-scale plant and difficulties in obtaining spare parts to effect needed repairs are major contributors to the rather low capacity-utilization rate. The low rate at the medium-scale plant is attributed to lapses in the supply of clay to the factory; this is the result of the inability to hire mechanical excavation and loading equipment, because of high cost, and difficulties associated with using manual excavation methods.

Direct comparison of production costs of the three plants is made difficult by the fact that the types of products differ. However, both the medium- and small-scale plants produce standard solid bricks, and it is seen that the production cost at the medium-scale plant is twice that at the small-scale plant. Compared with other medium-scale plants which produce hollow clay blocks the unit production cost of the products of the large-scale plant is found to be competitive.

Table 5. Incidence of energy cost in production cost and sale price of products from different scales of brick plant

Plant

A

B

C

D

E

Plant size (million bricks)

0.5

5

5

5

30

Production cost (Rs/1000 bricks)

196

362

613

367

527

Coal cost as a percentage of production cost

58.6

45.6

32.3

53.9

31.3

Coal cost as a percentage of selling price

46

36.7

28.2

39.6

23.6

Energy cost as a percentage of selling price (coal and electricity)

46

44.5

47.5

52.1

52.2

Table 6. Capital investment and production characteristics of selected brick plants

Plant

A

B

C

D

E

Scale of production (million bricks/year)

0.5

5

5

5

30

Capital investment (Rs thousands)

150

800

3823

1398

11736

Cost of production (Rs/1000 bricks)

196

356

613

367

527

Capital cost (Rs/1000 bricks)

30

160

764

280

391

Rate of return on capital (percentage)

14.4

35.7

10.3

49.8

31.7

Work-days per 1000 bricks

6.0

5.0

4.5

2.3

The labour employed per unit output in the medium-scale plants is twice that employed in the small-scale plant and 1.8 times the labour in the large-scale plant. These figures give the impression that the small-scale plant is more labour-saving compared with the other plants. However, considering the low levels of capacity utilization in these plants and the maintenance at the same time on the payroll of a large number of senior management staff and administrative support personnel, it is obvious that the labour/output ratios presented above are distorted and do not give a true picture of the actual labour-utilization potential of the different production scales. The small-scale plant does not employ any high-level professional staff as compared with the 10 per cent and 8 per cent of such personnel of the labour force in the large-scale and medium-scale plants, respectively.

The quality of the products of the large- and medium-scale plants are comparable. The hand-moulded bricks from the small-scale plant suffer from relatively high water absorption and lower compressive strength. The quality achieved is, however, acceptable for the construction of single-storey buildings where much of the output of the small plant is used.

The study concluded that:

(a) The quality of clay used for brick production is the same for all scales of production;

(b) The small-scale brick plants have an advantage over large-scale plants in the use of energy. Apart from lower energy-consumption rates, they also make use of waste materials like sawdust briquettes and palm-kernel shells and do not suffer from the effects of interruptions in electric power supply;

(c) The small-scale brick plants are labour-intensive and rely on a high proportion of semi-skilled and unskilled labour;

(d) The relative investment in capital items is low in the small-scale plant compared with the large one. Besides, there is little dependence on foreign exchange which has become a serious bottle-neck in the operations of large- and medium-scale plants. Recent massive devaluation of the local currency has increased several-fold the local component of the loan and interest repayments on imported machinery and equipment.

(e) Generally, the performance of the fully-mechanized large-scale plant has been poor and it has failed to realise its potential in terms of production capacity since its inception over 10 years ago. Some of the medium-scale plants with imported equipment have also had operational problems that have limited the achievement of high capacity-utilization rates.

D. Ghana: production of concrete blocks

Three scales of production were defined for the study as follows:

(a) Small-scale producers with a daily output of about 800 sandcrete (concrete) blocks;

(b) Large-scale production units with an output of about 8000 sandcrete blocks a day;

(c) Medium-scale production units with an output between the other two, but with a typical daily output of about 3000 blocks a day.

The basic raw materials used at all scales of production are ordinary Portland cement and sand. About 25 per cent of all producers use, in addition, quarry dust in the raw-material mix. Because they have their own means of transport, the large-scale plants usually procure their sand and quarry dust direct form the sand pits and quarries. Small- and medium-scale producers have to subcontract such supplies to transport owners and other agents.

