Agronomic efficiency of selected phosphorus fertilisers derived from secondary raw materials for European agriculture. A meta-analysis

Abstract

Phosphorus (P) is a macronutrient essential for all living organisms. Food production has become highly dependent on mineral Pfertilisers derived from phosphate rock, a non-renewable and finite resource. Based on supply risk and economic importance for the European Union, phosphate rock and elemental P have been identified as critical raw materials. Moreover, P dissipation can lead to adverse impacts on the aquatic environment. The production and use of P-fertilisers derived from secondary raw materials could possibly contribute to a more sustainable agriculture in line with a circular economy. Biogenic and industrial resources and waste streams can be converted into value added materials, such as precipitated phosphate salts, thermal oxidation materials and derivates, and pyrolysis and gasification materials. A condition is, however, that the P must be recovered in a plant-available form and that the recovered P-fertiliser supports plant growth and nutrient uptake in European agroecosystems. Here, we review the agronomic efficiency of selected P-fertilisers derived from secondary raw materials by comparing plant responses relative to those after mined and synthetic P-fertiliser application in settings relevant for European agriculture, using meta-analyses. The major points are the following: (1) precipitated phosphate salts show similar agronomic efficiency to mined and synthetic Pfertilisers, with results that are consistent and generalisable across soil and crop types relevant for European agriculture; (2) thermal oxidation materials and derivates can deliver an effective alternative for mined and synthetic P-fertilisers, but the relative agronomic efficiency is dependent on the feedstock applied, possible post-combustion manufacturing processes, and the length of the plant growing season; (3) the agronomic efficiency of pyrolysis and gasification materials remains indeterminate due to a lack of available data for European settings. It is concluded that the agronomic efficiency of selected P-fertilisers derived from secondary raw materials supports their use in conventional and organic European agricultural sectors.

Options for Improved Phosphorus Cycling and Use in Agriculture at the Field and Regional Scales

“…Recovered products may also be economically and/or energetically expensive to produce or have low bioavailability to crops, making their use undesirable compared with soluble fertilizers made from mined phosphate rock (Egle et al, 2016; Mayer et al, 2016; Roy, 2017). However, the many benefits of P recovery from waste streams, including reduced environmental impairment, improved function of wastewater treatment plants, and the social benefit of local P fertilizer sources, make P recovery and reuse as fertilizer worthy of investigation (Cordell et al, 2011; Mayer et al, 2016; Roy, 2017; Huygens and Saveyn, 2018). While most currently available P recovery technologies are not economically viable, the business case for P recovery from wastes can be improved by taking into account environmental and social benefits, as well as through co‐recovery of valuable products such as organic matter, other nutrients, metals such as gold and silver, and even water (Mayer et al, 2016).…”

“…Struvite is generally considered a slow‐release fertilizer due to its low solubility in water and relatively slow dissolution in soil (Bridger et al, 1962; Cabeza et al, 2011; Achat et al, 2014; Talboys et al, 2016). The value of struvite as a crop fertilizer has been investigated in many recent studies (Gell et al, 2011; Katanda et al, 2016; Degryse et al, 2017; Katanda et al, 2019) and summarized in several thorough reviews (Liu et al, 2013; Rahman et al, 2014; Kataki et al, 2016; Ahmed et al, 2018; Möller et al, 2018; Peng et al, 2018) and one meta‐analysis (Huygens and Saveyn, 2018). …”

“…Studies comparing P uptake of struvite‐fertilized crops identified buckwheat ( Fagopyrum esculentum Moench; Talboys et al, 2016), red clover (Wollmann et al, 2018), soybean (Rech et al, 2019), and canola (Katanda et al, 2016) as crops with higher struvite‐P mobilization capabilities relative to other crops. Several authors indicated that root exudation of carboxylates by crops such as buckwheat, Brassica spp., and many grasses may enhance dissolution of struvite (Katanda et al, 2016; Talboys et al, 2016; Huygens and Saveyn, 2018), although results from a pot study assessing solubility of three different struvites indicated no change in P solubilized due to addition of synthetic low molecular weight organic acids instead of water (Rech et al, 2019). In a pot study, narrow‐leaf lupine ( L. angustifolius L. subsp.…”

“…Among recovered P products, struvite recovery through precipitation and crystallization from wastewater and sewage sludge shows promise as a cost-effective technique yielding a relatively pure product (Ronteltap et al, 2007;Schürmann et al, 2012;Lou et al, 2018) with greater value as a fertilizer than many other recovered P products (Cabeza et al, 2011;Vogel et al, 2017b;Huygens and Saveyn, 2018;Wollmann et al, 2018). Further, Weissengruber et al (2018) concluded that potentially toxic element and persistent organic pollutant accumulations would be low to negligible even after 200 yr of struvite application (at 11 kg P ha -1 yr -1 ).…”

“…Finally, we examine the link between PUE and the emerging movement toward a circular economy, as P recovery from human and animal waste streams is viewed as essential for achieving greater PUE (Withers et al, 2015). Phosphorus recycling and recovery at the regional scale are discussed generally, but we have focused in particular on struvite (magnesium ammonium phosphate hexahydrate, NH 4 MgPO 4 ·6H 2 O) because its use as a recycled P fertilizer to help balance regional and global P cycles is gaining momentum in a variety of agricultural settings and production systems, as it avoids some of the issues that biosolids and municipal solid waste compost carry in terms of contaminants and/or low P composition (Egle et al, 2016; Huygens and Saveyn, 2018; Möller et al, 2018; Peng et al, 2018) and it is not constrained by the logistics of longer distance transport associated with manure (Withers et al, 2015). We acknowledge that the majority of literature found and cited in this review is from temperate agricultural systems, and while the concepts behind PUE are expected to be similar in tropical agriculture, the details of the actions to address PUE may differ.…”