Capitol Corridor, San Joaquins Transitioning to Renewable Diesel

San Joaquin and Capitol Corridor at Emeryville, Calif. Photo: Pi.1415926535/Wikipedia

Renewable diesel (RD), a locomotive fuel made from renewable raw materials and considered more sustainable than its fossil fuel counterpart, will soon be deployed on two California intercity passenger rail services.

On May 8, when a storage tank is slated for delivery at the Oakland Maintenance Facility, Capitol Corridor and San Joaquins locomotives will begin transitioning to RD. The goal is having the entire fleet on RD by end of the month.

The Capitol Corridor Joint Powers Authority (CCJPA) initiated exploration of alternative fuel options in collaboration with the California Air Resources Board (CARB). The California State Transportation Agency (CalSTA) “stepped up to fund the testing and worked with the passenger rail equipment manufacturers to ensure the efficacy of the new fuel source,” said Robert Padgette, CCJPA Managing Director. CalSTA also worked with the U.S. Environmental Protection Agency (EPA) to obtain certification.

CCJPJ Chair Robert Raburn noted that the project “was a collaborative effort of statewide partners committed to advance California’s goal of zero emissions.” Raburn added.

CCJPA worked with Amtrak, fuel distributor RD contractor Western States Oil and Neste, the world’s largest producer of RD, to successfully complete testing of Neste MY Renewable Diesel™ in August 2022. RD certification followed in November 2022. Neste MY Renewable Diesel “is fully compatible with all diesel engines and current diesel fuel distribution infrastructure, so the Capitol Corridor did not need any extra investments or modifications to make the switch,” CCPJ noted. “Made from sustainably sourced, 100% renewable raw materials, Neste MY Renewable Diesel™ can reduce up to 75% of GHG emissions over its life cycle compared to fossil diesel.”

According to Neste, the GHG emission reduction varies depending on the region-specific legislation that provides the methodology for the calculations (e.g. EU RED II 2018/2001/EU for Europe and U.S. California LCFS for the U.S.), and the raw material mix used to manufacture the product for each market.

Transitioning to a more sustainable fuel is aimed to reduce a fleet’s environmental impact, but it requires technical expertise, funding as well as regional and federal oversight. The U.S. EPA has stringent standards  reduce PM (particulate matter) and other harmful emissions from locomotive engines (the current standard for new locomotives is Tier 4), as well as for the type of fuel. Capitol Corridor and San Joaquin services, the latter operated by Amtrak California for the San Joaquin Joint Powers Authority (SJJPA), share a locomotive fleet consisting of EMD F59PHIs , Siemens Chargers  equipped with Cummins Tier 4-compliant QSK95 diesel engines, and Wabtec (former GE) P32-8WHs. 

“Switching to RD has been a strategic initiative for the San Joaquins,” Brian Schmidt, SJJPA Director of Equipment Services, said. “SJJPA would like to thank CCJPA for its leadership in converting our shared fleet to renewable diesel. Our collective commitment to reducing greenhouse gas emissions has taken a large step forward.”

”As we implement on our Climate Commitment, we welcome new ways to support Amtrak trains in California, including the 170-mile-long Capitol Corridor route,” said Jeanne Cantu, Amtrak Vice President, California. “We are thrilled that the pilot’s success allows us to operate on renewable diesel resulting in fewer lifecycle emissions throughout California.”

RD is chemically similar to crude oil-based diesel but made from renewable raw materials such as used cooking oil and animal fat byproducts. It differs from biodiesel, which is made, for example, from soybeans. “Because RD is produced by utilizing the already existing carbon stored in the renewable raw materials in nature, when the fuel is combusted, the carbon dioxide it emits is not considered as adding new carbon to the atmosphere,” CCPJ said. “The use of fossil diesel, on the contrary, releases new carbon dioxide and other greenhouse gases, contributing to climate change. Other emissions, such as fine particulates and nitrogen oxides may also be reduced using renewable diesel, which improves local air quality.”

FAME (Fatty Acid Methyl Ester) is the generic chemical term for diesel fuel derived from renewable sources. It is used to extend or replace mineral diesel and gas oil used to fuel on- and off-road vehicles and static engines. FAME consists of acids created during the transesterification of vegetable oils and animal fats to create biodiesel. These high molecular weight oils and fats react with short chain alcohol in the presence of a catalyst, usually potassium hydroxide, to produce lower molecular weight esters.

Wabtec (which does not currently offer passenger locomotives) has more than 40 freight units operating with various blends of fuels, for example, 20% biodiesel and 80% renewable diesel. “Biodiesel is close to diesel, but with more waxes and paraffins and other elements,” explained Wabtec Executive Vice President and Chief Technology Officer Eric Gebhardt in a recent Railway Age article on alternative locomotive power. “It’s chemically different. Renewable diesel is hydrogenated, so it’s a pure form of the diesel molecule. In fact, it’s a little too pure, so it requires additives to improve viscosity. We’ve approved up to 5% biodiesel and up to 30% renewable diesel for our locomotives, and we’re trying to get to 20% biodiesel and up to 100% renewable diesel. Both types come from the same feedstocks. We need to understand what engine parts would have to be changed out burning these different types of fuels—things like hoses and seals. We want to understand the deterioration factors, the impact on fuel injection systems, for example, to stay within current emissions compliance standards. Fuel injectors have very precise passages. We need to make sure we can reach the NOx and particulate matter requirements.

“We’re working with our customers through field tests, inspecting these units to make sure we know what the maintenance intervals need to be. We’re less concerned about the metals (internals). We don’t think any of those would be a large concern, with the right lubricity (the measure of friction reduction) and viscosity (the measure of a fluid’s resistance to flow) additives. We’re paying close attention to how elastomers and hoses, the rubber components, will interact. We have a program with the Class I’s, and we don’t see any reasons why we won’t be successful with this. Longer term, it’s going to be important for our customers to understand the availability and cost of these fuels. Some parts of the U.S. have significant subsidies—California, for example. The price points might vary in different parts of the U.S.”