Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2026
Authors
Trine Eggen Carl Einar Amundsen Robert Barneveld Aksel Bernhoft Barbara Alexandra Bukhvalova Gunnar Sundstøl Eriksen Belinda Flem Christiane Kruse Fæste Tron Øystein Gifstad Merete Grung Veronika Sele Kaja Helvik Skjærven Øystein Sæle Stefan Trapp Christian Vogelsang Håvard SteinshamnAbstract
This report presents a risk assessment of organic contaminants in sewage sludge and sewage-sludge-based products used on agricultural land in Norway, under current and alternative fertiliser regulations and management practices. It identifies a limited number of substances of concern for soil health, aquatic organisms, animal health, and human health, and provides a scientific basis for evaluating circular economy, organic fertilisers, and the safe recycling of bioresources in agriculture. Background and purpose The Norwegian fertiliser regulations was revised in 2025 to support reduced pollution, better utilisation of nutrients, fulfilment of international obligations, simplification, and facilitation of nutrient recycling. In Norway, 50 to 60 per cent of sewage sludge is used on agricultural land, compared with around 40 per cent in the EU. Norway has many small wastewater treatment plants and a long tradition of using treated sludge in agriculture. At the same time, incineration is less common in Norway than in many other European countries, partly because Norwegian wastewater treatment largely relies on chemical phosphorus precipitation (chemical separation of phosphorus). In recent years, new products based on sewage sludge have been developed, such as pellets, biochar and struvite (a fertiliser product recovered from wastewater that makes it possible to recycle phosphorus and nitrogen for agricultural use). At the same time, knowledge about organic contaminants in sewage sludge has increased. On this basis, the Norwegian Food Safety Authority asked VKM to assess the risks associated with organic contaminants in sewage sludge and sludge-based products. Terms of reference and scope VKM was tasked with identifying organic contaminants in sewage sludge and assessing which substances were relevant to include in the risk assessment. The assignment also covered products made from sludge, such as biochar, ash and struvite. Risks were to be assessed for the use of sludge on agricultural land over a period of up to 100 years. If current practice could lead to undesirable effects, alternative application rates and uses were also to be evaluated. In addition, less stringent rules for use in the cultivation of vegetables and on grassland used for mowing and grazing were to be assessed. The assessment covered possible effects on soil-dwelling organisms, aquatic organisms, livestock and humans. Combined effects of multiple substances were not assessed in detail. Methods and scenarios The risk assessment was based on data for more than 1,000 organic contaminants measured in Norwegian sewage sludge. For some pharmaceuticals that had not been analysed, levels were estimated using consumption data and modelling. Substances were prioritised based on occurrence, properties, degradation, mobility and toxicity. A model was developed to calculate how organic contaminants may accumulate and spread in soil, water and plants over time. The calculations were used to assess exposure for soil- and water-dwelling organisms, livestock and humans. The model accounted for climate and soil conditions in five regions in Norway. A wide range of scenarios for the use of sewage sludge and sludge-based products in the cultivation of cereals, potatoes, vegetables and grass were assessed. These included current practice, reduced application rates, use every ten years and annually, different intervals between application and cultivation or grazing, and the use of pellets, biochar, struvite and liquid digestate from sewage sludge. The effects of thermal hydrolysis were also assessed. Summary of main findings Norwegian monitoring data show that municipal sewage sludge contains many different organic contaminants, but levels vary widely between treatment plants and regions. The levels of several legacy pollutants, such as PCBs, PAHs and PBDEs, have decreased over time but are still present in sludge and remain relevant because they degrade slowly and can accumulate in the environment. PFAS are regularly detected, particularly PFOS and other long-chain PFAS. Pharmaceuticals and newer industrial chemicals often occur at low levels but with large variation. Several substances found at the highest concentrations are linked to cosmetics and personal care products. The different sludge-based products have different risk profiles. Pellets are expected to pose roughly the same or slightly lower risk than dewatered sludge. Struvite contains very low levels of organic contaminants and was consistently associated with low risk. Biochar is distinctive in that pyrolysis reduces many organic contaminants, but there is still uncertainty related to the possible formation of new compounds and how residues may be bound or released over time. For soil-dwelling organisms, the assessment showed that