How are people exposed to diesel exhaust

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Diesel fuel is widely used throughout our society. It powers trucks that deliver products to our communities, buses that carry us to school and work, agricultural equipment that plants and harvests our food, and backup generators that can provide electricity during emergencies. It is also used for many other applications. Diesel engines have historically been more versatile and cheaper to run than gasoline engines or other sources of power. Unfortunately, the exhaust from these engines contains substances that can pose a risk to human health.

In 1998, the California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment (OEHHA) completed a comprehensive health assessment of diesel exhaust. This assessment formed the basis for a decision by the California Air Resources Board (ARB) to formally identify particles in diesel exhaust as a toxic air contaminant that may pose a threat to human health.

The American Lung Association of California (ALAC) and its 15 local associations work to prevent lung disease and promote lung health. Since 1904, the American Lung Association has been fighting lung disease through education, community service, advocacyand research.This fact sheet by OEHHA and ALAC provides information on health hazards associated with diesel exhaust.

What is diesel exhaust?

Diesel exhaust is produced when an engine burns diesel fuel. It is a complex mixture of thousands of gases and fine particles (commonly known as soot) that contains more than 40 toxic air contaminants. These include many known or suspected cancer-causing substances, such as benzene, arsenic and formaldehyde. It also contains other harmful pollutants, including nitrogen oxides (a component of urban smog).

How are people exposed to diesel exhaust?

Diesel exhaust particles and gases are suspended in the air, so exposure to this pollutant occurs whenever a person breathes air that contains these substances. The prevalence of diesel-powered engines makes it almost impossible to avoid exposure to diesel exhaust or its byproducts, regardless of whether you live in a rural or urban setting. However, people living and working in urban and industrial areas are more likely to be exposed to this pollutant. Those spending time on or near roads and freeways, truck loading and unloading operations, operating diesel-powered machinery or Diesel exhaust contains more than 40 toxic air contaminants working near diesel equipment face exposure to higher levels of diesel exhaust and face higher health risks.

What are the health effects of diesel exhaust?

As we breathe, the toxic gases and small particles of diesel exhaust are drawn into the lungs. The microscopic particles in diesel exhaust are less than one-fifth the thickness of a human hair and are small enough to penetrate deep into the lungs, where they contribute to a range of health problems.

Diesel exhaust and many individual substances contained in it (including arsenic, benzene, formaldehyde and nickel)have the potential to contribute to mutations in cells that can lead to cancer. In fact, long-term exposure to diesel exhaust particles poses the highest cancer risk of any toxic air contaminant evaluated by OEHHA. ARB estimates that about 70 percent of the cancer risk that the average Californian faces from breathing toxic air pollutants stems from diesel exhaust particles.

In its comprehensive assessment of diesel exhaust, OEHHA analyzed more than 30 studies of people who worked around diesel equipment, including truck drivers, railroad workers and equipment operators. The studies showed these workers were more likely to develop lung cancer than workers who were not exposed to diesel emissions. These studies provide strong evidence that long-term occupational exposure to diesel exhaust increases the risk of lung cancer. Using information from OEHHA’s assessment, ARB estimates that diesel-particle levels measured in California’s air in 2000 could cause 540 “excess” cancers (beyond what would occur if there were no diesel particles in the air) in a population of 1 million people over a 70-year lifetime. Other researchers and scientific organizations, including the National Institute for Occupational Safety and Health, have calculated cancer risks from diesel exhaust that are similar to those developed by OEHHA and ARB.

Exposure to diesel exhaust can have immediate health effects. Diesel exhaust can irritate the eyes,nose, throat and lungs, and it can cause coughs, headaches, light-headedness and nausea. In studies with human volunteers, diesel exhaust particles made people with allergies more susceptible to the materials to which they are allergic, such as dust and pollen. Exposure to diesel exhaust also causes inflammation in the lungs, which may aggravate chronic respiratory symptoms and increase the frequency or intensity of asthma attacks.Diesel engines are a major source of fine-particle pollution.The elderly and people with emphysema, asthma, and chronic heart and lung disease are especially sensitive to fine-particle pollution. Numerous studies have linked elevated particle levels in the air to increased hospital admissions, emergency room visits, asthma attacks and premature deaths among those suffering from respiratory problems. Because children’s lungs and respiratory systems are still developing, they are also more susceptible than healthy adults to fine particles. Exposure to fine particles is associated with increased frequency of childhood illnesses and can also reduce lung function in children.

What is being done to reduce the health risks from diesel exhaust?

