Life Cycle Assessment (LCA) of utilizing rice husk as alternative in Portland clinker production fuel

The recent record of the environmental impact of clinker and cement production increased the awareness of the international and domestic community with the role of the industry to global climate change. Since the more than half of the cement’s carbon footprint are attributed to clinker production which is a very energy intensive process, a number of companies explored the possibility of co-firing their cement kilns with biomass or municipal residual wastes. Rice husk is a carbon neutral fuel and was used as the alternative fuel and was been co-fired with the primary fuel, Indonesian Coal. The study was intended to determine the optimum rice husk co-firing settings that will yield the maximum life cycle assessment benefits under a defined set of economic, process, and product quality constraints using Exhaustive Grid Search algorithm. The simulated optimum results equivalent to 64% rice husk thermal substitution proved that this agricultural byproduct is a sustainable source of alternative energy, which provides the maximum environmental life cycle benefit. The simulated result found to have no significant negative impact on cement kiln stability and product quality due to predefined set of constraints that limits the dependent variables within the desirable operating boundary. Cement plant in the Philippines that perform co-processing of rice husk perform only a maximum thermal substitution equivalent to 23%, although the theoretical calculation suggested more than twice the actual heat consumption, this will be difficult to accomplish. This is due to steady supply of rice husk, and existing equipment set-up that restrict the increase of thermal substitution beyond the 23%. The final optimum percentage heat substitution of rice husk is between 24 – 25% after considering the fuel feeding and combustion chamber limitations