The clean car

Technological measures and the myth of the clean car

The reduction of unit CO2 emissions thanks to technological improvements is played out at several levels: the engine and fuels of course but also aerodynamics, weight, rolling resistance, braking energy recovery, fuel consumption. accessories, etc. and manufacturers and engineers regularly promise us “clean” vehicles in the near future. This qualifier, somewhat overused, applies poorly to the issue of climate change. Because, if scientific and technological advances do exist, their record with regard to greenhouse gases is mixed. In any case, reading the figures, it is difficult to see how technology alone could solve the problem. The new PNLCC measures that can be classified in the “technological improvements” category only account for 7% of the reduction effort to be made (PNLCC objective: - 4 MteC for 2010).

In 1998, an agreement has been reached between Europe and the Association of European Car Manufacturers (ACEA agreement) in which manufacturers based in the EU are committed to lowering the average emissions of their new cars to 140 g of CO2 per km on the 2008 horizon (against 185 g / km in 1995). The measurement is made on an official standard driving cycle excluding the use of safety accessories (reinforcements, ABS brakes, etc.) and comfort, especially air conditioning and therefore in conditions far removed from actual use. Today, the threshold to reach is still far since the average European emissions amount to 164 g / km in 2002 and that the expected decline is slowed down by the entry into force on the off-road market and spacious type vehicles. break or minivan. To this commitment was added from 2000 the promise to launch ranges of cars rejecting less than 120 g / km. As an indication, today in France, 2,7% of cars sold emit less than 120 g CO2 / km. Finally, remember that this ACEA agreement is included in the accounting of the reference scenario of the PNLCC (the same one that will not allow France to achieve its reduction objectives) and that this measure does not fit into the scenario with all of the new measures and in the effort to reduce - 4 MTEC for 2010.

Technological progress is double-edged.

Consumers play an important role in accepting technological advances. But, if they adopt small city cars (SMART type), they also let themselves be tempted by disproportionate and very polluting models, like the very fashionable urban 4 × 4. Thus, since 2001, we have noted for France a sharp slowdown in the drop in average CO2 emissions from new vehicles (162 g of CO2 per km in 2000, 156 in 2001, 155 in 2002 and in 2003), probably due to the increase in the sale of spacious vehicles and off-road vehicles 37 (see also previous chapter)

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Research on traditional engines focuses on optimizing fuel consumption. A success ? In 10 years, the average consumption of the French fleet decreased by 9,2%, again according to the standardized cycle. But this evolution is mainly due to the commercial success of Diesel, a little more sober than the gasoline engine. And it hides another reality: if the engines work better, the new vehicles see their power, their capacity and their weight increase. Added to this is the proliferation of on-board equipment (air conditioning, guidance systems, etc.) which leads to significant additional consumption of more than 20%. The actual consumption of vehicles is one liter 100 km above the normalized cycle and this gap increases: cars are more and more powerful and provide a (illusory) sense of security that drives drivers to ride Faster and faster.

Automotive air conditioning: a major problem

Estimates suggest that HFCs could be responsible for 7 at 13% of GHG emissions in 2050. In 2001, the IPCC concluded that concentrations of HFC-134a (refrigerant commonly used in automotive air conditioning) are growing almost exponentially. The boom in the use of air conditioning in automobiles (from 9% to about 80% in Germany in a decade) threatens to incur high levels of HFC use, especially since 'a subject of total ignorance on the part of consumers. It should be known that even today improved air conditioning systems leak HFC after only 5 years of use.

Another essential element that must be taken into account: the renewal time of the car fleet. Indeed, the median lifetime of a car is about 15 years, so we must take into account the time of inertia for the actual use of new technologies. Concerning aircraft, similar (but smaller) announcements have been heard: for example a reduction of 10% in the next 10 years of kerosene consumption. The renewal time of the aircraft fleet is about several decades.

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The development of alternative engines (electric and alternative vehicles).

Some manufacturers are announcing the transition to the "hydrogen era" with fuel cell engines. Since they only discharge water locally, they will improve the quality of the air in the city. But, in terms of greenhouse effect, caution is needed: because this hydrogen that replaces gasoline will have to be produced somewhere, and some technologies prove to be inefficient and just as CO2 emitting! This requires a rigorous analysis of the life cycle. Unless opting for the nuclear path, which emits very little greenhouse gas but raises other environmental concerns, and / or renewable energy, which may very well be unable to meet the current demand without extensive energy saving program. In the current state of the art, the overall efficiency of the electrolysis-hydrogen cell is lower than that of conventional gasoline or diesel. Only dies with a hybrid engine or with a methane or methanol fuel cell seems to be able to offer a better return.


Gasoline and diesel are the two most commonly used fuels but also the most emitting CO2. For 15 000 km traveled, a petrol car discharges an average of 2 700 kg of CO2, diesel 2 400 kg of CO2 and
in LPG 2 300 Kg of CO2. Even if it is a question of remaining very cautious about the technical progress which alone will not be able to
To solve the problem of global warming, we must not ignore or ignore alternatives to the conventional thermal vehicle.

Thus, after the mistakes of the electric car (no breakthrough on the French market: 132 electric vehicles sold in 1995 against 113 in 2003), manufacturers offer hybrid vehicles (combining gasoline and electric engines) and gas vehicles. These models, which lead to lower CO2 emissions, are not very successful in our country. For gas, the need to store at high pressure and to set up rather heavy infrastructures constitutes a significant obstacle except in the case of communities wishing to equip
their fleet of vehicles made to make many displacements in urban centers.


Their large-scale use dates back to the 70s for Brazil and the 90s for Europe. In 1992, European agricultural policy imposed the set-aside of 15% of the cereal area, in order to control the volume of production. Since fallow crops for non-food purposes are accepted, they can therefore be used for energy purposes, through biofuels or biofuels. Biofuels are produced from biomass (energy from plants) and are part of the family of renewable energies. They appear today as an alternative to conventional fuels with interesting potential since their use would reduce GHG emissions and certain pollutants. Abroad, they are sometimes used pure, but in France, they are mixed at the level of 2 to 5% of conventional gasoline and diesel fuels (except 30% for the diester for heavy vehicles). We can distinguish two major sectors: the vegetable oil - ester sector from oilseeds (rapeseed and sunflower) and the alcohol - ethanol sector from beet, cane and wheat crops.

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The CO2 released during the combustion of biofuels corresponds to the quantity absorbed during plant growth. In terms of CO2 emissions from "sink to wheel" (ie life cycle analysis), biofuels have significantly lower levels than conventional fuels. The use of ester (sunflower and rapeseed) is preferable to that of ethanol (wheat and beet).

Pure vegetable oils (sunflower and rapeseed) are the least energy-consuming. In addition, the presence of oxygen in the biofuel molecules improves their combustion and reduces the number of particles from unburned hydrocarbons, as well as carbon monoxide. On the other hand, extreme vigilance is needed on the growing conditions of farmland and fallow land. In fact, an irrational use of nitrogenous fertilizers would lead to a release of N2O as well as soil and water pollution that could counterbalance the positive ecological balance related to the combustion of biofuels.

This text is extracted from the report: Transport and climate change: a high-risk junction published by the Climate Action Network April 2004.

You can download the report in its entirety here: Transport and climate change

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