Changing the renewable fuel standard to a renewable material standard: bioethylene case study

Area of Science:

• Environmental Science
• Chemical Engineering
• Policy Analysis

Background:

• The U.S. Renewable Fuel Standard (RFS2) faces challenges meeting targets due to limited ethanol demand.
• A narrow policy scope restricts broader biomass utilization.
• Chemical conversion of bioethanol offers a potential avenue for increased biomass use.

Purpose of the Study:

• To evaluate the greenhouse gas (GHG) implications of a flexible RFS2 policy incorporating bioethanol for chemical production (bio-LDPE).
• To compare life-cycle GHG emissions of bio-based products with conventional fossil-based products.
• To assess the viability of different biomass feedstocks for producing low-GHG bio-products.

Main Methods:

• Monte Carlo simulation used to estimate life-cycle GHG emissions.
• Analysis of conventional low-density polyethylene (LDPE) derived from natural gas.
• Life-cycle GHG emissions assessed for bioethanol and bio-LDPE from U.S. corn, U.S. switchgrass, and Brazilian sugarcane.

Main Results:

• Conventional LDPE has a mean GHG emission of 1.8 kg CO2e/kg.
• Corn-based bioethanol and bio-LDPE do not meet regulatory GHG targets.
• Switchgrass and sugarcane derived products show potential for meeting GHG targets, with switchgrass exhibiting negative emissions.

Conclusions:

• A flexible RFS2 policy including bio-LDPE enhances policy effectiveness without compromising GHG reduction goals.
• Bio-LDPE offers greater GHG reductions than bioethanol for imported Brazilian products.
• Policy expansion is recommended to leverage biomass potential and improve GHG outcomes.