EPA Conducts Study On Biodiesel Emissions

There has been increasing interest in recent years in the use of biodiesel as a substitute for petroleum-based diesel fuel.

Biodiesel is derived from plant or animal fat-based oils or their transesterified counterparts. Studies have found biodiesel use decreases emissions of hydrocarbons and particulate matter while increasing emissions of nitrogen oxides. Several municipalities and states are considering mandating the use of low levels of biodiesel in diesel fuel.

Using existing data, EPA's "Biodiesel Emissions Analysis Program" seeks to quantify the air pollution emission effects of biodiesel for diesel engines that have not been specifically modified to operate on biodiesel. The program will examine the emission impacts of biodiesel and biodiesel/diesel blends for both regulated and unregulated pollutants, as well as fuel economy.

The program is not intended to include investigations of other aspects of biodiesel use, such as:

• Engine durability
  
• Renewability/full fuel lifecycle emissions
  
• Materials compatibility
  
• Biodiesel production feedstocks or costs
  
• Fuel storage stability
  
• Cold flow properties
  
• Lubricity
  
• Cost

The statistical analyses expected to be conducted will correlate emission impacts (in terms of percent change with respect to a baseline fuel) with the concentration of biodiesel in a biodiesel/diesel blend. These emission impacts may be nonlinear and could potentially be a function of any of the following variables or others deemed important during the course of the analysis:

• Engine/vehicle technology
  
• Base fuel to which biodiesel is added
  
• Light versus heavy-duty
  
• Highway versus non-road
  
• Test cycle
  
• Type of biodiesel

The degree to which these variables can be taken into account will depend on the amount and type of available data.

The complete database of biodiesel emissions data being used as the basis of EPA's "Biodiesel Emissions Analysis Program" has been posted on the EPA Web site.

Updated: April 28, 2003