Abstract
Development and optimization of nutrient recovery technologies for agricultural waste is on the rise. The full scale adoption of these technologies is however hindered by complex legal aspects that result from lack of science-based knowledge on characterization and fertilizer performance of recovered end-products. Ammonium sulfate (AS) and ammonium nitrate (AN), end-products of (stripping-)scrubbing technology, are currently listed by the European Commission as high priority products with the potential of replacing synthetic N fertilizers. The legal acceptance of AS and AN will be highly dependent on critical mass of scientific evidence.This study describes four different (stripping-)scrubbing pathways to recover ammonia with an aim to (i) assess product characteristics of ammonium nitrate (AN) and ammonium sulfate (AS) produced from different installations, (ii) evaluate fertilizer performance of recovered end-products in greenhouse (Lactuca sativa L.) and full field (Zea mays L.) scale settings and (iii) compare the observed performances with other published studies. Results have indicated that the recovered products might have a different legal status, as either mineral N fertilizer or yet as animal manure, depending on the used (stripping-)scrubbing process pathway. Nevertheless, no significant differences in respect to product characterization and fertilizer performance of AN and AS have been identified in this study as compared to the conventional use of synthetic N fertilizers. This indicates that recovered AS and AN are valuable N sources and therefore might be used as N fertilizers in crop cultivation.
Highlights
The total N in ammonium sulfate (AS) is present 100% in the form of NH4-N, whereas total N in ammonium nitrate (AN) can be found in the form of NH4-N and NO3-N
The percentage of NH4-N and NO3-N in AN measured in this study was 55 and 45%, respectively (Table 1)
The use of nitric acid contributes to the presence of NO3-N, and increases the N concentration in the recovered product
Summary
The livestock sector is currently responsible for 14.5% of all human-induced greenhouse gas (GHG) emissions (Sakadevan and Nguyen, 2017) It generates large nutrient surpluses of on-farm nitrogen (N) and phosphorus (P) that may lead to a pollution of water bodies. To protect European watercourses, the Nitrates Directive (91/676/EEC) was implemented in 1991 with the aim to limit the application of N from animal manure up to 170 kg N haÀ1 yÀ1 in Nitrate Vulnerable Zones (NVZs) (European Commission, 1991) These zones are mostly located in European regions known for high livestock density, such as Flanders (Belgium), the Netherlands, Denmark, Brittany (France), Po Valley (Italy), Ireland, Aragon and Catalonia (Spain).
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