Practical aspects of biowastes conversion to fertilizers

The paper presents different aspects of biomass-based fertilizer production along with technological challenges, relevant law — the European Union guidelines concerning renewable resources, in particular bio-based wastes valorization for fertilizer purposes — and products introduction to the market. Fertilizer technology employs different types of biosolids: sewage sludge, ashes from sewage sludge, agricultural residues, and food waste. Organo-mineral fertilizers can be formulated from different mass streams of biological origin: biomass processed by biological conversion (aerobic or anaerobic), chemical conditioning (acids or alkali), or thermal processes (combustion, pyrolysis). Through a combination of different types of processed biomass (e.g., biosolids conditioned with mineral acid can be neutralized and granulated with ashes from the biomass combustion) and by composition correction, it is possible to produce organic-mineral fertilizers. Particular attention was paid to relevant law (agriculture and non-agricultural applications) and technological problems such as large-scale installations. The available fertilizer production technologies constitute a part of the concept of bio-based circular economy, which in turn could lead to sustainable development as envisioned by the new European Green Deal strategy.