1. |
- Azzi, Elias, et al.
(författare)
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Modelling biochar long-term carbon storage in soil with harmonized analysis of decomposition data
- 2024
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Ingår i: Geoderma. - 0016-7061 .- 1872-6259. ; 441
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Tidskriftsartikel (refereegranskat)abstract
- The climate change mitigation benefits of biochar systems arise largely from carbon storage in biochar. However, while biochar is increasingly recognized as a carbon dioxide removal technology, there are on-going scientific discussions on how to estimate the persistence of biochar carbon when biochar is used in soils. Estimates vary from decades to millennia, building on different modelling approaches and evidence. Here, we revisited the persistence estimates derived from extrapolation of biochar incubation experiments, with the aims of making incubation data available, modelling choices transparent, and results reproducible. An extensive dataset of biochar incubations, including 129 biochar decomposition time series, was compiled and is made available alongside code for its analysis. Biochar persistence correlations were sensitive to data selection procedures and to the curve fitting modelling step, while soil temperature adjustments methods had less impact. Biochar H/C ratio remained the main predictor of biochar persistence, in line with previous research, regardless of the extrapolation assumptions (multi-pool exponential functions or power function) used in curve fitting. The relation between H/C and percentage of biochar carbon remaining after 100 years (BC100) was better explained by a power model than a linear model, with R2 values between 0.5 and 0.9. Using multi-pool exponential functions, estimated BC100 varied between 90 % and 60 % for H/C from 0 to 0.7. However, using power functions, BC100 was constrained between 90 % and 80 % for the same H/C range. Additional information about the biochar, the pyrolysis conditions or the environmental incubation conditions did not significantly increase explained variance. Notably, the dataset lacks observations at H/C ratios below 0.2, of biochar made from manure and biosolids, biochar from processes other than slow pyrolysis, field studies, and incubation temperatures below 10 °C, which should guide future experimental work. The detailed analysis performed in this study does not cast doubts on the longevity of biochar carbon storage; rather, it confirms previous knowledge by critically examining the modelling, elucidating the assumptions and limitations, and making the analysis fully reproducible. There is a need for further interdisciplinary work on integration of various theories and approaches to biochar persistence, ultimately leading to the formulation of policy-relevant conclusions.
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2. |
- Irunde, Regina, et al.
(författare)
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The natural magnesite efficacy on arsenic extraction from water and alkaline influence on metal release in water
- 2023
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Ingår i: Applied Geochemistry. - : Elsevier BV. - 0883-2927 .- 1872-9134. ; 155, s. 105705-105705
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Tidskriftsartikel (refereegranskat)abstract
- Arsenic (As) removal studies were carried out through batch experiments to investigate the performance of the locally available calcined magnesite mineral rocks from Tanzania. Natural water from a stream source in Tanzania and the prepared synthetic water at the laboratory were used for the studies. Parameters such as initial As concentration, calcined magnesite dosage, contact time and pH were evaluated for As removal using an overhead rea×2 shaker. Arsenic concentration was reduced from 5.3 to 1.1 mg/L As(V) at 180 min when 0.5 g/L calcined magnesite was applied to a synthetic water sample, whereas the concentration of 117 μg/L As(V) and 5.2 μg/L As(III) was reduced to below 0.1 μg/L in natural water. An increase in calcined magnesite dosage resulted in increased As removal up to below 0.01 mg/L. The calcined magnesite raised the pH of the water sample from 6.8 to 10 when the applied dosage increased between 0.002 g/L and 0.05 g/L. The pH was constant at around 10 even when the amount of 0.05 g/L was added 2000 times. Despite the high pH, the amount of magnesium released in water was low. The calcination of magnesite at 500 ◦C increased surface area by 4 times as compared to the natural magnesite and X-ray diffraction showed presence of MgCO3 phase as the dominant phase at this temperature. The reaction kinetics of As removal on 0.5 g/L calcined magnesite fitted with the pseudo-second-order (R2 = 0.96). Reaction isotherm was strongly fitted with Freundlich isotherm (R2 = 0.98). Linear regression and artificial intelligence neural network showed the As removal was influenced by both contact time and pH. Arsenic can be removed from As water using calcined magnesite and will be suitable for water treatment around gold mining areas.
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3. |
- Karan, Shivesh Kishore, et al.
