Evaluating the use of rice residue ash in cement-based industries in the Philippines – Greenhouse gas reduction, transportation, and cost assessment

Abstract

In the Philippines, biomass-fueled cogeneration plants use sugarcane bagasse, rice husk, or a mix of agricultural residues as feedstock. Burning these residues results in the continuous generation of ash, accumulating over time and needing appropriate disposal. As a preliminary, the annual potential amount of rice husk and rice straw generation, the available energy that could be recovered, and potential ash generation in the Philippines were estimated in this study. More specifically, the contribution of generated ashes toward reducing greenhouse gas (GHG) emissions when used to displace part of the required cement in cement-based industries was assessed and evaluated. Residues from paddy rice could provide up to ∼10,444 GWh of electrical energy when used as fuel. Utilization of the generated fly ashes (∼634 kt rice straw fly ash and ∼267 kt rice husk fly ash) alone could, on average, reduce ∼681 kt CO2_eq annually. The transportation of the ashes before their utilization entails significant GHG emissions. However, transporting the ash within the critical distance of 2,995 km would ensure a positive net reduction. In addition, the handling and transportation cost of coal, rice, and sugarcane ashes within the archipelago was also evaluated and compared. The resulting costs (0.94–6.8 USD/40-kg bag) of different ashes are competitive with the current cement retail price (4.00–7.45 USD/40-kg bag). Potential applications, impacts, limitations, and foreseen challenges in using rice residue ashes are also discussed.