The main capital items in a small-scale block plant are an electrical block press (which has gradually replaced the manual press) and production shed, and a single-room office building. Basic hand tools are shovels, headpans and batch boxes, which are used in batching materials and mixing them before pressing. The large-scale plant is mechanized with equipment including a stationary fully-automated hydraulic press, concrete batching plant, mechanized mixers, pay loader, mobile cranes, tipper trucks, haulage trucks, forklifts and concrete truck-mixers. Other capital items include large production sheds, workshops, office and stores buildings and a tower silo. The total capital investment in the large-scale plant is almost 500 times that in the small-scale plant for a design capacity which is only about 20 times higher. In terms of investment per unit of output the relative ratio is only 2.3; however, since the large-scale plant is operating at 35 per cent capacity, the relative investment ratio between the large- and small-scale plants is about 5.

Calculation of energy-cost levels per unit of product proved to be difficult, especially in the large-scale plant because different other items such as concrete pipes are produced. Average cost figures were therefore estimated. The energy cost per block for the large-scale plant was 30 times that for the small-scale plant. Energy accounted for 5 per cent of the direct production cost in the large-scale plant compared with 0.2 per cent in the small-scale plant. The contribution of labour to production costs in the small-scale plant was 10 per cent compared with 2 per cent in the large-scale plant. The total direct production cost was 10 per cent higher in the large plant than in the small plant. The selling price figures which reflect other production costs (depreciation, amortization, interest etc.) show a 50 per cent advantage in favour of the small-scale plant. The study established that there is hardly any carriage of concrete blocks beyond 50 kilometres in any of the scales of production. It was also apparent that new groups of small-scale producers emerged around new housing development sites, and the patronage by the developers was very good because of very reduced transport costs.

The large-scale plant has a total labour force of 238, 60 per cent of whom are involved in direct production activities. Professional management staff constitute 2.5 per cent of the labour force. The small-scale plant has a workforce of six comprising a manager, a supervisor and four production labourers. The total investment per labour in the large-scale plant is 12 times that for the small-scale plant.

Periodic shortages in cement supply constitute a major production constraint at all production levels but more so at the large-scale plant. Within each of the three years from 1985 to 1987, about 20 per cent of normal production time was lost in the large-scale plant because of cement shortages. The small-scale producer, however, suffered very little disruption, not depending primarily on bulk cement like the large-scale plant, but operating largely by buying bagged cement on the open market. Machinery dependability is another constraint that affects the productivity of the large-scale plant. The use of obsolete equipment exacerbates the maintenance problems since spare parts are difficult to procure. It is estimated that 7.5 per cent of production time in the large-scale plant is lost because of breakdown of essential machines.

Table 7. Capital investment, production costs and economic viability of lime plants at various scales of production


Plant

A

B

C

D

E

F

Scale (tons per day)

3

3

10

20

30

40

Output (tons per year)

900

900

2400

4800

7200

9600

Capital investment (Rs thousands)

450

450

2174

4136

5264

6920

Production cost (Rs/ton)

766

638

948

713

621

737

Market price (Rs/ton)

880

700

1100

900

900

1000

Profit per ton of output (Rs/ton)

114

62

152

187

279

263

Capital investment per ton of output (Rs/ton)

500

500

905

899

731

706

Return on investment (percentage)

22.8

12.4

16.7

20.7

38.1

36.6

The study established that all three scales of production, small, medium and large, produce good quality blocks; the large-scale plant turns out slightly better quality blocks because of the incorporation of quarry dust with gritty stones in the raw-material mix and the adoption of better quality-control practices including the curing of the blocks. Some small-scale producers, anxious to maximize profits, produce poor quality blocks which result in a high percentage of breakages. Since most of the blockwork of buildings is jointed and rendered in mortars that are richer than the mixes of the blocks, minor lapses in product quality could be tolerated.

In summary, the study established the advantages of the small-scale concrete-block plant over the large-scale plant with respect to capital investment, employment-generation potential, use of installed production capacity, dependence on imported equipment and spare parts. Improvement of quality control to ensure better quality products from small-scale plants should be accorded priority attention.

E. India: production of burnt bricks

Burnt-brick production in India is basically a small-scale sector activity. It is estimated that out of the current annual production of 50 billion bricks, 5 billion are produced by cottage-scale plants of 0.25-1.0 million bricks capacity, while 44.75 billion are accounted for by small-scale plants of 2-5 million annual capacity. Only 250 million bricks, a mere 0.5 per cent of total annual output, are produced in large-scale plants of 15-30 million annual capacity.

