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Microplastics in liquid biofertilizers: An overlooked threat to agricultural soil?

Bertoldi, Crislaine LU orcid ; Zanke, Michael ; Pucetaite, Milda LU ; Hansson, Maria C LU orcid ; Troein, Carl LU orcid and van Praagh, Martijn LU (2026) In Environmental Pollution 398.
Abstract

This study investigated the presence of microplastics (MPs, >5 μm to <2 mm) in biofertilizers and estimated their mass input to Swedish agricultural soils. Collective samples from representative biogas facilities were analyzed using optical microscopy and optical photothermal infrared (O-PTIR) spectroscopy, with selected MPs examined by scanning electron microscopy (SEM). The highest MPs concentration detected was 888 items g -1. Preliminary observation indicates that MPs abundance was moderately correlated with the proportion of food waste used as biogas feedstock. Mass concentrations reached up to 6.19 ± 0.56 mg MPs kg -1 (dw) biofertilizer. Estimated inputs to agricultural soils ranged from 0.4 ± 0.06 to... (More)

This study investigated the presence of microplastics (MPs, >5 μm to <2 mm) in biofertilizers and estimated their mass input to Swedish agricultural soils. Collective samples from representative biogas facilities were analyzed using optical microscopy and optical photothermal infrared (O-PTIR) spectroscopy, with selected MPs examined by scanning electron microscopy (SEM). The highest MPs concentration detected was 888 items g -1. Preliminary observation indicates that MPs abundance was moderately correlated with the proportion of food waste used as biogas feedstock. Mass concentrations reached up to 6.19 ± 0.56 mg MPs kg -1 (dw) biofertilizer. Estimated inputs to agricultural soils ranged from 0.4 ± 0.06 to 2.0 ± 0.31 g MPs ha -1 yr -1, corresponding to a total annual input of 114 ± 17 to 377 ± 126 kg of plastics to Swedish soils via biofertilizer application. The total predicted environmental concentration (PEC total) after 50 years was estimated at 0.11 mg kg -1 soil for mineral-amended soils and 1.52 mg kg -1 for sewage sludge-amended soils, indicating that MPs from biofertilizer represent only a minor fraction of total soil MPs contamination. Fragments dominated the MPs composition (98%), with most particles in the 5-50 μm size range. Polymer identification was achieved for 71% of particles, with paint-derived materials being most abundant (23%). Compared with other biosolids such as sewage sludge, biofertilizers represent a minor but measurable pathway for MPs inputs to agricultural soils. Nevertheless, the dominance of small-sized particles and long-term accumulation highlights the need to consider possible adverse effects of repeated biofertilizer application on soil ecosystems.

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author
; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
epub
subject
in
Environmental Pollution
volume
398
article number
128078
publisher
Elsevier
external identifiers
  • pmid:41974409
ISSN
0269-7491
DOI
10.1016/j.envpol.2026.128078
language
English
LU publication?
yes
additional info
Copyright © 2026. Published by Elsevier Ltd.
id
72cacaa1-4b6c-4ac8-b673-09164ae852d4
date added to LUP
2026-04-16 14:34:21
date last changed
2026-04-18 03:28:07
@article{72cacaa1-4b6c-4ac8-b673-09164ae852d4,
  abstract     = {{<p>This study investigated the presence of microplastics (MPs, &gt;5 μm to &lt;2 mm) in biofertilizers and estimated their mass input to Swedish agricultural soils. Collective samples from representative biogas facilities were analyzed using optical microscopy and optical photothermal infrared (O-PTIR) spectroscopy, with selected MPs examined by scanning electron microscopy (SEM). The highest MPs concentration detected was 888 items g  <sup>-1</sup>. Preliminary observation indicates that MPs abundance was moderately correlated with the proportion of food waste used as biogas feedstock. Mass concentrations reached up to 6.19 ± 0.56 mg MPs kg <sup>-1</sup> (dw) biofertilizer. Estimated inputs to agricultural soils ranged from 0.4 ± 0.06 to 2.0 ± 0.31 g MPs ha  <sup>-1</sup> yr <sup>-1</sup>, corresponding to a total annual input of 114 ± 17 to 377 ± 126 kg of plastics to Swedish soils via biofertilizer application. The total predicted environmental concentration (PEC  total) after 50 years was estimated at 0.11 mg kg <sup>-1</sup> soil for mineral-amended soils and 1.52 mg kg <sup>-1</sup> for sewage sludge-amended soils, indicating that MPs from biofertilizer represent only a minor fraction of total soil MPs contamination. Fragments dominated the MPs composition (98%), with most particles in the 5-50 μm size range. Polymer identification was achieved for 71% of particles, with paint-derived materials being most abundant (23%). Compared with other biosolids such as sewage sludge, biofertilizers represent a minor but measurable pathway for MPs inputs to agricultural soils. Nevertheless, the dominance of small-sized particles and long-term accumulation highlights the need to consider possible adverse effects of repeated biofertilizer application on soil ecosystems. </p>}},
  author       = {{Bertoldi, Crislaine and Zanke, Michael and Pucetaite, Milda and Hansson, Maria C and Troein, Carl and van Praagh, Martijn}},
  issn         = {{0269-7491}},
  language     = {{eng}},
  month        = {{04}},
  publisher    = {{Elsevier}},
  series       = {{Environmental Pollution}},
  title        = {{Microplastics in liquid biofertilizers: An overlooked threat to agricultural soil?}},
  url          = {{http://dx.doi.org/10.1016/j.envpol.2026.128078}},
  doi          = {{10.1016/j.envpol.2026.128078}},
  volume       = {{398}},
  year         = {{2026}},
}