(573m) Exploring the Effect of Facility Construction in Biofuel Life Cycle Analyses through Greenhouse Gas Emissions

Life cycle analysis (LCA) has been widely used as a crucial tool to determine the environmental benefits of biorefineries. While extensive LCA research has been conducted on the environmental footprints of various biofuels and bioproducts, the environmental impact of facility construction has not been well understood and quantified in the field of biorefinery LCA.

Most LCAs on biofuels and bioproducts to date neglect the effect of facility construction in their assessment. In the regulatory domain, the Environmental Protection Agency (EPA) implemented the Renewable Fuel Standard (RFS) to promote biofuel use. The guideline for biorefinery LCA for the fuel production and distribution stage under this standard particularly specified that emissions associated with physical infrastructure (i.e., facility construction) are not included in the EPA’s assessment¹. On the other hand, no quantitative studies have been done to verify or support such assumptions. The goal of this study is to address this gap by quantifying the Greenhouse gas (GHG) emissions associated with the construction of equipment used in biorefineries to validate such assumptions.

This study investigates two bioprocess pathways based on technical reports from the National Renewable Energy Laboratory (NREL) and examines the potential emissions from biorefinery infrastructure. The equipment sizing for pressure vessels and storage tanks is performed following the ASME Boiler and Pressure Vessel Code and the API 650, respectively. GHG emissions associated with the production of pressure vessels and storage tanks are estimated based on equipment weight and emission factors of construction materials from Norgate et al. (2007) and the Ecoinvent database. Emissions related to pump and conveyor belt production are determined on OpenLCA with the Ecoinvent database. Four different methods are used to determine the weight and material consumption of pressure vessel manufacturing, thus further characterizing the GHG emissions from biorefinery equipment construction. This study also conducts a scenario analysis on emissions calculated with three different head types for pressure vessels. Additional scenario analysis is performed with emission factors for carbon steel and stainless steel production from Norgate et al (2007), the Ecoinvent database, Jing et al. (2019), Burchart-Korol (2013), Renzulli et al. (2016), and the Greenhouse gases, Regulated Emissions, and Energy use in Technologies (GREET) model.

Preliminary results indicate equipment construction contributes a small fraction to the baseline biorefinery GHG emissions. This fraction is higher as more environmentally friendly approaches are utilized to produce biofuel, but it is still low. Furthermore, the GHG emissions from equipment construction vary depending on the method used to calculate pressure vessel weight. The variation primarily stems from the undefined design temperature, design pressure, and dimensions of the pressure vessels and the heuristics each method employs to find these unspecified parameters. Also, there is a significant deviation in GHG emissions from equipment construction between using the Flanged and Dished head and the other two head types (Hemispherical and 2:1 Semi-Elliptical) for all the pressure vessels in the plant. This is because the Flanged and Dished wall thickness is higher than the thickness of the other two head types which leads to higher head weight. Additionally, emissions also vary with different data sources for stainless steel and carbon steel emission factors, which is due largely to deviations in emission factors and differences in carbon steel and stainless steel weight fractions.

The results of our study suggest the EPA’s assumption to exclude facility construction from its biorefinery LCA requirement under the RFS is justifiable. Future studies should expand the scope of the LCA and incorporate a landscape of biorefinery design scenarios to have a holistic understanding of the environmental impact of biorefinery facility construction.

1. US EPA. Lifecycle Analysis of Greenhouse Gas Emissions under the Renewable FuelStandard. https://www.epa.gov/renewable-fuel-standard-program/lifecycle-analysis-g... (accessed 2023-05-08).