Adam O´Toole

Forsker

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

Sted
Steinkjer

Besøksadresse
Innocamp Steinkjer, Skolegata 22, Bygg P 1. etasje, 7713 Steinkjer

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Sammendrag

Background Biochar-based fertilizer products (BCF) have been reported to increase both crop yield and N-use efficiency. Such positive effects are often assumed to result from the slow-release of N adsorbed on BCF structures. However, a careful review of the literature suggests that actual mechanisms remain uncertain, which hampers the development of efficient BCF products. Scope Here, we aim at reviewing BCF mechanisms responsible for enhanced N uptake by plants, and evaluate the potential for further improvement. We review the capacity of biochar structures to adsorb and release N forms, the biochar properties supporting this effect, and the methods that have been proposed to enhance this effect. Conclusions Current biochar products show insufficient sorption capacity for the retention of N forms to support the production of slow-release BCFs of high enough N concentration. Substantial slow-release effects appear to require conventional coating technology. Sorption capacity can be improved through activation and additives, but currently not to the extent needed for concentrated BCFs. Positive effects of commercial BCFs containing small amount of biochar appear to result from pyrolysis-derived biostimulants. Our review highlights three prospects for improving N retention: 1) sorption of NH3 gas on specifically activated biochar, 2) synergies between biochar and clay porosities, which might provide economical sorption enhancement, and 3) physical loading of solid N forms within biochar. Beyond proof of concept, quantitative nutrient studies are needed to ascertain that potential future BCFs deliver expected effects on both slow-release and N use efficiency.

Sammendrag

Biochar-based fertilizer products (BCF) are receiving increasing attention as potential win-win solutions for mitigating climate change and improving agricultural production. BCFs are reported to increase yields through increased N use efficiency, an effect which is often assumed to result from the slow-release of adsorbed N forms into the soil. Here, we review the magnitude of this effect, the potential for further improvement and the need to consider other mechanisms in product development. Current high-N commercial BCFs are mostly physical blends of biochar and mineral fertilizer, with little evidence of slow-release effects supported by sorption mechanisms. For such products, the main effect potentially results from root-growth promoting factors and from increases in soil pH and Eh and stimulation of beneficial micro-organisms in the rhizosphere, which all result in an increase in uptake of specific nutrients. Our reanalysis of literature data indicates that the median sorption capacity of untreated biochar for mineral N forms requires applying 200 times more biochar than N fertilizer. This ratio needs reducing by at least an order of magnitude for producing efficient sorption-based BCFs. Activation of biochar with acids and oxidizing agents, as reported in many studies, appears to only marginally increase sorption capacity in absolute values. Fixation of clay and organics within the porous structure of biochar appears a more promising technology, suggesting that macro- and mesoporosity is a key biochar property that deserves greater scrutiny and research towards making efficient sorption-based BCFs. Mechanisms of action and dose responses need to be more systematically studied in order to devise products that combine positive effects and can be used within realistic agronomic management practices. Long-term effects resulting from accumulated annual inputs of BCF also need to be better evaluated in terms of nutrient cycling and the progressive improvement of soil health.

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Limiting temperature rise below 2 °C requires large deployment of Negative Emission Technologies (NET) to capture and store atmospheric CO2. Compared to other types of NETs, biochar has emerged as a mature option to store carbon in soils while providing several co-benefits and limited trade-offs. Existing life-cycle assessment studies of biochar systems mostly focus on climate impacts from greenhouse gasses (GHGs), while other forcing agents, effects on soil emissions, other impact categories, and the implications of a large-scale national deployment are rarely jointly considered. Here, we consider all these aspects and quantify the environmental impacts of application to agricultural soils of biochar from forest residues available in Norway considering different scenarios (including mixing of biochar with synthetic fertilizers and bio-oil sequestration for long-term storage). All the biochar scenarios deliver negative emissions under a life-cycle perspective, ranging from -1.72 ± 0.45 tonnes CO2-eq. ha−1 yr−1 to -7.18 ± 0.67 tonnes CO2-eq. ha−1 yr−1 (when bio-oil is sequestered). Estimated negative emissions are robust to multiple climate metrics and a large range of uncertainties tested with a Monte-Carlo analysis. Co-benefits exist with crop yields, stratospheric ozone depletion and marine eutrophication, but potential trade-offs occur with tropospheric ozone formation, fine particulate formation, terrestrial acidification and ecotoxicity. At a national level, biochar has the potential to offset between 13% and 40% of the GHG emissions from the Norwegian agricultural sector. Overall, our study shows the importance of integrating emissions from the supply chain with those from agricultural soils to estimate mitigation potentials of biochar in specific regional contexts.

