California ARB considering four new low-carbon fuel pathways; Neste renewable diesel and sugarcane molasses ethanol
California Air Resources Board (ARB) staff has posted four new Low Carbon Fuel Standard (LCFS) pathways to the LCFS web site. (Earlier post.) Among the new pathways to be considered is the production of renewable diesel from Australian tallow at Neste Oil’s Singapore plant. Others are sugarcane molasses ethanol from Guatemala; mixed feedstock to biodiesel from Texas; and a new ARB-staff-developed pathway for North American landfill gas.
The Low Carbon Fuel Standard, approved in April 2009, requires that suppliers of transportation fuels meet an average declining standard of carbon intensity (CI) —expressed in grams of CO2 equivalent per megajoule of fuel energy (g CO2e/MJ)—that will provide a 10% reduction in greenhouse-gas emissions for all fuels used in California by 2020. The CI of a fuel is determined by the sum of all greenhouse gas emissions associated with the production, transportation, processing and consumption of a fuel (its pathway).
The baseline CI value for gasoline is 95.86 g CO2e/MJ; for diesel fuel, it is 94.71 g CO2e/MJ.
As new lower CI fuels are developed and approved, they are added to the LCFS Lookup Table for use by regulated parties under the LCFS. New pathways can be added to the LCFS Lookup Table in two ways: fuel providers may apply to ARB for new pathways under the regulatory “Method 2” process, and ARB staff may develop new pathways internally.
Neste Oil renewable diesel: 33.46 gCO2e/MJ. Neste Oil Singapore Pte Ltd. produces NExBTL non-ester renewable diesel (RD) from multiple feedstocks at its plant in Singapore. (Earlier post.) The plant produces approximately 250 million gallons of RD annually.
Neste applied for an LCFS pathway covering the RD produced from Australian tallow at its Singapore plant. This feedstock is rendered in Australia and shipped by ocean tanker an estimated 4,548 nautical miles to the Neste plant. Because Neste purchases its feedstock from various Australian rendering plants, it calculated its pathway rendering emissions using data from a sampling of Australian rendering facilities. Once the rendered tallow has been converted to renewable diesel, the finished fuel is transported an estimated 7,677 nautical miles by ocean tanker to Los Angeles.
Neste’s process generates a propane-rich off-gas as a biogenic co-product. The high pressure portion of this off-gas (both high- and low-pressure gas is generated) is supplied via a dedicated pipeline to a hydrogen plant located on Jurong Island.
There it displaces natural gas that would otherwise have been consumed as both a process fuel and a feedstock at the steam-methane reformer. The hydrogen supplied by the plant is piped back to the Neste plant where it is used for hydrotreatment. The low pressure propane-rich off gas is sent to a natural gas steam boiler which provides process heat to the RD plant.
Neste calculated its pathway CI to be 33.46 gCO2e/MJ. This CI includes a 3.75 gCO2e/MJ credit for the natural gas displaced by the propane-rich off-gas from the RD plant. This proposed carbon intensity value includes feedstock rendering, transportation of the rendered feedstock to the refinery, renewable diesel production, finished fuel transportation to California, and vehicle tailpipe emissions.
When data on the electrical and thermal energy consumption at the specific rendering plants supplying Neste’s plant becomes available, Neste will provide that data to staff in order to verify the carbon intensity of the feedstock rendering phase of Neste’s Australian tallow pathway.
ARB staff has recommended that Neste Oil’s application for a pathway be approved.
Pantaleon Sugar Holdings S.A. sugarcane molasses ethanol: 22.75 gCO2e/MJ. Pantaleon Sugar Holdings (Bio-Etanol S.A) is a company based in Guatemala that produces and exports ethanol derived from sugarcane molasses. Sugarcane is harvested on company-owned and partnership farms, and then transported to the sugar mill. After the sugarcane has been crushed, all of the cane juice is sent to sugar production. A by-product of the sugar production process is molasses, which is recycled into the production process to recover additional sugar crystals.
After recovery of the optimum amount of crystalline sugar from the molasses, the remainder of the molasses byproduct stream is sent to the ethanol distillery for fermentation and distillation, resulting in the production of anhydrous ethanol. A portion of the molasses byproduct is also sold in the marketplace.
The Pantaleon facility also generates and utilizes process heat and electricity from bagasse combustion for all its industrial operations. Surplus electricity produced is exported to the local electrical grid.
The major difference between the proposed Pantaleon pathway and the Brazilian sugarcane-based ethanol pathways in the LCFS tables is in the type of feedstock: Pantaleon uses molasses, a by-product from the sugar production process, whereas Brazilian producers largely use pure sugarcane juice for ethanol production. (Brazilian sugarcane ethanol pathways in the LCFS tables have CIs ranging from about 70-80 gCO2e/MJ.)
