The final report of the abonoCARE growth core, a consortium project designated VP 4, presents a detailed life‑cycle assessment of two phosphorus‑rich fertilizers produced from sewage‑sludge ash. The study compares a single‑component product, P38, with a multi‑component product, NPS 7‑24‑8, both derived from the same feedstock but differing in formulation and phosphorus content. The analysis covers raw‑material acquisition, transport, chemical processing, and product manufacture, and quantifies energy consumption in megajoules per kilogram of finished product (EE [MJ kg⁻¹]) and greenhouse‑gas emissions in kilograms of CO₂ per kilogram of product (CF [kg CO₂ kg⁻¹]).

For P38, the total energy requirement is 17.53 MJ kg⁻¹ and the CO₂ emission is 1.17 kg CO₂ kg⁻¹. The bulk of these figures originates from the production and transport of phosphoric acid, which alone accounts for 15.75 MJ kg⁻¹ and 0.82 kg CO₂ kg⁻¹. Transport of phosphoric acid over 1 300 km contributes an additional 1.34 MJ kg⁻¹ and 0.09 kg CO₂ kg⁻¹. The manufacture of the final product adds 0.39 MJ kg⁻¹ and 0.25 kg CO₂ kg⁻¹. In contrast, the NPS product requires only 12.84 MJ kg⁻¹ and emits 1.02 kg CO₂ kg⁻¹. The reduced energy and emissions stem mainly from a lower demand for phosphoric acid: the NPS formulation contains 3.5 % phosphorus (8 % phosphate) versus 5 % phosphorus (11.2 % phosphate) in P38. Consequently, the NPS route saves roughly 27 % of the energy and 13 % of the CO₂ per tonne of finished fertilizer relative to P38.

When normalised to the amount of recycled phosphorus, the energy intensity rises slightly for the NPS product. Per kilogram of recovered phosphorus, P38 consumes 321.53 MJ and emits 16.76 kg CO₂, whereas NPS uses 358.06 MJ and emits 23.90 kg CO₂. The higher values for NPS reflect the additional processing steps required to incorporate the sludge ash into a multi‑component formulation.

The report also evaluates the dissolution behaviour of the sludge ash in various mineral acids. Experiments with 2 M hydrochloric acid and 2 M sulfuric acid at pH 1.0 achieved the highest solubility, dissolving nearly 50 % of the ash. Nitric acid performed less effectively. The dissolution efficiency was strongly dependent on pH; lower pH values increased the release of phosphorus and heavy metals. Temperature and reaction time also influenced the outcome, with lower temperatures over longer periods yielding comparable results to higher temperatures over shorter times.

The abonoCARE VP 4 consortium, comprising academic research institutes and industry partners, coordinated the project over several years. The joint final report synthesises contributions from each partner, detailing the experimental work, data analysis, and comparative assessment against alternative phosphorus‑recycling technologies. The project was funded under the German federal research programme, aiming to advance sustainable fertilizer production and reduce reliance on virgin phosphate rock.