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Fra 2017 til 2019, utførte partnere i dette prosjektet en rekke forsøk i ulike produksjonssystemer (Kyr, Gris, Kalkun, Mink, og sau) for å teste påstanden at behandling av husdyrgjødsel med kommersielle bio-preperater (bestående av Effektiv Microrganismer (EM) og melasse) kan fører til konsevering av nitrogen via redusert tap av ammoniak. Forsøkene fulgte doseringsråd og fremgangsmåte anbefalte EM-produkt leverandør for behandling av ulike fjøsopsett og husdyrgjødseltyper (f.eks. blaut, talle, strø). Målinger i de ulike forsøk inkludert kjemisk analyse av gjødsel, ammoniakk (NH3) i fjøsluftet, dyrehelsevurderinger, subjektiv luktvurdering utført av bønder, og testing av effekt av behandlet husdyrgjødsel på grassavling og gjødselhåndtering. Tilbakemeldinger fra deltagerende bønder og NLR var at EM-behandlet husdyrgjødsel hadde bedre konsistens og var lettere å spre enn ubehandlet gjødsel. De opplevde også mindre sterkt lukt fra gjødsela enn de var vant til. I motsetning til det som var forventet hadde ikke bio-preperater noen effekt på verken nitrogeninnhold i gjødselen, grassavling, eller infiltrasjonstid for spredt husdyrgjødsel. Ammoniakknivået i fjøsluft var lavere i EM-behandlet kalkunfjøs enn i ubehandlet fjøs, men datavariabiliteten var for høy for å gi et sikkert svar på dette. En gjennomgang av publisert forskning på dette fagområdet bekrefter lite NH3-reduserende effekt fra tilsetning av EM preperater (alene) til blautgjødsel. Dette er fordi blautgjødsel allerede har en rik og mangfoldig bakteriesammensetning hvor tilsatte bakterier har liten evne til å etablere seg. Men flere publisert forsøk viste at lacto-fermentering og bio-forsuring av husdyrgjødsel var mulig å oppnå hvis man tilsatte en tilstrekkelig mengde av enten glucose eller stivelse til husdyrgjødsel, som deretter stimulerte melkesyre-produserende bakterier som allerede er tilstede i gjødselen, og fører til en selv-forsuring og N-konsevering av husdyrgjødsel. For videreføring av denne metoden i Norge, anbefaler vi flere vitenskapelig forsøk og praktisk testing med tilsetning av sukker/stivelse i form av restråstoff fra primærnæringene eller matindustrien (f.eks. kornavrens, melasse, usalgbar frukt og grønt, o.a.) som et tiltak for bio-forsuring av husdyrgjødsel under lagring. Hvis bonden må betale for sukker til bioforsuring kan metoden bli for dyr å gjennomføre.

Sammendrag

Rapporten gir en oversikt over klimatiltak for landbruket i Trondheim, både for jord- og skogbruk. Vi ser på potensialet for utslippsreduksjoner, muligheter for karbonlagring, klimarisiko og klimatilpasning. Verdiskapingspotensiale av tiltak er inkludert. Rapporten gir også oversikt over hvordan landbruksrelaterte utslipp fanges opp i Norges klimagassregnskap under FNs klimakonvensjon, internasjonale avtaler og klimamål. Det vises til utvidet sammendrag.

Sammendrag

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.

Sammendrag

En økning i karbonlagring i landbruksjord er angitt som et viktig klimatiltak både internasjonalt og i Norge. Tiltaket er godt begrunnet: Jorden inneholder to til tre ganger så mye karbon som atmosfæren, noe som innebærer at relative små endringer i innhold av karbon i jord kan ha betydelige effekter på CO2-innholdet i atmosfæren og det globale klimaet. Det er godt dokumentert at intensive jordbruksmetoder har ført til en reduksjon i jordkarbon og derfor ønskes det en reversering av denne trenden (dvs. økt karbonbinding i jord), som tiltak både for klima og matproduksjon. I denne rapporten er det gjort vurderinger av hvordan dette kan gjøres i Norge og hvilken klimaeffekt som kan oppnås...

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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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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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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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.