A series of laboratory experiments were performed in continuously-operating reactors, fed with mixtures of OMW and DPM at various concentrations. It was concluded that co-digestion of OMW with DPM is possible without any dilution of OMW or addition of any chemicals. Biogas production was slightly higher when OMW was added to DPM up to a critical concentration (about 40%, expressed as contribution of OMW to the volatile solids of the mixture), after which production is decreased. The results were
further verified by scaling up to a continuously-operating pilot-plant reactor digesting DPM, and confirmed that no negative impact was imposed by adding OMW up to the above critical value.