Detection of simulated leaks from geologically stored CO2 With 13C monitoring

Precise methods for the detection of geologically stored CO2within and above soil surfaces are an impor-tant component of the development of carbon capture and storage (CCS) under terrestrial environments.Although CO2leaks are not expected in well-chosen and operated storage sites, monitoring is required bylegislation and any leakage needs to be quantified under the EU Emissions Trading Directive. The objec-tive of the present research was to test if13C stable isotope motoring of soil and canopy atmosphere CO2increases our detection sensitivity for CCS-CO2as compared with concentration monitoring only. A CO2injection experiment was designed to create a horizontal CO2gradient across 6 m × 3 m plots, which weresown with oats in 2011 and 2012. Injected CO2was methane derived and had an isotopic signature of−46.2‰. The CO2concentrations were measured within the soil profile with passive samplers and at sev-eral heights within the crop canopies. The CO2fluxes and their13C signatures were also measured acrossthe experimental plots. In situ monitoring and gas samples measurements were conducted with a cavityring down spectrometer (CRDS). The plots displayed hot spots of injected-CO2leakage clearly detectableby either concentration or isotopic signature measurements. In addition, the13C signature measurementsallow us to detect injected CO2in plot regions where its presence could not be unequivocally ascertainedbased on concentration measurement alone.acceptedVersio

Characterization, Stability, and Plant Effects of Kiln-Produced Wheat Straw Biochar

Biochar is a promising technology for improving soil quality and sequestering C in the long term. Although modern pyrolysis technologies are being developed, kiln technologies often remain the most accessible method for biochar production. The objective of the present study was to assess biochar characteristics, stability in soil, and agronomic effects of a kiln-produced biochar. Wheat-straw biochar was produced in a double-barrel kiln and analyzed by solid-state 13C nuclear magneticresonance spectroscopy. Two experiments were conducted with biochar mixed into an Ap-horizon sandy loam. In the first experiment, CO2 efflux was monitored for 3 mo in plant-free soil columns across four treatments (0, 10, 50, and 100 Mg biochar ha−1). In the second experiment, ryegrass was grown in pots having received 17 and 54 Mg biochar ha−1 combined with four N rates from 144 to 288 kg N ha−1. Our kiln method generated a wheat-straw biochar with carbon content composed of 92% of aromatic structures. Our results suggest that the biochar lost <0.16% C as CO2 over the 90-d incubation period. Biomass yields were not significantly modified by biochar treatments, except for a slight decrease at the 144 kg N ha−1 rate. Foliar N concentrations were significantly reduced by biochar application. Biochar significantly increased soil water content; however, this increase did not result in increased biomass yield. In conclusion, our kiln-produced biochar was highly aromatic and appeared quite recalcitrant in soil but had no overall significant impact on ryegrass yields.acceptedVersio

Climate change mitigation potential of biochar from forestry residues under boreal condition

Forest harvest residue is a low-competitive biomass feedstock that is usually left to decay on site after forestry operations. Its removal and pyrolytic conversion to biochar is seen as an opportunity to reduce terrestrial CO2 emissions and mitigate climate change. The mitigation effect of biochar is, however, ultimately dependent on the availability of the biomass feedstock, thus CO2 removal of biochar needs to be assessed in relation to the capacity to supply biochar systems with biomass feedstocks over prolonged time scales, relevant for climate mitigation. In the present study we used an assembly of empirical models to forecast the effects of harvest residue removal on soil C storage and the technical capacity of biochar to mitigate national-scale emissions over the century, using Norway as a case study for boreal conditions. We estimate the mitigation potential to vary between 0.41 and 0.78 Tg CO2 equivalents yr−1, of which 79% could be attributed to increased soil C stock, and 21% to the coproduction of bioenergy. These values correspond to 9–17% of the emissions of the Norwegian agricultural sector and to 0.8–1.5% of the total national emission. This illustrates that deployment of biochar from forest harvest residues in countries with a large forestry sector, relative to economy and population size, is likely to have a relatively small contribution to national emission reduction targets but may have a large effect on agricultural emission and commitments. Strategies for biochar deployment need to consider that biochar's mitigation effect is limited by the feedstock supply which needs to be critically assessed.acceptedVersio

