SiEUGreen - D2.3 Blue Technology (T2) Ready- 1
Creators: name: Melesse Eshetu Moges
name: Føreid, Bente
name: Mæhlum, Trond
name: Pandey, Manoj K
name: Jenssen, Petter
name: Linjordet, Roar
Publisher: name: Zenodo
Year: 2021

description: The SiEUGreen project aims to enhance the EU-China cooperation in promoting urban agriculture for food security, resource efficiency, and smart, resilient cities. Circular economy and utilization of domestic organic urban waste resources for the production of fertilizer and soil amendment products for urban and peri-urban agriculture, as well as energy for local use, are essential aspects of the showcases in Fredrikstad and Changsha, especially. The conversion of waste resources and water handling in the SiEUGreen project termed Blue Technology. This deliverable, D2.3 “Blue Technology (T2) Ready 1”, is based on research and investigations carried out in the first 18-month project period. We have evaluated four blue technologies related to the processing of liquid waste for recycling in the SiEUGreen showcases: (1) Liquid Bio-digestate anaerobic digestion as a source of plant nutrients, (2) Struvite precipitation from anaerobic digestion and urine, (3) Production of microalgae from biogas digestate and (4) Nitrification of liquid waste. The latest updated status and the potential challenges in the implementation of these technologies in SiEUGreen showcases are provided in fact sheets. Presentation in fact-sheets facilitates later upgrading to practice abstracts. Human excreta (blackwater) and organic household waste (OHW) contain high amounts of plant nutrients and organic matter, but may also contain pathogens and residues of pharmaceuticals or personal care products (PPCP´s). To utilize the energy in the waste, biogas is produced. Biogas production is covered in D2.1. The potential of anaerobic liquid digestate as a source of plant nutrient recovery was tested. Liquid bio-digestate contains essential and readily available plant nutrients. However, the direct application of liquid digestate as fertilizer has been challenged because of health-related risks. Recent studies on post-treatment of the anaerobically digested effluent of source-separated blackwater demonstrated is an essential step for safe and sustainable recycling and reuse of these renewable resources. Precipitation of struvite from urine and anaerobically treated blackwater has been investigated in the NMBU laboratories. For developing an efficient way of producing struvite from urine and anaerobically treated liquid digestate, Seawater and MgCl2 have been tested as magnesium sources. Moreover, the electro flocculation technique has been tested as an alternative method. Preliminary results of experiments on urine and anaerobically treated blackwater for struvite precipitation using seawater and Mg-plates (with and without current) demonstrated promising options as alternative sources for Mg. However, the fertilizer quality and effect of struvite precipitated from anaerobically digested blackwater and organic household waste on plant production will be further investigated in the showcases. Microalgae are fast-growing photosynthetic organisms, which have the potential to be exploited as an alternative source of feed and food additives, biofertilizers, etc. In a separate project, the production of microalgae biomass using liquid biogas digestate as alternative means of nutrient recovery has been tested and promising results have been obtained. It is proposed to demonstrate both struvite and algae production from filtered digestate in the Fredrikstad showcase. Algae can be used for fodder or as an organic fertilizer. Nitrification of liquid waste is another important liquid fertilizer processing technique. Nitrification of urine is tried in the NIBIO laboratories. Two types of reactors were tested in a laboratory-scale using stored human urine with a 5-50% dilution rate: 1) a moving bed bioreactor (MBBR) and 2) a multipass paced-bed biofilter using porous lightweight aggregates. A smell-free and chemically stable liquid fertilizer product was obtained. Both the MBBR and biofilter appear to be suitable methods for urine nitrification making an attractive fertilizer for urban gardens. 5 Further studies will be performed during showcase implementation for removal of PPCP´s and the fertilizer quality of different products.