Abstract
Struvite recovered from waste streams is considered as a sustainable alternative to commercial phosphate (P) fertilizers manufactured from P rock. In this study, struvite was recovered from swine wastewater and pre-treated as air-dried material (AM), microwave irradiated material (MM), oven-dried material (OM), and incinerated material (IM) to reduce the moisture content. Based on their solubility and crystalline nature, AM and IM were selected for further experiments. The nutrient leaching loss and fertilizing value of AM and IM were evaluated in comparison to commercial fused superphosphate (FSP) fertilizer. Soil columns were used to quantify ortho-phosphate (O-P) and ammonium nitrogen (NH4-N) leaching in soil from the test materials. Among the test materials, the average leaching rate of O-P for FSP and AM was significantly different from the control and IM (p < 0.05). The average leaching rate of NH4-N among the test materials did not show any significant difference (p > 0.05). Sudan grass growth was examined with standard (urea supplemented) and high (20x, without urea) application of test materials in pot and soil box trials, respectively, to study the fertilizing value AM and IM. There were no significant differences among the test materials, except for the control, in terms of growth rate and fresh and dry matter yield in the pot trials (p > 0.05). When AM, IM, and FSP were applied in increasing amounts (20x) without urea supplement, Sudan grass growth was 50% lower in IM and was found to be significantly different from AM and FSP (p < 0.05). The results suggest that struvite pre-treated as AM could be an effective sustainable and eco-friendly alternative to commercial P fertilizers and thus helps to ensure agricultural sustainability.
Highlights
Phosphorus (P) is one of the essential elements required for growth and cellular function of all life forms and is obtained primarily from rock phosphate
Previous studies reported that very pure forms of struvite can be recovered from swine wastewater at pH 8.0 to 9.0 and an Mg:P molar ratio of 0.8:1 to 1.2:1 [22,30,31]
All the ingredients in the struvite recovered from animal wastewater originated from the animal feedstock containing low heavy metal and the recovered struvite needs lesser efforts to purify for target use such as fertilizer and in chemical industries [21]
Summary
Phosphorus (P) is one of the essential elements required for growth and cellular function of all life forms and is obtained primarily from rock phosphate. The phosphate rock reserves are nonrenewable and estimated to be 70,000 million tons as P2O5 [1]. 40 million tons of phosphate rock has been used for fertilizer, feed additive, and detergent production [2]. The consumption of P is increasing by 1.5% per year and with the present consumption rate, the P reserves are expected to diminish within the 90–300 years [2,3,4]. Due to non-substitutability and high economic importance, the European Commission (EC) has included phosphate rock to the list of 20 critical raw materials [5,6]. An alternative, sustainable, and renewable source of P is needed to meet the demands of agriculture and livestock
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