Biogas is acknowledged worldwide as an increasingly important renewable energy source. After treatment, the upgraded biogas (biomethane) can be injected into the existing natural gas infrastructure, or it can be compressed for usage as a vehicle fuel. Upgrading of biogas by chemical absorption is considered among the most attractive scrubbing technologies. There are disadvantages though when using alkylamines, such as the energy-intensive regeneration step, degradation of the amines and the potential to form harmful chemical compounds. However, the latter disadvantages could be overcome by using non-conventional methods. In our lab-scale experiments, aqueous ammonia derived from air-stripping of a lime-treated anaerobic digestate proved very effective as biogas scrubber, decreasing carbon dioxide substantially (over 90%), and removing hydrogen sulfide (H2S) completely. Moreover, the alkaline aqueous effluent of the latter air-stripping process was very effectively neutralized by the biogas, while it also exhibited an important scrubbing potential (removing CO2 and H2S partially). Based upon the above experimental results, the flowsheets of an ammonia air-stripping/wet-scrubber and a biogas scrubbing unit, at a semi-industrial scale, were constructed and presented. Taking advantage of both the above acid gas chemical scrubbers could prove very beneficial for a cost-effective conversion of biogas to biomethane.