| 11. |
- 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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| 12. |
- 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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| 13. |
- 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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| 14. |
- Azzi, Elias Sebastian, et al.
(författare)
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Life cycle assessment of urban uses of biochar and case study in Uppsala, Sweden
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Biochar is a material derived from biomass pyrolysis that is used in urban applications. The environmental impacts of new biochar products has however not been assessed. Here, the life cycle assessments of 5 biochar products were performed for 7 biochar supply-chains in 2 energy contexts. The biochar products (tree planting, green roofs, landscaping soil, charcrete, and biofilm carrier) were benchmarked against reference products and the 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 if biochar stability is high, all biochar products had a better climate performance than the reference, 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, depending on biochar supply-chains and materials substituted, with trade-offs between sectors and impact categories. This said, several use phase effects of biochar were not included in the assessment due to knowledge limitations. In Uppsala’s new district, biochar demand was around 1700 m3 year-1 during the 25 years of construction. By 2100, 23% of the biochar accumulated in landfills, raising questions for 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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| 15. |
- 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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| 16. |
- Azzi, Elias Sebastian, et al.
(författare)
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Prospective Life Cycle Assessment of Large-Scale Biochar Production and Use for Negative Emissions in Stockholm
- 2019
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 53:14, s. 8466-8476
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Tidskriftsartikel (refereegranskat)abstract
- Several cities in Sweden are aiming for climate neutrality within a few decades and for negative emissions thereafter. Combined biochar, heat, and power production is an option to achieve carbon sequestration for cities relying on biomass-fuelled district heating, while biochar use could mitigate environmental pollution and greenhouse gas emissions from the agricultural sector. By using prospective life cycle assessment, the climate impact of the pyrolysis of woodchips in Stockholm is compared with two reference scenarios based on woodchip combustion. The pyrolysis of woodchips produces heat and power for the city of Stockholm, and biochar whose potential use as a feed and manure additive on Swedish dairy farms is explored. The climate change mitigation trade-off between bioenergy production and biochar carbon sequestration in Stockholm's context is dominated by the fate of marginal power. If decarbonisation of power is achieved, building a new pyrolysis plant becomes a better climate option than conventional combustion. Effects of cascading biochar use in animal husbandry are uncertain but could provide 10-20% more mitigation than direct biochar soil incorporation. These results help design regional biochar systems that combine negative carbon dioxide emissions with increased methane and nitrous oxide mitigation efforts and can also guide the development of minimum performance criteria for biochar products.
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| 17. |
- Azzi, Elias Sebastian, et al.
(författare)
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Small-scale biochar production on Swedish farms : A model for estimating potential, variability, and environmental performance
- 2021
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Ingår i: Journal of Cleaner Production. - : Elsevier Ltd. - 0959-6526 .- 1879-1786. ; 280
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Tidskriftsartikel (refereegranskat)abstract
- Several small-scale pyrolysis plants have been installed on Swedish farms and uptake is increasing in the Nordic countries. Pyrolysis plants convert biomass to biochar for agricultural applications and syngas for heating applications. These projects are driven by ambitions of achieving carbon dioxide removal, reducing environmental impacts, and improving farm finances and resilience. Before policy support for on-farm pyrolysis projects is implemented, a comprehensive environmental evaluation of these systems is needed. Here, a model was developed to jointly: (i) simulate operation of on-farm energy systems equipped with pyrolysis units; (ii) estimate biochar production potential and its variability under different energy demand situations and designs; and (iii) calculate life cycle environmental impacts. The model was applied to a case study farm in Sweden. The farm's heating system achieved net carbon dioxide removal through biochar carbon sequestration, but increased its impact in several other environmental categories, mainly due to increased biomass throughput. Proper dimensioning of heat-constrained systems is key to ensure optimal biochar production, as biochar production potential of the case farm was reduced under expected climate change in Sweden. To improve the environmental footprint of future biochar systems, it is crucial that expected co-benefits from biochar use in agriculture are realised. The model developed here is available for application to other cases.
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| 18. |
- Berglund, Örjan, et al.
(författare)
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Land use on organic soils in Sweden – a survey on the land use of organic soils within agriculture and forest lands during 1983-2014
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Data from the Geological Survey of Sweden (SGU), the Swedish Board of Agriculture and the Swedish National Forest Inventory were used in a GIS analysis to evaluate the distribution of organic soils (OS) used for agriculture and forestry in Sweden. The status of agricultural soils and agricultural land use changes were also studied, based on the most recent data available from the SGU. The total surface area of OS in Sweden was estimated to be 6 207 284 ha (15.2% of the land surface area), which is less than reported in previous assessments (Berglund and Berglund, 2008; Berglund et al., 2009). Of the total OS area 98.2% was peat, of which 4.7% was shallow peat and 2.5% 40K peat (peat determined using gamma radiation data). The remaining 1.8% were gyttja soils. Total agricultural area under EU regulations (i.e. on the EU agriculture block map) in Sweden was 3 232 039 ha (7.9% of the land surface area) and most of this was arable land (82.8%). Pasture occupied approx. 16% of the area, the land use on the remaining 1.2% is unknown. Agricultural area on OS (AOS) based on SGU-data and the EU agriculture block map was estimated to be 225 722 ha which is 7% of the total agricultural area based on EU agriculture block maps and 9.0% based on the national maps over agricultural land areas provided by the Swedish Board of Agriculture. More than 50% of AOS was arable land whereas approx. 40% was divided between pasture and unmanaged arable land. The remaining area was wetland, unknown or other land use type. In comparison to previously studies in 2003 (Berglund and Berglund, 2008) and 2008 (Berglund et al., 2009), both the total agricultural area and AOS area have decreased, probably due to structural changes in agriculture. The decline has been sharper for the surface area of AOS than for the total agricultural area. Among the Swedish National Forest Inventory plots, 12.3% were located on OS. Land use changes recorded on the Forest Inventory plots were mostly from arable land to other land uses rather than from other land uses to arable land both in total area and in OS.
