A biorefinery approach to exploit digestate as key feedstock in the energy – nutrient nexus

Çallı B. (Executive), Akgül D.

EU Supported Other Project, 2022 - 2023

  • Project Type: EU Supported Other Project
  • Begin Date: January 2022
  • End Date: December 2023

Project Abstract

The BioDEN project aims to create extra revenues for the biogas sector via developing a technology cascade approach for an integrated enhanced biogas production and efficient recovery of nutrients (N, P, K) as (novel) bio-fertilisers from digestate. Indeed, besides its energy potential, animal manure is rich in nutrients, which remain in the digestate after AD. By efficiently extracting these nutrients on the biogas plant premises, they can be, in a next phase, marketed as full-fledged substitutes of petrochemical-based mineral fertilisers, hereby creating new business cases and revenues for the sector, and decrease our dependency on natural gas or rock phosphate for securing mineral N and P needs. Our main elements of focus are: (i) biogas production via anaerobic digestion (AD), (ii) ammonia recovery via stripping and scrubbing, (iii) phosphorus recovery via precipitation and adsorption and (iv) integrated value chain assessment, including pot trials and scenario analyses. Although some of the processes already receive attention in research and in industry, effective linking of the processes to obtain a successful cascade is still missing. Concretely, the BioDEN-project will result in (i) 10-20% more biogas (at constant input) compared to standard current practice, due to reduced ammonia inhibition, release of bio-available organic matter and high organic loading rates, (ii) a, increase in CH4 content of the biogas by 3-5% due to CO2-stripping, (iii) optimised processes for the recovery of nutrients into novel (ammonium citrate, ammonium bicarbonate) and known (ammonium sulphate, struvite, calcium phosphate) bio-fertilisers.