current practice may pose a long term risk for some substances. After quality assessment of the data, 19 organic substances showed potential risk, including certain pharmaceuticals, cosmetic-related substances, plastic related compounds, PAHs and PFOS. Lower application rates reduced risk but did not eliminate it. For some persistent substances, annual application could result in a higher cumulative load than application every ten years. For aquatic organisms, under current practice one substance exceeded the risk threshold, the pharmaceutical fenbendazole, but the assessment is uncertain. In scenarios with less stringent conditions or alternative uses, several substances were considered capable of posing a risk to the aquatic environment. For livestock, the calculations generally showed low levels of individual substances in feed rations. Risk was highest for grazing animals, as soil ingestion is an important exposure pathway, and with the use of liquid digestate from sewage sludge, direct intake may also contribute. Delayed grazing after application of products was found to reduce exposure. At the same time, some substances, particularly bisphenols and certain pharmaceuticals, are highlighted as relevant to animal health, and combined effects cannot be ruled out. For humans, current use of sewage sludge is generally assessed to pose relatively low risk to food safety for most of the substances examined. At the same time, an increase in organic contaminants in agricultural soil is undesirable. The report highlights PFAS, PCBs, dioxins, PAHs, PBDEs, siloxanes, bisphenol A, octocrylene and several pharmaceuticals as important for food safety, because dietary exposure to some of these substances is already considered undesirable or of concern. For individuals with high consumption of locally caught freshwater fish, exposure is generally assumed to be limited, but for some individuals it may be relevant. Main conclusion Norwegian data show that sewage sludge contains many organic contaminants, but levels vary widely. Most substances appear to pose low risk to soil-dwelling and aquatic organisms, and low health risk to livestock and humans. Some persistent substances may give rise to concern over time. Struvite was consistently associated with low risk, while pellets, biochar, sewage sludge and liquid digestate from sewage sludge have more complex risk profiles. For humans and livestock, risk is generally low under current practice, but certain groups of substances are undesirable because the overall burden is already high or of concern. The report concludes that some substances should be prioritised for further investigation and follow-up. In summary: VKM concludes that most organic contaminants in sewage sludge pose low risk, but that some organic contaminants may give rise to concern over time. This particularly applies to persistent substances that can accumulate in soil. The report therefore highlights the need for further investigation through the collection of more data and knowledge to support future risk assessments.
Authors
Daniel Moreno-Fernández Patricia Adame Johannes Breidenbach Isabel Cañellas Christoph Fischer Kari T. Korhonen Jan Máslo Nerea Oliveira John Redmond Thomas Riedel Mitja Skudnik Iciar AlberdiAbstract
Forest diversity is a multidimensional concept comprising different components such as species diversity, functional diversity, structural diversity and genetic diversity. These diverse elements are recognised as being connected to the health and functioning of forest ecosystems and human well-being. However, information on forest diversity at broad spatial scales is scarce. Thus, the primary goal of this study is to quantify compositional diversity (i.e., tree species heterogeneity) and structural diversity (i.e., tree size heterogeneity) across a wide climatic gradient in European forest ecosystems, while also examining the influence of forest attributes and climatic variables on these two key components of forest diversity. Using harmonised data from eight European National Forest Inventories (n = 146,235 plots), we calculated Shannon’s Diversity Index as a measure of compositional and structural diversity. Finally, we estimated measures of forest diversity at three spatial scales ( α , β and γ -diversity) for each country. Basal area was positively related to compositional and structural diversity. In contrast, the quadratic mean diameter of the trees in each plot presented both positive and negative relationships with compositional and structural diversity, respectively. Climatic variables played a minor role, with precipitation and temperature showing a positive association with forest compositional and structural diversity. Furthermore, our findings revealed a positive link between compositional and structural diversity. Finally, the compound analyses of α , β , and γ-diversity emerged as key elements in interpreting compositional patterns at landscape scale. Results revealed strong scale dependence (from local to landscape level) in diversity metrics across countries, thereby highlighting the importance of reporting national forest information at multiple spatial scales.
