Atmospheric carbon removal via industrial biochar systems : a techno-economic-environmental assessment

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May 22, 2023, 7:29:59 PM5/22/23

Title:Atmospheric carbon removal via industrial biochar systems : a techno-economic-environmental assessment
Author:Fawzy, Samer
Awarding Body:Queen's University Belfast
Current Institution:Queen's University Belfast
Date of Award:2023
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The present global efforts to tackle climate change stipulate an objective of limiting global temperature rise to 2°C by the end of the century while pursuing measures to keep it below 1.5°C. An in-depth investigation of climate change mitigation strategies was carried out, detailing 3 major approaches, namely emissions reduction, atmospheric carbon removal and radiative forcing geoengineering. On the basis of the findings, it was determined that current emission reduction efforts, as well as future emission reduction commitments announced globally, are insufficient to meet the 2015 Paris agreement targets, and that carbon removal must be integrated with emission reduction efforts in order to reduce global temperatures over the coming decades. Based on an assessment of the prominent carbon removal technologies, it was determined that carbon removal via industrial biochar systems is a very promising approach. Accordingly, the dimensions related to biochar-based carbon removal systems were explored in detail. This covered potential feedstocks, feedstock analytical techniques, potential production technologies, biochar properties with a special focus on carbon stability, the impact of processing configurations on production yield and biochar properties, as well as potential by-product valorization routes. Furthermore, the investigation discussed the concept of biochar as a negative emissions technology and introduced potential carbon reservoirs and a variety of value-adding applications. Moreover, the current status of the emerging carbon removal economy and participation requirements were presented. Overall, with the emergence of the new carbon removal economy, research focused on system design, process optimization, and techno-economic-environmental assessments of biochar-based carbon removal projects was found to be critical moving forward. As prospective feedstocks, several materials, including olive tree pruning residues, sesbania sesban, and cotton stalks, were investigated experimentally. Kinetic models were developed for the pyrolytic degradation of such materials using a sophisticated thermo-kinetic tool, Advanced Kinetics and Technology Solutions (AKTS), and conversion predictions were constructed under various heating configurations. The results of the investigations provided a comprehensive understanding of the materials' behaviour during pyrolysis and the information aided in subsequent modelling and optimization. Moreover, olive tree pruning residue biomass was selected for further investigation. Finally, the carbon removal potential of an industrial biochar system in Spain was holistically examined. The objective was to assess the techno-economic environmental aspects of large-scale olive tree pruning residue pyrolysis for atmospheric carbon removal, using an integrated assessment framework that is based on current market dynamics. The framework included i) biochar production and optimization, ii) biochar characterization, iii) plant design and process modelling, iv) life cycle analysis, v) carbon removal quantification, and vi) economic modelling. Production optimization using Response Surface Methodology (RSM) was carried out, aiming to maximize yield, production throughput and stable carbon content while prioritizing stability. It was determined that optimized biochar production was attained at 650°C and 15 min residence time. Furthermore, a biochar plant with a biomass processing capacity of 6.5 tonne per hour (20% moisture content) was designed for further analysis. A thermodynamic model was developed using Advanced System for Process Engineering (ASPEN Plus) software, and the process was determined to be self sufficient with the availability of surplus energy. Moreover, a life cycle assessment (cradle-to-grave) revealed that approximately 2.68 tCO2 are permanently removed from the atmosphere per tonne of biochar produced, after accounting for the carbon footprint of the entire process. This corresponds to a carbon removal capacity of 3.26 tCO2 per hour and the removal of approximately 24,450 tCO2 annually. The economic assessment revealed that the project is profitable; however, profitability is sensitive to pricing of the carbon removal service and biochar. A project internal rate of return (IRR) of 22.35% was achieved at a price combination of EUR 110 per tonne CO2 removal and EUR 350 per tonne biochar, and a feedstock cost of EUR 45 per tonne (delivered with 20% moisture), where service and product pricing are both within the lower bound of market pricing. If the project was exclusively designed to offer a carbon removal service, a minimum price of EUR 206 per tonne CO2 removal is required to achieve project profitability, based on the same feedstock cost. The results indicate the feasibility of biochar-based carbon removal systems, however, the business model, type of feedstock, choice of technology, pricing decisions and ability to negotiate favourable terms and prices for feedstock supply are critical to the success of this approach. The findings demonstrate the viability of immediately deploying large-scale biochar-based carbon removal via pyrolytic conversion of olive tree pruning residues to address the climate crisis.
Supervisor:Rooney, David ; Wu, ChunfeiSponsor:Bryden Centre
Qualification Name:Thesis (Ph.D.)Qualification Level:Doctoral
EThOS DOI:Not available
Keywords:Atmospheric carbon removal ; techno-economic-environmental Assessment ; biochar ; Industrial Biochar Systems ; climate change mitigation ; kinetic modelling ; life cycle analysis ; economic modelling
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