Passersby may have noted a crane towering over the Four Seasons Hotel last week, just out of misting range of the nearby Swann Fountain.
The crane was hoisting microturbines to the roof, to help generate the hotel's energy (equal to getting 509 cars off the road annually), and as a bonus, hauling up the wooden frames and bags of house-blend compost for what is to be a modest kitchen garden.
It was certainly the most visible bit of greening going on in the city's hard-pressed feeding sector. But it had plenty of company behind the scenes - from the bottled water that has vanished from tabletops to Penn's decision to cut back on cafeteria trays to cut food waste and save on washing-water bills.
In this environment, as it were, the imperatives of cost-cutting have moved eco-consciousness closer to the center of nearly everyone's plate.
If you happened to visit the restroom at Coquette Bistro in Queen Village, or Oyster House at 15th and Sansom (or a host of other places), you likely would have encountered another secret, if hardly silent, weapon.
It is called the Xlerator hand dryer. With a roaring whoosh akin to a mini-jet engine, it blasts your hands dry in little more than 10 seconds, way quicker than those wheezing old dryers - and far more energy-efficient than paper towels.
That's not getting into the pure joy of witnessing your hands dry in a flash: Slow food, not drying!
The green initiatives have put local produce in the visitors dining room at Jefferson Hospital. They've resulted in nickel discounts if you bring your own shopping bag to Whole Foods. Local brewers back eco-fests.
So the activity at Four Seasons was not surprising, though it was surprisingly extensive. (The hotel even has its own reusable water-bottling system now.)
For the roof-top garden, food scraps had been collected from its Fountain and other dining rooms and hauled - in a truck piloted by engineering director Marvin Dixon and powered by used cooking oil - to a compost farm in Royersford, 35 miles northwest of the city.
The farm is called Two Particular Acres. It was the first of its kind to get a state license to accept food waste in order to turn it into healthy soil, a bit of alchemy achieved, according to owner Ned Foley, by blending in leaf waste and manure, crop residue and mulch hay.
He compared it to baking: You mix your recipe of organic materials, aiming for a good carbon-nitrogen ratio, then let it cook; it gets as hot as 160 degrees, killing off pathogens and most weed seeds.
The 1,600-pound bags that made the return journey to Four Seasons were from the farm's "2007 vintage," blended into a lighter aggregate that is better suited - for obvious reasons - for rooftop applications.
It is getting to the end of summer in these parts. But the chefs at the hotel have their fingers crossed.
They are vowing to plant onions and garlic, broccoli rabe and rosemary. Maybe pumpkins.
Who knows? In this bountiful season of trayless cafeterias, cooking-oil trucks and quick-dry Xlerators, they may even get a crop.