Adam O.Toole

Forsker

(+47) 920 19 805
adam.otoole@nibio.no

Sted
Steinkjer

Besøksadresse
Statens Hus, Strandvegen 38, 7734 Steinkjer

Sammendrag

Norway is strongly committed to the Paris Climate Agreement with an ambitious goal of 40% reduction in greenhouse gas emission by 2030. The land sector, including agriculture and forestry, must critically contribute to this national target. Beyond emission reduction, the land sector has the unique capacity to actively removing CO2 from the atmosphere through biological carbon storage in biomass and in soils. Soils are the largest reservoir of terrestrial carbon, and relatively small changes in soil carbon content can have an amplified mitigation effect on the Earth’s climate. Therefore, improved management of soils for carbon storage is receiving a lot of attention, for example through international political initiatives such as the “4-permill” initiative. However, in Norway, many mitigation measures targeting soil carbon might negatively impact food production and economic activity. For example, soil carbon storage can be increased by shifting from cereal crop production to grasslands, but Norway already has abundant grassland and a comparatively small area dedicated to cereals. Another such issue is cultivation on drained peatland, where food is produced at the expense of large losses of soil carbon as CO2 to the atmosphere. Therefore, there is a need to look for win-win solutions for soil carbon storage, which benefit both food production and climate mitigation. Large-scale conversion of agricultural and forest waste biomass to biochar is such an option, and is considered the activity with the largest potential for soil carbon sequestration in Norway. Biochar has been demonstrated to have a mean residence time exceeding 100 years in Norwegian field conditions (Rasse et al, 2017), and no negative effects on plant and soils has been observed. However, despite the convincing benefits of biochar as a climate mitigation solution, it has not yet advanced much beyond the research stage, notably because its effect on yield are too modest. Here, we will first present the comparative advantage of biochar technology as compared to traditional agronomy methods for large-scale C storage in Norwegian agricultural soils. We will further discuss the need for developing innovations in pyrolysis and nutrient-rich waste recycling leading to biochar-fertilizer products as win-win solution for carbon storage and food production.

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Sammendrag

The application of biochar to soils is a promising technique for increasing soil organic C and offsetting GHG emissions. However, large-scale adoption by farmers will likely require the proof of its utility to improve plant growth and soil quality. In this context, we conducted a four-year field experiment between October 2010 to October 2014 on a fertile silty clay loam Albeluvisol in Norway to assess the impact of biochar on soil physical properties, soil microbial biomass, and oat and barley yield. The following treatments were included: Control (soil), miscanthus biochar 8 t C ha1 (BC8), miscanthus straw feedstock 8 t C ha1 (MC8), and miscanthus biochar 25 t C ha1 (BC25). Average volumetric water content at field capacity was significantly higher in BC25 when compared to the control due to changes in BD and total porosity. The biochar amendment had no effect on soil aggregate (2–6 mm) stability, pore size distribution, penetration resistance, soil microbial biomass C and N, and basal respiration. Biochar did not alter crop yields of oat and barley during the four growing seasons. In order to realize biochar’s climate mitigation potential, we suggest future research and development efforts should focus on improving the agronomic utility of biochar in engineered fertilizer and soil amendment products.

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Sammendrag

Evaluating biochars for their persistence in soil under field conditions is an important step towards their implementation for carbon sequestration. Current evaluations might be biased because the vast majority of studies are short-term laboratory incubations of biochars produced in laboratory-scale pyrolyzers. Here our objective was to investigate the stability of a biochar produced with a medium-scale pyrolyzer, first through laboratory characterization and stability tests and then through field experiment. We also aimed at relating properties of this medium-scale biochar to that of a laboratory-made biochar with the same feedstock. Biochars were made of Miscanthus biomass for isotopic C-tracing purposes and produced at temperatures between 600 and 700°C. The aromaticity and degree of condensation of aromatic rings of the medium-scale biochar was high, as was its resistance to chemical oxidation. In a 90-day laboratory incubation, cumulative mineralization was 0.1% for the medium-scale biochar vs. 45% for the Miscanthus feedstock, pointing to the absence of labile C pool in the biochar. These stability results were very close to those obtained for biochar produced at laboratory-scale, suggesting that upscaling from laboratory to medium-scale pyrolyzers had little effect on biochar stability. In the field, the medium-scale biochar applied at up to 25 t C ha-1 decomposed at an estimated 0.8% per year. In conclusion, our biochar scored high on stability indices in the laboratory and displayed a mean residence time > 100 years in the field, which is the threshold for permanent removal in C sequestration projects.

