Browsing by Subject "Carbon sequestration"

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    Biochar amendment for C sequestration in a temperate agroecosystem : implications for microbial C- and N-cycling
    (2018) Bamminger, Chris; Kandeler, Ellen
    Climate warming will have great impact on terrestrial ecosystems. Different soil properties such as temperature and moisture will be altered, thereby influencing C- and N-cycles, microbial activity as well as plant growth. This may contribute to the observed increase in soil greenhouse gas (GHG) emissions under climate change. Therefore, new options are needed to mitigate theses projected consequences. Biochar is primarily suggested to be effective in long-term C sequestration in agricultural soils due to its long-term stability. In addition, it could be applied to improve various soil properties, plant growth and to reduce soil GHG emissions. To date, knowledge about such beneficial biochar effects in soil under predicted warming climate is extremely scarce. In the first study, a slow-pyrolysis biochar from Miscanthus x giganteus feedstock (600 °C, 30 Min.) was incubated for short time (37d) under controlled laboratory conditions in agricultural soil in the presence of earthworms and N-rich litter (Phacelia tanacetifolia Benth.). Biochar increased microbial abundances and the fungal-to-bacterial PLFA ratio after 37 days in arable soil applied with litter suggesting improved living conditions for microorganisms with biochar. Fungi may benefit most from newly created habitats due to colonizable biochar pores and surfaces. Additionally, fungi could have also mineralized small amounts of recalcitrant biochar-C during plant litter decomposition. Without litter, biochar led to interactions between earthworms and soil microorganisms resulting in enhanced bacterial and fungal abundances. This indicates better growth habitats for soil microbes in earthworm casts containing biochar. Soil respiration and metabolic quotients (qCO2) and N2O emissions (in litter treatments) were decreased after biochar application suggesting a more efficient microbial community and underscoring the GHG mitigation potential of the used biochar. The field experiment, investigated in the second and third study, focused on the stability and long-term soil C sequestration potential of comparable Miscanthus biochar (850 °C, 30 Min.). Related effects on soil GHG emissions, physical, chemical and microbiological soil properties as well as plant growth were determined in an agroecosystem at year-round elevated soil temperature (+2.5 °C, since 2008). The second study investigated the short-term effects of biochar on microbial abundances and growth of winter rapeseed during the first year after field application to a warmed temperate arable soil. It was found that fungal biomass and the fungal-to-bacterial ratio were increased in the warmed biochar plots only after three months in the presence of spring barley litter from the previous growing season. The disappearance of this effect points to an overall high stability of the investigated biochar. Moreover, biochar proved to be effective in mitigating negative effects of seasonal dryness on microbial abundances and early plant growth in the dry spring period in 2014. However, biochar had no effect on final aboveground biomass of winter rapeseed at harvest in the first growing season. As shown in the third study, after two vegetation periods of winter rapeseed and spring wheat, the assumption that plant productivity in already fertile temperate arable soils is unlikely to be further enhanced with biochar amendment, was confirmed. Total CO2 emissions after two years were not reduced by biochar and remained unchanged even under warming suggesting a high degradation stability of the used biochar. N2O emissions were increased in biochar-amended soil at elevated soil temperature, presumably due to enhanced water and fertilizer retention with biochar. By using the global warming potential (GWP100) of total soil GHG emissions, the storage of biochar-C in soil was estimated to compensate warming-induced elevated soil GHG emissions for 20 years. To conclude, this thesis revealed that biochar may have only minor influence on soil microorganisms and crop growth in temperate, fertile arable field soils. However, it was shown that biochar could be a valuable tool for C sequestration in temperate arable soils, thus potentially offsetting a warming-induced increase in GHG emissions. In order to face climate change impacts, more long-term studies on microbiological effects and the C sequestration potential of biochar in cultivated soil under warming are urgently needed.
