Cement, Energy and Environment

polluters pay for disposal of wastes. The foreign cement companies claim zero fuel cost, as the expense on coal is offset by the tipping fees received for the waste fuels from polluting industries. Unfortunately in India the polluters put price for their wastes to the disposers or else they dispose the wastes in land-fill which is dangerous to environment. The cement industry uses fly ash to produce cement. They also use gypsum which is otherwise waste by-product of fertilizer industry. The prices of both have steeply gone up resulting in less usage. The significant role of Fly ash and slag in GHG emission reduction: If one tonne of pure limestone (CaC0 3 ) is calcined, it will evolve 0.44 tonne of C0 2 , nearly half of its weight. In one tonne of clinker making nearly one tonne of C0 2 is emitted into the atmosphere. The additives in the cement replace the emission-intensive clinker in direct proportion and hence contribute to significant GHG emission reduction. The table below compares the C0 2 emission for manufacturing of various types of cement. C0 2 emission per tonne of OPC, PPC, and PSC: I Clinker Fly ash Slag + Calcination (CaC03=CaO+C02 ) 540 kg 0 kg 0 kg Fossil Fuel buming(Coal) 340 kg 0 kg 0 kg Electricity up to clinkerisation 60 kg 0 kg 0 kg Electricity for cement grinding 30 kg 30 kg 50 kg OPC PPC PSC (30% Flyash) (50% Slag) C02 emission per tonne of cement 932 kg 650 kg 482 kg Research is going on the world over, to find substitute for cement but so far no commercially viable alternative could be found. Cement demand is rising at a rate much higher than fall in emission resulting in increase of net emission. At the time when countries are fighting for net reduction of GHG emission. the cement industry may continue to be emission-intensive in near future, since there is less scope to change cement chemistry for energy efficiency. However, there is good scope to educate the users to go for energy-efficient cement product for the bui ldings. Cement Industry is facing regulatory pressure posed by the PAT scheme. It makes sense for cement manufacturers to replace/retrofit old machinery with modern high– efficient machinery irrespective of the regulatory pressure since it would help them to become more competitive. By capturing waste energy, waste heat recovery system would make inefficient units more energy- efficient even without switching over to energy-efficient technology. Alternate fuel usage by Indian cement industry is abysmally low whereas western countries have achieved as high as 80% substitution . High cost, irregular supply and difficulties in getting permit from regulatory authorities discourage the use of wastes as alternate fuels. Potential of Cement kilns as efficient incinerators which can destroy any hazardous substance without harm to environment is hardly exploited. Strict enforcement of law on polluters and simpl ifying permit procedures for cement industry would enable extensive use of alternate fuels and save fossil fuels. Extensive research is going on "carbon capture" to mitigate GHG emission . "Carbon capture" attempts to capture C0 2 from ki ln gases and store underground or use the same for growing algae . It may become feasible and viable in future. Until then, Production and usage of more and more PPC is the best way to reduce GHG emission. '