Start-up of a multi-stage system for biogas production and solid waste treatment in low-tech countries

Vegetable fruit garden wastes were treated anaerobically using a multistage Dranco system. The digesters were composed of three 50 L vessels kept in mesophilic conditions. They were operating at 14.5-17% TS. By controlling the pH in the system, the start-up for biogas production was shortened to 60 days. The pH correction was a buffering which enhanced methanogenic activity in the digesters. With a loading rate of 4.1 kg VS/m³reactor.day, the production of biogas was 5 m³/m³reactor.day, and 60-70% methane content. This allowed making a multisystem by starting every 3 weeks with new vessels in order to maintain biogas production, to be used in industries or in local communities in low-tech countries. The designed model was started in Kinshasa (Congo) where a project is expected to treat one ton of solid waste on a daily basis, for a production of 100 m³ biogas. This cost effectiveness of the system is demonstrated and presents the opportunity for biowaste treatment coupled with environmental protection and substantial energy recovery.