Strategies for the production of a stable blended fertilizer of anaerobic digestates and wood ashes

•Stabilization of anaerobic digestate via wood ash based treatment to avoid pollution•Acid dose and ash type were responsible of the sorption processes for stabilization•Adsorption of sulfate and lactate was responsible of greater reduction of samples’ pH•pH zero point charge led to addition of ashes to digestates under alkaline conditions•Hydrochloric acid and nitric acid enabled (ad)sorption of ammonia at alkaline pH >11