Stefan Josef Hörtenhuber, Michaela Clarissa Theurl og Kurt Möller
The results show that many recycled P fertilizers (RPFs; e.g., digestates from urban organic wastes, biosolids and their ashes, meat and bone meal (MBM) and its recycling products) are competitive in terms of LCA results compared with conventional P fertilizers. For each of the P recycling sources, one or more treatment options were identified, which have more favorable LCA results than the conventional references. For sewage sludge, we found that direct application of the stabilized biosolids, and incineration with application of the ash showed the lowest LCA impacts per kg P; their treatments even generated net credits from added values. The same applies for the anaerobic digestion treatment of urban organic wastes. For MBM, low environmental impacts were identified for each of the analyzed treatment options, especially for anaerobic digestion, incineration, feeding with application of manure and direct application. Similarly, low environmental impacts and net credits were found for directly applied biomass ash. Some organically based RPFs demonstrate added values, i.e., as nitrogen and potassium fertilizer effect, energy gains during the treatment, or a humus sequestration potential. If these added values are considered in the LCAs, 11 out of 17 RPFs will have advantageous effects for the majority of addressed impact categories.