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    Payments for environmental services : incentives through carbon sequestration compensation for cocoa-based agroforestry systems in Central Sulawesi, Indonesia
    (2008) Zeller, Manfred; Seeberg-Elverfeldt, Christina; Schwarze, Stefan
    Up to 25 percent of all anthropogenic greenhouse gas emissions are caused by deforestation, and Indonesia is the third largest greenhouse gas emitter worldwide due to land use change and deforestation. On the island of Sulawesi in the vicinity of the Lore Lindu National Park (LLNP), many smallholders contribute to conversion processes at the forest margin as a result of their agricultural practices. Specifically the area dedicated to cocoa plantations has increased from zero (1979) to nearly 18,000 hectares (2001). Some of these plots have been established inside the 220,000 hectares of the LLNP. An intensification process is observed with a consequent reduction of the shade tree density. This study assesses which impact carbon sequestration payments for forest management systems have on the prevailing land use systems. Additionally, the level of incentives is determined which motivates farmers to desist from further deforestation and land use intensification activities. Household behaviour and resource allocation is analysed with a comparative static linear programming model. As these models prove to be a reliable tool for policy analysis, the output can indicate the adjustments in resource allocation and land use shifts when introducing compensation payments. The data was collected in a household survey in six villages around the LLNP. Four household categories are identified according to their dominant agroforestry systems. These range from low intensity management with a high degree of shading to highly intensified shade free systems. At the plot level, the payments from carbon sequestration are the highest for the full shade cocoa agroforestry system, but with low carbon prices of ? 5 tCO2e-1 these constitute 5 percent of the cocoa gross margin. Focusing on the household level, however, an increase of up to 18 percent of the total gross margin can be realised. Furthermore, for differentiated carbon prices up to ? 32 tCO2e-1 the majority of the households have an incentive to adopt the more sustainable shade intensive agroforestry system. A win-win situation seems to appear, whereby, when targeting only the shade intensive agroforestry systems with carbon payments, the poorest households economically benefit the most and land use systems with high environmental benefits are promoted.
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    The potential of certification for climate change mitigation in the agri-food sector : a case study of carbon neutral certified coffee from Costa Rica
    (2017) Birkenberg, Athena; Birner, Regina
    Advancing economic, social and environmental sustainability in the agri-food sector is increasingly pursued by various actors along global value chains. One option to address sustainability concerns is to use voluntary sustainability standards and certifications/labels as market-based governance tools for self-regulation. Recently, the demand for particular climate standards and labels has increased, however little is known about their potential and challenges. Individual aspects of such voluntary sustainability certifications have been investigated, such as the effectiveness and impact of certifications or the purchasing decisions of consumers. However, a holistic and interdisciplinary approach by considering the complete value chain is rare and, thus challenges are overlooked and proposed solutions remain limited in scope. Moreover, LCA-based certifications addressing climate change mitigation present a new field of research. Against this background, this thesis aims to elicit the challenges and potential of sustainability certification in the agri-food sector. Taking the case of the world’s first carbon neutral certified coffee, the complete chain – from standard development to consumer choices – has been examined. This coffee is produced by Coopedota, a Costa Rican cooperative of small-scale farmers, and exported to a family-run specialty coffee roaster, Hochland Kaffee Hunzelmann GmbH, in Germany. In the case under consideration, a newly released and highly prescriptive standard for carbon neutrality, the Publicly Available Specification (PAS) 2060, has been adopted since 2011. PAS 2060 is the first independent international standard for carbon neutrality that provides a common definition and a recognized method that is based on a life cycle assessment (LCA). To achieve carbon neutrality, the respective greenhouse gas (GHG) emissions are compiled, before continuous reduction activities are executed and the residual GHG emissions are offset by purchasing carbon credits. Costa Rica is relevant because it is actively pursuing carbon neutrality at the national level and the case of Coopedota serves as a pioneer in this field. In this thesis, an interdisciplinary case study approach is used to investigate in a holistic manner the challenges of carbon neutral certification in the agri-food sector. The study is guided by a conceptual framework developed from relevant literature on voluntary sustainability standards. The three specific objectives of the thesis are: (1) identify the success factors that made the carbon neutral certification in Coopedota possible and understanding the major challenges related to the standards implementation; (2) estimate the potential of on-farm carbon sequestration to compensate for the coffee carbon footprint and reduce carbon offsetting; and (3) estimate the willingness to pay for a carbon neutral label among German consumers of specialty coffee. This thesis contains three main chapters in addition to a general introduction and discussion. The first chapter addresses existing knowledge gaps regarding the role of social network dynamics, actor characteristics and linkages for successful pioneering in sustainable development, and investigates the challenges of implementing PAS 2060 by Coopedota. Qualitative research methods, such as in-depth interviews, participatory social network and process mapping as well as field observations were applied. The study found the prior achievements of the cooperative (e.g. compliance to ISO norms) and a ‘fertile ground’ in terms of ongoing climate change mitigation policies, as important factors for the successful implementation of the standard. Further success factors were a strong central and visionary actor and a diverse network of supporting actors from science, business and politics. The main challenges in implementing the carbon neutral certification were the acquirement of reliable farm data and the advertisement and communication of a carbon neutral label. The second chapter focuses on the problem that biogenic carbon sequestration is rarely considered in LCA-based standards. To estimate the annual potential of biogenic carbon accounting in coffee-agroforestry systems (CAFS) a literature review was conducted and the carbon sequestration based on a carbon inventory at the coffee farms was modeled. The results of a 20-year simulation show that on average, CAFS at Coopedota can compensate the carbon footprint of coffee by approximately 160% annually. Simultaneously, a trade-off between carbon sequestration and productivity at reduced inputs appears, which should be minimized. In the third chapter a marginal willingness to pay (WTP) of € 1.70 for a carbon neutral label was identified on a 250g package of specialty coffee by a discrete choice experiment among German consumers. Yet this marginal WTP was lower than the marginal WTP among the same consumers for direct trade claims or a Fair Trade certificate. Direct trade claims refer to the situation where direct trade relations exist; however, they are not certified and only declared by the retailer, as in the case of the family-run coffee roaster Hochland Kaffee Hunzelmann GmbH. Moreover, a positive synergistic effect was discovered for the combination of the carbon neutral label with direct trade claims. However, a public awareness on the contribution of agriculture to climate change is missing, as is the familiarity of the public with carbon concepts. Concluding, LCA-based certification for carbon neutrality can be a promising market-based tool for the agri-food sector to mitigate climate change. Such certification holds promise because it addresses recent demands for climate relevant information on agri-food products, while benefitting producers, the environment and consumers alike. Examples of these benefits include a potential increase in resource use efficiency, identification and minimization of GHG emission hot spots and trustworthiness among consumers due to the prescriptive nature of the standards. Additionally, the interdisciplinary case study approach enabled the identification of multi-faceted challenges and recommendations. One recommendation is that an agricultural perspective needs to be integrated into the standard by, for example, enabling the accounting of biogenic carbon sequestration. Such carbon accounting would prevent criticism of carbon offsetting and foster synergies between climate change mitigation, sustainability, and resilience. Particularly in the case of higher carbon prices, carbon accounting would be economically interesting but further research is needed to provide a robust dataset to enable it. Independent from a potential premium price for the label, access to capital and governmental support programs, especially for smallholders in less developed countries, can foster the implementation of greener technologies and allow stakeholders to benefit from increased efficiencies. The findings of this thesis indicate that coupling a carbon standard with existing sustainability standards, which use similar datasets, could ease the acquirement of reliable farm data on GHG emissions and reduce costs. Moreover, a coupling of standards could ensure additional sustainability practices, beyond the climate aspect, as already associated by consumers. This study also indicates that to establish markets for carbon neutral products, consumers first have to be aware of the extent of the agri-food sector’s contribution to climate change and consumer responsibility in tackling this problem through their purchasing behavior. This thesis further illustrates the importance of innovators in advancing development goals. Taking action on climate change mitigation and shaping a more sustainable agri-food sector requires strong initiatives and visionaries on the ground, as exemplified by the pioneering case of Coopedota.