I have aan MSc in Plant Physiology from the University of Oslo and a PhD in Agroecology from the University of Copenhagen. I have worked in the UK and US and joined NIBIO/Bioforsk in 2014.
- Carbon and nutrient cycling in the plant-soil system
- Simulation modelling
- Isotope studies
- Carbon sequestration in soil
- Decomposition processes, microbial and photodegradation
- Organic residues e.g. digestate (residue from biogas production), compost, fish sludge, urine
- Treatment of organic residues, e.g. composting, vermicomposting, nitrification
- Nutrient use efficiency of organic residues as fertilizers for plants
- Greenhouse gas emissions after application of organic residues to soil and during composting
Composting and anaerobic digestion are the most common ways to treat organic residues. Sometimes the organic rest after anaerobic digestion is also composted. In this study we investigated greenhouse gas emissions from composting raw food waste compared to composting solid digestate of food waste. Cumulative methane emissions over 3 weeks were found to be almost 12 times higher from composting digested food waste than from raw food waste suggesting that the microbial community transferred from the anaerobic digestion to the compost process enhanced these emissions. Cumulative nitrous oxide emissions were also higher when composting solid digestate was compared to composting raw food waste, but the global warming potential was mostly driven by the impact of methane emissions. In conclusion, methane production during digestate composting can be high, therefore eliminating methane producing microbes in digestate before composting could be a promising way to reduce greenhouse gas emissions.
Purpose Anaerobic digestion produces renewable energy, biogas, from organic residues, but also digestate, a valuable organic fertiliser. Previous studies have indicated that digestate contains ample plant available nitrogen (N), but there are also concerns about greenhouse gas (GHG) emissions after application of digestates to soil. The aim of this study was to compare digestate and undigested feedstock for fertiliser effect as well as greenhouse gas emissions during the next season. Methods Digestate and its feedstock, manure, were compared as N fertilisers for wheat. Mixing digestate with biochar before application was also tested. After harvest, soil samples were frozen and dried. Then GHG emissions immediately after a re-wetting of dry soil and after thawing of frozen soil were measured to determine emissions after a non-growing season (dry or cold). Results All N in digestate was plant available, while there was no significant N fertiliser effect of the undigested manure. N2O emissions were higher after a dry season than after freezing, but the undigested manure showed higher emissions during thawing than those detected during thawing of soils from any of the other treatments. Conclusion Anaerobic digestion makes N available to plants, and when residues with much N that is not plant available the first season are used, the risk of N2O emission next spring is high.
Report – Environmental Effects of Stratospheric Ozone Depletion, UV Radiation,and Interactions with Climate Change: Update 2020
P.W. Barnes, J.F. Bornman, K.K. Pandy, ...
No abstract has been registered
This assessment by the Environmental Effects Assessment Panel (EEAP) of the United Nations Environment Programme (UNEP) provides the latest scientific update since our most recent comprehensive assessment (Photochemical and Photobiological Sciences, 2019, 18, 595–828). The interactive effects between the stratospheric ozone layer, solar ultraviolet (UV) radiation, and climate change are presented within the framework of the Montreal Protocol and the United Nations Sustainable Development Goals. We address how these global environmental changes affect the atmosphere and air quality; human health; terrestrial and aquatic ecosystems; biogeochemical cycles; and materials used in outdoor construction, solar energy technologies, and fabrics. In many cases, there is a growing influence from changes in seasonality and extreme events due to climate change. Additionally, we assess the transmission and environmental effects of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is responsible for the COVID-19 pandemic, in the context of linkages with solar UV radiation and the Montreal Protocol.
Popular scientific article – Digestate - an undervalued resource turned problem? Experiences of a Norwegian researcher in India
No abstract has been registered
Purpose Biogas residues, digestates, contain valuable nutrients and are therefore suitable as agricultural fertilizers. However, the application of fertilizers, including digestates, can enhance greenhouse gas (GHG) emissions. In this study different processes and post-treatments of digestates were analyzed with respect to triggered GHG emissions in soil. Methods In an incubation experiment, GHG emissions from two contrasting soils (chernozem and sandy soil) were compared after the application of digestate products sampled from the process chain of a food waste biogas plant: raw substrate, digestate (with and without bentonite addition), digestates after separation of liquid and solid phase and composted solid digestate. In addition, the solid digestate was sampled at another plant. Results The plant, where the solid digestate originated from, and the soil type influenced nitrous oxide (N2O) emissions significantly over the 38-day experiment. Composting lowered N2O emissions after soil application, whereas bentonite addition did not have a significant effect. High peaks of N2O emissions were observed during the first days after application of acidified, liquid fraction of digestate. N2O emissions were strongly correlated to initial ammonium (NH4+) content. Conclusion Fertilization with dewatered digestate (both fractions) increased N2O emission, especially when applied to soils high in nutrients and organic matter.
