Ammonium Sulphate from a Bio-Refinery System as a Fertilizer—Agronomic and Economic Effectiveness on the Farm Scale

Abstract

This paper presents the results of a pot experiment aimed at the assessment of the agronomic and economic effectiveness of ammonium sulphate from an agro bio-refinery (Bio-AS). The Bio-AS was obtained by means of the ammonia stripping process from effluent after struvite precipitation from a liquid fraction of digestate. The agronomic effectiveness of Bio-AS in a pot experiment with maize and grass in two different soils, silty loam (SL) and loamy sand (LS), was investigated. The fertilising effect of Bio-AS was compared to commercial ammonium sulphate fertilizer (Com-AS) and control treatment (without fertilisation). The crop yields were found to depend on both soil type and nitrogen treatment. Crop yields produced under Bio-AS and Com-AS exceeded those under control treatments, respectively for SL and LS soils, by 88% and 125% for maize and 73% and 94% for grass. Crop yields under Bio-AS were similar to those under the Com-AS treatment. The fertilizer use of Bio-AS affected the chemical composition of plants and soil properties similarly as Com-AS. This suggests that Bio-AS from a bio-refinery can replace industrial ammonium sulphate, resulting in both economic and environmental benefits.Energies 2019, 12, 4721 2 of 15 ammonia (NH 3 ), nitrous oxide (N 2 O), and hydrogen sulphide (H 2 S) to the atmosphere [8,9]. Due to intensification of animal production observed in EU agriculture, the European Commission regulated the use of organic fertilizers in the Nitrates Directive adopted on 12 December 1991. It aimed at water quality protection across Europe by prevention of pollution of the ground and surface waters with nitrates from agricultural sources and by promoting the use of good farming practices. One of the major restrictions was the limitation of the amount of nitrogen applied, taking into account the crop needs, all nitrogen inputs and soil nitrogen supply, as well as the maximum amount of livestock manure to be applied (corresponding to 170 kg nitrogen per hectare per year) [10]. The Dutch government negotiated special derogation allowing use of 250 kg·N·ha −1 in organic fertilizers under the condition of more efficient use of nitrogen from animal sources, which is included in the Dutch Manure Policy [11] and also encompasses regulations limiting the use of P from organic fertilizers. Many studies report considerable farm-gate N surplus for dairy farms per unit area, for example 138 kg N ha −1 year −1 in Sweden, 223 kg·N·ha −1 ·year −1 in the Netherlands, and 240 kg·N·ha −1 ·year −1 in Denmark [12]. So far, the dominant method of processing of animal waste has been anaerobic digestion. The process results in the production of biogas and digestate [13]. Biological conversion of organic compounds during anaerobic digestion considerably reduces the odour as compared to untreated manures [14][15][16]. Both the nitrogen and phosphorus content in the digestate are comparable with untreated manure; however, in contrast to livestock manures, the digestate is characterized by the presence of the nutrients in solub...

Environmental and Economic Sustainability of Swine Wastewater Treatments Using Ammonia Stripping and Anaerobic Digestion: A Short Review

“…In this regard, the literature complains unsatisfactory results, as more attention has been paid to the recovery technologies [51] than to the quality and agronomic effects of recovered nutrients. Szymanska et al [69] carried out an experiment in pots on maize and grass in silty loam and loamy sand soils. Compared to soil without fertilisation, these authors found crop yields under the recovered fertiliser (88% and 73% for maize and grass, respectively) that were similar as the yields under the commercial products (125% and 94%, respectively) regardless of the type of soil.…”

“…Moreover, this study showed that the nitrogen in the recovered ammonium sulphate is entirely under the mineral form (100% as NH 4 + -N), such as the synthetic nitrogen fertiliser. The absence of phosphorous in ammonium sulphate can be considered a positive aspect, because the nitrogen requirements of crops can be satisfied without exceeding the phosphorous application rates [51].The results obtained in the literature suggest that the ammonium sulphate recovered in bio-refinery can replace the industrial ammonium sulphate used as fertiliser in crop cultivation with evident economic and environmental benefits [51,69].…”

Duckweed from a Biorefinery System: Nutrient Recovery Efficiency and Forage Value

“…The farm-scale biorefinery was located at the Experimental Dairy Farm "De Marke" in Hengelo (Gld), the Netherlands. The scheme and description of the biorefinery and the physicochemical properties and the fertilizing value of the recovered products (struvite and ammonium sulphate) were presented in other authors' works [26][27][28][29].…”

Correlations between the Composition of Liquid Fraction of Full-Scale Digestates and Process Conditions

“…Currently, new technologies for processing liquid fractions of digestates are still being explored [17]. One of the possibilities is through nutrient recovery such as struvite (STR) precipitation [18] and ammonia stripping (to produce ammonium sulphate (AS)) [6,[19][20][21], combined ozone treatment and ultrafiltration [22], combined system with aerobic granular sludge batch reactors and ultrafiltration [23], or utilizing fly ash as a chemical precipitant [24].…”