Myth 1: Low-sulphur diesel is clean fuel

Supporting ultra low sulphur diesel (ULSD) over CNG, Tata Energy Research Institute (TERI) director R K Pachauri said there was enough evidence abroad that “ULSD is a better option” (The Times of India, March 28, 2001).

Union petroleum minister Ram Naik and Delhi transport minister Parvez Hashmi have said that “the Centre and Delhi government have decided to request the Supreme Court to allow buses to run on low sulphur diesel along with CNG buses in Delhi” (The Indian Express, April 7, 2001).

A report on a study conducted in Australia — filed in the Supreme Court conclusively states that low sulphur diesel (0.05 per cent sulphur content) along with oxidation catalyst is a “better” fuel than CNG and LPG (The Times of India, March 25, 2001).

Fact

TERI is raking up a controversy based on a few outdated and unproven studies to bring diesel back and ignoring a range of other studies that prove that CNG engines are far cleaner than the currently available diesel ones

Though TERI defines ULSD as diesel with 0.005 per cent sulphur while quoting studies from abroad, it advocates diesel with sulphur content of 0.05 per cent (500 ppm) and Euro II diesel technology as an immediate strategy.

There are now numerous studies available that show that only reducing sulphur in diesel will make only a negligible impact on the particulate emissions from vehicles — between merely 5 per cent and 22 per cent. Therefore, it is false to claim that a marginal reduction of sulphur content is enough to make diesel an environmentally acceptable fuel.

Diesel begins to compare with other environmentally acceptable fuels only when it comes as part of a package with advanced diesel technology, state of the art exhaust treatment devices like continuously regenerating particulate traps along with diesel fuel with only 0.001 per cent (10 ppm) sulphur content and low aromatics content. But this combin ation is still experimental and not yet commercially viable.

Disinformation campaign

Just two days after the Supreme Court ruled that it would not entertain any relaxation of the July 28, 1998 order to move the entire bus fleet of Delhi to CNG, TERI opened up the diesel vs CNG debate by issuing a pamphlet Delhi’s Transport and the Environment: shaken but not stirred to create confusion and delay implementation.

TERI rests its entire opposition to CNG on the basis of one set of measurements .obtained from a London bus tested in Millbrook in 1996/1997 for the London Transport Buses. This study claims to have found that a Euro II diesel bus, running on ULSD (sulphur content of 0.005 per cent) and fitted with a continuously regenerating trap (CRT) — to control particulate emissions — achieves lower emissions than CNG buses.

What TERI omits to say is that after publication this study has come under serious scrutiny by other agencies that have found it flawed in terms of the methodology used. Various experts commenting on the London bus study say that it compares apples with oranges and does not give full details on the condition of the bus that was tested. The International Association for Natural Gas Vehicles (IANGV) has criticised this report on the ground that the difference in particulate matter emissions “most probably originates from excessive oil consumption of the CNG bus used by London Transport Buses. No detailed information on the condition of the test vehicles is available.”1

TERI then flashes results from yet another study conducted in 1998, by an Expert Reference Group (ERG) set up in western Australia to recommend the best fuel for buses in Perth. This “study” concluded on the basis of a literature survey that ULSD (with 0.005 per cent sulphur) with a CRT is the best option from an environmental point of view. At the same time, the report on the basis of the same London bus study concludes that even diesel with a sulphur content of 500 ppm (0.05 per cent, that is, same quality as the diesel currently available in Delhi) and with an oxidation catalyst is better than CNG when it comes to particulate emissions.2

The selective use of information by TERI is astounding because while using these studies to discredit the Supreme Court’s decision, TERI conveniently fails to mention that another study — a more recent one — done in March 2000, this time under the aegis of the Australian government, has trashed the ERG’s 1998 study.