Popular science – Threats to soil biodiversity - global and regional trends
George G. Brown, Miguel Cooper, Monica Kobayashi, ...
No abstract has been registered
Purpose Sorption could be a way to concentrate nutrients in diluted waste streams to bring more nutrients back to agriculture. The aim of this work was to model the fate of sorbed NH4+ content in liquid waste streams by adding nitrogen (N) sorbed to a sorbent, zeolite, and study its effect on early growth and potential leaching losses. Methods A pot experiment with two soil types and wheat as test crop was conducted. Mineral N in soil was measured, and a leaching experiment performed. 15N labelled ammonium was sorbed to zeolite. The fertilizer effect was then compared to ammonium fertilizer applied the conventional way, with and without zeolite. Results Early uptake of sorbed ammonium was reduced by 56% compared to ammonium applied conventionally, and soil uptake compensated only very early. Nitrate concentration in leachates was reduced by 12% in sandy soil when N was applied sorbed to zeolite. However, leaching of water through the profile increased 71% when N was applied sorbed to zeolite, so that there was only a tendency to lower N losses when N was applied sorbed to zeolite. Conclusion Ammonium-N sorbed to zeolite is less plant available than conventionally applied N but may also be less prone to leaching losses.
Sorption could be a way to concentrate nutrients in diluted waste streams to bring more nutrients back to agriculture. However, the sorbed nutrients must be plant available. The aim of this work was to investigate how plant available nitrogen (N) added sorbed to zeolite and is compared to conventionally added N. First, 15N labelled ammonium was sorbed to a sorbent, zeolite, in an aqueous solution. Then, the fertilizer effect was compared to the ammonium fertilizer and added the conventional way, with and without zeolite. A pot experiment with two soil types (chernozem and sandy soil) and wheat as test crop was used. Results indicated that the fertilizer effect of sorbed ammonium in the first growth cycle is about 50% of ammonium added conventionally. The sorbent itself had a positive effect in sandy soil, but not in chernozem. N uptake without added N was higher in chernozem than in sandy soil and more N from fertilizer was left in the soil after the experiment in the chernozem than in the sandy soil. In conclusion, ammonium added sorbed is plant available to some extent, but less so than conventionally added ammonium.
Biofertilizers, fertilizers made from organic residues, could replace some mineral fertilizers, reducing energy consumption and resource mining. The main treatment options are composting, anaerobic digestion, drying, pyrolysis and combustion, they can be used alone or in combination. The quality of biofertilizers depend both on the original residue and on the treatment, but in most cases not all the nutrients are immediately available to plants. It is difficult to predict how available the nutrients are, and when they will become available. The methods to assess and predict nutrient availability are reviewed. Furthermore, the effect of biofertilizers on the environment in the form of nutrient losses and greenhouse gas emissions are reviewed and compared to mineral fertilizers. There is a need to produce biofertilizers with better and more predictable qualities, and also to understand their effects over multiple seasons.
Purpose: Due to environmental concerns, efforts are made to replace the use of peat in horticultural growth media by organic wastes. Four growth media were prepared with the purpose of achieving adequate physical and chemical properties for plant production. Materials and methods: Growth media prepared from mixtures of coir (C) and paper sludge (P), respectively, with two biogas digestates from food waste (D1 and D2), were tested. These mixtures, 20% D1 or D2 + 80% C or P (v/v), were evaluated as growth media for tomato (Solanum lycopersicum L.) and lettuce (Lactuca sativa L.). Results and conclusion: The growth media were all physically stable during the growing period, provided all the macronutrients and most of the micronutrients necessary for plant growth, adequate pH conditions, as well as an adequate electrical conductivity. The mixture of D2 and P produced the highest biomass compared to a mineral fertilised peat (control), with a biomass production of 76% of the control for lettuce and 54% for tomato. Causes for the biomass reduction relative to the control may be related to ammonium toxicity effects, and/or limited plant-available water. The digestates, particularly D1, seemed also to have a phytotoxic effect on the germination.