Brick-production technology is predominantly manual with the bricks burnt in either field clamps or the Bull trench kiln. There has, however, been a gradual introduction into the industry of locally-designed and -manufactured semi-mechanized brick plants and high-draught kilns promoted by the Central Building Research Institute (CBRI) and the National Buildings Organization (NBO). Imported fully mechanized plants were promoted in the 1960s in important cities to cope with the large demand for bricks. Only four of the nine plants originally set up are still in operation, the remaining have had to close down because of non-viability.

In the study of the technical and economic viability of different scales of production, five plants representing the different technologies in the cottage-, small- and large-scale sectors were selected from five different states in the country. Plant A is a manually-operated plant in the cottage sector employing a clamp kiln and producing 0.5 million bricks annually. Plant B is fully labour-intensive and uses a Bull trench kiln. Plant C is semi-mechanized and uses an extrusion machine designed by CBRI. Plant D, which is also semi-mechanized, is fitted with a soft-mud brick machine designed by NBO. Plant E is a fully-mechanized plant.

The clay deposits used by the small-scale plants are allowed to be worked to a depth of 1-1.5 metres only after which they are abandoned. This is a constraint on the long-term operations of such plants. The mechanized plants work their deposits to a depth of 5 metres and their operations are thus confined to a smaller working area compared with the small-scale plants. No machinery is used for mining and preparation of clay, moulding and firing of bricks in plants A and B except for the use of a water pump in the latter. Machinery breakdowns in plant D are claimed to be negligible compared with plant C which experiences some breakdown, especially because of the use of an artificial drier. Lost time in plant E because of machinery and equipment breakdowns is estimated at four to five weeks in a year.

Coal is the predominant fuel used for brick burning in India, regardless of the scale of production, except that at the cottage level agricultural residues, cattle dung and firewood are used. The cost of coal delivered to brick plants is affected significantly by transport costs. For example, in Delhi and Madras, coal costs Rs750 per ton if delivered by rail and Rs 1000 by road, as against a pithead cost of Rs450 per ton. In plant B some electrical energy is used for pumping water with a 10 HP motor. In plants C, D and E a lot of electrical energy is required for extrusion, and for drying in the case of plant E. The data presented in table 5 show that nearly 60 per cent of the production costs of the cottage-level plant is accounted for by fuel consumption. Of the small-scale plants, the NBO-designed plant has the highest ratio of coal cost to production cost of 54 per cent. The large-scale plant recorded the lowest percentage of 31.3. When electrical energy consumption is taken into account, however, a different picture emerges. With respect to the product selling price, the percentage energy cost increases from 23.6 to 52.2 in the case of plant B. For plant A the ratio remains unchanged because the energy used is entirely thermal.

Table 6 presents a comparative analysis of the five brick plants with respect to capital investment and performance. The traditional small-scale plant with a Bull trench kiln has clear advantages over the large-scale mechanized plants and also the semi-mechanized plants in the small-scale sector. It has the lowest production costs and a return on investment exceeded only by the small-scale plant using the NBO brick machine. In terms of capital cost per unit output, the traditional plant has a 1:2.5 advantage over the large-scale plant and a 1:5 advantage over the small-scale plant with the CBRI brick machine. The traditional labour-intensive plant also uses about three times the labour employed by the large-scale plant for the same output and has clear advantages over the other small-scale plants.

In spite of the relative production cost advantages of the small-scale brick plants, there is still great potential for improving the efficiency of the Bull trench kiln which is a common feature of their production technology. It has been established that coal consumption could be reduced by 25 per cent using a moving steel chimney or by 15 per cent if a fixed brick chimney were to be installed. These improvements would also help to increase the yield of first class bricks from 70 to 90 per cent.

F. India: production of lime

The total annual lime production in India is about 5.5 million tons, and 52 per cent of this amount is produced by plants of a capacity up to 10 tons per day which are classified as cottage-and small-scale. The other two scales of production, medium- and large-scale, account for the remaining 48 per cent of total production. At all levels of production, there is practically no dependence on any imported inputs as all the equipment, including kilns and mechanized systems, where required, are manufactured locally.

Lime plants in the cottage sector are hereditary family businesses with average production size of 1 ton per day. Lime produced in this sector is meant for captive consumption within the village or a few villages within a distance of 10 kilometres and is used in agriculture, road stabilization and village house construction.

