EMISSIONS REDUCTIONS WITH BIODIESEL
Since Biodiesel is made entirely from vegetable
oil, it does not contain any sulfur, aromatic hydrocarbons, metals
or crude oil residues. The absence of sulfur means a reduction
in the formation of acid rain by sulfate emissions generating
sulfuric acid in our atmosphere. The reduced sulfur in the blend
will also decrease the levels of corrosive sulfuric acid accumulating
in the engine crankcase oil over time.
The lack of toxic and carcinogenic aromatics (benzene, toluene
and xylene) in Biodiesel means the fuel mixture combustion gases
will have reduced impact on human health and the environment.
The high cetane rating of Biodiesel (49 to 62) is another measure
of the additive's ability to improve combustion efficiency.
An engine running on 100% Biodiesel would have NO aromatic emissions
and the Biodiesel would be much safer to store and handle. In
addition, Biodiesel blends have reduced emissions of polyaromatic
hydrocarbons, another group of potentially carcinogenic substances
found in petroleum.
*A wealth of information can be found in the
handbook entitled "Technical Handbook for Marine Biodiesel
In Recreational Boats" by Randall von Wedel, Ph.D from CytoCulture
International, Inc.
Carbon Monoxide
Emissions
Carbon monoxide gas is a toxic byproduct of all
hydrocarbon combustion that is also reduced by increasing the
oxygen content of the fuel. More complete oxidation of the fuel
results in more complete combustion to carbon dioxide rather than
leading to the formation of carbon monoxide. In the 1998 report
by the Southwest Research Institute on the effects of Biodiesel
on truck engine exhaust emissions, the levels of carbon monoxide
were shown to be reduced from 8% to 22% with a B-20 blend, depending
on the type of engine . When the fuel was switched from low-sulfur
petroleum diesel to neat Biodiesel, there was a 28% to 37% drop
in the carbon monoxide emissions.
Lower Hydrocarbon
Emissions
As an oxygenated vegetable hydrocarbon,
Biodiesel itself burns cleanly, as well as improve the efficiency
of combustion in blends with petroleum fuel. At a 20% Biodiesel
blend, there will be a noticeable change in the odor and smoke
in the exhaust. Older engines should also emit less soot under
load and less carbon black during startup2.
Independent research programs in Europe and the U.S. have shown
that Biodiesel in a 20 percent blend with petroleum diesel created
a significant reduction in visible smoke and odor. The studies
documented the reduction in hydrocarbons, carbon monoxide and
particulate matter.
Several emissions reduction studies have been performed by the
Southwest Research Institute (SWRI) over the past 5 years. In
a 1994 study on light diesel trucks, Biodiesel in a 20% blend
(B-20) was shown to reduce particulate matter (PM) by 14% in new
engines2*. Even
greater reductions have been experienced with older engines1.
Polyaromatic
Hydrocarbon Emissions
Polyaromatic hydrocarbons (PAHs) are a
class of heavy oil petroleum hydrocarbons defined by their complex
ring structures and unique qualities. They consist of multiple
benzene ring structures that make them insoluble, slow to burn
and carcinogenic. Using Biodiesel at a 20% blend has been shown
to reduce PAH emissions between 12 to 29 %. The same series of
tests demonstrated pure Biodiesel reduces PAH emissions from 68
to 74%2.
Smoke
and Soot Reductions
Smoke (particulate material) and soot (unburned fuel and carbon
residues) are of increasing concern to urban air quality problems
that are causing a wide range of adverse health effects for their
citizens, especially in terms of respiratory impairment and related
illnesses.
Biodiesel lacks the heavy petroleum oil residues normally found
in diesel fuel. The result is an engine operating with Biodiesel
will have less smoke, and soot produced from unburned fuel. Additionally,
as Biodiesel is oxygenated, there is an increased combustion efficiency
even for the petroleum blend fraction. The benefits are reduced
particulate material and unburned fuel emissions, which are even
more pronounced in older engines with direct fuel injection systems.
In the 1996 study performed by the Southwest Research Institute,
the effect of oxygen content (by percent oxygen) on the production
of particulates smoke and soot was studied using the same Cummins
diesel test engine cited above. The study established, for example,
that a B20 blend reduces particulate soot by approximately 30%.
Emissions from an engine burning No. 2 low-sulfur diesel were
compared with those from an engine using the B20 blend in combination
with an oxidation catalyst. Compared with the low-sulfur No. 2
diesel, the B-20 blend with an oxidation catalyst reduced particulate
matter by 45%, total hydrocarbons by 65%, and carbon monoxide
by 41%2.
