Long-term performance of anaerobic digestion for crop residues containing heavy metals and response of microbial communities

- Stability of AD was evaluated for the treatment of heavy metal-containing crop residues.
- Changes of microbial communities during digestion were identified using pyrosequencing.
- AD process remained stable throughout the experimental periods without effects of heavy metals.
- Microbial communities did not suffer from heavy metals and conformed to the substrate.

In order to investigate the long-term stability on the performance of the anaerobic digestion process, a laboratory-scale continuous stirred-tank reactor (CSTR) was operated for 1100 days with sunflower harvested in a heavy metal contaminated site. Changes of microbial communities during digestion were identified using pyrosequencing. According to the results, soluble heavy metal concentrations were lower than the reported inhibitory level and the reactor performance remained stable up to OLR of 2.0 g-VS/L/day at HRT of 20 days. Microbial communities commonly found in anaerobic digestion for cellulosic biomass were observed and stably established with respect to the substrate. Thus, the balance of microbial metabolism was maintained appropriately and anaerobic digestion seems to be feasible for disposal of heavy metal-containing crop residues from phytoremediation sites.