Lime production in the small-scale sector is carried on throughout the year in batch or continuous kilns of vertical-shaft design. Production capacity ranges from 3 to 10 tons per day. The kilns used are based on designs by the Khadi and Village Industries Commission, (KVIC) and the Central Building Research Institute, (CBRI). While coal is the fuel commonly used, there are a few 3-ton-per-day plants located close to the coast which burn seashells with charcoal. The small-scale sector caters to the needs of the formal building sector.

In the large-scale sector, plant sizes range commonly from 20 to 40 tons per day but plants with 100 tons per day or more capacity are also in production. The former plants are based on traditional or improved kiln designs developed by the National Buildings Organization (NBO) while the latter, which are mostly captive plants for the steel, chemicals, paper and sugar industries, use improved traditional or modern rotary kilns with oil-firing systems. These plants are not allowed to market their lime for general consumption in the building industry.

In the analysis of technical and economic viability, plant sizes in the 3- to 40-ton-per-day range were studied because they are the main stay of the building industry. The selected plants represent a cross-section of the lime industry in three main lime-producing states, Andhra Pradesh, Madhya Pradesh and Uttar Pradesh.

Raw materials requirements with respect to quantity are essentially the same for small- and large-scale plants, which in most cases, have their own quarries for ensuring regular supplies of limestone. In the cottage sector, kankar, a time-tested impure limestone is used to produce lime of reasonable quality. Coal is the predominant fuel used. The large-scale plants achieve better consumption rates than the smaller plants, about 0.4 and 0.6 tons per ton of output, respectively. The labour force for the 3-ton-per-day plant averages 12, comprising 2 regular and 10 casual employees. The 40-ton-per-day plant employs 17 regular and 50 casual workers. On the basis of 1000 tons of annual output, the small-scale plant employs about twice the labour of the large-scale plant.

Comparative data on investment and production costs for lime plants varying in size from 3 to 120 tons per day are given in table 7. Plants A, B, D and E are within 300-400 kilometres of coal fields, while C and F are some 1200 kilometres away. Plants A and B use coal of inferior quality resulting in a consumption rate of 0.66 tons/ton of lime produced compared with the norm of 0.4. Plant E draws coal from the same source as B but, with a more efficient kiln, it achieves half the norm of coal consumption. Plant F is the closest to a limestone deposit of very good quality but furthest from a source of coal (about 1200 kilometres). Other characteristics of the different plants outlined below summarize the important influences between the production technologies and the level of capital investment for the different scales of production.

Plants A and B: KVIC design with refractory lining and outer brickwork; no insulation. The plants have no skip-hoist or mechanical feeding arrangements. There are no hydrators and no laboratories. Work single shift.

Plant C: Same as A and B but with a hydrator and manually-operated pulley system for feeding the kiln. Also works single shift.

Plant D: NBO design with refractory inner lining and outer stone masonry work with external reinforced concrete bonding to control buckling. It has a semi-mechanical feeding arrangement, bucket elevator and belt conveyor, screen, heat exchanger and 3-tier hydrator. Also a single-shift plant.

Plant E: Practically the same as plant D in design but has a blower attachment in the kiln for improving heat distribution, a dust collector and a mechanical hydrator. It is almost fully-mechanized. Works two shifts.

Plant F: Same as plant E except that the kiln construction is 225-mm inner refractory lining encased by red brickwork further encased by an outer steel shell. It is completely mechanized and works three shifts.

The analysis shows that:

(a) Capital investment per ton of output for the large-scale 40-ton-per-day plant is approximately 1.5 times that for the small-scale 3-ton-per-day plant (plant A); the 10-ton-per-day plant, which is also small-scale, had the highest unit investment cost arising mainly from the high cost of the hydrator relative to the plant size;

(b) The large-scale plant achieved a slightly lower total production cost than the 3-ton-per-day plant; the 10-ton-per-day plant had the highest production cost, about 28 and 24 per cent higher than the production cost of the 40-ton-per-day and the 3-ton-per-day plants, respectively;

(c) The 3-ton-per-day plant has a higher labour rate per unit of output, about twice that offered by the 40-ton-per-day plant;

(d) The small-scale plant achieves a good rate of return on investment, though the large plants recorded a higher rate.

The study concluded that the small-scale, 3-ton-per-day plant is ideal for quicklime production as a local industry and that hydrated lime production cannot be viable except in the 30-to 40-ton-per-day range.