(författare)
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A spatial framework for prioritizing biochar application to arable land : A case study for Sweden
- 2023
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Ingår i: Resources, Conservation and Recycling. - : Elsevier BV. - 0921-3449 .- 1879-0658. ; 189, s. 106769-
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Tidskriftsartikel (refereegranskat)abstract
- The biochar-agriculture nexus can potentially generate several benefits ranging from soil carbon sequestration to the reduction in nutrient leaching from arable soils. However, leveraging these benefits requires spatially-explicit information on suitable locations for biochar application. This study provides a flexible multicriteria framework that delivers spatial indications on biochar prioritization through a biochar use indication map (BUIM). The framework was exemplified as a case study for Swedish arable land through three different prioritization nar-ratives. The BUIM for all the narratives revealed that a significant fraction of the Swedish arable land could potentially benefit from biochar application. Furthermore, arable land that scored high for a given narrative did not necessarily score high in the others, thus indicating that biochar application schemes can be adjusted to various objectives and local needs. The framework presented here aims to promote the exploration of different avenues for deploying biochar in the agricultural sector.
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4. |
- Rijk, Ingrid, 1985-
(författare)
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Effects of heavy metal contamination on carbon and nitrogen cycling : An ecological approach to assess risks to soil functions
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Soil contamination with heavy metals may disrupt soil microorganisms with important roles in carbon (C) and nitrogen (N) cycling. However, there is a lack of understanding on how microorganisms are affected in soil, which may lead to a mismatch when assessing risks of contaminants to field soils.The overall aim of this thesis was to assess effects on C and N cycling in heavy-metal contaminated soils under realistic conditions. Two historically contaminated sites and two outdoor field trials were studied. A variety of microbial responses, such as in situ microbial soil respiration, biomass, and N cycling microbial guilds was applied, which were linked to slower responding plant and soil variables and stable isotopic content δ13C and δ15N.Lower microbial activity, accumulation of soil C and a lower soil and plant δ15N showed that high lead (2000 mg kg-1) content was slowing down C and N cycles in a grassland area. In a former wood impregnation site, microbial biomass ceased below 5 cm depth while no effects in upper soil (2300 mg kg-1 copper) were observed. In a mesocosm study, responses of N cycling microbial guilds were mostly shaped by soil type. Neither total nor soluble copper, a proxy for bioavailability, could explain the effects on N cycling microbial communities. Finally, addition of biochar and peat to a moderately contaminated soil was shown to immobilize contaminants and N simultaneously, thereby being a promising remediation method to improve ecological soil quality in situ.In summary, this thesis provides an increased understanding and a reality-check on effects on C and N cycling in heavy-metal contaminated soils. The different intensities of the ecosystem effects in the two field soils, and soil specificity of microbial responses in the N cycle, stress the need for site-specific approaches.
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5. |
- Azzi, Elias Sebastian, et al.
(författare)
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Life cycle assessment of urban uses of biochar and case study in Uppsala, Sweden
- 2022
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Ingår i: Biochar. - : Springer Nature. - 2524-7972 .- 2524-7867. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- Biochar is a material derived from biomass pyrolysis that is used in urban applications. The environmental impacts of new biochar products have however not been assessed. Here, the life cycle assessments of 5 biochar products (tree planting, green roofs, landscaping soil, charcrete, and biofilm carrier) were performed for 7 biochar supply-chains in 2 energy contexts. The biochar products were benchmarked against reference products and oxidative use of biochar for steel production. Biochar demand was then estimated, using dynamic material flow analysis, for a new city district in Uppsala, Sweden. In a decarbonised energy system and with high biochar stability, all biochar products showed better climate performance than the reference products, and most applications outperformed biomass use for decarbonising steel production. The climate benefits of using biochar ranged from - 1.4 to - 0.11 tonne CO2-eq tonne(-1) biochar in a decarbonised energy system. In other environmental impact categories, biochar products had either higher or lower impacts than the reference products, depending on biochar supply chain and material substituted, with trade-offs between sectors and impact categories. However, several use-phase effects of biochar were not included in the assessment due to knowledge limitations. In Uppsala's new district, estimated biochar demand was around 1700 m(3) year(-1) during the 25 years of construction. By 2100, 23% of this biochar accumulated in landfill, raising questions about end-of-life management of biochar-containing products. Overall, in a post-fossil economy, biochar can be a carbon dioxide removal technology with benefits, but biochar applications must be designed to maximise co-benefits.
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6. |
- Karltun, Erik
(författare)
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Biochar-Fertilizer Blends-a Valuable Soil Amendment for Asparagus Cultivation?
