A New Method for Capturing CO₂ from Effluent Gases Using a Rice-Based Product

Abstract

In 2013, UAE imported around 772 million kilograms of rice, making it one of the largest consumers of this popular grain in the world. However, 40% of rice available in the market is discarded, contributing to the country’s CO2 footprint. Given that CO2 emissions are recognized as a significant contributor to climate change and efforts aimed at their reduction are proving insufficient for combatting the global increase in temperature, various approaches aimed at its removal from the atmosphere have been proposed. The goal of this study is to contribute to this initiative by proposing a new method for CO2 removal based on a special gas contact device filled with buffered puffed rice cakes obtained by heating in a purposely designed sealed chamber at high pressure to obtain layers with 9−12 mm thickness. The resulting cakes are subsequently immersed in a sodium hydroxide liquor (0.25−2.5 M) to increase the moisture content to 5% and pH to >11.0. In the experiments, different rice structures (stacked layers, rice grains, and multi-spaced layers) were tested, varying the CO2 percentage in the simulated effluent gas (1−15%). The highest CO2 uptake value (7.52 × 10−3 mole CO2/cm2 rice cake surface area) was achieved using 10% CO2 and a 500 mL/min flow rate with rice cakes of 80 mm diameter, comprising 12 mm thick layers that occupied 20% of the device volume. These results indicate that the proposed design exhibits high CO2 removal efficiency and should be further optimized in future investigations.

Keywords

• CO₂ capturing
• rice waste
• contact device
• puffed rice cakes
• sodium hydroxide liquor