G. Mauritius: production of cellular concrete blocks

The type of concrete block commonly produced in Mauritius is the cellular block which, as defined in British standard, BS 6073 on Precast Masonry Units, has cavities which do not pass through the block. The annual production of blocks is around 12 million, spread among about 25 production plants, four of which are in the large-scale sector (more than 10,000 blocks per day) and 10 in the small-scale sector producing 500-1000 blocks per day. Three production plants, one each in the large-, medium- and small-scale categories, were selected and surveyed. These plants which are all privately owned produce 10,800, 2100 and 700 blocks per day, respectively.

The large- and medium-scale plants both use the stationary block-making machine where the blocks are produced on a flat pallet, and then transported for curing on a pallet, to another position.

The small-scale plant uses the mobile “egg-laying” machine which casts a set of blocks on the floor and then moves on to an adjacent position for the next set of blocks. The machine used by the small-scale producer is fabricated locally from imported parts. It is sturdy, easy to operate and requires very little maintenance. The other items of equipment are an electrically-operated concrete mixer and two wheelbarrows for transferring the concrete to the “egg-laying” machine.

The machinery of the large-scale producer was obtained as a complete package, from batching of materials to carrying of blocks, from overseas. Installation of the plant also required assistance from the overseas manufacturer, although repair and maintenance are carried out entirely by local staff. The main items of machinery and equipment used at the large-scale plant are as follows;

(a) Three silos for storing cement, fine aggregate and coarse aggregate;

(b) A conveyor belt which transfers the raw materials to the mixer;

(c) A paddle concrete mixer to which water is added automatically;

(d) The moulding/casting unit which produces 12 152-mm blocks at a time;

(e) Some 1000 pallets on which the blocks are cast;

(f) Moving platform which conveys the green blocks to a robot;

(g) A robot which moves on rails with a capacity of 300 blocks;

(h) A moving platform which carries the cured blocks deposited by the robot to outside the building;

(i) Four diesel-operated fork-lift trucks for transporting the blocks.

The investment required for setting up the large-scale plant is about 150 times that of a small-scale plant. In terms of capital investment per unit output the ratio is about 10 to 1.

The raw material inputs in block-making are basically the same irrespective of the level of technology used. Cement is obtained from the same source. While the large-scale plant operates its own quarry from which aggregates are procured, the small-scale producer has to make purchases from a distant quarry. However, the quality of the aggregates is about the same. All the three plants surveyed use electricity as the main energy source. There are many other small-and medium-scale block producers who use diesel-operated equipment, but the cost of energy in the total production cost is so small, even for the large-scale producers, that there appears to be no justification for searching for a cheaper source of energy.

The study clearly shows that small-scale block plants are more labour-intensive than medium- or large-scale ones. It was found that the small plant employs about 10 times more labour, for the same volume of output, than the large-scale plant. While the small-scale plant requires labour with low-level skills which is easily available on the market, the labour to operate the fork-lifts or the automated plant of the large-scale producer needs to be skilled and requires training. The medium- and large-scale plants have employed specific managerial and professional staff while at the small-scale plant, the owner and his sons act as the manager, secretary, accountant and supervisor as the need arises.

An interesting finding of the study is that the cost of block from the small-scale plant is higher than that from the large-scale plant, MauR 5.78 compared with MauR 4.73. This is due mainly to the significantly high cost incurred by the small-scale plant in the procurement of aggregates. The prevailing conditions of shortage of building materials and the boom in the construction industry, however, ensure a ready market for the products of all the plants. As block-production plants of all scales are spread over the whole island, transport costs from plant to construction site are more or less the same irrespective of where the blocks are procured.

In sum, the study showed that;

(a) The small-scale block plant is more labour-intensive than the large-scale plant and does not require the services of highly qualified management personnel;

(b) The investment cost per unit of output for the small-scale plant is about one tenth that for the large-scale plant;

(c) Even though the small-scale plant has a higher production cost, it is able to dispose of its products with a reasonable profit margin;

(d) At all scales of production, maintenance of production machinery and equipment is carried out locally.

H. United Republic of Tanzania: production of burnt bricks

Burnt bricks are produced and used widely throughout the various regions of the country. Large quantities of the bricks are made in artisan plants using field clamps. At the other end of the technology scale, there is a modern automated brick plant which commenced production in 1985. In this case study, four sites representing a cross-section of the various technologies and scales of production employed in brickmaking in the United Republic of Tanzania were investigated. These sites are Ruaha Valley/Iringa, Usambara Development Corporation (USADECO) at Soni, Kowak Brickworks and Kisarawe Brick Factory.