Improvements to diesel fuel and diesel engines have already reduced emissions of some of the pollutants associated with diesel exhaust. However, diesel exhaust is still one of the most widespread and toxic substances in California’s air.

ARB’s Diesel Risk Reduction Plan, when fully implemented,will result in a 75 percent reduction in particle emissions from diesel equipment by 2010 (compared to 2000 levels), and an 85 percent reduction by 2020. The plan calls for the use of cleaner-burning diesel fuel, retrofitting of existing engines with particle-trapping filters, and the use in new diesel engines of advanced technologies that produce nearly 90 percent fewer particle emissions, as well as the use of alternative fuels.

The use of other fuels, such as natural gas, propane and electricity offer alternatives to diesel fuel. All of them produce fewer polluting emissions than current formulations of diesel fuel. As a result of ARB and local air-quality regulations, public transit agencies throughout California are using increasing numbers of passenger buses that operate with alternative fuels or retrofitted equipment.


Procurement of Diesel Vehicles

Bangladesh has no manufacturing base for motor vehicles. Most of the commercial diesel vehicles are imported from India, Japan and few from China. As the new commercial vehicles imported by Bangladesh are all going to be higher than EORO I emission standards, there is no problem in this respect.

· In the Import Policy 2003-2006, import of motor vehicles not older than 4 years is allowed. The policy further states that used motor vehicles can be imported only from the country where they have been manufactured. The emission standards set in the schedule 6 of the Environment Conservation Rules do not specify the emission standards for imported old vehicles. Only explanation that can be provided regarding the emission standards of the old imported vehicles is that they must comply with the in-use vehicle emission standards. From Japan it is not a problem, because export of used vehicle is an institutionalized business. Japan Auto Appraisal institute publishes a Yellow Book with chassis number and year of manufacturing. In case of India, the export of used vehicles is not so institutionalized and regulated. Taking advantage of this lacuna, diesel vehicles far older than the specified age limit are being imported from India. This unregulated import of old diesel vehicles from India can have very serious environmental consequences.

· The Import Policy also permits import of reconditioned and used engines and gear-boxes not older than 5 years for bus, truck, mini and micro bus. Bangladesh is about to introduce emission standards of Euro I for new vehicles. But if the import of old engines without any emission standards are permitted to import than the introduction of emission standards for new vehicles will not bring desired outcome.

1 Diesel Quality and sulfur content

Bangladesh currently consumes about 23, 00,000 metric tons of diesel annually. 30% of the diesel consumed for irrigation and remaining is mostly as transport fuel. The Bnagladesh Standards and Testing Institute decides specification for diesel and the Bangladesh Petroleum Corporation is the sole importer of petroleum products other than lubricants. The current level of sulfur content in diesel is 2500-ppm and the government does not have any immediate plan to reduce diesel sulfur to 500-ppm because of the price differential between 2500-ppm and 500-ppm sulfur diesel.

Bangladesh currently does not have any auto fuel policy. In other countries, there is a plan for the improvement of auto fuel over a period of time that enables manufacturer of automobiles, importers and all other stakeholders to prepare for any change. Lack of any auto fuel policy makes it difficult to regulate contents in fuels. In case of introduction of low sulfur diesel, infrastructure is also a great problem. In case of introduction of low sulfur fuel, there will be a severe dearth of infrastructure in storage and marketing. To overcome this dearth of infrastructure, a huge investment will be need. Mobilizing financial resources for the purpose is a huge task for the GoB.

Diesel Adulteration

Earlier on adulteration of diesel with kerosene was rampant. But by reducing price difference between these 2 products and also by dyeing the kerosene it could be reduced substantially.

Quality of Lubricants

Unlike other petroleum products, private sector can import lubricants. Bangladesh imports about 80,000 MT of lubricants annually by public and private sector companies. There is allegation of adulteration in lubricants. Government notifies specifications for lubricants but enforcement is lacking in case of adulteration.

Use of Alternative Fuels

The most viable and abundantly available automobile alternative fuel in Bangladesh is the CNG. The introduction of CNG is a success story for Bangladesh. It started in 1983 through a World Bank under pilot project with setting up of 4 CNG stations in Dhaka. Later on private sector was also involved in expansion of CNG and proved to be highly successful. Current statistics on CNG filling stations, conversion workshops and number of converted vehicles are as follows.


