Idle Resource Conversion Through Thermal and Chemical Methods into Value-Added Products

• Main Author: Gale, Mark Mitsuo
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2022
• Subjects: Agriculture; Chemical engineering; Environmental engineering
• ISBN: 9798837547317

Idle resource utilization will be a part of the solution for climate change. Agricultural waste like corn stover (CS) is predominantly left on the field and can be sustainably collected. Plastic waste is a growing environmental issue that is in dire need of methods to reduce accumulation. Agricultural and plastic waste have the potential to be converted into valuable products which can offset the reliance on nonrenewable resources. This dissertation evaluates the physiochemical properties of the solid fraction, biochar, of hydrothermal carbonization (HTC), slow pyrolysis (SP), and co-pyrolysis (CoSP). SP and CoSP utilize oxygen-free environments along with high temperatures to carbonize a carbon feedstock. HTC uses an oxygen-free environment with subcritical water and more moderate temperatures to carbonize. Furthermore, this work explores the chemical activation of the biochar generated from the aforementioned methods to create an upgraded product, activated carbon (AC). This study reports the influence of parameters during carbonization on the biochar and subsequent AC. The subcritical water in HTC played a crucial role in the more efficient degradation of biomass when compared to SP. The ACs from the direct method and HTC removed up to 98% of the vanillin, the highest removal of any of the ACs, and produced the highest surface area. The study of CoSP produced key insights on how polystyrene (PS) and polyethylene terephthalate (PET) interacts with CS. PS is a hydrogen donor and produces lower quality biochar and AC. PET produced high surface area biochar from the acids and oligomers formed during degradation. The oligomers are microplastics which are observed to be on the surface of the biochar and have potential environmental and health concerns. After activation, some of the CS-PET samples had a reduction of surface area due to the interactions between KOH and the products formed during thermal degradation of PET. Overall, the ACs produced from CS and plastics were lower quality in surface area and adsorption capabilities when compared with AC made from CS only. Additional idle resource utilization projects have the foundation developed and await a new researcher.