California’s battle to cut emissions with biofuels burns in new truck engines

diesel biofuel
A fuel nozzle from a biodiesel fuel pump is seen in this photo illustration taken at a gas station in San Diego. REUTERS/Mike Blake

Renewable diesel is touted as a cleaner fuel, but a recent study showed the fuel is failing to meet a measure to reduce pollution from new truck engines – giving pause to California regulators who support increased production.

The state, the nation’s largest auto market, has taken aggressive steps to reduce fossil fuel emissions from all vehicles while encouraging the production of renewable diesel – seen as key to reducing emissions in hard-to-electrify sources. like trucking.

The efforts are part of California Low Carbon Fuel Standard (LCFS), a rule designed to reduce the carbon intensity of the state’s transportation fuel.

Renewable diesel reduces greenhouse gas emissions compared to petroleum-based diesel. The fuel has also been promoted as a way to reduce emissions of nitrogen oxides (NOx), a harmful pollutant that contributes to ozone degradation and causes respiratory problems.

However, according to a study published by California Air Resources Council (CARB) in November.

CARB found in these New Technology Diesel Engines, or NTDEs, running on 100% renewable diesel, NOx emission increases were not statistically significant compared to CARB diesel,

This could affect how regulators revise the LCFS, which has boosted investment in renewable diesel, made from vegetable fats and oils.

State regulators are considering changes to the LCFS that align with a 2022 update on how to bring the state to carbon neutrality by 2045. The study means regulators may need to determine whether renewable diesel increases emissions in areas with poorer air quality.

CARB said it has “identified several questions about the study results” that require further evaluation and will accept public comments on the study until the end of January.

Regulators did not respond to a request for comment.

Heavy-duty vehicles are one of the biggest contributors to NOx emissions – a precursor to ozone and particulate formation. According to United States Environmental Protection Agency.

Companies and regulators had previously claimed that renewable diesel reduced NOx emissions by 10%, citing results from previous studies that looked at fuel performance in older engines.

But trucks with newer engines running on renewable diesel did not significantly reduce NOx emissions, the study found. Although these NTDEs are present in only 43% of the state’s commercial vehicle registrations, they account for more than 75% of the miles driven among the state’s heavy-duty fleet.

“CARB threw caution to the wind and opened the door to the unlimited use of renewable diesel without properly studying the impact of NOx emissions in NTDEs,” said Pat McDuff, general manager of California Fueling, based in Glendale, in a public comment submitted in January.

He urged California regulators to reverse regulatory changes that prohibit his company from selling fuel additives intended to reduce NOx emissions in biodiesel.

The state is trying to bring 19 regions into compliance with air quality standards enacted in 2015. In two regions – the South Coast and the San Joaquin Valley airshed – CARB has targeted the reduction of air emissions from NOx as a way to improve air quality. In 2020, regulators passed new regulations aimed at reducing NOx emissions by 90% by 2027.

Renewable diesel generally reduces emissions of greenhouse gases and other pollutants, said Tristan Brown, associate professor of energy resource economics at SUNY and adviser to the Climate Action Council of New York.

Brown noted that most biodiesel blends in the United States are 20% or less. “The real question is how much NOx is emitted by NTDE engines at 10% volumes and 20% biodiesel blend levels, and that’s not reported by the study,” Brown said.


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