In this work, experimental and modelling investigations were conducted on biochars pyrolyzed at 350 °C and 600 °C, to determine the effect of pyrolysis temperature, hydrogen peroxide activation and pH on copper and zinc removal, in comparison with commercially available activated carbons. Characterization of biochars was performed by BET surface area, elemental analysis and FTIR spectroscopy. Experiments results demonstrated that biochar pyrolyzed at 600 °C adsorbed both copper and zinc more efficiently than biochar pyrolyzed at 350 °C. Chemical activation by H2O2 increased the removal capacity of biochar pyrolyzed at 350 °C. All investigated biochars showed a stronger affinity for copper retention, with a maximum adsorption capacity of 15.7 mg/g while zinc was 10.4 mg/g. The best adsorption performances were obtained at pH 5 and 6. Langmuir adsorption isotherm described copper adsorption process satisfactorily, while zinc adsorption was better described by Freundlich isotherm.
Exposure to sunshine is known to play a role in litter decomposition in some semi-arid areas. The aim of this study was to find out if it also plays a role in higher latitude environments in peat litter decomposition and could contribute to an explanation to the patchy nature of peat litter decomposition. Peat litter from 5 microenvironments (top of slope, bottom of slope, ridge, ryam and hollow) and put out and exposed to the sun or shaded over a summer in Western Siberia, 26 km west of the town of Khanty-Mansiysk. Afterwards the peat litter was incubated in the laboratory - at field capacity or submerged in peat water - and CO2 and methane emission measured. Chemical composition of exposed and control peat litter was also investigated using stepwise extraction. The results indicate that exposure to sunlight does increase subsequent decomposition rate in most peat litters when incubated at field capacity, but the difference between the treatments levelled off at the end of the 2 weeks incubation in most peat litter types. The total extra carbon loss was calculated to be up to about 2 mg C m− 2 over a season. When incubated submerged previous photo-exposure had less effect on CO2 evolution then when incubated at field capacity. No methane emission was recorded in any treatment. Some differences in chemical composition between exposed and shaded peat litters were found that could help explain the differences in subsequent decomposition rate. The results indicate that photodegradation could play a role in peat litter decomposition at higher latitudes when peat is disturbed and exposed to sunshine. However, the effect of photo-exposure in these areas is much smaller than observed in semi-arid areas at lower latitudes.
Academic – Presence of black carbon in soil due to forest fire in the New Jersey pine barrens
Bente Føreid, J. Lehman, C. Wuster, ...
No abstract has been registered
Soil cores from a field growing barley and barley mutants without root hairs under conventional and minimum tillage were sampled. They were X-ray scanned to produce a 3D image and then the roots were washed out and weight and length were determined by conventional means. Root volume and surface area were then calculated from the 3D images using state of the art software and methodology, and the measured and calculated measures were correlated. The only strong and significant correlation was between measured weight and calculated volume for mutants without root hairs. It is concluded that the software cannot segment out very small roots, but segmentation accuracy also depends on root structure in some unknown way. Any study using X-ray computed tomography to quantify roots as they grow in situ should start with a calibration for the conditions in question.
UV effect on the carbon cycle – Global Environmental Effects Assessment Panel
The Environmental Effects Assessent Panel assesses the effects of the Montral protocol as well as UV effects on the carbon cycle.
Producing advanced bio-based fertilizers from fisheries wastes - SEA2LAND
The aim of SEA2LAND is to valorize waste/residues from fishereis and aquaculture as fertilisers and soil improvers. This is a European project with partners from Malta and other Meditranean countries in the south to Norway in the north as well as in Chile in South America. A large number of products will be developed and tested across Europe. The goal is to develop products ready for market. In Norway we will focus on fish sludge from aquaculture.
Greenhouse gas emissions from biogas digestate applications to rice production systems
Digestate, organic residues from biogas production, are good fertilizers. However, application of digestate can stimulate greenhouse gas production. Greenhouse gas emission from rice production is particularly problematic, because rice is grown flooded. This project, RICEDIG aims to find how digestate application affect greenhouse gas emissions in flooded rice production systems.
SiEUGreen: Sino-European innovative green and smart cities
Resource-efficient urban agriculture for multiple benefits – contribution to the EU-China Urbanisation Partnership