Graduation Year

2022

Document Type

Thesis

Degree

M.S.C.H.

Degree Name

MS in Chemical Engineering (M.S.C.H.)

Degree Granting Department

Chemical Engineering

Major Professor

Babu Joseph, Ph.D.

Co-Major Professor

John N. Kuhn, Ph.D.

Committee Member

George Philippidis, Ph.D.

Keywords

Efficiency, Environmental Impact, LCA, Process Feasilibility, Renewable Energy

Abstract

Natural Gas (NG) is one of the major sources of energy currently used in the United States. Its major applications include generating electricity, domestic, and industrial heating purposes and as a transportation fuel. The largest component of NG is methane, and it contains trace amounts of hydrocarbons, some CO2 and water vapor.

Biogas (produced by anaerobic digestion (AD) of biomass) upgraded to have high purity methane (often termed as biomethane or renewable natural gas) can be used as an alternative to NG. The upgrading techniques may include CO2 separation from the biogas stream or via to a methanation facility where CO2 can be reacted with H2 to form CH4. This allows further enrichment of the CH4 in the stream. The biggest advantage of this biomethane is that it has a gas composition similar to NG and can therefore be injected into the existing pipeline infrastructure for distributing NG.

One of the proposed methods for producing RNG is by CO2 methanation using landfill gas as the source. This process utilizes H2 produced from water electrolysis for the methanation step. Herein, we have modeled a RNG production facility using Aspen Plus to produce RNG with 95.7 mol% methane content. The RNG product meets the NG pipelines specifications for direct injection.

The techno-economic sensitivity studies show that the RNG produced is not currently competitive with NG and is heavily dependent on the production price of H2. A life cycle assessment of the RNG production process was performed. A comparative study showed that the proposed process is capable of reducing the emissions by 70% in comparison to a biomethane production via High Temperature Water Scrubbing of biogas.

A life cycle assessment (LCA) of the RNG production process was performed. A comparative study showed that the proposed process is capable of reducing the emissions by 70% in comparison to a biomethane production via High Temperature Water Scrubbing of biogas.

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