A sustainability assessment for use on land or wastewater treatment of the digestate from bio-waste.

The sustainability of use on land or by processing in a wastewater treatment plant of the digestate from bio-waste was investigated. Sustainability was assessed following a triple bottom line approach entailing environmental, social and economic consequences. A methodology for developing an integrated sustainability indicator was also defined. Global warming and acidification were about 40 kgCO2eq/m3 and 0.7 molcH+eq/m3 and 90 kgCO2eq/m3 and 1.1 molcH+eq/m3 for wastewater treatment and use on land, respectively. The impact on human health for use on land was about 3.5 × 10-4 (DALY), six times higher than wastewater treatment but quite negligible when compared to the DALY associated with other diseases in the same area. Costs calculated for wastewater treatment ranged from about 18 €/m3 up to 35 €/m3, about ten times higher than those related to use on land. The integrated sustainability indicator that was developed indicated higher sustainability for use on land and the relevant influence of such finding with respect to the environmental consequences.