Life Cycle Assessment of pretreatment technologies for anaerobic digestion of source-separated organic household waste

The environmental performance of two pretreatment technologies for source-separated organic waste was compared using life cycle assessment (LCA). An innovative pulping process where source-separated organic waste is pulped with cold water forming a volatile solid rich biopulp was compared to a more traditional pretreatment method using a screw press.

The inventory of the technologies was constructed including the mass balance, amount of biogas produced, nutrient recovery rates, and produced biomass quality. The technologies were modelled in the LCA-model EASETECH and the potential environmental impacts including a number of non-toxic and toxic impact categories were assessed.

No big difference in the overall performance of the two technologies was observed. The difference for the separate life cycle steps was, however, more pronounced. More efficient material transfer in the scenario with waste pulping resulted in a higher biogas output and nutrient recovery and, thus, the higher impact savings related to biogas production and digest utilization.

Meanwhile, larger reject amount in the scenario with screw press led to more savings obtained by utilization of the reject in this scenario.