Paper, plastic? How about ceramic?

A disposable coffee cup made of paper rather than plastic is obviously better for the planet, right?

Think again. Green choices are seldom that clear-cut.

Growing the cotton in a 100 percent organic cotton T-shirt required hundreds of gallons of water. For a Philadelphian, a bottle of wine trucked from California will have a larger carbon footprint than brought by ship from France. Compact fluorescent bulbs save energy but contain mercury.

When life-cycle assessment (LCA) gets added to the green equation, the moral complexities multiply, says Daniel Goleman in his new book Ecological Intelligence. LCA deconstructs a product's components, weighing the industrial processes involved and the environmental impact from beginning to final disposal.

The mind-boggling exercise makes any "green" decision feel like a Faustian bargain.

Take the coffee cup. According to an analysis that Goleman cites, a hot-drink paper cup consumes 33 grams of wood, while a polystyrene one uses about 4 grams of fuel oil or natural gas. The production of a paper cup requires 36 times as much electricity and results in 580 times the volume of wastewater as making a plastic cup.

But making that plastic cup produces pentane, which increases greenhouse gases. But then again, a paper cup left to biodegrade in a landfill releases methane.

And these calculations don't even include the human health effects, another ingredient in a process that makes it nearly impossible to determine which product is greener.

In the meantime, the goal is always to consider the impact of your choices, and pick products that likely cause the least amount of harm - in this case, a reusable mug.

"The real task," said environmental historian Ryan Edgington, a visiting assistant professor at Haverford College, "is to become a smart green consumer."