Potential of low carbon materials facing biodeterioration in concrete biogas structures

Anaerobic digestion, a renewable energy source, is the degradation of organic waste into biogas, mainly composed of CH 4 and CO 2 . The sector is expanding rapidly due to its multiple environmental and economic benefits. This process is implemented industrially in concrete structures that are in direct contact with the biowaste being digested and the gas produced. Both phases can damage concrete through (i) the presence of volatile fatty acids, dissolved CO 2 , ammonium, and microbial biofilm in the liquid phase, and (ii) high concentrations of CO 2 and various concentrations of H 2 S in the gas phase. In order to develop more sustainable concrete biogas units, long-term, in-situ experiments were carried out in a semi-industrial scale digester to provide new insights into the performance levels and deterioration mechanisms of various low-CO 2 binders, including alkali-activated metakaolin (geopolymer), alkali-activated slag (AAS), and supersulfated cements (SSC), in comparison to calcium aluminate cement (CAC) and Portland cement based matrices. In the running conditions explored, carbonation of the cementitious matrices was predominant over other deterioration phenomena in both the digester liquid and the gas phases. Alkali-activated metakaolin and calcium aluminate cement performed better with few degradations observed. Supersulfated cements and alkali-activated slag showed an intermediate behaviour with good performance in the acidic liquid phase but low performance in the CO 2 -rich gas phase. Graphical abstract