Author ORCID Identifier

https://orcid.org/0000-0002-6177-0485

Semester

Summer

Date of Graduation

2024

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Division of Forestry and Natural Resources

Committee Chair

Jingxin Wang

Committee Co-Chair

Charlene Kelly

Committee Member

Charlene Kelly

Committee Member

Jamie Schuler

Abstract

This study investigated the long-term carbon stock of central Appalachian mixed hardwood forests under several harvesting strategies. The strategies were optimized to maximize both long-term carbon sequestration and timber supply during harvest using Mixed-Integer Linear Programming (MILP) models. Clear-cut (CC), Partial cut (PC), and mixed harvesting methods to unharvested conditions over 190 years were studied. Initially, harvested forests showed lower sequestration rates than unharvested forests but eventually surpassed them, with CC showing the highest rates over time. Younger forests, particularly those aged 85 to 130 years, exhibited peak carbon sequestration rates. Regarding carbon stock, the unharvested scenario initially had the highest levels. However, harvested forests eventually exceeded this stock when considering external carbon pools such as carbon stored in wood products and biochar carbon, produced from logging residues. PC harvesting achieved the highest total carbon sequestration, surpassing unharvested levels after 160 years, followed by CC and mixed harvesting at around 180 years. CC yielded the highest timber harvest, followed by mixed and PC methods, storing more carbon in wood products outside the forest and less within the forest stands. Mixed harvesting provides a balanced approach between PC and CC, especially when higher timber yields are required in some harvests. The carbon neutrality coefficient (CNC) for both CC and PC was estimated. A value just below 1 indicates nearly complete carbon recovery post-harvest, close to 0 suggests significant carbon loss due to harvesting, and above 1 means the forest has surpassed pre-harvest carbon stock levels. The CNC for this study ranged from 0.52 to 1.55 for CC and PC over 100 years, when calculated in 20-year intervals post-harvest. Our findings emphasize the importance of optimized harvest schedules for enhancing long-term carbon sequestration while meeting timber demands. The study concludes that a comprehensive accounting of all carbon pools, including harvested wood and residue utilization, is essential for a comprehensive assessment of carbon sequestration and for a fair comparison of the carbon benefits between harvested and unharvested forests.

Forest harvest generates a large quantity of logging residues, which are often left on-site to decay or are burned, thus emitting stored carbon back into the atmosphere. However, using these residues to produce biochar with portable biochar production systems can sequester carbon for hundreds to thousands of years. This study explored the potential of utilizing logging residues for biochar production and carbon sequestration. A techno-economic analysis of biochar production using three biochar production systems (BPS): Biochar System Inc. (BSI), Air Curtain Burner (ACB), and Char Boss (CB) was conducted. Eight production scenarios were developed based on the number of BPS units used, combinations of the BPS, and the quantity of feedstock used. The cost of biochar production ranged from $397 to $946 per metric ton, while the cost of carbon sequestration ranged from $515 to $1229 per metric ton. The ACB system had the lowest biochar production cost ($397 to $401 per metric ton) compared to the biochar produced from two units of CB ($479 per metric ton) and two units of BSI ($946 per metric ton). In terms of production efficiency, when one ACB unit and two CB units processed the same quantity of feedstock, the ACB unit completed the process in 107 days, while the CB units took 332 days, both working 8 hours per day. Although the CB produced 220% more biochar than the ACB, its cost per metric ton was 19% higher due to its lower feedstock consumption rate, leading to longer operating days and higher costs. For the BSI system, the potential scaling up of production capacity needs to be considered for a fair economic comparison with other systems. In conclusion, this study underscores the importance of utilizing forest logging residues for on-site or near-forest biochar production as a viable approach to mitigating carbon emissions and enhancing carbon sequestration.

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