SiEUGreen - D2.1 Green Technology (T1) Ready
Creators: name: Linjordet, Roar
name: Føreid, Bente
name: Melesse Eshetu Moges
name: Morken, John
Publisher: name: Zenodo
Year: 2021

description: The report presents an evaluation of biogas reactors for possible use in small scale urban settings, as well as use of organic waste to produce alternative growth media by composting and for production of insects or worms as fish feed in aquaponic systems. Biogas production from toilet waste (blackwater) and organic household waste is a key treatment technology in Fredrikstad showcases in the SiEUGreen project. The anaerobic treatment is a complicated process regulated by several factors. For the showcase in Fredrikstad the project has evaluated four different anaerobic sludge bed reactors with enhanced biomass retention that are currently in use: the Upflow Anaerobic Sludge Bed (UASB) system, the Upflow Sludge Blanket Anaerobic Baffled Reactor (USBABR), the Anaerobic Membrane Bioreactor (AnMBR), and the Antec Biofilm (AB) system. The UASB system is well tested and has a small footprint, but the high tower feature of the reactor may be a critical issue when the reactor is to be installed indoors. The USBABR is a new prototype reactor developed in Norway and tested on source-separated blackwater. The performance is comparable with the standard UASB, but with a much smaller footprint. Tests are being performed at pilot scale, but there is no experience with the combination of blackwater and milled food waste. AnMBR is a combination of anaerobic digestion and membrane bioreactor. It maximizes the effectiveness of the anaerobic process with a minimum space requirement. The integration of the membrane in the anaerobic reactor allows complete physical retention of bacterial flocs and most of the suspended solids, and this reactor therefore offers good disinfection capacity. The main drawbacks of the AnMBRs are the low membrane flux, membrane fouling, and high capital and operational costs.. The Antec Biofilm reactor is a plug flow reactor with biofilm technology. It has a compact design and can be easily installed indoors. The experience with blackwater is limited with this reactor, but results for sewage sludge and cattle manure are promising. The reactor has been tested for SIEUGreen with pig slurry (surrogate for blackwater), toilet paper and food waste. Preliminary data indicate that the reactor capacity is far from optimally utilized, and that additional food waste may be needed to achieve a net positive energy output.. Composting is aerobic decomposition of organic material. It can be done on different scales, from industrially to composting in gardens, and can therefore easily be adapted to urban farming systems. Often the material needs to be cut into smaller pieces prior to composting. The simplest way of composting is in rows (windrows) that are turned regularly. To compost food waste etc. this way, it is usually necessary to mix it with other waste products (e.g. garden waste, wood chips) to get enough air into the mixture and also get a more optimal C:N ratio. There are also several enclosed composting reactors on the market. When composting in urban areas, it is important to place the composting such that any nuisance from smell is avoided. Often reactors or at least enclosed composting will be preferred. Co-composting of organic household waste /green waste and solar dry toilet residue can produce an alternative growth medium to peat and can be implemented in different showcases. Using an organic waste product to cultivate insects or worms as fish feed has been evaluated and can be of interest in connection to the aquaponic systems. Insect production from waste resources needs special expertise and can be complicated in small scale urban settings.