Norske gårdbrukeres vurderinger av biokull og andre klimatiltak

Formålet med denne rapporten har vært å undersøke gårdbrukeres holdninger til ulike klimatiltak, og særlig biokull. Vi gjennomførte en elektronisk spørreundersøkelse i 2021 med 896 respondenter. Det var mest sannsynlig at gårdbrukerne ville gjennomføre klimatiltaket drenering, etterfulgt av bedre utnytelse av mineralgjødsel og bruk av fangvekster. For klimatiltak som bare er aktuelle for husdyrprodusenter, var friskere dyr det mest sannsynlige tiltaket de ville gjennomføre, etterfulgt av bedre utnyttelse av husdyrgjødsel og bedre grovfôrkvalitet. Bekymring for globale klimagassutslipp, kjennskap til klimaavtalen, ingen eller lav stillingsprosent utenfor gårdsbruket og lav alder økte sannsynligheten for å gjennomføre tiltak. De aller fleste gårdbrukerne var svært enige i at det er viktig at klimatiltak i landbruket ikke slår beina under andre goder som kulturlandskap, biologisk mangfold og levende bygder og at klimatiltak i landbruket ikke må redusere norsk matproduksjon. De aller fleste var uenige i at landbruket må redusere klimagassutslippene sine ved å ha færre drøvtyggere. Litt over halvparten av gårdbrukerne var interesserte i å bruke biokull i gårdsdrifta dersom de agronomiske fordelene er større enn kostnadene. Den viktigste faktoren som kan bidra til at gårdbrukerne vurderer å bruke biokull er at prisen på biokull blir så lav at de agronomiske fordelene blir større enn de økonomiske ulempene, etterfulgt av at det innføres tilskuddsordninger, at de får betalt for å binde karbon i jorda og at de får økt kunnskap om ulike bruksmåter og agronomiske effekter.Norske gårdbrukeres vurderinger av biokull og andre klimatiltakpublishedVersio

Soil organic matter molecular composition and state of decomposition in three locations of the European Arctic

Increased mineralization of the organic matter (OM) stored in permafrost is expected to constitute the largest additional global warming potential from terrestrial ecosystems exposed to a warmer climate. Chemical composition of permafrost OM is thought to be a key factor controlling the sensitivity of decomposition to warming. Our objective was to characterise OM from permafrost soils of the European Arctic: two mineral soils—Adventdalen, Svalbard, Norway and Vorkuta, northwest Russia— and a ‘‘palsa’’ (ice-cored peat mound patterning in heterogeneous permafrost landscapes) soil in Neiden, northern Norway, in terms of molecular composition and state of decomposition. At all sites, the OM stored in the permafrost was at an advanced stage of decomposition, although somewhat less so in the palsa peat. By comparing permafrost and active layers, we found no consistent effect of depth or permafrost on soil organic matter (SOM) chemistry across sites. The permafrost-affected palsa peat displayed better preservation of plant material in the deeper layer, as indicated by increasing contribution of lignin carbon to total carbon with depth, associated to decreasing acid (Ac) to aldehyde (Al) ratio of the syringyl (S) and vanillyl (V) units, and increasing S/V and contribution of plant-derived sugars. By contrast, in Adventdalen, the Ac/Al ratio of lignin and the Alkyl C to O-alkyl C ratio in the NMR spectra increased with depth, which suggests less oxidized SOM in the active layer compared to the permafrost layer. In Vorkuta, SOM characteristics in the permafrost profile did not change substantially with depth, probably due to mixing of soil layers by cryoturbation. The composition and state of decomposition of SOM appeared to be site-specific, in particular bound to the prevailing organic or mineral nature of soil when attempting to predict the SOM proneness to degradation. The occurrence of processes such as palsa formation in organic soils and cryoturbation should be considered when up-scaling and predicting the responses of OM to climate change in arctic soils.acceptedVersio