Brickmaking in the Ruaha Valley is carried out as an off-peak-farming activity during the dry season, from June to September, every year. About 300 to 400 brickmakers converge on the valley and produce almost 30 million bricks during the three-month period. They work either under contract to make bricks for individuals, groups or institutions or as self-employed workers who make bricks for their own use and for sale. Hand-moulding techniques are used and the bricks are dried in the sun and fired in clamps with firewood. The bricks produced are used mainly in nearby Iringa but some find a market in Dar es Salaam, 500 kilometres away.

The USADECO brickworks at Soni undertakes brick production throughout the year except during heavy rains when difficulties are encountered in transporting clay and firewood. Production at the plant is semi-mechanized. Clay mining is done manually while the moulding process is mechanized. The factory employs 24 labourers, 2 skilled workers for brick-burning and 5 administrative staff including a manager, foreman, administrator and clerk/typist. The Kowak brickworks is operated by a village as one of its income-generating activities. Labour-intensive production methods are used but there are permanent drying sheds and kilns which ensure year-round production. The village has also established woodlots through an afforestation programme to supply the fuelwood requirements of the factory.

The Kisarawe Brick Factory is fully automated with artificial drying chambers and a tunnel kiln using fuel oil. The factory has an installed capacity of 20 million bricks but in 1988 actual production was only 4.5 million, equivalent to 22 per cent capacity utilization. The factory has been plagued by liquidity problems due to inadequate initial working capital and these have been compounded by the low level of operations and low selling prices of finished products. It has had to close down on occasions because of its inability to meet energy bills. The factory has failed to generate enough cash to pay the increased loan instalments and interest charges arising from devaluations of the local currency. Unexpectedly high increases in the price of furnace oil have also contributed to the current high production cost. In brief, at the time of the study the Kisarawe Brick Factory had failed to achieve the projected levels of economic viability.

From the descriptions of the operations of the four sites in the foregoing paragraphs, it is clear that the first three modes of production are basically small-scale, with the USADECO plant operating as a semi-mechanized enterprise. The findings of the study are summarized as follows:

(a) Firewood appears to be the only source of energy for burning bricks in small-scale production centres. Furnace oil is utilized only at the modern Kisarawe factory. The fuel cost per brick in the large-scale plant is about 20 times the cost in the small-scale plants.

(b) The bricks produced by traditional brickmakers in the Ruaha Valley are sold at between TSh 1.00 and TSh 2.00 compared with a selling price of TSh 7.00 per brick for products of the large-scale Kisarawe plant. Incidentally, the bricks produced by the small-scale USADECO plant, which is semi-mechanized, also sell at TSh 7.00 while the Kowak brick factory produces bricks which sell at TSh 4.00 per unit.

(c) The small-scale labour-intensive brick plants in the Ruaha Valley and the Kowak brick plant employ a direct labour force of approximately 10 per million bricks produced. However, the capital-intensive Kisarawe brick factory operating at 22 per cent capacity has a direct labour force of 26 per million bricks. Besides, this plant has a supporting administrative and management staff of over 30 compared with the five required at the Kowak and USADECO brick plants. The large-scale plant with a very high capital investment is therefore more labour-intensive than the small-scale traditional plants, which is a technological contradiction.

(d) The capital investment per million bricks at the large-scale plant is TSh 36.8 million at the current production level compared with TSh 1.2 million at the Kowak small-scale plant which is equipped with a permanent silo, drying sheds, a soil laboratory and an administrative block. The seasonal production units in the Ruaha Valley require an investment of less than TSh 3000 per million bricks. Even if the large-scale plant produced at full capacity, the investment rate would be TSh 8.3 million per million bricks which is still seven times the investment in the Kowak brick plant. The capital investment per workplace (direct production labour) at the large-scale plant is TSh 1.1 million compared with only TSh 87,500 at the Kowak brick plant.

The study concluded that highly mechanized brick plants, such as the Kisarawe brick factory are not a viable technological option for brick production in the United Republic of Tanzania because of:

(a) Heavy investment both in terms of local and foreign currency;

(b) High energy costs resulting in high production costs.

(c) High cost of basic infrastructure such as transport and water supply;

(d) Dependence on imported spare parts as well as expatriate staff and highly trained operators.

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