This new report entitled “Lifecycle Emissions Analysis of Alternative Fuels for Heavy Vehicles” by the Australian government’s Council for Scientific and Industrial Research Organisation (CSIRO) clearly states “We used a risk-weighted scoring system, based on estimates of human health risk to rank the fuels. On a life-cycle basis, the gaseous fuels (LPG and CNG) give the lowest contribution to air pollution on this criterion.”3 Diesel is very low in the list of ten fuels they considered. The report has even questioned the method employed in the earlier 1998 study and says that the only data available for estimating emissions of vehicles using low sulphur diesel is based on only one London transport bus (see box: Trashed by science: pro-diesel report takes a beating). The report clearly brings out that CNG is much cleaner than both low sulphur diesel and ULSD in terms of all pollutants except non-methane volatile organic compounds (see table 1: The cleanest one).

Still trying hard to discredit CNG, TERI flashes another study conducted by the New York State Department of Environmental Conservation along with Johnson Matthey, the manufacturer of CRTs, that compares emissions results of diesel buses based on their tests with the test results of CNG buses borrowed from tests done elsewhere in the US and Canada. It gives no clue about the conditions of the CNG buses used in the study.4

Though TERI uses this study to promote diesel buses, it understates the fact that the study has considered diesel buses that are fitted with CRTs and running on 30 ppm sulphur (0.003 per cent) diesel. After all this, TERI advocates Euro II diesel buses with oxidation catalysts for Delhi.5

Bus operators in Delhi, the Delhi transport department and the Union ministry of petroleum and natural gas (MOPNG), and their supporters are still hoping that if Euro II diesel with 500 ppm sulphur (0.05 per cent) somehow can be labelled as a clean fuel they won’t have to do anything extra than run their old buses on the diesel already available in the capital. MOPNG is canvassing for the use of diesel with 500 ppm sulphur and Euro II diesel bus technology instead of CNG. It claims that this would reduce emissions by 70 per cent from Euro I level, but further reduction in sulphur content of diesel would not have any substantive effect on emissions. Therefore, the ministry believes that CNG is unnecessary if Euro II diesel buses are available.

Is low sulphur diesel a clean fuel?

Tests done across the world show that even with a major reduction in sulphur content in diesel particulate emissions reduce only marginally (see table 2: Marginal decrease and graph 1: Small difference).

Diesel begins to compare with CNG only when ULSD, that is, diesel with sulphur content below 30 ppm (0.003 per cent) comes as a package with advanced diesel technology, and state of the art engine emission control systems including CRTs. But this option is still not commercially viable.

What holds promise for diesel vehicles is the application of state of the art CRTs in combination with other catalytic converters and ultra low sulphur diesel with less than 30 ppm sulphur (see table 3: Trapping the particles). This combination of technology and fuel is coming into only those markets where very stringent emissions standards have been legislated such as California, the rest of the US and in some countries of Europe like Sweden. Such a combination is also seen as necessary to meet the Euro

Sources:

1.    Anon 2000, World-wide Fuel Charter, European Automobile Manufacturers Association, Alliance of Automobile Manufacturers, Engine Manufacturers Association, Japan Automobile Manufacturers Association, April, p 37.
2.    Melinda B Serman et al 1998, Emissions Comparison of alternative fuels in an advanced Automotive Diesel Engine, Interim Report for Department of Energy, Energy Efficiency and Renewable Energy, Office of Transportation Technologies, Office of Advanced Automotive Technologies, Southwest Research Institute, San Antonio, USA, mimeo.
3.    Peter Ahlvik et al 1999, PoT-India: Possible Abatement of Air Pollution from Urban Traffic in India, Ecotraffic R&D AB, Stockholm, Sweden, mimeo.
4.    Chiu L et al 2000, Performance and emission effect of ultra low sulphur diesel on double deck (Euro I) bus, paper presented at Better Air Quality, Motor Vehicle Control and Technology Workshop, Bangkok, mimeo.
5.    Wilkinson 2000, ULSD fuels, paper presented at Better Air Quality, Motor Vehicle Control and Technology Workshop, Bangkok, mimeo.
6.    Anon 2001, Summary Report, Department of Environment and Transport for the Regions/Society for Motor Manufacturers and Traders/CONCAWE,