Abstract

At the Norwegian Institute of Bioeconomy Research (NIBIO, formerly Bioforsk), biochar has been a topic of research since 2009 through both laboratory and field studies. Initial results demonstrated that biochar produced from clean biomass is safe to use on agricultural soils, and that pyrolysis temperatures of ≥370 °C are necessary for producing biochar that is resistant to decomposition on a timescale of 100 years. Further work identified the chemical transformations that are responsible for biochar stability and contributed to finding the best indicator of this stability. Throughout the years, we have had close collaboration with industry and farmers in Norway, where now industrial networks are in action and there is financial support for the implementation of biochar technology. Despite the convincing benefits of biochar as a climate mitigation solution, it has only slowly advanced beyond the research stage, notably because its effect on yield are too modest. There is therefore a need for win-win biochar solutions benefiting both food production and climate mitigation. Such a solution is the development of biochar fertilizers, which capitalizes on the capacity of biochar to capture and release nutrients. As biochar properties largely depend on pyrolysis conditions and feedstock properties, our current work contributes to the selective design of biochars for the purpose of improving nutrient use efficiency.

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Abstract

The aim of this work was to investigate whether the agronomic traits of vermicompost prepared from partially stabilised sewage sludge digestate after thermophilic composting were more favourable than those of conventional compost. The effects of various additives (green waste, spent mushroom compost, wheat straw, biochar) were also tested after 1.5 months precomposting followed by 3 months vermicomposting with Eisenia fetida or by compost maturing. Vermicomposting did not result in significantly more intensive mineralisation than composting; the average organic carbon contents were 21.2 and 22.2% in vermicomposts and composts, respectively. Hence, the average total (N: 2.4%; P: 1.9%; K: 0.9%) and available (N: 160 mg/kg; P: 161 mg/kg; K: 0.8%) macronutrient concentrations were the same in both treatments. The processing method did not influence the organic matter quality (E4/E6) either. However, on average the concentration of the plant growth regulator kinetin was more than twice as high in vermicomposts.

Abstract

We investigated dissipation, earthworm and plant accumulation of organic contaminants in soil amended with three types of sewage sludge in the presence and absence of plants. After 3 months, soil, plants and earthworms were analyzed for their content of organic contaminants. The results showed that the presence of plant roots did not affect dissipation rates, except for galaxolide. Transfer of galaxolide and triclosan to earthworms was significant, with transfer factors of 10–60 for galaxolide and 140–620 for triclosan in the presence of plants. In the absence of plants, transfer factors were 2–9 times higher. The reduced transfer to worms in the presence of plants was most likely due to roots serving as an alternative food source. Nonylphenol monoethoxylate rapidly dissipated in soil, but initial exposure resulted in uptake in worms, which was detected even 3 months after sewage sludge application. These values were higher than the soil concentration at the start of the exposure period. This indicates that a chemical's short half-life in soil is no guarantee that it poses a minimal environmental risk, as even short-term exposure may cause bioaccumulation and risks for chronic or even transgenerational effects.

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Abstract

Green roofs are used increasingly to alleviate peaks of water discharge into the sewage systems in urban areas. Surface runoff from roofs contain pollutants from dry and wet deposition, and green roofs offer a possibility to reduce the amounts of pollutants in the water discharged from roofs by degradation and filtering. These pollutants would otherwise enter wastewater treatments plants and ultimately end up in sewage sludge that is spread on agricultural soils. The most common substrates used in green roofs have limited capacity for filtration and sorption. Also, more sustainable alternatives are sought, due to the high carbon footprint of these materials. Biochar is a carbon-rich material produced by pyrolysis of biomass, and several types of biochar have been described as good sorbents and filter materials. Biochar is also a light and carbon negative material, which may fulfill other desired criteria for new green roof substrates. We here report on an experiment where two types of biochar, produced from olive husks at 450 °C or from forest waste at 850 ° C were mixed with volcanic rock or peat, and tested for retention capacity of phenanthrene and six heavy metals in a column experiment with unsaturated gravimetric water flow lasting for 3 weeks. The results suggest that biochar as a component in green roof substrates perform better than traditional materials, concerning retention of the tested pollutants, and that different types of biochar have different properties in this respect.

Abstract

Matching high performing varieties of legumes with effective symbiotic N-fixing bacteria can potentially enhance production volumes and economic returns when cultivating grain legumes. We investigated whether field inoculation with local or introduced Rhizobia to six different varieties of faba bean improved growth, nitrogen (N) fixation and protein content in a field experiment in Southern Norway. In 2016, a full factorial experiment featuring three inoculation treatments (a mixture of four morphotypes of Rhizobia isolated from locally grown faba bean, a mix of two efficient and well documented Rhizobium strains from Latvia, and a non-inoculated control treatment) and six faba bean (Vicia faba) genotypes (Agua Dulce, Bauska, Jõgeva, Gloria, Julia, Lielplatones) was set up in an experimental field with sandy loam soil with no recent legume culture history (>10 years). At late flowering/early pod formation stage we quantified N fixation of the crop using the N-15 natural abundance method, using weeds from the same plots as reference plants. We also assessed morphological and phenological characters, seed yields and protein levels at plant maturity. Clear differences were observed, and detailed results from this study will be presented at the conference (analyses are still pending). This research is a part of the EU FP7 project Eurolegume.

Abstract

Sewage sludge is an important amendment that enriches soils with organic matter and provides plants with nutrients such asnitrogenandphosphorus.However,knowledgeonthe fateandeffectsof organic pollutants presentin the sludge on soilorganisms is limited.In the present study, the uptake of triclosan, galaxolide, and tonalide in the earthworm Dendrobaena veneta was measured 1 wk afteramendment of agricultural soil with sewage sludge, while elimination kinetics were assessed over a 21-d period after transferring worms toclean soil. After 1-wk exposure, earthworms had accumulated 2.6  0.6 mgg1galaxolide, 0.04  0.02 mgg1tonalide, and0.6  0.2 mgg1triclosan. Both synthetic musks were efficiently excreted and below the limit of quantification after 3 and 14 d ofdepuration for tonalide and galaxolide, respectively. Triclosan concentrations, on the other hand, did not decrease significantly over thedepuration period, which may lead to the transfer of triclosan in the food web.