Biogas Desulfurization by Pelletized Biomass Ash in a Fixed Bed Arrangement

The removal of H2S is a prerequisite to the energetic valorization of biogas in combined heat and power (CHP) plants. Conventionally, the final step in desul-furization involves filtration over granular activated carbon (GAC). Rising market prices for GAC have fostered research on alternative filtration media. Here we investigated the feasibility of globally available biomass ash (BA) as a cost-efficient alternative. A filter column (V = 2.4 L) was loaded with 800 g BA (10 % moisture) and upstream-fed with a total of 2.76 m³ raw biogas sampled from a food waste fermentation plant. At the outlet H2S, O2, CO2 and CH4 were moni-tored. The H2S was completely sequestered by the filter material and no breakthrough was observed, resulting in a load of 0.26 wt. % H2S. XRF analyses suggested even further potential. First tests with a new, static batch reactor using a feed of >99 vol.-% H2S and pelletized BA achieved H2S uptakes of up to 4 wt.-%, outweighing the reported uptake capacity of conven-tional GAC. Further investigations are underway to assess the pelletized BA under flow-through condi-tions. Results will pave the way to scale up the system and test it under real world conditions at a food waste fermentation plant.