Argonne National Laboratory’s Systems Assessment Center has released the 2020 version of the suite of GREET models and associated documentation. The GREET (Greenhouse Gases, Regulated Emissions, and Energy use in Transportation) tool provides a common, transparent platform for lifecycle analysis (LCA) of of the energy and environmental effects of a wide variety of transportation fuels and vehicle technologies in major transportation sectors (i.e., road, air, marine, and rail) and other end-use sectors, and energy systems.
Vehicle technologies include conventional internal combustion engines, hybrid-electric systems, battery-electric vehicles, and fuel-cell-electric vehicles. Fuel/energy options include petroleum fuels, natural gas-based fuels, biofuels, hydrogen, and electricity.
LCAs conducted with the GREET platform permit consideration of a host of different fuel production, and vehicle material and production pathways, as well as alternative vehicle utilization assumptions.
Argonne has expanded and updated the model in various sectors in GREET 2020; some (but certainly not all) of the major changes include:
CO2 utilization (e-fuels) and carbon capture and sequestration (CCS). Argonne added a new “E-fuel” tab that covers several e-fuel production pathways. Users can evaluate the impacts on energy use, water consumption, and emissions of e-fuel production pathways using different hydrogen (H2) and electricity sources. Further, the team implemented a CCS option for capturing and sequestering fermentation CO2 in corn ethanol plants in the EtOH tab.
CO2-derived ethanol. Argonne evaluated life-cycle greenhouse gas (GHG) emissions of ethanol produced via gas fermentation and electrochemical reduction processes from the CO2 emitted from corn ethanol plants. (Argonne researchers are publishing a paper on the topic.)
CO2-derived FT fuels and methanol. GREET now includes two e-fuel pathways with Fischer-Tropsch (FT) synthesis process and two e-fuel pathways for methanol (MeOH) production using CO2 (from corn ethanol plants) and renewable H2.
Supply chain sustainability analysis (SCSA) of six biofuel production pathways. The SCSA takes the life-cycle analysis approach to identify energy consumption and environmental sustainability hotspots that could be mitigated through improved process materials and energy conversion efficiencies.
Delivery of high-purity CO2 for algae growth. Energy consumption for the compression and delivery of high-purity (>95%) CO2 from natural gas steam methane reforming, ammonia manufacturing facilities, and corn ethanol plants are added to the “Algae” tab.
PFAD to Renewable Diesel. A pathway of palm fatty acid distillate (PFAD) to renewable diesel (RD) is now added to the “BioOil” tab.
New pathways for co-optimized fuels and engines. The team added four pathways for fuels for use in engines co-optimized with drop-in biofuel blends to improve engine performance. Two of the pathways produce isobutanol and aromatic rich hydrocarbons (ARHC) as two bio-blendstocks. Blended with a petroleum gasoline blendstock, these bio-blendstocks are designed to improve engine efficiency for light-duty, boosted-spark ignition (BSI) engines.
The other two pathways produce bio-blendstocks capable of reducing engine-out emissions for mixing-controlled compression ignition (MCCI) engines in heavy-duty vehicles. These MCCI fuels are both diesel-like bio-blendstocks blended with conventional diesel.
Renewable natural gas and lactic acid production from wet waste feedstocks. Argonne evaluated the life-cycle GHG emissions of renewable natural gas (RNG) and lactic acid (LA) production from four waste feedstocks (wastewater sludge, food waste, swine manure, and fats, oil, and grease [FOG]) via anaerobic digestion (AD) and arrested AD, respectively, in collaboration with National Renewable Energy Laboratory (NREL). The results show that both waste-derived RNG and LA production pathways bring significant GHG emission reduction benefits.
Green ammonia. The following low-carbon alternative ammonia production pathways have been implemented in GREET 2020 release. The stoichiometric N2 and H2 is compressed and enters the electricity-driven Haber-Bosch synthesis loop to produce ammonia, with high purity N2 obtained from air separation technologies, namely, cryogenic distillation and pressure swing adsorption; and high purity H2 produced from various technologies: 1) low-temperature electrolysis; 2) high-temperature electrolysis; 3) as a by-product from chlor-alkali processes; and 4) as a by-product in steam cracker plants. Users can choose between different N2 and H2 production technologies. In addition, users can specify the shares between conventional and low- carbon ammonia production pathways to determine the impacts of ammonia production on the downstream activities.
Hydrogen and fuel cell vehicles: by-product H2 from steam cracker. To estimate the energy use and air emissions of by-product H2 from steam crackers (listed as steam cracker by-product H2 pathway), Argonne has updated the steam cracking process using reported operational data from the US steam cracking facilities.
Electricity generation efficiency and criteria air pollutant emission factors. Argonne made several updates to characterize emission factors, generation efficiencies, and generation technology mixes of the US electricity generation sector. The team also generated state-specific life-cycle energy usage, water consumption, and pollutant emission results from electricity generation based on state-specific fuel and generation technology mixes, electricity generation efficiencies, and transmission and distribution losses.
Update of specific energy and bill of materials of lithium-ion batteries. GREET 2020 updates the specific energy and bill-of-materials (BOMs) of lithium-ion batteries (LIBs) for electric vehicles (EVs), including battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in electric vehicles (PHEVs). Updates to the specific energy and BOMs were based on the most recent version of Argonne’s Battery Performance and Cost (BatPaC) model. There is also a new LIB cathode chemistry, LiNi0.5Mn0.3Co0.2O2 (NMC 532).
Nickel pathway updates and additions. GREET 2020 updates life-cycle analyses of the production of class I nickel and battery-grade nickel sulfate based on industry data, compiled by the Nickel Institute, that represent 52% of global class I nickel production and 15% of global nickel sulfate production in 2017.
Lithium pathway updates and additions. The team expanded and updated the structure of lithium production pathways in the model—specifically, the expansion and updating of pathways for lithium extracted from spodumene ore and converted into lithium carbonate (Li2CO3) and lithium hydroxide (LiOH).
Methanol as marine fuels. Six discrete methanol pathways for maritime applications are added to the GREET Marine Fuels Module (Marine_WTH tab). These pathways include methanol derived from natural gas, flare gas, biomass, renewable natural gas, coal, and black liquor.