Cement, Energy and Environment

Landfilling CETP sludge, with a moisture content of approximately 60%, is currently landfilled. The sludge is not landfilled during the monsoon season and stored temporarily inside CETP using tarpaulin covers. The landfill design includes base and boundary sealing, leachate collec on system but no gas collec on system, thus landfill gases are released to the atmosphere. The leachate collected from the landfill is sent to the CETP for treatment in Mul ple Effect Evaporator (MEE) as it is expected to contain high Chemical Oxygen Demand (COD). The environmental impacts associated with landfilling are leachate (heavy metals and organic loading), emissions to the air (CO , CH , other 2 4 hydrocarbons), the energy inputs (fuel for transport and heavy machineries) and material inputs for the construc on of the engineered landfills (HDPE, clay, gravel, topsoil). To prevent contamina on of groundwater, the landfill has leachate collec on system; the collected leachate is sent to CETP for treatment. The emissions are assumed to occur during a poten ally long- me span a er the deposi on of the waste and two phases are dis nguished: the short-term phase < 100 years and the long- term phase > 100 years (Doka, 2003). In this study, the emissions to air are assumed to be mostly methane and carbon dioxide with a 50/50 ra o in volume (IPCC, 2006). These emissions have been es mated using the US EPA model LandGEM (Landfill Gas Emissions Model, Version 3.02) and the results are: 48.2 g CH /kg 4 sludge and 132 g CO /kg sludge. 2 The other emissions to air (hydrocarbon), considered minor, are not included due to lack of data. The construc on of the landfill has been modelled using data from Ecoinvent centre (2007) with modifica ons to simulate the context in Vapi. The distance to the landfill from CETP plant is assumed to be 10 km. Incinera on The incinerable wastes from Vapi are sent to Ankleshwar (160 km north of Vapi), to Dahej (250 km north of Vapi) and to Saurashtra Enviro Private Limited in Kutch (600 km north of Vapi). Es mated incinerable waste genera on from Vapi is 5% of the total waste generated. All hazardous waste incinerators need auxiliary fuel input to maintain high combus on temperatures; an energy input above 23 MJ/kg of waste is necessary to maintain a complete combus on (Doka, 2009). The calorific value of filter pressed sludge is 3.34 to 4.18 MJ/kg and on dry basis calorific value is 7.53 to 8.37 MJ/kg. It is assumed that energy containing wastes such as plas c wastes will be fed together with the CETP sludge to reduce the auxiliary fuel input such as light fuel oil. Typically, energy is recovered either for use in the process, genera ng steam and electricity. Waste to Energy (WtE) plants involving only genera on of electricity in steam turbines has low efficiency; usually less than 30% due to heat loss. Electricity producers are also some mes reluctant to accept electricity to the grid from such plants as the deliveries are unstable. District hea ng only happens in colder countries during winter me, e.g. Scandinavia and not an op on for India. The incinera on of the waste leads to direct air and water emissions as well as land use burdens. Indirect burdens originate from the consump on of ancillary materials, energy and infrastructure materials. It is assumed that the sludge has more than 50% of inert substances such as incombus ble oxides (majorly SiO but also 2 60