A New York Times article this week concludes that major oil and gas companies are, as the headline roared, “Loath to Follow Obama’s Green Lead.” Such stories bashing Big Oil’s slim investment in renewable energy tend to fall short by failing to consider how renewables intersect with an oil company’s core business, and this one is no exception.

As the Times ably demonstrates, Big Oil is freezing or cutting investment in renewable energy and doing so from a relatively small base. It notes that Shell, which has frozen spending on wind, solar, and hydrogen energy, has invested just $1.7 billion on alternative energy projects since 2004, compared to $87 billion to keep its oil and gas flowing.

That should come as little surprise, since Big Oil’s insubstantial and fickle commitment to renewable energy goes back decades. Following the 1973 oil shock, for example, U.S. oil majors of the time such as Mobil and Chevron embraced photovoltaics, only to dump the projects when oil prices crashed and OPEC’s power waned a decade later. British Petroleum’s promise to go “Beyond Petroleum” already looked weak five years ago when it ditched production of next-generation cadmium-telluride thin-film photovoltaics–technology that Arizona-based First Solar has since ridden to the top of the world PV market.

Big Oil has a limited attention span for renewables because such firms are not, despite their marketing claims, “energy” companies. They are marketers of specific energy products–primarily petroleum refined into motor fuels and natural gas for heating. Power generation, the focus of most renewables, is but a secondary market for their natural gas.

As Christopher Flavin, president of the DC-based Worldwatch Institute, put it to me a few years ago, “There couldn’t be anything more different than selling devices to make electricity on rooftops and selling gas at the pump.” Flavin’s comment ran in my 2005 look at GE’s leap into renewables, which at the time elicited similar but unwarranted skepticism. He was among those who noted that power generation was a key market for GE’s equipment, and time has proved him right as GE continues to expand investment in renewables and energy efficiency.

The exception to Big Oil’s retreat from renewables–its ongoing support for biofuels developments–cements the “core markets” analysis. Biofuels are, at present, the best response to the return of battery-powered electric vehicles after a century of suffering at the hands of the internal combustion engine and Big Oil’s liquid fuels. Biofuels provide a natural product for gas stations, and blending with gasoline and diesel fuels will sustain the latter for decades.

Given the practical and policy challenges arrayed against biofuels, its supporters will need all the help they can get from Big Oil. According to a report in DomesticFuel.comlast week, fuel trackers with the Department of Energy’s Energy Information Agency say that the United States will likely fall short of legislated goals for cellulosic ethanol: 100 million gallons of cellulosic ethanol in 2010, rising to 4.3 billion gallons by 2015.