Abstract
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Abstract
Landfilling remains a widely used and economically viable waste disposal method, particularly in regions with limited access to advanced treatment technologies. However, once these sites reach capacity and are closed, their long-term environmental management becomes a critical concern for municipalities and stakeholders. This study explores post-closure landfill management strategies by examining three closed landfill cases in Norway. A literature review was conducted to establish a baseline understanding of current practices and gaps. Despite previous research on landfill gas utilization and waste-to-energy technologies, there is a lack of empirical, site-specific studies addressing the long-term aftercare and post-closure management of closed landfills in European contexts. Therefore, this study addresses this gap by providing a case-based assessment of closed landfill management practices in Norway. Findings were synthesized using a SWOT (Strengths, Weaknesses, Opportunities, Threats) analytical framework to assess both internal and external influencing factors. The results highlight key strengths, including existing gas monitoring systems and recycling efforts, as well as critical weaknesses, such as infrastructure instability and limited historical assessment data. Opportunities are found in areas such as methane mitigation, circular economy integration, and land reuse planning, while threats include financial constraints and long-term maintenance concerns. Drawing on these insights, the study emphasizes the importance of developing integrated aftercare strategies that incorporate environmental monitoring, risk assessments, and cost-benefit analyses tailored to site-specific conditions. These insights are valuable for stakeholders, including municipalities, policymakers, landfill owners, national authorities, industries, and waste management companies, in shaping future initiatives for repurposing landfills.
Abstract
Plant genotypes can vary in multiple functional traits due to adaptation to heterogenous environments. However, whether such variation can extrapolate to effects on soils and further on performance of subsequent plants, thus generating a genotypic variation in soil legacy, remains unclear. In this study, we studied how plant genotypic variation impacts soil legacy when exposed to aboveground insect herbivores. We used 11 wild genotypes of woodland strawberry (Fragaria vesca L.) experimentally exposed to leaf beetles (Galerucella tenella) to condition live soil. We then replaced the conditioning plants with naïve plants to examine soil legacy effects on growth and resistance on the subsequent plant genotype (referred to as the focal genotype) against the generalist herbivore Spodoptera littoralis. This allowed us to test the extent to which plant genotypic variation in soil legacy is altered by aboveground herbivory. We found an overall positive soil legacy effect of woodland strawberry, indicated by 69.9% higher belowground biomass of the subsequent focal genotype grown in conditioned soil compared to in unconditioned soil. We also observed a genotype-dependent soil legacy effect on performance of S. littoralis indicated as relative growth rates reduced by 37.9% on the subsequent focal genotype in soil conditioned by the focal genotype itself compared to by other genotypes, though the legacy effect was cancelled out when conditioning genotypes were exposed to G. tenella herbivory. A genotypic variation was further detected in soil legacy on the efficiency of conversion of ingested food by S. littoralis caterpillars feeding on the focal genotype. However, the genotypic variation was only present when the focal genotype was excluded from the conditioning genotypes at the exposure of G. tenella herbivory. Collectively, our study shows a conditional plant genotype-dependent soil legacy effect on herbivore resistance (measured as herbivore performance) rather than on plant growth, and the magnitude of the legacy effects depends on both the identity of the conditioning genotypes and the measures of the herbivore resistance. The findings of this study provide new insights into how plant genotypes or herbivory affects soil feedback on plant growth and herbivore resistance.
Abstract
Abstract Defence priming enhances plant responsiveness to future stress following prior exposure, and has been extensively characterised in annual model species as a reversible state associated with faster or stronger defence activation. However, studies in long-lived plants indicate that priming responses can be elicitor-specific, developmentally variable and closely linked to environmental history. In trees, priming is often strongest in early life stages, while in mature individuals defence responses are more frequently associated with direct activation and stabilised regulatory states. Evidence across systems shows that priming can operate over multiple timescales, from short-term reversible responses to longer-lasting effects that influence response thresholds and activation kinetics. Epigenetic mechanisms, including DNA methylation and chromatin modification, contribute to these processes and may persist across cell divisions or developmental transitions. Together, these findings highlight the importance of developmental stage and temporal context in shaping plant defence responses.
