Wood ash biomethane upgrading system: A case study

In this work, a biomethane fuel was obtained from biogas, using a solid matrix of ashes obtained from a central heating plant fed by wood. Biomethane composition was studied in an experimental pilot plant that treats organic waste through dry anaerobic digestion. European limits were considered and respected for the biomethane injection into the gas grid. The process was able to completely remove carbon dioxide (CO2) during its initial phase. After 50 h of test CO2 concentration started to appear in the outlet gas. This behaviour is related to the ash content, reactive phases (e.g., Ca hydroxides) and fine particle size (<0.2 mm). Coupled with the CO2 removal, European limits for the biomethane injection into the gas grid must consider also trace compounds (Limits for Sulphur 150 mg/Nm(3) and CO2 3%vol.). After 95 h of the experimental test, the gas injection limits are still maintained both for total sulphur trace compounds and both for CO2 limits. Uptake of 0.7 g/kg for H2S and 115 g(CO)(2) /kg(ash) were registered from the pilot plant. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

In this study, biomethane fuel was obtained from biogas using solid matrix obtained from a wood-fed central heating plant. The composition of biomethane and its injection limits into the gas grid were analyzed. The process showed effective CO2 removal initially, but limitations related to ash content and reactive phases were observed after prolonged testing period.