Dear EarthTalk: I’ve been hearing about the great gas mileage for Volkswagens that use diesel fuel. But is it better for the environment to use diesel or unleaded gasoline? -- K. Cronk, Bay City, MI

In the past, diesel fuel was always considered dirtier than gasoline. But newer standards regulating sulfur content and improved technology in diesel engines have made diesel somewhat kinder to the environment. Many eco-advocates now tout diesel as a viable and preferable alternative to regular unleaded gasoline.

2009 Volkswagen Jetta TDI Clean Diesel

Where diesel fuel really shines over gasoline is improved fuel economy thanks to its higher “energy density”: Diesel contains more power per liter than gasoline. Today’s diesel engines have 20-40 percent better fuel economy than their gasoline counterparts, which some say more than makes up for the fact that they also produce about 15 percent more greenhouse gases. This greater efficiency means that diesel engines emit less carbon monoxide and carbon dioxide and fewer hydrocarbons than gasoline engines.

Diesel’s downside is that it emits larger amounts of nitrogen compounds and particulate matter (soot) that can cause respiratory problems and even cancer. The California Air Resources Board (CARB) attributes 70 percent of that state’s cancer risk from airborne toxins to soot from diesel cars and trucks. Nationwide, studies have shown a 26 percent mortality increase for those living in soot-polluted areas.

But diesel’s dark side is getting a little brighter, thanks to new technologies such as Mercedes-Benz’ BlueTEC system (now used in many VW, Audi and Chrysler diesel models) that filters particulates while improving overall engine performance. The Diesel Technology Forum (DTF), a trade association of carmakers, engine builders and petroleum distributors, reports that technologies now commonplace in new diesel engines reduce the tailpipe output of particulate matter by as much as 90 percent and nitrogen oxides by some 50 percent compared to diesel engines on the road just a decade ago.

“The industry has made significant strides in recent years to develop diesel systems that are cleaner and more efficient than ever before,” reports DTF. “Thanks to state-of-the-art engines, cleaner-burning fuels, effective emissions-control systems, and advancements in the fuel injection system, it would take 60 trucks sold today to equal the soot emissions of one 1988 truck.” U.S. Environmental Protection Agency (EPA) data shows that airborne diesel particulate levels fell by more than 37 percent during the 1990s.

Meanwhile, continually improving fuel efficiency standards in the European Union (where the majority of new cars purchased in many member countries use diesel fuel) are forcing carmakers to design more fuel efficient, less polluting vehicles around the world. After all, there’s no sense in designing better engines for one region with high standards and another for areas with less stringent rules. Another green benefit of diesel-powered engines is their ability to run on plant-derived biodiesel instead of petroleum-based diesel. And in the near future consumers may be able to shop for new diesel-electric hybrid cars now on the drawing boards of major automakers around the world. For now, consumers looking to buy a new or used car—diesel or otherwise—can see how different models stack up in regard to efficiency and emissions via the FuelEconomy.gov website, a joint effort of the EPA and the U.S. Department of Energy.

Photo: Chris Luckhardt, courtesy Flickr

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The report from the World Business Council for Business Development (WBCSD) - Vision 2050: The New Agenda for Business – calls on businesses around the world to “develop strategies that would enable a global population of some 9 billion people to live well within the resources of the planet by 2050.”

A group of twenty-nine companies - led by Alcoa, PricewaterhouseCoopers, Storebrand and Syngenta – helped develop the report, which focuses on “the roles that business must play over the next few decades to enable society to move toward being sustainable.”

Alcoa Executive Vice President and Chief Technology Officer Dr. Mohammad A. Zaidi, who co-chaired the 18-month project, said: “The world already has the knowledge, science, technologies, skills and financial resources needed to achieve Vision 2050. However, concerted global action in the next decade will be required to bring these capabilities and resources together, putting the world on the path to sustainability.”

The World Business Council for Sustainable Development (WBCSD) is a CEO-led, global association of some 200 companies dealing exclusively with business and sustainable development. Members are drawn from more than 36 countries and 22 major industrial sectors.

The Vision 2050 report identifies a “critical pathway” that includes:

• Addressing the development needs of billions of people, enabling education and economic empowerment, particularly of women, and developing radically more eco-efficient solutions, lifestyles and behavior;
• Incorporating the cost of externalities, starting with carbon, ecosystem services and water;
• Doubling of agricultural output without increasing the amount of land or water used;
• Halting deforestation and increasing yields from planted forests;
• Halving carbon emissions worldwide (based on 2005 levels) by 2050, with greenhouse gas emissions peaking around 2020 through a shift to low-carbon energy systems and highly improved demand-side energy efficiency;
• Providing universal access to low carbon mobility; and
• Delivering a four-to-tenfold improvement in the use of resources and materials.

"Making these changes – and more – will enable us to consume just over one planet’s worth of ecological resources in 2050, as opposed to the 2.3 planets we will be using if we continue on the business-as-usual path we are on today,” the report says.

Vision 2050 suggests that the “transformation ahead” represents “vast opportunities” in a broad range of business segments as the global challenges of growth, urbanization, scarcity and environmental change become “the key strategic drivers” for business in the coming decade.

In natural resources, health and education alone, the broad order of magnitude of some of these could be around US$ 0.5-1.5 trillion per annum in 2020, rising to between US$ 3-10 trillion per annum in 2050 at today’s prices, which is around 1.5-4.5% of world GDP in 2050, according to the report.

WBCSD said project member companies on Vision 2050 were Accenture, Alcoa, Allianz, ArcelorMittal, The Boeing Company, Duke Energy Corporation, E.ON, Eskom, Evonik Industries, FALCK Group, Fortum Corporation, GDF SUEZ, GrupoNueva, Holcim, Infosys Technologies, Osaka Gas Co., PricewaterhouseCoopers, The Procter & Gamble Company, Rio Tinto, Royal Philips Electronics, Sony Corporation, Storebrand, Syngent  International, The Tokyo Electric Power Company, Toyota Motor Corporation, Umicore, Vattenfall, Volkswagen and Weyerhaeuser Company.

The Vision 2050 report can be downloaded here.