- 2022
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Ingår i: Journal of Soil Science and Plant Nutrition. - : Springer Science and Business Media LLC. - 0718-9508 .- 0718-9516. ; 22, s. 691-705
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Tidskriftsartikel (refereegranskat)abstract
- A short-term field trial was carried out with the purpose to examine the impact of 2 different biochar fertilizer blends (BFB) on soil fertility and crop yield for a crop with a high revenue per hectare. The biochar field trial with 5 different treatments was conducted in a 2-year-old asparagus plantation on postglacial sand soil on Gotland. Besides the control (C), a biochar-fertilizer blend ("Amino Terra Substrate", ATS) of hard-wood biochar, molasses, vinasse and effective microorganisms was applied close to the asparagus row root zone in low and high application volumes of 2 ton ha(-1) (ATS-L) and 4 ton ha(-1) (ATS-H) biochar dry mass. Another biochar-fertilizer blend (CP) of rejected grain/wood biochar, cattle manure and water was applied in application volumes of 1.25 t ha(-1) (CP-L) and 2.5 ton ha(-1) (CP-H) biochar dry mass. BFB addition increased the organic carbon content, total nitrogen content, ammoniacal and nitrate nitrogen content and the plant available water storage capacity (compared to the control) and decreased soil bulk density and soil pH. In the first harvest season after BFB application, the average asparagus shoot yield exceeded (fell short of) the fertilized control by + 3.2% (ATS-H), - 0.4% (CP-L), - 5.0% (ATS-L) and - 5.1% (CP-H). In the second season after BFB application, the average asparagus shoot yield exceeded the fertilized control yield by + 10.1% (CP-L), + 8.7% (ATS-H), + 6.5% (CP-H) and + 2.8% (ATS-L). It can be concluded that the application of biochar fertilizer blends had a positive impact on soil fertility monitored within the first harvest year and the asparagus yield in the second harvest year under the observed field conditions.
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7. |
- Kätterer, Thomas, et al.
(författare)
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Maize grain yield responses to realistic biochar application rates on smallholder farms in Kenya
- 2022
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Ingår i: Agronomy for Sustainable Development. - : Springer-Verlag Italia s.r.l.. - 1774-0746 .- 1773-0155. ; 42:4
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Tidskriftsartikel (refereegranskat)abstract
- Despite efforts to increase agricultural production sustainably in sub-Saharan Africa, large gaps remain between actual and potential yield of food crops. Adding biochar to degraded cropland soils in the African tropics has significant potential to enhance crop productivity. Biochar-based farming can also mitigate climate change, through soil carbon storage. This study involved six smallholder farms at sites in eastern, central, and western Kenya that are characterized by different pedo-climatic conditions. We examined the response of non-fertilized and fertilized maize monoculture to three dosages of biochar that are realistic for domestic production by farmers at each of the sites over four growing seasons. Commonly available biomass wastes in each agro-ecosystem (coconut shells, coffee husks, maize cobs) were used as feedstock for biochar, which was applied at 1, 5, and 10 Mg ha−1 at the start of the experiment. Across seasons and fertilizer treatments, maize grain yield (dry matter) showed consistently positive responses, with an average increase of 1.0, 2.6, and 4.0 Mg ha−1, respectively, above the control for the three biochar application rates. Absolute responses of maize grain yield to specific biochar doses were similar across the four investigated seasons and replicate farms within sites, and uncorrelated to yield levels in the control treatment. Here, we show for the first time that yield response to biochar decreased with increasing application rate, indicating that it may be better to spread a given amount of biochar over a large area rather than concentrating it to a smaller area, at least when biochar is applied along plant rows at rates ≥1 Mg ha−1, as in our experiment. This study demonstrated that application of biochar, locally produced from available biomass residues, is a promising approach to enhance agricultural production and carbon storage on smallholder farms under a wide range of pedo-climatic conditions in Kenya.
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8. |
- Lundblad, Mattias, et al.
(författare)
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Sveriges klimatrapportering - markanvändning och skogsbruk
- 2022
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Ingår i: Fakta. Skog. - 1400-7789.
