Pierre-Adrien Rivier
Research Scientist
(+47) 920 10 480
pierre-adrien.rivier@nibio.no
Place
Ås H7
Visiting address
Høgskoleveien 7, 1433 Ås
Authors
Paloma Sánchez-Argüello Gema Sáez-Salto Alice Budai Pierre-Adrien Rivier Simon Weldon Antonio Martín-EstebanAbstract
Compost application is a widely recommended practice to maintain and improve soil fertility. However, such a practice could be a main entry path for plastic into soil. Accordingly, in the present work, two different compost samples, obtained with and without biochar, were analyzed to investigate how composting can affect the presence of microplastics (MPs). The substrate of both samples (consisting of a mixture of household food waste and animal manure) was also analyzed for comparative purposes. Samples were processed by oxidation, flotation, and filtration. MPs on the filters were observed, counted, and size-calibrated using both a stereomicroscope and an inverted microscope. MPs larger than 1 mm were further characterized by attenuated total reflectance Fourier-transformed infrared spectroscopy (ATR-FTIR). In parallel, mesoplastics (0.5–2 cm) were recovered from substrate and compost and extracted in methanol for testing in vitro cytotoxicity. The estimated concentration of MPs ranged from 820 to 1340 fragments/kg of dry sample, depending upon the sample. Three polymers represented the totality of identified plastic items: polyethylene (PE, including both low and high density), polyethylene terephthalate (PET), and polypropylene (PP) in order of abundance. Nevertheless, cytotoxicity was only observed in mesoplastic extracts from the substrate and could not be attributed to the identified plastic items themselves, suggesting that cytotoxic effects could have been caused by contaminants adsorbed to plastics or by the leaching of plastic additives during the extraction process. In summary, the composting process reduced the cytotoxicity of plastic extracts and the presence of MPs in compost, which could be attributed to the fragmentation of plastics.
Abstract
Denne rapporten presenterer resultater fra forsøk med åtte ikke-kalkbehandlete og fire kalkbehandlete kjemisk felte norske avløpsslam, samt biokull fremstilt av avløpsslam. Formålet med forsøkene var 1) å undersøke fosforeffekten av kalkbehandlet avløpsslam, og 2) å videreutvikle NIBIOs kalkulator for beregning av plantetilgjengelig fosfor i organiske gjødselvarer til å inkludere en valgmulighet for kalkbehandlet avløpsslam. Kjemisk fraksjonering viste at fosfor i ikke-kalkbehandlet slam hovedsakelig var bundet til aluminium- og jern(hydr)oksider. Kalkbehandling og pyrolyse dannet kalsiumfosfatforbindelser med ulik løselighet. I et veksthusforsøk med bygg (Hordeum vulgare) ble alle slambehandlinger tilført tilsvarende 9 kg fosfor per dekar. Likevel ga seks av åtte ikke-kalkbehandlete slamprodukter ikke signifikant høyere fosforopptak enn kontrollen uten fosfor. Kalkbehandlet slam ga signifikant høyere fosforopptak enn ikke-kalkbehandlet slam, mens biokull ikke økte fosforopptaket i bygg sammenlignet med kontrollen. Opptakseffektiviteten til fosfor i bygg avtok med økende tilførsel av mineralfosfor. Dette viser at praksisen med å tilføre ≥25 kg fosfor per dekar med avløpsslam i tilførselsåret gir lite effektiv utnyttelse av slam som fosforressurs. Den avtagende responsen gjorde det ikke mulig å beregne nøyaktige mineralgjødselekvivalenter for alle behandlinger, og det var derfor heller ikke mulig å utvikle en predikeringsmodell for kalkbehandlet slam. Det foreslås mindre justeringer av den eksisterende modellen som ligger bak NIBIOs kalkulator for beregning av plantetilgjengelig fosfor i kjemisk felt avløpsslam (https://pkalkulator.nibio.no).
Authors
Thiago Inagaki Junbin Zhao Claire Douheret Pierre-Adrien Rivier Jihong Liu Clarke Nicholas ClarkeAbstract
Earthworms enhance compost mineralization, improving its fertilizer value and soil quality (biological activity, structure). However, they often increase greenhouse gas (GHG) emissions, particularly nitrous oxide (N₂O), via nitrogen mineralization. Combining biochar with compost may mitigate these emissions while further boosting soil benefits alongside earthworm activity. We present preliminary results from a soil incubation (2 months) experiment testing this synergy. Using a Norwegian loam Cambisol, a 2x2x2 factorial design (four replicates) assessed the presence/absence of earthworms (Lumbricus terrestris - 10 adults/jar), compost (manure/food waste - 60 Mg ha⁻¹ equivalent), and rice-straw biochar (700°C pyrolyzed - 20 Mg ha⁻¹ equivalent). We hypothesized that earthworm and compost addition may present synergistic effects in improving N mineralization with consequent enhanced GHG emissions. We expect that biochar may counteract these emissions and potentially present positive effects for soil quality. The goal was to develop a biochar-compost-earthworm system creating a fertilizer with higher nutrient availability and lower GHG emissions. In the first week of the incubation, we found that higher CO2 and N2O productions were associated with the presence of compost. Earthworms could further enhance the carbon decomposition but appeared to mitigate CH4 production. Further analysis will be carried out with a focus on GHG emissions (CO₂, CH₄, N₂O) and nitrogen mineralization dynamics.