Production and characterization of spruce wood and bark biochar

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Kunnskapsstatus for utslipp og binding av karbon i jordbruksjord

I denne rapporten er det gitt en litteraturoversikt over hovedprinsippene for binding og tap av karbon fra dyrket jord og de viktigste faktorene som styrer karboninnholdet i jord. På grunnlag av kartlegging utført av Norsk institutt for skog og landskap er det gjort en beregning av karboninnhold og karbonmengder i dyrket jord i Norge fordelt på hovedgrupper av mineraljord og organisk jord. Endringer av karboninnhold i jord i Skandinavia er diskutert på grunnlag av forsøk og praktisk drift. Muligheter og potensial for binding av karbon i Norge er gjort på grunnlag norsk og utenlandsk forskning samt beregninger av status for nåværende karboninnhold.publishedVersio

A re-analysis of NH4+ sorption on biochar: Have expectations been too high?

Sorption of nutrients such as NH4+ is often quoted as a critical property of biochar, explaining its value as a soil amendment and a filter material. However, published values for NH4+ sorption to biochar vary by more than 3 orders of magnitude, without consensus as to the source of this variability. This lack of understanding greatly limits our ability to use quantitative sorption measurements towards product design. Here, our objective was to conduct a quantitative analysis of the sources of variability, and infer which biochar traits are more favourable to high sorption capacity. To do so, we conducted a standardized remodelling exercise of published batch sorption studies using Langmuir sorption isotherm. We excluded studies presenting datasets that either could not be reconciled with the standard Langmuir sorption isotherm or generated clear outliers. Our analysis indicates that the magnitude of sorption capacity of unmodified biochar for NH4+ is lower than previously reported, with a median of 4.2 mg NH4+ g−1 and a maximum reported sorption capacity of 22.8 mg NH4+ g−1. Activation resulted in a significant relative improvement in sorption capacity, but absolute improvements remain modest, with a maximum reported sorption of 27.56 mg NH4+ g−1 for an activated biochar. Methodology appeared to substantially impact sorption estimates, especially practices such as pH control of batch sorption solution and ash removal. Our results highlight some significant challenges in the quantification of NH4+ sorption by biochar and our curated data set provides a potentially valuable scale against which future estimates can be assessed.publishedVersio

Modelling short-term CO2 fluxes and long-term tree growth in temperate forests with ASPECTS

peer reviewedThe net ecosystem exchange (NEE) Of CO2 between temperate forests and the atmosphere governs both carbon removal from the atmosphere and forest growth. In recent years, many experiments have been conducted to determine temperate forest NEE. These data have been used by forest modellers to better understand the processes that govern CO, fluxes, and estimate the evolution of these fluxes under changing environmental conditions. Nevertheless, it is not clear whether models capable of handling short-term processes, which are mostly source-driven, can provide an accurate estimate of long-term forest growth, which is potentially more influenced by sink- and phenology-related processes. To analyse the interactions between short- and long-term processes, we developed the ASPECTS model, which predicts long-term forest growth by integrating, over time, hourly NEE estimates. Validation data consisting of measurements of NEE by eddy-covariance and forest carbon reservoir estimates were obtained from mixed deciduous and evergreen experimental forests located in Belgium. ASPECTS accurately estimated both: (1) the NEE fluxes for several years of data; and (2) the amount of carbon contained in stems, branches, leaves, fine and coarse roots. Our simulations demonstrated that: (1) NEE measurements in Belgian forests are compatible with forest growth over the course of the 20th century, and (2) that forest history and long-term processes need to be considered for accurate simulation of short-term CO2 fluxes