(As on November 2006)

Sl Item Nos/Amount Location/Type
01 CNG Filling Stations in operation 136 Dhaka-85
02 CNG Filling Stations to come to operation by January, 2007 14 Dhaka-04
03 CNG Conversion Workshops 87 Dhaka-52
04 CNG-converted vehicles 60,557 Dhaka-50, 664
05 CNG Vehicles in Bangladesh 99,004
06 CNG Filling Stations established on government land 29
07 CNG Filling Stations established in existing Petrol Filling Stations 40
08 Amount of natural gas used as CNG 23.00 mmcm

It may be mentioned here that CNG has also been expanding in other cities outside Dhaka and it got a tremendous boost after the recent global fuel price hike.

In order to popularize CNG use as auto fuel government is following the policy to keep a huge price difference with petrol and diesel. Currently CNG price is Taka 8.50 per m³ while price of octane Taka 54.75 per liter, petrol is Taka 52.83 per liter and diesel is Taka 30.96 per liter. So, diesel is 4 times, while octane and petrol are about 7 and 6.5 times respectively costlier than CNG. The reason and rationale for following such a policy is quite clear.

· First, to save valuable foreign currency in importing of petroleum products, and;

· Second, to address the problem of air pollution.

But the government should make some appropriate amendments in the Motor Vehicle Ordinace 1983 to give a sound legal basis by clearing recognizing CNG as an auto fuel and conversion to CNG a legal thing. The Government in a notification in 1 March 2005 under The Explosive Act, 1884 has made codes for CNG conversion kits and fitting procedure and scrutinizes the imported of the items at the time of import. In India, under the relevant Act rules for CNG kits, accessories and their testing had been formulated. But comprehensive rules yet to be formulated on CNG kits, accessories and their testing. In case of Bangladesh, the CNG codes on motor vehicle conversion and conversion kits as prescribed in the CNG Rules 2005 have to be incorporated in the Motor Vehicle Ordinance 1983. This is necessary to enforce the codes while carrying out fitness inspections of CNG vehicles that are paramount for ensuring vehicle safely using CNG.

So far, CNG technology (filling station, cylinder, conversion kits etc.) has entered into the market of Bangladesh from various countries like New Zealand, Brazil, Italy, South Korea and India. But CNG buses are being imported from mainly from 2 countries-China and India. As is apparent from the present market scenario, the operators of CNG vehicles have opted for new CNG vehicles rather than spending money on the conversion of the diesel vehicles to CNG. From the view point of both safety and emission control this is definitely the better option.

New and in-use emission standards & Inspections

Bangladesh has formulated emission standards for vehicles under the Environment Conservation Rules 1997. The new standard has been notified in 2005. But at present there exists no equipped laboratory to test new vehicles for their compliance of standards. So there is a need for establishing such a laboratory. Moreover, roadside checking of emission standards can be apart of an audit program to check the emission profiles of vehicles and create awareness. To have the in-use emission standard enforced, it is necessary to make it a part of the annual fitness test of a vehicle. In India, the emission standards for both new and in-use vehicles have been made part of relevant Ordinance and Rules to make it mandatory to meet new and in-use emission standards to in order to obtain both registration and fitness certificate. Unless, the same is done in case of Bangladesh, enforcement of the in-use emission standards will not take place.

Diesel sulfur content

Particulate emission from older generation diesel vehicles, that is the old technology vehicles, is mostly carbon based. Sulfates emitted in exhaust, due to the presence of sulfur in diesel, through secondary atmospheric reactions forms particulates. The issue of sulfur reduction needs to be addressed once issue of carbon based particulate emission from diesel engines due to inadequate technology has been addressed. To operate diesel engines of EURO II and above, sulfur content in the diesel cannot be more than 500-ppm. CNG is a clean and indigenous fuel for Bangladesh but for public transport system of a city to be totally dependent on a single energy source is not advisable. Low sulfur diesel busses, which are also considered clean fuel busses, may operate in the city. Currently Bangladesh imports about 90% of its diesel from abroad with a sulfur content of 2500-ppm. Since Bangladesh imports most of its diesel, it is possible to import 500-ppm sulfur diesel to introduce clean fuel buses. Before introducing clean diesel busses in Dhaka, separate storage and distribution network for 500-ppm sulfur must be considered.

In use Vehicle Inspection

Experts opine that however good is the technology of a vehicle in use, an out of tuned or maintained vehicle is as polluting as a low technology vehicle. It is, therefore, important that regulatory inspection program is in place compelling the vehicles owners to maintain their vehicles regularly and properly. Experiences in other countries show that privatizing the regulatory inspection to small private workshop owners do not yield expected results. It is therefore, recommended to have centralized and computerized vehicle inspection centers with emission testing arrangement having public oversight.

Enforcement of In-use Vehicle Emission standard

During the annual fitness test and pre-registration inspection Bangladesh Road Transport Authority (BRTA) should ensure compliance to the emission standards.

