Why is the recovery of nutrients necessary?

The scarcity of resources, elevated energy costs and the growing environmental awareness have in the last years increased the focus on circular economy. Waste is now regarded as a potential resource and source of income.

The purpose of FUBAF is

  • To develop essential parts of the circular economy for energy production and utilization of nutrients in urban waste and wastewater for the production of food
  • To develop a concept for upgrading a conventional wastewater treatment plant to a Water Resource Recovery Facility (WRRF)
  • To demonstrate the concept at Avedøre Wastewater Treatment Plant (WWTP) with a capacity of 400,000 PE, which will be a showcase for Danish environmental technology in international size
  • To demonstrate synergies in co-operation on resource utilization across the water, waste and energy sectors

Expected results

By the end of the project by mid-2020, it is intended that:

  • Avedøre WWTP has been transformed into a WRRF.
  • A concept for upgrading and a model for transforming a conventional wastewater treatment plant into a WRRF is in place.
  • New technologies included in the concept have been demonstrated at pilot scale.
  • Synergies in co-operation on resource utilization across the water, waste, agriculture and energy sector have been demonstrated.
  • A robust circular economy has been demonstrated for the production and use of biogas, the recovery of nutrients and the production of single cell protein from KOD (Source-separated organic waste) for use in animal feed.
  • The transformation of a WRRF is documented in relation to life cycle environmental impacts and financial costs.

 

The project contains  three technical work packages. Two additional work packages are defined for the purpose of documenting the transformation of the wastewater treatment plant to a Water Resource Recovery Facility , preparing an LCA, as well as dissemination of the project. Read more about the individual packages below.

WP1: Anaerobic digestion

WP1 will be based on experience gained in WP6 of the Lighthouse project VARGA. The work package will cover the first two steps in the production line: anaerobic digestion and upgrading of biogas with hydrogen. Membranes from LiqTech will be used for the biological upgrading of biogas. Required hydrogen will be supplied through LiqTech’s ceramic membranes.

The composition of the biogas produced from sludge will be compared with  biogas produced using source separated organic household waste. In addition, the quality of the upgraded biogas will be compared to natural gas.

WP2: Nutrients recovery

WP2 includes the development of a novel microbial electrochemical system termed submersible microbial desalination cell (SMDC). SMDCs  can be easily integrated into the existing wastewater infrastructure to demonstrate the practical applicability and long-term continuous operation of ammonia recovery from ammonia-rich wastewaters (e.g., reject from dewatering of anaerobic digested sludge or digestate). Among the components which are essential for optimization, electrodes play an important role in the  generation of current and the costs of system construction. Therefore, different electrodes (e.g., activated carbon, graphene, carbon paper/felt/fiber brush) will be tested. Advanced electrode modification technologies (e.g., ammonia gas process, heat treatment, and nanofabrication with conductive metals) will also be employed to improve the electron flow which is essential for ammonia recovery.

DTU’s experience with nanofabrication of electrodes will help to achieve these goals. In addition, the ratio of electrode and reactor volume is an important parameter for system optimization and up-scaling. Thus, the effect of different ratios on  system performance will be investigated. At the end of WP2, up-scaling of the SMDC reactor for pilot-scale demonstration will be conducted.

WP3: Single Cell Protein production

In WP3 the produced and upgraded biogas from WP 1, as well as the nutrients produced in WP 2 will be converted into Single Cell Protein. LiqTech will provide ceramic membranes for the fermentation process. At DTU Environment an initial microbial screening will be performed based on protein content and amino acid profile to identify favorable strains of  Methane Oxidizing Bacteria (MOB). The nutrients from WP2 will be fed to a fermenter containing a  MOB culture. Operational conditions will be optimized to achieve  higher productivity and lower costs. Biomass density, macromolecular composition, purity of the SCP and trace pollutants will be monitored.

In parallel, UniBio will also produce Single Cell Protein from the upgraded biogas using their pilot scale facility. The quality of the produced protein will be analyzed and compared to the requirements of downstream users for animal feed production.

WP4: Circular economy

In WP4 the proposed concept will be evaluated in the frame of circular economy. The sustainability and feasibility of producing high value product in the form of Single Cell Protein from urban bio-waste will be evaluated using LCA and the eco-efficiency approach. On the one hand, WP4 helps to identify the environmental hotspots of the process with the aim to decrease the environmental footprint. On the other hand, it helps to evaluate whether the proposed production line can compete with existing and emerging alternative products from an environmental perspective. Synergies with the VARGA project can partly be obtained, since LCA is performed in the VARGA project as well.