Characteristics of Alkaline Wastewater Neutralization for CO₂Capture from Landfill Gas (LFG)

Abstract

In this study, a lab-scale apparatus is used for removal of carbon dioxide (CO2) from a landfill gas (LFG) mixture using a chemical absorption technique. Alkaline wastewater obtained from a nearby industry is used as a chemical absorbent, and a comparison is performed with liquid ammonia solution and sodium hydroxide (NaOH) solutions. The absorptive capacity of the liquid solvents is obtained by the respective “equilibrium breakthrough curves”. The maximum CO2 loading for 0.1 M NaOH, 0.2 M NaOH, wastewater, and 2, 5, and 10 wt % ammonia are 0.41, 0.6, 1.7, 0.7, 1.6, and 2.6 mol of CO2/L, respectively. Alkaline wastewater proved to be a highly effective CO2 absorbent because of its high alkalinity, which occurred from the presence of ammonia. Raman spectroscopy was conducted to confirm that the reactions occurring inside the wastewater followed a trend similar to aqueous ammonia. Methane purified from this process can be further used for different applications. Hypothetical prices are calculated when wastewater absorption is applied to the purification of LFG. LFG sites of 1 million and 5 million tons are considered, and the cost of pipeline gas generated (won/mmBTU) is estimated using simple economical relations.