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Sammendrag

Biokull er ett av klimatiltakene med høyest potensiale for å kunne forbedre karbonregnskapet til den norske landbrukssektoren (Klif, 2010). Det er for tiden stor interesse for biokull i Norge innenfor privat sektor, frivillige organisasjoner, universiteter og forskningsinstitutter. Adopsjon av biokull som et karbonlagringstiltak er delvis avhengig av dets agronomiske egenskaper og den totale sikkerheten biokull utgjør for miljøet. I 2011, startet det 3 biokull forsøk i Ås, Sel, og Notodden for å undersøke effekten av biokull på feltet under norske forhold. Første års resultater fra 3 felt viste ingen signifikant effekt av biokull på plantevekst og jordkjemiske forhold. Økotoksikologiske lab-studier visste ingen negative effekter av biokull på meitemark, som var brukt som en indikator for jordhelse. Biokull ført til høyere vannlagringskapasitet i siltig sandjord, men ikke på lettleire. Isotopiske studier fant mindre enn 3 % nedbrytning av biokull-C i feltet i det første året, som representerer minst 20 ganger saktere nedbrytning av C enn upyrolysert halm. Konklusjon fra første året var at biokull kan brukes som et tiltak for å øke karbon i jordsmonnet uten at det går utover matproduksjon.

Sammendrag

Biokull ble undersøkt i 2 feltforsøk i Norge i 2011 for å se på karbonlagring og jordforbedrings- potensial. Første års resultater viser at biokull var svært stabil i forhold til vanlig biomasse og hadde ingen negative effekt på avling eller jordkvalitet. Derfor kan vi ikke se noen konflikt ved å kombinere økt karbonlagring og matproduksjon. Flere års erfaring på felt trengs for å gi en mer sikker vurdering.

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Sammendrag

Termisk behandling av biomasse for produksjon av biodrivstoff og biokull antas å være en strategi med stort potensial som klimatiltak. Det er stort behov for kunnskap om kostnader ved slik produksjon og mulighet til utnyttelse av biokull og pyrolyseolje med tanke på størst mulig klimaeffekt. Denne rapporten er finansiert av Klima og forurensingsdirektoratet (Klif) og gir en oppdatering av kunnskapsstatus om lovende termiske prosesser som produserer 2.generasjons biodrivstoff.

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Sammendrag

Biochar soil amendment is advocated to mitigate climate change and improve soil fertility. A concern though, is that during biochar preparation PAHs and dioxins are likely formed. These contaminants can possibly be present in the biochar matrix and even bioavailable to exposed organisms. Here we quantify total and bioavailable PAHs and dioxins in a suite of over 50 biochars produced via slow pyrolysis between 250 and 900 °C, using various methods and biomass from tropical, boreal, and temperate areas. These slow pyrolysis biochars, which can be produced locally on farms with minimum resources, are also compared to biochar produced using the industrial methods of fast pyrolysis and gasification. Total concentrations were measured with a Soxhlet extraction and bioavailable concentrations were measured with polyoxymethylene passive samplers. Total PAH concentrations ranged from 0.07 μg g–1 to 3.27 μg g–1 for the slow pyrolysis biochars and were dependent on biomass source, pyrolysis temperature, and time. With increasing pyrolysis time and temperature, PAH concentrations generally decreased. These total concentrations were below existing environmental quality standards for concentrations of PAHs in soils. Total PAH concentrations in the fast pyrolysis and gasification biochar were 0.3 μg g–1 and 45 μg g–1, respectively, with maximum levels exceeding some quality standards. Concentrations of bioavailable PAHs in slow pyrolysis biochars ranged from 0.17 ng L–1 to 10.0 ng L–1which is lower than concentrations reported for relatively clean urban sediments. The gasification produced biochar sample had the highest bioavailable concentration (162 ± 71 ng L–1). Total dioxin concentrations were low (up to 92 pg g–1) and bioavailable concentrations were below the analytical limit of detection. No clear pattern of how strongly PAHs were bound to different biochars was found based on the biochars’ physicochemical properties.