On a recent Sunday, a curious crowd gathers near the busy intersection of 13th Avenue and Colorado Boulevard, bundled and hooded against an ominous sky. There are grandmothers from the suburbs and hipsters who look like they’d feel at home in Capitol Hill. There is a young couple with a toddler, stuffed animal in tow; there’s a grade-schooler snapping photos on an iPhone; there’s even one four-legged family member in attendance. Why is this 40-plus-strong motley crew braving the elements on a chilly, early spring day? To listen to a woman called “Jungle Judy” Elliott talk about dirt, garbage, and microorganisms. Held at Gove Garden, a working demonstration site, this is the first free composting class of the year, provided courtesy of Denver Urban Gardens (DUG) and Denver Recycles.

Everyone is asked to introduce themselves and say one thing they’d like to learn over the two-hour class. Some have never so much as diverted a banana peel from the trash can; others have year-old compost piles already in their yards that just aren’t maturing into the nutrient-rich, earthy smelling soil amendment Elliott has us feel and sniff on our way in. “I’ll be checking pockets on the way out,” she jokes.

Elliott starts by explaining that the conditions for a happy, healthy (and not stinky!) pile are similar to what our bodies need to thrive: a roof over our heads, movement, water, and a balanced diet of non–junk food that comes in chewable-size pieces. For the “shelter” requirement, she doesn’t recommend a specific bin or system. Instead, she takes us around the garden and shows us nearly a dozen examples of ways to house a pile, including the cinder block DIY construction pictured above, a snow fence enclosure, and an open pile (a father lifts his toddler to let him feel the open pile, at right), all covered with tarps, and a variety of commercial bins, such as the tumbler style (below).

She expands upon the step-by-step directions she provided for a 5280 feature earlier this year (“33 Things Every Coloradan Should Know How To Do”), demonstrating how to chop up a pile, pointing out what the white streaks of bacteria should look like, expanding upon what can go in and what can’t—only use weeds that haven’t gone to seed; if you don’t have enough dry leaves saved from the fall, get some straw—and elaborating on the benefits and many uses of compost (if you go, ask about “compost tea,” which you can mix up, ferment, and use on transplants for disease suppression). But perhaps the most valuable part of the class is the Q&A session at the end when attendants pick Elliott’s brain, which is packed with more than 20 years of knowledge about composting, about their individual issues: “Can I put my compost pile near my fence?” Not unless it’s well-insulated or in a shady spot; see the steam coming off this pile? It’s 130 degrees in there. “My pile isn’t decomposing; what’s wrong?” Do you have enough—that’s two-thirds of the pile—carbon material, the fiberous brown stuff? Are you turning it once every week or two? Does it feel like a wrung-out sponge? “What if I want to do vermicomposting?” DUG holds monthly worm-specific classes throughout the summer; come back for one of those!

The rain holds off, and we all leave energized with new confidence and a printed guide to backyard composting (English on one side, Spanish on the other) to help us remember what we learned. But if we forget or run into problems, it’s comforting to know that Jungle Judy—or one of her trainees, many of whom attended this first class as part of DUG’s Master Composter Program—will be at Gove Garden most Saturday mornings and Wednesday evenings throughout the summer, ready to offer up free expertise and trouble-shooting with a smile and a shovel in hand.

Click here for the 2014 class schedule; participants must register at least one week in advance online or by calling 303-292-9900.

Don’t have the space or time for a compost pile right now? Check out Denver’s compost collection program. For about $120 a year, you can receive a bin for your household’s organic waste, weekly pickup service, and the satisfaction of knowing you’re doing your part in reducing the amount of organic material we send to the landfill each year—more than 50 percent of the total trash haul in Denver.

Follow copy chief Jessica Farmwald on Twitter at @JessicaKF.