Comparison of Sodium Lignosulfonate and Derived Biochar for Influencing Methane Bioevolution

The major bottlenecks in an anaerobic digestion system are process instability and inactive microbes. The comparison of sodium lignosulfonate (SL) and its derived biochar (BC) additions for influencing the anaerobic process of glucose was extensively investigated at 37 ± 1 °C in a batch test. SL addition markedly reduced methane (CH4) yield (MY), resulting in 100 mL/g glucose, whereas the MY with SL-derived BC obviously increased, giving 415 mL/g glucose. SL could inhibit microbial activity versus BC. The modified Gompertz model reliably showed the relationship between SL or BC concentration and CH4 production with a high correlation coefficient. SL could encapsulate microbes, causing a significant decrease in the total probabilities for microbial contacts. Some groups on the surface of SL, like sulfonyl and phenolic hydroxyl groups, were toxic to these anaerobes. However, the BC without sulfonyl group provided considerable pores for microbial immobilization, promoting direct interspecies electron transfer in the CH4 bioevolution process.