According to new research from Cranfield University’s Sustainable Manufacturing Systems Centre, the sole focus on vehicle tailpipe emissions as a measure of environmental impact in the car manufacturing industry has led to serious unintentional costs.

In order to cut CO2 emissions and fuel use, the automotive industry has been encouraged to use lightweight aluminum in the manufacture of vehicles. Cranfield’s study raises concerns that this method results in a far higher cost to the environment than the savings achieved through reduced tailpipe emissions.

The study, a ‘cradle to grave’ investigation of the total energy and CO₂ emissions impact of passenger vehicle engine production, focused on the most representative engine in use globally –  a 1.6 litre four-cylinder engine. Aluminum models were compared with the more traditional cast iron engines.

Despite the lighter weight of aluminum, the production of each aluminium cylinder block consumes 1.8 to 3.7 times more energy than the production of cast iron. What’s more, over 70% of global aluminum production is based on fossil fuels. The result? An energy-intensive production phase which generates more than 10 kilogram of CO2 per kilogram of aluminum.

A typical aluminium-engined car would need to be driven between around 115,000 miles and 348,000 miles before there were any environmental benefits from the lower fuel use involved.

Research lead and head of Sustainable Manufacturing at Cranfield University, Professor Mark Jolly, said: “Current legislation takes such a narrow view of what makes a car environmentally-friendly that it has caused more damage than good.

“Legislation encourages engineers to use low-density materials, forcing them to swim in dirty water. It’s critical that governments and consumers start to look at the whole life-cycle involved in manufacturing vehicles, not one indicator, with more holistic policies that actually reduce CO2 emissions rather than just presenting the image of doing so.”

He continues to explain that consumers may be misled, thinking they are making a sustainable choice when presented information is based solely on emissions.

“There are also major implications for the electric vehicle market – seen to be the future in terms of environmentally friendly transport. But, again, taking the life-cycle into account you have to highlight the potential horrendous impacts of manufacturing the batteries.”