A program can be started where in BRTA and Police provides mobile phone numbers to the general public to inform the registration number of smoking vehicles on the road. BRTA then can notify owners of smoking vehicles to present them for emission inspection.

Fine or penalty for not compliance with emission standard can be enhanced.



The cost to produce and deliver diesel fuel to customers includes the costs of crude oil, refinery processing, marketing and distribution, and retail station operation. The retail pump price reflects these costs and the profits (and sometimes losses) of the refiners, marketers, distributors, and retail station owners. The relative share of these cost components to the retail price varies over time and among regions of the country. Figure 2 illustrates the percentage share for each major cost element of the national average retail price as of May 2008.

The price at the pump also includes Federal, State, and local taxes. In 2008, Federal excise taxes were 24.4 cents per gallon and State excise taxes averaged about 22.0 cents per gallon.2 Some States and county and city governments levy additional taxes. The retail price also reflects local market conditions and factors such as the location and the marketing strategy of the owner. Some retail outlets are owned and operated by refiners, while others are independent businesses that purchase diesel fuel for resale to the public.

Why are diesel fuel prices higher than gasoline prices?

Historically, the average price of diesel fuel has been lower than the average price of gasoline. However, this is not always the case. In some winters where the demand for distillate heating oil is high, the price of diesel fuel has risen above the gasoline price. Since September 2004, the price of diesel fuel has been generally higher than the price of regular gasoline all year round for several reasons. Worldwide demand for diesel fuel and other distillate fuel oils has been increasing steadily, with strong demand in China, Europe, and the United States, putting more pressure on the tight global refining capacity. In the United States, the transition to ultra-low-sulfur diesel fuel has affected diesel fuel production and distribution costs. Also, the Federal excise tax on diesel fuel is 6 cents higher per gallon (24.4 cents per gallon) than the tax on gasoline.


Besides excise taxes, the following are the main factors that affect diesel fuel prices:

Cost and supply of crude oil: Crude oil prices are determined by worldwide supply and demand, and over the past few years increasing demand has put intense pressure on available supplies. The Organization of Petroleum Exporting Countries (OPEC) exerts significant influence on prices by setting an upper production limit on its members who produce about 40 percent of the world’s crude oil. OPEC countries have essentially all of the spare production capacity, and possess about two-thirds of the world’s estimated crude oil reserves. Prices spike in response to disruptions in the international and domestic supply of crude oil, such as the Arab oil embargo in 1973, the Iran/Iraq war in 1980, the current war in Iraq, unrest in the Niger River delta region of Nigeria, and the hurricanes in the Gulf of Mexico in 2005.

Tight refining capacity and international diesel fuel demand: U.S. refineries have been operating at around 90-percent capacity over the last 10 years. Most other countries rely even more heavily on distillates and diesel fuel than does the United States, and refining capacity is tight worldwide. U.S. diesel fuel prices are more and more affected by competing international demand for refined distillates.

Figure 3. Diesel Fuel Prices Follow Crude Oil

Product supply/demand imbalances: Prices of transportation fuels are generally more volatile than prices of other commodities because the U.S. vehicle fleet is so heavily dependent on petroleum and few alternative fuels are available. If supply declines unexpectedly due to refinery problems or lagging imports, diesel inventories (stocks) may decline rapidly. When stocks are low and falling, some wholesalers and marketers may bid higher for available product. If the diesel fuel transportation system cannot support the flow of surplus supplies from one region to another quickly, prices will remain comparatively high. These are normal price fluctuations experienced in all commodity markets.

Seasonality in the demand for diesel fuel and distillates: While U.S. diesel fuel demand is fairly consistent and generally reflects the overall health of the economy, prices tend to gradually rise during the fall, decline in the late winter, rise through the early spring, and then drop a bit in the summer. Seasonal upward pressure on diesel prices also results from demand by farmers in the summer, cold weather in the winter, and stores building up inventories during the winter holiday season.

Transportation Costs: Transportation costs generally increase with increasing distance between the retail location and distribution terminals and refineries. Areas farthest from the Gulf Coast (the source of nearly half of the diesel fuel produced in the United States) tend to have higher prices.

Regional operating costs and local competition: The cost of doing business by individual dealers can vary greatly depending on where the dealer is located. These costs include wages and salaries, benefits, equipment, lease/rent, insurance, overhead, and State and local fees. Even retail stations next to each other can have different traffic patterns, rents, and sources of supply that affect their prices. The number and location of local competitors can also affect prices.


