Biogas produced in wastewater treatment plants and landfills has valuable energy content. Biogas is mainly composed of methane and carbon dioxide, and it constitutes a renewable energy source since it is a product of the anaerobic digestion of biomass. The use of this fuel also contributes to reduce greenhouse gases emissions. However, biogases also contain several trace compounds such as siloxanes that must be removed. The combustion of these silicones, widely present in industrial and domestic products, causes severe damage to the biogás energy recovery systems. The most widely used technique for the removal of siloxanes is non-regenerative adsorption into activated carbon (AC). However, despite the spread industrial use of this technology, little is known about the mechanisms involved in the siloxane adsorption process.
The thesis “Siloxane removal in the energy recovery of biogas: Sequential adsorption/oxidation processes” by Alba Cabrera-Codony, represents a significant improvement for the biogas upgrading processes that leads to its energy recovery. In this thesis alternative adsorbents for the siloxane removal were studied and the mechanisms involved in the siloxane adsorption were elucidated. This allowed improving the yield of the adsorption and regeneration technologies using both activated carbons and zeolites. Moreover, several technologies based on advanced oxidation processes were applied in order to regenerate and reuse the exhausted adsorbents.