The CO2 content in biogas has several effects that need to be considered, such as affecting its calorific value or energy value. The higher the CO2 content, the lower the heating value of the biogas. One way to absorb CO2 is by carbonation using a solution of Ca(OH)2 to become CaCO3. Synthesis of CaCO3 by carbonation to obtain high quality products is still being carried out in terms of phase, morphology, and particle size. Ca(OH)2 slurry was prepared with various concentrations, namely 0.05 M, 0.07 M, and 0.1 M. Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM–EDS) and X-Ray Diffraction (XRD) test carried out to analyze the properties of CaCO3. The Precipitated Calcium Carbonate (PCC) crystalline phase at all concentrations is all calcite with scalenohedral morphology. The difference in the concentration of Ca(OH)2 has a significant effect to CO2 absorption and the morphology of PCC. The higher the concentration of Ca(OH)2 slurry, the higher the percentage of CO2 absorption in biogas, but with the effect of likely forming scalenohedral morphology that are commonly used in the paper industry to enhance opacity.