Abstract

Energy and useful materials can be produced by applying biological and thermal conversion processes such as anaerobic digestion and pyrolysis. Agricultural and industrial wastes seem to be the most attractive substrates since they are essentially unlimited resources. Pyrolysis has been used mostly for the conversion of biomass to bio-crude and biochar, a stable form of nearly pure carbon that has application in many agricultural and environmental applications. There is a widespread literature describing use of biochar as an additive to stabilize the anaerobic digestion process. We studied the effects that biochar has on the biomethane potential (BMP) during anaerobic digestion of a model food waste under mesophilic conditions (37ºC). Mixed food waste (FW) and dry manure (DM) were first converted into biochar at 500 and 800ºC using a laboratory pyrolysis furnace. Biochar loadings of 0, 0.5, 1, and 2 %g/gVS were added into 500 mL digester vessels. It was found that biochar provides enhanced stability when added to AD because biochar acts as a buffer in the system. Food waste biochar produced at 500ºC with a loading of 1% resulted in an increase of 11.7% in BMP when compared to the control. It was determined that biochar produced at lower temperature has lower pH and a greater effect in the upgrading of biomethane. Based on the experimental results, a techno-economic analysis (TEA) model was developed to understand the value that adding biochar would have to an operating digester, assuming a 10% enhancement in methane production with 1% biochar addition, based on the total mass of waste processed. The model included a sensitivity analysis in which an increase in food waste loading of 1, 5, 10 and 20% to the AD system was studied. The TEA revealed that food waste tipping fees drive the economics of working AD systems and that the addition of biochar has the possibility of boosting the economics for scenarios where biochar is purchased at low to mid-range prices, or when a pyrolysis system is installed on-site to produce biochar.

Publication Date

5-2020

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

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