Abstract
Closing loops is a key smart resource management priority in Flanders. The nitrogen (N) cycle in particular needs urgent attention, as current unsustainable management of ammoniacal nitrogen heavily impacts vulnerable ecosystems and our health. A key opportunity for smarter and more resource-efficient N management, is N recovery from gaseous and liquid waste streams, lowering emissions, replacing removal as N2 and/or decreasing required industrial production of synthetic fertiliser. The most established approach for N recovery is acid scrubbing, applied either on ammoniacal air or after stripping NH3 from a slurry or wastewater. However, the use of mineral acids is expensive and dangerous, and their production causes adverse environmental impacts. Furthermore, the typically obtained ammonium sulphate solution acidifies agricultural soils, linked to extra costs for liming. Nitraliser is an innovative and sustainable concept to biotechnologically produce protons and nitrate in a nitrifying biofilm reactor (bioconvert), recirculating over an upstream scrubber (capture) and over a downstream electrochemical cell or electrodialysis unit (concentrate). Research challenges relate to nitrification under extreme conditions, and to the design, operation parameters and coupling strategy with the other subunits. The obtained nitrate-based solutions have cost, safety and environmental advantages to acid scrubbing, and do not lead to soil acidification.
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