Biodiesel – Cleaner Fuel for Diesel Engines


Biodiesel is probably the most affordable option for dramatically reducing most pollution from a diesel vehicle engine or generator. Biodiesel is a diesel type fuel produced from soybean oil or other vegetable oils or animal fats, either from plants grown for that purpose or by recycling waste restaurant grease.  



- Drop in replacement for petroleum diesel fuel, meaning no modification of the diesel engine is necessary. Can be used in a blend or as a complete replacement, stored in regular diesel tanks and pumped with same equipment

- BTU content is higher than No. 1 diesel and only slightly below No 2 diesel

- Only a fraction of most emissions (from DoE NREL stats – tests reported by World Energy show even more dramatic reductions)

 - oxygenated fuel provides more complete combustion

 - 78% less life cycle CO2 (most of the CO2 released in combustion is recaptured by the plants that it comes from)

 - almost 100% less sulfur dioxide

 - 56% less hydrocarbons

 - 55% less particulates

 - 43% less carbon monoxide

 - no carcinogenic benzene, major reduction in other airborne toxics and carcinogens

- Safer to handle than petroleum diesel

 - virtually non toxic

 - biodegradable

 - much higher flashpoint - (300F vs 125F)

- Better lubricating qualities than petroleum diesel, even at low percentage blends (20% or less)

- Domestically produced from renewable crops such as soybeans directly or by recycling fats from restaurant cooking oil wastes

- Exhaust smells like french fries

- Good net energy efficiency – for every unit of fossil energy used to produce biodiesel, 3.37 units of biodiesel energy are created.

- Proven extensively in vehicular diesel engines and generators

- EPAct credits available - one for every 450 gallons of biodiesel purchased.


** Disadvantages:

- Potential slight increase in nitrous oxide emissions (up to 10% depending upon blend). Reportedly World Energy ( has come up with an additive that significantly reduces NOx emissions to meet South Coast Air Quality Management District (Southern California) strict NOx standards ( Retarding timing and other methodologies have been successfully used to reduce NOx emissions below standard diesel fuel levels (

- Slight decrease in fuel economy (about 10% for pure biodiesel)

- Thickens more than diesel fuel in cold weather, may need to use blends in sub freezing conditions.

- More expensive



- Make sure that the fuel meets ASTM specifications for purity

- Check fuel filters during the first few weeks if changing over from petroleum diesel. Biodiesel is a solvent and cleans accumulated petroleum gunk out of the engine and delivery system during initial use which can clog filters rapidly (a good problem to have).

- Keep it out of freezing temperatures. 100% neat biodiesel begins to freeze around 25F. Indoor or underground storage is usually fine.

- Individually dry soaked rags or store in safety can to avoid spontaneous combustion (nothing dramatic – just the same precautions you need for other vegetable oils, like linseed oil)

- As with petroleum based diesel, use within one year to ensure quality

- Check with the engine manufacturer to determine if any natural or butyl rubber components are used in the engine as pure biodiesel can degrade these over time. Replacement with compatible elastomers or use of a blended biodiesel will eliminate this problem. The recent switch to low sulfur diesel fuel has lead many manufacturers to switch components already. Mostly an issue with pre 1993 equipment.


**What it costs:

Individual 55 gallon drums were priced around $4.00/gallon delivered in mid 2001 when I last checked. Costs go down rapidly with volume and have been in the $2.00-$2.50 range wholesale (incl taxes and delivery) depending upon quantity and delivery costs. An Olympian station on Third and 23rd streets in San Francisco started selling biodiesel at retail in May of 2001 for $3.15/gallon. Reportedly it is cheaper than natural gas in bulk. With EPAct credit advantages biodiesel can be a least cost alternative for fleets regulated by EPAct. One California healthcare facility (see below) has reported that it is cheaper than the clean air diesel blend they are required to burn otherwise


**Who is using it:

By 2001 About 80 major fleets, including transit authorities, school districts, government fleets and national parks were using biodiesel according to the National Biodiesel Board. More than 100 biodiesel demonstrations, including three one-million-mile tests and more than thirty 50,000-mile tests, have logged more than 10 million road miles with biodiesel blends. Local California examples include the recycling truck fleet of Berkeley’s Ecology Center ( and of San Jose‘s Green Team refuse fleet ( ) and now the entire City of Berkeley truck fleet (all running on 100% biodiesel) ( ).


It is also being used for construction equipment, heating boilers and emergency generators, including the St. Mary’s Medical Center in Long Beach, California. The staff at St. Mary’s claim that biodiesel has proven less expensive than the Amber 365 petroleum diesel blend that they must burn to meet clean air regulations.

( Times 6-16.pdf)


**More information resources:

USDOE Biofuels program

           or write or

National Alternative Fuels Data Center

           or call the Hotline (800) 423-1363

National Biodiesel Board


Fact sheets:

Biodiesel—the Clean, Green Fuel for Diesel Engines (Basic overview by DoE/NREL, two pages)

Biodiesel FAQ (Berkeley Ecology Center, 2 pages)

Benefits of Biodiesel (by the National Biodiesel Board, 2 pages) of Biodiesel.PDF

Biodiesel Offers Fleets a Better Alternative to Petroleum Diesel (Focus on fleet use by DoE/NREL, 4 pages)


**My personal experience with biodiesel

In 1994 with Greenpeace, I coordinated a 5 month, 25,000 mile tour of a mobile solar generator on a semi tractor trailer fueled by biodiesel in blends ranging from 25 to 100%. No problems except that we had to learn the hard way about being careful with old soaked rags. We received lots of comments about how good the truck exhaust smelled.


**Beyond Biodiesel: Solar electric generation:

The cleanest greenest alternative for electricity generation is probably solar electric in most situations. Installing a photovoltaic power system on your rooftop can make you part of the solution, feeding clean solar electricity back in to the grid at maximum power on those sunny afternoons when the utility system is most likely to be overstrained by air conditioning and needs it most. (PowerLight (  510-540-0550 in Berkeley California, but with offices around the US) is the firm I am aware of that probably knows the most about commercial scale systems.


At this stage in the technology solar electric is best for grid tied systems or backing up relatively small loads (100kwh or less). If you are not grid tied or are seeking backup for outages, you will need batteries, or something to store the electricity, even if the outage comes on a sunny day. You need to be able to keep the voltage steady when a cloud passes over and, of course, you need to be ready for the outage to happen at night or on cloudy days as well. Storage issues with wind energy are similar. Storage technology is primitive compared to the solar modules that make the electricity.




Compiled by Tom Lent. Last update September 24, 2003

Statistics primarily from DoE/NREL fact sheets and web sites with some information derived from the National Biodiesel Board site and some from personal experience