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Annan publikation (populärvet., debatt m.m.)abstract
- SLU sammanställer Sveriges rapportering av utsläpp och upptag av växthusgaserfrån markanvändning och skogsbruk.Om man undantar markanvändning och skogsbruk var Sveriges utsläpp avväxthusgaser under 2020 46 miljoner ton CO2-ekvivalenter.Markanvändning och skogsbruk bidrog samma år till ett nettoupptag på40 miljoner ton CO2-ekvivalenter, varav skogsmark stod för 96 %.Det största nettoupptaget av kol i levande biomassa sker i produktionsskog,men upptaget per arealenhet är något större i skog som skogsägarnafrivilligt undantagit från skogsbruk
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9. |
- Azzi, Elias, 1992-
(författare)
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Biochar systems across scales in Sweden : An industrial ecology perspective
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Biochar – the carbon rich residue derived from biomass pyrolysis – is recognised as a potential solution to remove carbon dioxide from the atmosphere, while simultaneously delivering socio-environmental benefits through biochar use as a material. Perceived as a sustainable innovation, biochar has raised interest throughout the world. Sweden has witnessed a rising interest for biochar over the past decade, leading to investments in modern biochar production capacity and the development of various biochar-based products. However, as for any emerging technology, it is necessary to study its environmental performance in a systematic manner to guarantee that environmental expectations meet reality, and to enable science-based policy support.This thesis examined the energy, climate and environmental impacts of biochar production and use, supporting on-going and future projects in Sweden. Four case studies were designed, set respectively in Stockholm, Nyköping, Helsingborg and Uppsala areas. The case studies analysed biochar production at various scales, from different biomass feedstocks, and biochar use in urban and rural applications. The main method applied was life cycle assessment, complemented with material flow analysis and energy systems modelling. In addition, a framework was developed to conceptualise and classify environmental effects of biochar in a life cycle perspective. The results showed that biochar systems can deliver more climate change mitigation than conventional bioenergy when energy systems are already rather decarbonised and if biochar stability is high. Biochar carbon sequestration provided the main climate change benefit, but smaller additional benefits were obtained from some material uses of biochar. When compared with reference systems, biochar solutions lead to shifts of burdens between sectors and environmental impact categories. It is possible to integrate pyrolysis to both large district heating networks and decentralised heating systems, but it will lead to a net increase in biomass consumption and related environmental impacts, relative to direct combustion of biomass. In the second half of the century, the need for management of biochar-containing soil masses will arise from today’s emerging urban applications. The case studies illustrated new uses of biochar and quantified several environmental benefits from biochar use. However, gaps remain between biochar effects present in the public discourse and their quantification in life cycle assessment. These differences were attributed to variability in the biochar effects, lack of knowledge, or inappropriate accounting framework. Overall, the thesis stresses the importance of analysing the potential of innovations to contribute to environmental goals by using parametrized life cycle models, depicting multiple contexts, and striving to identify suitability conditions rather than providing a definitive static answer.
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10. |
- Azzi, Elias Sebastian, et al.
(författare)
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Assessing the diverse environmental effects of biochar systems : An evaluation framework
- 2021
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Ingår i: Journal of Environmental Management. - : Elsevier BV. - 0301-4797 .- 1095-8630. ; 286
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Tidskriftsartikel (refereegranskat)abstract
- Biochar has been recognised as a carbon dioxide removal (CDR) technology. Unlike other CDR technologies, biochar is expected to deliver various valuable effects in e.g. agriculture, animal husbandry, industrial processes, remediation activities and waste management. The diversity of biochar side effects to CDR makes the systematic environmental assessment of biochar projects challenging, and to date, there is no common framework for evaluating them. Our aim is to bridge the methodology gap for evaluating biochar systems from a life-cycle perspective. Using life cycle theory, actual biochar projects, and reviews of biochar research, we propose a general description of biochar systems, an overview of biochar effects, and an evaluation framework for biochar effects. The evaluation framework was applied to a case study, the Stockholm Biochar Project. In the framework, biochar effects are classified according to life cycle stage and life cycle effect type; and the biochar?s end-of-life and the reference situations are made explicit. Three types of effects are easily included in life cycle theory: changes in biosphere exchanges, technosphere inputs, and technosphere outputs. For other effects, analysing the cause-effect chain may be helpful. Several biochar effects in agroecosystems can be modelled as future productivity increases against a reference situation. In practice, the complexity of agroecosystems can be bypassed by using empirical models. Existing biochar life cycle studies are often limited to carbon footprint calculations and quantify a limited amount of biochar effects, mainly carbon sequestration, energy displacements and fertiliser-related emissions. The methodological development in this study can be of benefit to the biochar and CDR research communities, as well as decision-makers in biochar practice and policy.
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