Nitrogen
Oxides
Although nitrogen oxides (NOx) are considered a major contributor
to ozone formation, they are also a reality of operating internal
combustion engines. Nitrogen oxides result from the oxidation
of atmospheric nitrogen at the high temperatures inside the combustion
chamber of the engine. They are not a result from contaminants
present in fuels. There are consistent reports of slight increases
(2-7%) in NOx emissions with Biodiesel blends that are attributable,
in part, to the higher oxygen content of the fuel mixture. More
oxygen and better combustion of the fuel also means more formation
of NOx emissions with Biodiesel blends.
Some reductions in NOx emissions can be attained by retarding
the timing of ignition and slowing the burn rate of the fuel in
the combustion chamber. In Europe, the delays in engine ignition
timing have been successfully combined with the use of catalytic
converters to achieve similar reductions in both NOx emissions
and hydrocarbon emissions from transit buses.
Biodiesel
Helps Reduce Greenhouse Gases
Unlike other "clean fuels" such as compressed natural
gas (CNG), Biodiesel and other biofuels are produced from renewable
agricultural crops that assimilate carbon dioxide from the atmosphere
to become plants and vegetable oil. The carbon dioxide released
this year from burning vegetable oil Biodiesels, in effect, will
be recaptured next year by crops growing in fields to produce
more vegetable oil starting material. The global community is
under considerable pressure from the international community (for
example, at the December 1997 Kyoto Conference) to take seriously
its efforts to reduce carbon dioxide, carbon monoxide and other
greenhouse gases released, in part, by the combustion of fossil
fuels in vehicles. Fossil fuel combustion accounts for 70% of
the total man-made CO2 contribution. Supplementing our dwindling
fossil fuel reserves with biomass-based fuels (Biodiesel, for
petrodiesel; biomass-based alcohols or hydrogen for gasoline)
helps reduce the accumulation of CO2.
Positive
Energy Balance for Solar Energy in Biodiesel
Although it takes fossil energy to produce and transport biofuel,
Biodiesel has a very favorable energy balance, especially relative
to energy-negative ethanol from corn. Biodiesel production has
positive energy balance ratios ranging from 2.5:1 (Institute for
Local Self-Reliance) up to 7.4:1 in Europe, depending on oil crop
and distance required to transport the raw materials.
References:
A great majority of the information described
above can be found in the following handbook published on the
web.
(1)Technical Handbook for Marine Biodiesel
In Recreational Boats: by Randall von Wedel, Ph.D CytoCulture International,
Inc.
(2)Sharp, C.A. (1996) Emissions and Lubricity
Evaluation of Rapeseed Derived Biodiesel Fuels, Southwest Research
Institute Study (San Antonio, TX) sponsored by the Department
of Energy and University of Idaho; presented at DOE Biodiesel
Emissions Testing Meeting, Seattle, WA, November 25, 1996.
(3) Perkins, L.A., Peterson, C.L. and Auld,
D.L. (1994) Durability Testing of Transesterified Winter Rape
Oil as Fuel in Small Bore, Multicylinder, DI, CI Engines, Report
from the University of Idaho, National Center for Advanced Transportation
Technology.
-Peterson, C.L. (1994), ed., Commercialization
of Biodiesel: Establishment of Engine Warranties, Conference Proceedings
November 9-10, 1994, National Center for Advanced Transportation
Technology, University of Idaho, Moscow, ID
-Peterson, C.L (1996) Development of Rapeseed
Biodiesel for Use in High-Speed Diesel Engines, Progress Report
for US Department of Energy, University of Idaho Department of
Biological and Agricultural Engineering, May 31, 1996.
-Peterson, C.L. and Reece, D.L. (1996) Emissions
Testing with Blends of Esters of Rapeseed Oil Fuel With and Without
a Catalytic Converter, SAE Technical Paper Series, International
Spring Fuels and Lubricants Meeting, Dearborne, MI, May 6-8, 1996.
-Peterson, C.L. and Reece, D.L. (1996) Emissions
Characteristics of Ethyl and Methyl Ester Rapeseed Oil Compared
with Low Sulfur Diesel Control Fuel in a Chassis Dynamometer Test
of a Pickup Truck, Transactions of the ASAE, 39 (3): 805-816,
May/June 1996.
(4) National Biodiesel Board, "Lubricity Benefits" http://www.biodiesel.org
(5) Paul Lacey, Southwest Research Institute,
Steve Howell, MARC-IV Consulting, Inc., SAE paper number 982567
"Fuel Lubricity Reviewed", , International Fall Fuels
and Lubricants Meeting and Exposition, October 19-22, 1998, San
Francisco, California.
(6) "Fuels for Diesel Engines-Diesel
Fuel Injection Equipment Manufacturers Common Position Statement",
Signed by Delphi Diesel Systems, Stanadyne Automotive Corp., Denso
Corporation, and Robert Bosch GmbH, issued June, 2000.