Retail diesel fuel prices are likely to remain elevated as long as crude oil prices and world demand for distillate fuels remain high. According to EIA’s June 2008 Short-Term Energy Outlook, national average retail diesel fuel prices will peak in the third quarter of 2008 at $4.75 before falling to $4.11 per gallon by the fourth quarter of 2009, primarily due to the forecast for the price of West Texas Intermediate crude oil to average between $121 and $133 per barrel during this same period. However, the recent volatility seen in crude oil and petroleum product prices, if continued, may significantly alter these price projections.

The phase-in of the U.S. Environmental Protection Agency’s (EPA) sulfur standards for diesel fuels has the potential to continue to influence diesel fuel prices. The logistics of delivery of ULSD to retail service stations can be a challenge. Most ULSD travels through pipelines on the way to bulk terminals for final transfer by tanker truck to retail stations. Other diesel fuels and petroleum products with a higher-sulfur content in the pipeline, storage, and local distribution systems might contaminate ULSD (jet fuel, for example, can have 3,000 ppm of sulfur). If contaminated, it may not be possible to correct a ULSD fuel batch by blending with additional low-sulfur product, and contaminated batches have to be returned to a refinery for reprocessing, a difficult and expensive problem. Even without potential delivery problems, it costs relatively more to produce ULSD fuel.

Why are West Coast diesel fuel prices higher and more variable than others?

Diesel prices on the West Coast, especially in California (CA), are relatively higher than other regions of the country, partly because of taxes, but mainly because of supply issues. The State of California assesses a combined State and local sales and use tax of 7.25 percent on top of the 24.4 cents/gallon Federal excise tax and an 18.0 cents/gallon State tax. Washington’s tax of 34 cents/gallon is one of the highest in the country. Besides taxes, West Coast retail prices are more variable than others because there are relatively few supply sources: 21 of the 36 refineries located in West Coast states are in CA. California refineries need to be running at near full capacity just to meet in-state demand. If more than one refinery in the region experiences operating difficulties at the same time, the diesel supply may become very tight and prices may spike. The West Coast’s substantial distance from Gulf coast and foreign refineries is such that any unusual increase in demand or reduction in supply results in a large price response in the market before relief supplies can be delivered. The farther away the necessary relief supplies are, the higher and longer the price spike will be.



Diesel fuel

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Biodiesel fuel in an Erlenmeyer flask.

Diesel fuel (pronounced /?di?z?l/) in general is any liquid fuel used in diesel engines. The most common is a specific fractional distillate of petroleum fuel oil, but alternatives that are not derived from petroleum, such as biodiesel, biomass to liquid (BTL) or gas to liquid (GTL) diesel, are increasingly being developed and adopted. To distinguish these types, petroleum-derived diesel is increasingly called petrodiesel.<href=”#cite_note-0″>[1] Ultra-low sulfur diesel (ULSD) is a standard for defining diesel fuel with substantially lowered sulfur contents. As of 2007, almost every diesel fuel available in America and Europe is the ULSD type. In the UK, diesel is commonly abbreviated DERV, standing for Diesel Engined Road Vehicle (fuel).

Diesel engine

Main article: Diesel engine

Diesel engines are a type of internal combustion engine. Rudolf Diesel originally designed the diesel engine to use coal dust as a fuel. He also experimented with various oils, including some vegetable oils,<href=”#cite_note-2″>[3] such as peanut oil, which was used to power the engines which he exhibited at the 1900 Paris Exposition and the 1911 World’s Fair in Paris.<href=”#cite_note-3″>[4]


Diesel fuel is produced from petroleum and from various other sources. The resulting products are interchangeable in most applications.

Petroleum diesel

A modern diesel dispenser


Petroleum diesel, also called petrodiesel,<href=”#cite_note-4″>[5] or fossil diesel is produced from the fractional distillation of crude oil between 200 °C (392 °F) and 350 °C (662 °F) at atmospheric pressure, resulting in a mixture of carbon chains that typically contain between 8 and 21 carbon atoms per molecule.<href=”#cite_note-5″>[6]

Fuel value and price

Further information: Gasoline and diesel usage and pricing

The density of petroleum diesel is about 0.85 kg/l (7.09 lb/US gal), about 18% more than petrol (gasoline), which has a density of about 0.72 kg/l (6.01 lb/US gal). When burnt, diesel typically releases about 38.6 MJ/l (138,700 BTU/US gal), whereas gasoline releases 34.9 MJ/l (125,000 BTU/US gal), 10% less<href=”#cite_note-TEDB-6″>[7] by energy density, but 45.41 MJ/kg and 48.47 MJ/kg, 6.7% more by specific energy. Diesel is generally simpler to refine from petroleum than gasoline. The price of diesel traditionally rises during colder months as demand for heating oil rises, which is refined in much the same way. Because of recent changes in fuel quality regulations, additional refining is required to remove sulfur which contributes to a sometimes higher cost. In many parts of the United States and throughout the United Kingdom and Australia<href=”#cite_note-7″>[8] diesel may be higher priced than petrol.<href=”#cite_note-8″>[9] Reasons for higher priced diesel include the shutdown of some refineries in the Gulf of Mexico, diversion of mass refining capacity to gasoline production, and a recent transfer to ULSD, which causes infrastructural complications.[10]

