Waste-to-Wheel Analysis of Anaerobic-Digestion-Based Renewable Natural Gas Pathways with the GREET Model

Technical Report · Wed Dec 14 00:00:00 EST 2011

DOI:https://doi.org/10.2172/1036091· OSTI ID:1036091

Han, J. ^[1]; Mintz, M. ^[1]; Wang, M. ^[1]

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1. Argonne National Laboratory (ANL), Argonne, IL (United States). Energy System Division

In 2009, manure management accounted for 2,356 Gg or 107 billion standard cubic ft of methane (CH₄) emissions in the United States, equivalent to 0.5% of U.S. natural gas (NG) consumption. Owing to the high global warming potential of methane, capturing and utilizing this methane source could reduce greenhouse gas (GHG) emissions. The extent of that reduction depends on several factors - most notably, how much of this manure-based methane can be captured, how much GHG is produced in the course of converting it to vehicular fuel, and how much GHG was produced by the fossil fuel it might displace. A life-cycle analysis was conducted to quantify these factors and, in so doing, assess the impact of converting methane from animal manure into renewable NG (RNG) and utilizing the gas in vehicles. Several manure-based RNG pathways were characterized in the GREET (Greenhouse gases, Regulated Emissions, and Energy use in Transportation) model, and their fuel-cycle energy use and GHG emissions were compared to petroleum-based pathways as well as to conventional fossil NG pathways. Results show that despite increased total energy use, both fossil fuel use and GHG emissions decline for most RNG pathways as compared with fossil NG and petroleum. However, GHG emissions for RNG pathways are highly dependent on the specifics of the reference case, as well as on the process energy emissions and methane conversion factors assumed for the RNG pathways. The most critical factors are the share of flared controllable CH₄ and the quantity of CH₄ lost during NG extraction in the reference case, the magnitude of N₂O lost in the anaerobic digestion (AD) process and in AD residue, and the amount of carbon sequestered in AD residue. In many cases, data for these parameters are limited and uncertain. Therefore, more research is needed to gain a better understanding of the range and magnitude of environmental benefits from converting animal manure to RNG via AD.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Office of Sustainable Transportation. Vehicle Technologies Office (VTO)
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 1036091
• Report Number(s): ANL/ESD/11--6
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

02 PETROLEUM
03 NATURAL GAS
09 BIOMASS FUELS
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
ANAEROBIC DIGESTION
ANIMALS
CARBON
FOSSIL FUELS
FUEL CYCLE
GASES
GREENHOUSE EFFECT
GREENHOUSE GASES
LIFE CYCLE
MANAGEMENT
MANURES
METHANE
NATURAL GAS
PETROLEUM