Author’s Note: A Chicago Tribune reader wanted to know: Are disposable coffee cups made of Styrofoam more or less harmful to the environment than reusable mugs? Here’s how I answered, with much help from sustainability engineer Pablo Päster.
The debate over coffee cups-disposable or not-happens torunneth over with tough-to-measure variables. For instance, do you use a dishwasher? Is your model energy efficient? And: Just how clumsy are you? (Reusable mugs: Useless when broken.) Scientists analyze this issue in myriad ways, but overall, consensus is that brew imbibed from reusable, ceramic mugs is the most sustainable option.
But there’s many a slip twixt cup and lip. To reap environmental rewards of the mug, you’ll need to hand rinse it–putting it in your (energy-efficient) dishwasher only when absolutely necessary. That’s according to Pablo Päster, a San Francisco-based sustainability engineering consultant who also writes a column at AskPablo.org on the science of sustainability, including a technical analysis of this very issue.
In his analysis, Päster found that a ceramic mug has a higher total “material intensity”- a measure of resources used to manufacture a product (like the extracted clay and gas to heat the kiln)-than a Styrofoam cup. But the mug’s reusability-which means it can provide multiple “service units”-justifies its higher material intensity after about 46 uses. “If you have one cup of coffee daily for a year, that’s 365 ‘service units,'” says Päster. “That can be accomplished with either 365 disposable cups or one reusable mug.”