Use as vehicle fuel

Unlike petroleum ether and liquefied petroleum gas engines, diesel engines do not use high voltage spark ignition (spark plugs). An engine running on diesel compresses the air inside the cylinder to high pressures and temperatures (compression ratios from 15:1 to 21:1 are common); the diesel is generally injected directly into the cylinder near the end of the compression stroke. The high temperatures inside the cylinder cause the diesel fuel to react with the oxygen in the mix (burn or oxidize), heating and expanding the burning mixture in order to convert the thermal/pressure difference into mechanical work; i.e., to move the piston. (Glow plugs are used to assist starting the engine to preheat cylinders to reach a minimum operating temperature.) High compression ratios and throttleless operation generally result in diesel engines being more efficient than many spark-ignited engines.

This efficiency and its lower flammability and explosivity than gasoline are the main reasons for military use of diesel in armoured fighting vehicles like tanks and trucks. Engines running on diesel also provide more torque and are less likely to stall as they are controlled by a mechanical or electronic governor.

A disadvantage of diesel as a vehicle fuel in some climates, compared to gasoline or other petroleum derived fuels, is that its viscosity increases quickly as the fuel’s temperature decreases, turning into a non-flowing gel at temperatures as high as -19 °C (-2.2 °F) or -15 °C (5 °F), which can’t be pumped by regular fuel pumps. Special low temperature diesel contains additives that keep it in a more liquid state at lower temperatures, yet starting a diesel engine in very cold weather may still pose considerable difficulties.

Another rare disadvantage of diesel engines compared to petrol/gasoline engines is the possibility of runaway failure. Since diesel engines do not require spark ignition, they can sustain operation as long as diesel fuel is supplied. Fuel is typically supplied via a fuel pump. If the pump breaks down in an “open” position, the supply of fuel will be unrestricted and the engine will runaway and risk terminal failure.<href=”#cite_note-10″>[11]

Use as car fuel

Diesel-powered cars generally have a better fuel economy than equivalent gasoline engines and produce less greenhouse gas emission. Their greater economy is due to the higher energy per-litre content of diesel fuel and the intrinsic efficiency of the diesel engine. While petrodiesel’s higher density results in higher greenhouse gas emissions per litre compared to gasoline,<href=”#cite_note-11″>[12] the 20–40% better fuel economy achieved by modern diesel-engined automobiles offsets the higher per-litre emissions of greenhouse gases, and a diesel-powered vehicle emits 10-20 percent less greenhouse gas than comparable gasoline vehicles.<href=”#cite_note-12″>[13]<href=”#cite_note-13″>[14]<href=”#cite_note-14″>[15] Biodiesel-powered diesel engines offer substantially improved emission reductions compared to petro-diesel or gasoline-powered engines, while retaining most of the fuel economy advantages over conventional gasoline-powered automobiles. However, the increased compression ratios mean that there are increased emissions of oxides of nitrogen (NOx) from diesel engines. This is compounded by biological nitrogen in biodiesel to make NOx emissions the main drawback of diesel versus gasoline engines.

Use as generator and ships fuel

Diesel engines can operate on a variety of different fuels, depending on configuration, though the eponymous diesel fuel derived from crude oil is most common. The engines can work with the full spectrum of crude oil distillates, from natural gas, alcohols, gasoline, wood gas to the fuel oils from diesel oil to residual fuels.<href=”#cite_note-15″>[16] This is implemented by introducing gas with the intake air and using a small amount of diesel fuel for ignition. Conversion to 100% diesel fuel operation can be achieveved instantaneously.<href=”#cite_note-16″>[17]

Reduction of sulfur emissions

In the past, diesel fuel contained higher quantities of sulfur. European emission standards and preferential taxation have forced oil refineries to dramatically reduce the level of sulfur in diesel fuels. In the United States, more stringent emission standards have been adopted with the transition to ULSD starting in 2006 and becoming mandatory on June 1, 2010 (see also diesel exhaust). U.S. diesel fuel typically also has a lower cetane number (a measure of ignition quality) than European diesel, resulting in worse cold weather performance and some increase in emissions.<href=”#cite_note-17″>[18]