Ethanol produced from fermentation of the molasses is transported by truck to the western Guatemalan port of Puerto Quetzal, and loaded onto ocean-going tankers for shipment to California. Ethanol transport and distribution modes in California are assumed to be identical to those used in the Brazilian sugarcane ethanol pathway.
Although sugar and molasses are products of the same agricultural, feedstock transport, and production processes, the GHG emissions from those activities need to be allocated between the two products for proper lifecycle accounting. Pantaleon chose the market allocation methodology in which the total upstream and sugar production emissions are allocated on the basis of the relative share of total sales revenues that accrue to each product (sugar and molasses) for each ton of fermentable sugars in cane juice that enters the sugar production process. ARB staff agreed with that methodology.
Based on market price data for sugar and the by-product molasses ($400 and $150 per short ton, respectively), Pantaleon determined that 14.46 gCO2e/MJ fuel of upstream and sugar production emissions should be allocated to the production of the by-product molasses. When these upstream and sugar production emissions are combined with ethanol production, transport, and distribution emissions, total well-to-tank (WTT) life cycle GHG emissions for the Pantaleon pathway are estimated to be 18.65 g CO2e/MJ fuel.
Pantaleon’s electricity cogeneration and surplus export credit is 1.12 gCO2e/MJ of fuel produced. When applied to the WTT (well-to-tank) CI of ethanol, intensity (CI) of ethanol, this credit results in a net WTT CI of 17.53 gCO2e/MJ. When life cycle emissions due to land use changes (LUC), and the addition of denaturant to the ethanol fuel are added to the WTT CI estimate, the final WTW CI for the Pantaleon pathway is estimated to be 22.75 g CO2e/MJ of ethanol fuel produced. ARB staff recommends approval.
Endicott Biofuels mixed feedstock biodiesel: 10.05 gCO2e/MJ. Endicott Biofuels LLC will soon begin producing biodiesel from used cooking oil at its newly constructed plant in Port Arthur, Texas. During the development of this facility, Endicott formed a joint venture with an independent refiner, HollyFrontier Corporation. This collaboration resulted in an entity known as Sabine Biofuels II, LLC. The Port Arthur plant, which is currently undergoing commissioning, is designed to produce 30 million gallons of biodiesel annually.
Unlike the more common fatty-acid methyl ester process which cannot tolerate high fatty acid concentrations, the patented Sabine Process utilizes free fatty acids to produce biodiesel. This is accomplished via reactive distillation using the Davy process. Because the Sabine Process desires free fatty acids, all natural fats or oils are accessible but those fats or oils that are waste in nature are preferred. The Sabine Process can also process glyceride oils by breaking them down into their free fatty acid components in a pre-treatment step.
Sabine’s process yields a high BTU renewable co-product known as pitch. Because it is similar to number 6 heavy fuel oil in terms of heat content and viscosity, pitch can displace number 6 oil in the marketplace. Number 6 fuel oil is commonly used to fuel large ocean-going vessels. The co-product credit for pitch was calculated based on its ability to displace number 6 fuel oil in such vessels.
Sabine obtains rendered used cooking oil from sources in the Midwest. This feedstock is transported approximately 1,500 mile by rail the Port Arthur plant. The resulting BD is then transported approximately 1,600 miles by rail to California.
The pitch co-product from Sabine’s process yields a co-product credit of 5.85 gCO2e/MJ. This credit reduces Sabine’s overall pathway carbon intensity to 10.05 gCO2e/MJ. ARB staff recommends approval.
ARB: North American landfill gas to compressed natural gas: 33.02 gCO2e/MJ. ARB staff developed a pathway covering the production of biomethane from landfill gas (LFG-to-CNG) anywhere in North America. The biomethane produced under this pathway would be transported to California by pipeline, compressed, and made available to motor vehicles as compressed natural gas (CNG).
Most of the CA-GREET inputs used to develop ARB’s California LFG-to-CNG pathway were left unchanged in the full North American pathway. Only the following inputs were changed in order to make the resulting pathway available to as many North American LFG-to-CNG producers as possible:
- A pipeline transport distance of 3,600 miles;
- An electrical energy generation mix of 100% coal for the LFG recovery and processing phases.
- An LFG capture and processing efficiency of 77.2%—the lowest efficiency currently in use at North American Landfills.
- Fuel shares of 76.8% thermal and 26.2% electricity in LFG processing.
- A natural gas leak fraction of 0.15%