Semester

Summer

Date of Graduation

2023

Document Type

Dissertation

Degree Type

PhD

College

Davis College of Agriculture, Natural Resources and Design

Department

Division of Forestry and Natural Resources

Committee Chair

Jingxin Wang

Committee Member

John (Jianli) Hu

Committee Member

Edward M. Sabolsky

Committee Member

Jamie Schuler

Committee Member

Shawn Grushecky

Abstract

Four major studies were conducted in this dissertation to investigate the quality, availability, pretreatment, conversion, and utilization of forest logging residues in the eastern United States. The introduction and conclusion sections are found in the first and last chapters. The quality of various-year-naturally-decomposed softwood and hardwood forest logging residues from three subregions of the eastern United States was investigated in the second chapter. In the third chapter, the combustion and energy properties of hydrothermal, inert, and oxidative torrefied red maple were investigated. Finally, in the fourth and fifth chapters, KMnO4 surface-modified logging residue hydrochars were used to investigate the adsorption properties of single and mixed heavy metal solutions.

Specifically, the results of second chapter indicated that an increasing natural decomposition time leads to a decrease in density for both hardwood and softwood samples. The higher heating value (HHV) of hardwood ranges from 18.69 to 20.68 MJ/Kg, which is comparatively lower than that of softwood (ranging from 19.13 to 21.16 MJ/Kg). The change of HHV in hardwood trends opposite to that of softwood. The results of the ultimate analysis indicated that softwood exhibits a higher carbon content (47.98%-51.98%) than hardwood (46.06%-49.48%). In addition, hardwood has a higher volatile matter (76%-80.85%) and lower fixed carbon (16.97%-21.68%) content compared with softwood (71.10%-79.45% and 19.03%-23.69%, respectively). There was an observed increase in the absolute lignin content of softwood as the exposure time increased, whereas the trend for holocellulose was opposite. Additionally, the proportion of lignin in hardwood and holocellulose in softwood decreased as the duration of decomposition time increased. The rate of decomposition in the southeast region was observed to be faster than that in the central Appalachian region. If 50% of logging residues produced in 2023 were used, three distinct categories of biofuel, biochar, and wood pellet could be produced by 0.385-0.605 million tons, 1.21-1.76 million tons, and 5.06-5.39 million tons, respectively.

The results of third chapter showed that the physiochemical properties of hydrothermally treated (HT) samples changed dramatically compared to samples processed using inert (NT) and oxidative (OT) treatments. The HT method yielded 39.60±0.96% solid product, which is significantly lower than the OT (83.06±0.55%) and NT (91.42±0.89%) treatments. However, it has a higher fixed carbon content (44.40%) than both OT (24.74%) and NT (19.24%). With different heating rates, the weight loss of untorrefied (UT) stage 1 ranges from 70.3 to 72.1%, whereas HT decreases from 41.9 to 38.0%. For UT, OT, and NT, weight loss ranges from 59.9 to 74% at stage 1 and 22.0-37.9% at stage 2. The ranges for HT, on the other hand, are 37.7-41.9% and 53.0-57.9% for stage 1 and stage 2, respectively. Stage 1's sample Ea distribution follow HT>OT>UT≈NT, while the average combustion Ea of stage 2 sample distribution follow HT>OT>UT>NT. KAS calculates the highest value for stage 1 as 247.56 KJ/mol for HT and the lowest as 140.61 KJ/mol for UT.

The findings in fourth chapter indicate that the output of unmodified hydrochar (250-P), hydrochar produced through a direct process (250-1), and hydrochar produced through an indirect process (250-2) were 37.14±0.24%, 36.57±0.96%, and 29.01±0.79%, respectively. Sample 250-2 displays the highest carbon content (66.88%) among all specimens. The FTIR and XRD expressed that the surface-modified hydrochar undergoes significant alterations in chemical properties. In addition, it was observed that 250-P exhibited amorphous morphology, while 250-1 displayed uniformity in the size and shape of its colloidal carbonaceous spheres, and 250-2 exhibited surface-damaged carbon spheres. The adsorption capacity of 250-2 for Cd (II), Cu (II), and Pb (II) is higher than 250-1 and 250-P. The maximum adsorption capacities of 250-P, 250-1, and 250-2 for Pb (II) were 179.13mg/g, 158.34mg/g, and 182.98mg/g, respectively, when the adsorbent concentration was 1000mg/L. The Langmuir model is a more effective representation of adsorption for all samples in comparison to the Freundlich model. The adsorption efficiency of 250-2 surface-modified hydrochar surpasses that of 250-1 and 250-P.

In the fifth chapter, the results expressed that the yields for pristine (275-0), 0.5 (275-0.5), 1.0 (275-1.0), and 2.0g/L (275-2.0) KMnO4-modified hydrochar were 34.75±1.87%, 29.41±0.12%, 27.30±1.08%, and 25.68±0.64%, respectively. 275-1.0 had the highest intensity absorbance for FTIR, while the XRD results showed a slight difference. Furthermore, 275-0.5 and 275-1.0 had irregular-shaped particles with rough surfaces, indicating a higher surface area and porosity, whereas 275-0 and 275-2.0 had fewer particles and mesopores. The main functional groups on the surface of hydrochar were quinone-type carbonyl groups C=O and phenolic and ether groups C-O/C-O-C. For all heavy metal ions, 275-1.0 had the highest adsorption capacity at each time interval, followed by 275-0.5 and 275-0.

Embargo Reason

Publication Pending

Comments

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