Authors
Theresa Weigl Jorunn Børve Melissa Magerøy Hanne Larsen Carl Gunnar Fossdal Siv Fagertun RembergAbstract
The physiological disorder soft scald may cause losses in apple fruit storage. This study aimed at understanding the interplay between fruit maturity at harvest and storage temperature on soft scald development in the susceptible cultivar ‘Red Aroma’. Fruit harvested late and subsequently stored at −0.5 °C developed the significantly highest soft scald incidence. Overall ethylene and CO2-production was reduced in late harvested fruit stored at −0.5 °C, while fruit from the early harvest showed a cold-induced ethylene increase under the same storage conditions, suggesting an active cold-acclimation response. Clustering of RNA sequencing data and overrepresentation analysis revealed that transcripts involved in cell wall modification, ripening-associated signaling, antioxidant defense system and secondary metabolism were upregulated in late harvested fruit at harvest as well as soft scald-affected fruit after storage. In contrast, early harvested fruit at harvest and disorder-free fruit after storage showed higher expression of transcripts associated with abiotic stress resistance, such as leucine-rich repeat receptor-like kinases, protein kinases with tetratricopeptide repeat domains, and auxin response factor, indicating a potential link between early maturity and enhanced cold tolerance in ‘Red Aroma’ apple fruit.
Authors
Kathrin Yvonne Weber Erlend Grenager Sørmo Gerard Cornelissen Alice Budai Daniel Rasse Harald Bier Troy RobichaudAbstract
Biochar has emerged as a promising carbon dioxide removal (CDR) solution that combines long-term carbon storage with benefits for soil health, waste management, and industrial applications. This report provides a comprehensive assessment of the current state of biochar across feedstocks, production technologies, material properties, and end-use pathways, with a particular focus on its role in climate mitigation. Drawing on scientific literature and international case studies, the report evaluates the carbon sequestration potential, environmental performance, and technological maturity of biochar systems. It distinguishes between applications that deliver durable carbon removal and those that primarily contribute to emission reductions. The report further examines deployment barriers, including feedstock availability, regulatory frameworks, market development, and safety considerations, and reviews the status of biochar implementation across Mission Innovation countries. Based on these insights, it outlines key opportunities and recommendations to support the responsible scale-up of biochar as a climate solution.
Abstract
The experiment aimed to investigate the effectiveness of a Monil virtual fence collar for small ruminants on mature Norwegian White ewes at the NIBIO Tjøtta station. The study aimed to evaluate the animals' learning ability and welfare, compare two auditory cues (Original vs. Modified; collar treatment), and examine the effects of wool (Shaved vs. Unshaved) on the efficacy of the virtual fence system. A total of 16 ewes were randomly assigned to two groups of 8, each equipped with one of the collars, and further divided based on wool treatment. Two mirrored training arenas were set up for the two groups. For two days, the collared animals had unrestricted access to graze the entire arena (VF-Off). This was followed by two days of restricted access to 2/3 of the arena using the virtual fence collars (VF-On). After the fourth day, the animals were switched to the other arena as a crossover design, and the sequence of VF-Off and VF-On was repeated. Data collected included position and cue logs from the virtual fence collars, heart rate monitors, and observation data gathered through three methods: Video Surveillance, Direct Observation Time Budget, and Pressure Marks Assessment. Our results indicate that the ewes were able to learn to avoid restricted zones effectively, relying more on auditory cues than on electrical cues. The virtual fence cueing imposed short-lived stress (acute stress), with both behavioral and physiological metrics returning to baseline levels within five minutes. Additionally, exclusively auditory cues resulted in less stress compared to cues associated with electrical stimulation. No indicators of chronic behavioral stress were observed. However, we found that the collars needed to move freely on the animals' necks to prevent pressure marks, suggesting that the ewes should be shaved around their necks before wearing the collars. While collar treatment showed no significant effects, wool treatment indicated that the shaved group was more compliant with the virtual fence system due to reduced insulation, which enhanced the effectiveness of electrical cues. During the deployment with the unshaved group, there were three instances in which the animals received an electrical cue that did not elicit the animal response, allowing for their “escape” over the virtual fence boundary. Therefore, equipping the virtual fence on shaved animals is paramount for enhancing the system's reliability. If the suggestion is followed, the system can effectively be used for sheep without compromising animal welfare.