Environment hazards of sulfur

High levels of sulfur in diesel are harmful for the environment because they prevent the use of catalytic diesel particulate filters to control diesel particulate emissions, as well as more advanced technologies, such as nitrogen oxide (<href=”#NOx” title=”Nitrogen oxide”>NOx) adsorbers (still under development), to reduce emissions. Moreover, sulfur in the fuel is oxidized during combustion, producing sulfur dioxide and sulfur trioxide, that in presence of water rapidly convert to sulfuric acid, one of the chemical processes that results in acid rain. However, the process for lowering sulfur also reduces the lubricity of the fuel, meaning that additives must be put into the fuel to help lubricate engines. Biodiesel and biodiesel/petrodiesel blends, with their higher lubricity levels, are increasingly being utilized as an alternative. The U.S. annual consumption of diesel fuel in 2006 was about 190 billion litres (42 billion imperial gallons or 50 billion US gallons).<href=”#cite_note-18″>[19]

Chemical composition

Petroleum-derived diesel is composed of about 75% saturated hydrocarbons (primarily paraffins including n, iso, and cycloparaffins), and 25% aromatic hydrocarbons (including naphthalenes and alkylbenzenes).<href=”#cite_note-19″>[20] The average chemical formula for common diesel fuel is C12H23, ranging approximately from C10H20 to C15H28.

Diesel is immiscible with water.

Algae, microbes, and water contamination

There has been much discussion and misunderstanding of algae in diesel fuel.<href=”#cite_note-20″>[21] Algae need light to live and grow. As there is no sunlight in a closed fuel tank, no algae can survive. But some microbes can survive and feed on the diesel fuel.

These microbes form a colony that lives at the interface of fuel and water. They grow quite fast in warmer temperature. They can even grow in cold weather when fuel tank heaters are installed. Parts of the colony can break off and clog the fuel lines and fuel filters.

It is possible to either kill this growth with a biocide treatment, or eliminate the water, a necessary component of microbial life. There are a number of biocides on the market, which must be handled very carefully. If a biocide is used, it must be added every time a tank is refilled until the problem is fully resolved.

Biocides attack the cell wall of microbes resulting in lysis, the death of a cell by bursting. The dead cells then gather on the bottom of the fuel tanks and form a sludge; filter clogging will continue after biocide treatment until the sludge abates.

Given the right conditions, microbes will repopulate the tanks, and re-treatment with biocides will be necessary. With repetitive biocide treatments, microbes can form resistance to a particular brand. Trying another brand of biocide with another antibiotic may resolve the problem.

Road hazard

Petrodiesel spilled on a road will stay there until washed away by sufficiently heavy rain, whereas gasoline will quickly evaporate. After the light fractions have evaporated, a greasy slick is left on the road which can destabilize moving vehicles. Diesel spills severely reduce tire grip and traction, and have been implicated in many accidents. The loss of traction is similar to that encountered on black ice. Diesel slicks are especially dangerous for two-wheeled vehicles such as motorcycles.

Synthetic diesel

Main article: Synthetic fuel

Wood, hemp, straw, corn, garbage, food scraps, and sewage-sludge may be dried and gasified to synthesis gas. After purification the Fischer-Tropsch process is used to produce synthetic diesel.<href=”#cite_note-21″>[22] This means that synthetic diesel oil may be one route to biomass based diesel oil. Such processes are often called biomass-to-liquids or BTL.

Synthetic diesel may also be produced out of natural gas in the gas-to-liquid (GTL) process or out of coal in the coal-to-liquid (CTL) process. Such synthetic diesel has 30% lower particulate emissions than conventional diesel (US


Diesel fuel is widely used in most types of transportation. The gasoline-powered passenger automobile is the major exception.


See also: dieselization and diesel locomotive

Diesel displaced coal and fuel oil for steam power vehicles in the latter half of the 20th century, and is now used almost exclusively for combustion engine of self-powered rail vehicles (locomotives and railcars).


