Simultaneous addition of biochar and zero-valent iron to improve food waste anaerobic digestion

This investigation explored the combined effects of biochar (BC) and zero-valent iron (ZVI) on food waste anaerobic digestion (AD). The results showed that the AD performance was promoted by supplementing with BC or ZVI individually, and could be further improved by simultaneous addition of the two additives. The simultaneous addition of BC and ZVI further reduced the methanogenic lag phase by 13.3% as compared with ZVI added reactor, and raised the cumulative CH4 yield by 19.4% and the maximum CH4 generation rate by 24.5% compared to the BC added reactor. The reason behind these results was that BC and ZVI played different roles for the promotion effects. For example, BC had the greater ability to reduce the methanogenic lag phase as compared with ZVI. While ZVI could greatly enhance the hydrogenotrophic methanogenesis pathway, leading to higher CH4 yield and CH4 generation rate. Accordingly, simultaneous addition strategy could combine the unique advantages of BC and ZVI, and thus developed a complementary promotion effect on CH4 generation. This study suggested that the simultaneous addition of BC and ZVI could be considered as an effective way to improve AD performance.