Micronutrient dynamics after thermal pretreatment of olive mill solid waste

• Thermal pretreated OMSW has a higher methane production rate than unpretreated OMSW.
• Metal deficiency limits methane production.
• Metal dynamics in pretreated OMSW was studied using metal extraction scheme.
• Increase of available Co was coupled to the increase of methane production rate.
• Increase of bioavailable cobalt might be a good strategy to optimize biogas production.

This study investigated metal dynamics, and their bioavailability, before and after thermal pretreatment of olive mill solid waste (OMSW), using a sequential metal extraction scheme. The 11.5% increase of cobalt in the most available fraction after the pretreatment coupled to the increase of methane production rate have been a good indicator that the OMSW anaerobic digestion might be metal limited due to the lack of cobalt.