Main article: Aircraft diesel engine

The first diesel-powered flight of a fixed wing aircraft took place on the evening of September 18, 1928, at the Packard Motor Company proving grounds at Utica, USA with Captain Lionel M. Woolson and Walter Lees at the controls (the first “official” test flight was taken the next morning). The engine was designed for Packard by Woolson and the aircraft was a Stinson SM1B, X7654. Later that year, Charles Lindbergh flew the same aircraft. In 1929 it was flown 621 miles (999 km) non-stop from Detroit to Langley, Virginia (near Washington, D.C.). This aircraft is now owned by Greg Herrick and is at the Golden Wings Flying Museum nearby Minneapolis, Minnesota. In 1931, Walter Lees and Fredrick Brossy set the non-stop flight record flying a Bellanca powered by a Packard diesel for 84 hours and 32 minutes. The Hindenburg rigid airship was powered by four 16-cylinder diesel engines, each with approximately 1,200 horsepower (890 kW) available in bursts, and 850 horsepower (630 kW) available for cruising. Modern diesel engines for propellor-driven aircraft are manufactured by Thielert Aircraft Engines and SMA. These engines can run on <href=”#Jet_A” title=”Jet fuel”>Jet A fuel, which is similar in composition to automotive diesel and cheaper and more plentiful than the 100 octane low-lead gasoline (avgas) used by the majority of the piston-engine aircraft fleet.[citation needed]

The most-produced aviation diesel engine in history has been the Junkers Jumo 205, which, along with its similar developments from the Junkers Motorenwerke, had approximately 1000 examples of the unique opposed piston, two-stroke design power plant built in the 1930s leading into World War II in Germany.

Other uses

Poor quality (high sulfur) diesel fuel has been used as a palladium extraction agent for the liquid-liquid extraction of this metal from nitric acid mixtures. Such use has been proposed as a means of separating the fission product palladium from PUREX raffinate which comes from used nuclear fuel. In this system of solvent extraction, the hydrocarbons of the diesel act as the diluent while the dialkyl sulfides act as the extractant. This extraction operates by a solvation mechanism. So far, neither a pilot plant nor full scale plant has been constructed to recover palladium, rhodium or ruthenium from nuclear wastes created by the use of nuclear fuel.<href=”#cite_note-26″>[27]

Health effects

Main articles: <href=”#Diesel_engines” title=”Exhaust gas”>Exhaust gas#Diesel engines, <href=”#Emissions” title=”Diesel engine”>Diesel engine#Emissions, Diesel particulate matter, and Diesel exhaust air contaminants

Diesel exhaust from a truck

Diesel combustion exhaust is a major source of atmospheric soot and fine particles, which is a fraction of air pollution implicated in human heart and lung damage. Diesel exhaust also contains nanoparticles.

While the study of nanoparticles and nanotoxicology is still in its infancy, the full health effects from nanoparticles produced by all types of diesel are unknown. At least one study has observed that short term exposure to diesel exhaust does not result in adverse extra-pulmonary effects, effects that are often correlated with an increase in cardiovascular disease.<href=”#cite_note-27″>[28] Long term effects still need to be clarified, as well as the effects on susceptible groups of people with cardiopulmonary diseases.

It should be noted that the types and quantities of nanoparticles can vary according to operating temperatures and pressures, presence of an open flame, fundamental fuel type and fuel mixture, and even atmospheric mixtures. As such, the resulting types of nanoparticles from different engine technologies and even different fuels are not necessarily comparable. In general, the usage of biodiesel and biodiesel blends results in decreased pollution. One study has shown that the volatile component of 95% of diesel nanoparticles is unburned lubricating oil.<href=”#cite_note-28″>[29]


Diesel fuel is very similar to heating oil which is used in central heating. In Europe, the United States, and Canada, taxes on diesel fuel are higher than on heating oil due to the fuel tax, and in those areas, heating oil is marked with fuel dyes and trace chemicals to prevent and detect tax fraud. Similarly, “untaxed” diesel (sometimes called “off road diesel”) is available in some countries for use primarily in agricultural applications such as fuel for tractors, recreational and utility vehicles or other non-commercial vehicles that do not use public roads. Additionally, this fuel may have sulphur levels that exceed the limits for road use in some countries (e.g. USA).

This untaxed diesel is dyed red for identification,<href=”#cite_note-26_CFR_48.4082-1-29″>[30] and should a person be found to be using this untaxed diesel fuel for a typically taxed purpose (such as “over-the-road”, or driving use), the user can be fined (e.g. US$10,000 in the USA). In the United Kingdom, Belgium and the Netherlands it is known as red diesel (or gas oil), and is also used in agricultural vehicles, home heating tanks, refrigeration units on vans/trucks which contain perishable items such as food and medicine and for marine craft. Diesel fuel, or marked gas oil is dyed green in the Republic of Ireland and Norway. The term DERV (“diesel engined road vehicle”) is used in the UK as a synonym for unmarked road diesel fuel. In India, taxes on diesel fuel are lower than on petroleum, as the majority of the transportation that transports grains and other essential commodities across the country runs on diesel.