Biogas Upgrading: Analysis and Comparison between Water and Chemical Scrubbings

Biomethane is a renewable energy source that can be used, e.g., for transportation or injection in the natural gas grids. It is obtained from proper biogas treatment. Biogas is a mixture of mainly methane and CO2 that can be produced from livestock effluents, municipal and industrial sewage sludge, energy crops, agro-industrial wastes, MSW landfills (in this case the gas is commonly called "landfill gas") etc. In order to obtain biomethane, CO2 and other compounds must be removed from biogas. The type and the amount of pollutants depend upon the biogas source and determine which cleaning and upgrading techniques are the most suitable for gas purification. "Cleaning" is referred to as the pretreatment that allows the removal of all pollutants but carbon dioxide, while "upgrading" is the treatment for CO2 removal. Since there are no clear guidelines for choosing among different upgrading techniques, this work analyzes two of the most commonly used processes: the water scrubbing and the chemical scrubbing (using amine solutions). By means of process simulation with commercial packages (such as Aspen Plus®), a comparison among the performances of the two techniques is made.