ENERGY CONSIDERATIONS & BUILDING MATERIALS - A Case Study For India

In India a very high component of energy is invested in the manufacture of building materials and building components.  While engineering design efficiency in industrial products has been widely researched, work in the area of energy utilization and life cycle accounting of energy costs in building materials and buildings has been largely ignored.  The worsening energy crisis makes it imperative to analyze the energy content of the material against parameters of renewability, efficiency of use and local availability, as also its aggregated energy value.
 

Table (1) summarizes the building material demand and the energy demand in India at current levels of technology.  The total electricity generated in 1990-91 was 264.6 billion k Who including thermal, hydro and nuclear power.  Coal alone provides 60 percent of the total energy consumption in the building materials sector.  (The aluminium industry relying heavily on electricity, is excluded  from this analysis).  In the last one year rising coal costs have resulted in  a 14 percent price increase in the brick sector, 25 percent in the cement and 39 percent in fireclay products.  The construction sector in India, the single largest consumer of energy intensive materials, like steel and cement accounts for a large share of the total emissions.  This results from inefficient combustion technology and very high emission coefficient for coal.  Improved technology is urgently needed in areas related to basic raw material manufacture, conversion of fuel into energy and in the utilization of energy.

Bricks are produced extensively in India in batches ranging from 50,000 bricks in country clamps to 800,000 bricks in kilns.  The fuel is used in varying combinations: cow-dung cakes, agro-residues, coal and wood.  There are constant efforts at fuel substitution by business enterprises through the use of non-wood based biomass like rice-husk, bagasse and mustard stocks in place of wood.  But these innovations focus only on direct cost reductions, especially because conventional brickmaking thrives on low operating costs and maximum return on investment.  The Bulls-trench kiln with a movable chimney consumes 17-18t of coal/100,000 bricks as against 13t for the fixed chimney and only 12t for the high draught kiln.  The use of high draught kiln producing only 55 percent good quality bricks, is limited.  The movable chimney kiln offering low initial investments continues to be most popular choice inspite of excessive fuel consumption.  This widespread indifference has lead to a stagnation of technology and wasteful use of fuel leading to increased  CO₂ emissions.

Lime is another traditional material whose use as a building material is being marginalised.  Building lime, which forms 20 percent of the total lime output is the contaminated accounts for the other 80 percent catering primarily to the paper, textile and sugar industry.  The continuous vertical shaft kiln is the most commonly used technology which offers a marginal improvement over the traditional rectangular batch process kilns.  The fuel consumption in the lime industry has remained static at 2.5t of coal/t of lime fore the last decade.  Moreover lime which is a highly polluting industry due to the CO₂ evolved during the calcination of limestone, adopts almost on pollution control measures.

Both the above materials have to compete with industrial materials like cement and concrete blocks, because of rapid strides in technology development and improved energy efficiencies in the cement industry.  These industries, mainly in the large  scale sector, can afford environment control measure even at high initial costs, because of assured returns over a period of time.  With obvious economic benefits, there has been a marked downward trend in the energy content of cement.  As a result, concrete block walls are today at least 30 percent more efficient in their material energy content, when compared with brick walls.  There are entire belts in India, areas with vast reserves of stone, where concrete blocks are replacing bricks.  The coarse aggregate manufacturing units generate huge quantities  of stone dust, otherwise a waste, but which is a major constituent of concrete blocks.  This has lead to a symbiotic relationship between the two technologies.  In areas, where stone aggregates are not easily available and soil for bricks is not suitable, fly ash substitution is common.  Flyash acts as a filler and assists the burning process due to its residual calorific value.

An interesting backlash of the  imposed ban on the use of primary wood in government construction is the promotion of aluminium and steel structurals.  It has also promoted the introduction of new materials like medium density fibreboard and cement based boards.  All these materials are regrettably more energy intensive compared to wood or even plywood.  Through a comparison of the equivalent energy in medium density fibreboard and cement based boards (fig.1)  it is evident that the energy used in their manufacture is much greater than the respective energies for plywood.  Plywood manufacture involves the use of primary wood; implying depletion of forest reserves.  As a positive step towards sustainable enterprises, many of the plywood industries are investing in captive plantations of fast growing wood species.  This move ensures income and fuel wood to the local farmers, and these plantations are also a valuable sinks for CO_2.
 

Fig. 1: Energy in Wood-based Board
Medium density fibre (MDF)
Ply Board (PB)
Cement-Wood (CW)
Energy in kWh*/sqft

With emphasis on the social imperatives like employment generation and local production, the key determinants of a sustainable building economy are demonstrated by the example of plywood manufacture.  Development Alternatives, in the course of its research programme on “Energy Content of Building Materials”  focuses on the identification of technology gaps in the existing building materials sectors.  This will enable decision makers to assess energy requirements for different growth scenarios  as well as provide insights for influencing material development, fuel substitution and energy pricing issues.
 

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