Abstract

Agricultural wastes can be valuable materials because they are generated in large quantities all over the world and contain a variety of feedstocks. These feedstocks include dairy manure, food wastes, solid wastes and plastics. Current waste management techniques include landfilling and incineration, both leading to an increase in greenhouse gas emissions. However, alternative methods such as pyrolysis can present more sustainable pathways by transforming mixed wastes from the agricultural sector into value-added products such as biochar, bio-oil and syngas. Limited published literature has focused on producing biochar derived from co-pyrolysis of agricultural wastes with plastic wastes such as agricultural mulch films that are used for crop quality control. Most prior work has focused on fast co-pyrolysis of these materials, which favors bio-oil and syngas production rather than biochar. In this study, we explored the potential benefits of biochar generated from pyrolysis of agricultural solid wastes and co-pyrolysis of these wastes with agricultural mulch films plastics. We first produced and analyzed biochar derived from common biomass-based agricultural waste materials: hemp meal (HM), wood pellets (WP), pallet wood (PW) and hammer milled boxboard (HB) at two different temperatures (500 °C & 800 °C). These feedstocks were converted into biochar at laboratory conditions using a high temperature furnace with inert (N2) environment. We further studied the presence of low-density polyethylene (LDPE) agricultural mulch films in both hemp meal and wood pellets feedstocks at the same temperatures and at three different blend ratios of 100:0, 95:5 and 75:25wt.%. It was found that the presence of plastics had minimal effects on the biochar quality of the wood pellets. After processing, all biochar materials except that derived from hemp meal had high organic carbon content (Corg) and hydrogen to carbon (H:C) ratio less than 0.7, indicating long-term stability. Assessments of soil enhancement properties and heavy metals present in the biochar were also conducted. Additional analysis was performed to determine the effect of mid-point temperature pyrolysis temperature on the quality of the biochar product. Finally, carbon sequestration and techno-economic analyses were conducted to quantify the potential sustainability benefits of deploying a commercial scale pyrolysis system at a single farm for on-site waste processing. The computed carbon sequestration impact factors (t CO2e/t biochar) were consistent with prior studies modeling much larger systems, but profitability of biochar production was only achieved when processing wastes in a regional system including 10 times greater feedstock from surroundings farms, and assuming a relatively high biochar value of $500/t.

Library of Congress Subject Headings

Biochar--Analysis; Agricultural wastes as fuel; Biomass; Pyrolysis

Publication Date

5-2021

Document Type

Thesis

Student Type

Graduate

Degree Name

Sustainable Systems (MS)

Department, Program, or Center

Sustainability (GIS)

Advisor

Thomas A. Trabold

Advisor/Committee Member

Nabil Z. Nasr

Campus

RIT – Main Campus

Plan Codes

SUSTSY-MS

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