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| 19. |
- Chala, Workneh Bedada, et al.
(författare)
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Long-term addition of compost and NP fertilizer increases crop yield and improves soil quality in experiments on smallholder farms
- 2014
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Ingår i: Agriculture, Ecosystems and Environment. - : Elsevier BV. - 0167-8809 .- 1873-2305. ; 195, s. 193-201
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Tidskriftsartikel (refereegranskat)abstract
- Soil fertility decline due to low nutrient input is a constraint for sustainable agriculture in smallholder farming systems in Ethiopia. In this study, crop productivity and soil organic matter buildup were compared in soils receiving locally made compost, applied either alone or in combination with NP fertilizer. The experiments had four treatments: full dose of compost (C), full dose of fertilizer (F), half compost and half fertilizer (CF), and unfertilized control (control). The full dose of compost was equivalent to 2.4 t ha(-1) organic matter. The field study was conducted on four farm fields in the village Beseku, each representing different sub-villages. Participating farmers were selected based on their willingness and an assessment of dedication to carry out the experiment. The experiments, a randomized complete block design with three replications, were replicated across four farm fields. The treatments were repeated for six cropping seasons (years), and data on soil nutrient status and crop (maize, wheat, potato, and faba bean) harvests were collected. In the 0-10 cm soil layer, pH was (P < 0.05) lower in the F treatments than in the C and CF treatments. Compared with the F treatment, the soil organic carbon (SOC) and total nitrogen stocks increased (P < 0.05) by 4.60 and 0.42 t ha(-1) in C treatment, and by 4.74 and 0.45 t ha(-1) in CF treatment. Treatment effects on crop harvests were significant (P < 0.05) for all crops grown across the sites and seasons. The highest maize yield was obtained from CF, with relative harvest of 178% compared with the control and 126% compared with F, but was comparable to C. For wheat and potato, the yields obtained from CF, C and F were comparable. For faba bean, CF had a relative harvest of 145% over the control. Maize harvest was in the order of CF > F> C> control in the initial season, CF > C> F> control in the next three consecutive seasons, and C> CF> F> control in the final year of the experiment. The overall combined yield was in the order of CF > C> F> control for maize and faba bean, CF > F> C> control for potato, and F> CF > C> control for wheat. The addition of either compost alone or in combination with NP fertilizer improved soil properties and crop productivity, compared with control and only fertilizer addition. Therefore, compost addition can serve as a complement to fertilizer use and reduce dependence on mineral fertilizer in low-input crop production system. The apparent synergy between compost and fertilizer addition needs further research in order to be explained. (C) 2014 Elsevier B.V. All rights reserved.
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| 20. |
- Chala, Workneh Bedada, et al.
(författare)
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Soil nutrient build-up, input interaction effects and plot level N and P balances under long-term addition of compost and NP fertilizer
- 2016
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Ingår i: Agriculture, Ecosystems and Environment. - : Elsevier BV. - 0167-8809 .- 1873-2305. ; 218, s. 220-231
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Tidskriftsartikel (refereegranskat)abstract
- Decline in farmland soil fertility due to nutrient depletion is a concern for smallholder farmers in the highlands of Ethiopia. In this study we tested if long-term addition of compost, either alone or in combination with nitrogen (N) and phosphorous (P) fertilizer, affected available soil nutrient status, grain/tuber harvests, agronomic N use efficiency, and plot level N and P nutrient balances. The on-farm experiments were conducted on four farm fields for up to 6 years in Beseku, Ethiopia. A randomized complete block design was used, with four treatments: full dose of compost applied alone at 2.4 t ha(-1) DW organic matter (C); full dose of fertilizer (F); half compost and half fertilizer (CF); and, unfertilized control. In the upper 10 cm of the surface soil, several Mehlich-3 extractable nutrients (B, Ca, K, Mg, P, S, and Zn) had significantly higher concentrations in the C treatment (P < 0.01), and some in the CF treatment (P < 0.05) than in the control. Phosphorus was the only nutrient with a higher concentration in the F treatment than the control. Maize and faba bean showed added benefits (synergy) in terms of yield increase in the CF treatment and a better agronomic efficiency for added N. Plot level N balances were negative for all treatments except C, with strong depletion in the control (-76 kg N ha(-1) yr(-1)) and F (-65 kg N ha(-1) yr(-1)) treatments. When the N balance was compared to measured change in soil N, the F and control treatments were significantly (P < 0.05) lower than zero. N in the CF and C treatments was close to steady-state, i.e., the input of N in organic matter compensated for the loss of N through mineralization. The control treatment had a negative P balance of 11 kg P ha(-1) yr(-1), with moderately negative balance of 4 kg P ha(-1) yr(-1) in the C treatment. The CF and F treatments had positive P balances. Thus, the addition of compost, both alone or in combination with mineral fertilizer, can prevent N and reduce P mining and improve the nutrient status of the soil. When only NP fertilizer was used, the crop utilized all N that was mineralized indicating that the crop was N limited. (C) 2015 Elsevier B.V. All rights reserved.
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