Marshall Willoughby could pass for a homeless man as he sips coffee outside a neighborhood bar in his adopted hometown of Gary, Ind.

CHICAGO — Marshall Willoughby could pass for a homeless man as he sips coffee outside a neighborhood bar in his adopted hometown of Gary, Ind.

His eyebrows are wild and bushy, his worn clothes flaked with sawdust and spotted with grease. He smiles broadly and exposes a lower jaw holding too few teeth. But the passers-by from whom he cadges cigarettes know him, and if you know Marshall Willoughby even in passing, you know he has a home.

Willoughby, 66, would like to give tours of his house, a 120-square-foot geodesic dome made from Styrofoam panels covered with a thin layer of concrete. He likes to show off rough-hewn contraptions he has built to provide creature comforts: his laptop, tankless water heater and lights run on a bank of old batteries charged by solar panels, home-made windmills, or an Army surplus generator powered by a rough-hewn contraption that burns wood gas.

He pumps his water from his own well. He piles his waste beside his garden beds, composting his own feces into topsoil. In drums near his melon patch rest gallons of his urine, decanting into ammonia fertilizer. He gets about half his calories from his garden, the rest from occasional bike trips to the grocery store or a local hot dog stand.

With his gap-toothed grin and his yard strewn with rusting machines, Willoughby knows how it looks. In the most genial way possible, he will tell you that you are the crazy one.

"People are so damn ignorant about energy," he said.

Willoughby admits he lives at the extreme end of a spectrum of environmental awareness, that he lives as a survivalist surrounded by people who prefer to thrive.

He ascribes to the decades-old ethos of permaculture, defined by Willoughby as expending as little energy as possible in exchange for a maximum return, to replace all that is taken from the environment. Eat a carrot one day, pile your feces next to the garden patch the next.

In Chicago's Rogers Park neighborhood, Milton Dixon heads a permaculture meet-up group and knows which parks he can forage for crab apples to juice. He, and most of his peers, acknowledge that urban permaculture involves co-existing with nature and society.

Extreme sacrifice like Willoughby's can make one somewhat isolated from neighbors living a more conventional lifestyle.

"You don't want to be spending more calories to make food than you get from the food. If you do that in nature, you die," he said. "And do you want to expend the energy to be an outcast "… the weird guy who doesn't have a car, who's out picking berries at the side of the road?"

Willoughby doesn't care.

"He can start preaching pretty quickly when you first get to know him," said Grischa Kurz, a friend and neighbor. Kurz recalls visiting Willoughby last winter, when a fire damaged his hut. Friends offered to let him stay with them, to collect money to build him a new, slightly larger place.

"He did not seem interested at all," Kurz recalled.

Less committed people may have placed a brick in their toilet tank to save water. They may commute in hybrid cars. They may believe these small sacrifices make their lifestyle sustainable.

One day, Willoughby believes, there will be no gas for your cars and your toilet will not flush. If that day comes — and Willoughby believes it will soon — he will wake again on the floor of his dome, load wood into his generator, and his life will not have changed at all.

He has become acquainted with permaculture first out of concern for personal economy, then for the ecology, and finally, ideology.

His second guiding belief is "peak oil," a controversial theory that the earth's petroleum reserves are near their maximum output and that they will dwindle fast — faster, Willoughby thinks, than his neighbors will be willing to trade in their McMansions for domed sheds.

Both permaculture and peak oil align with everything that Willoughby's life has affirmed to him, a life that has valued improvisation.

For 20 years starting after he returned from service in Vietnam, Willoughby ran a successful auto repair business in Hyde Park, Ill., where his clients included University of Chicago students and faculty.

He wasn't home from Vietnam long when Middle East nations put an oil embargo in place, and he watched the polite society of his neighborhood fray. Graduate students scuffled with each other in lines for rationed gas. Women who wouldn't give a grease monkey like him the time of day were suddenly very interested, if he had access to a few gallons of fuel.

When the landlord lost the building to a bank, he was again without a lease or credit. His repair business, which had once counted 14 employees and consumed 70 hours of his week, was gone.

He moved to a friend's house in Gary and wound up delivering pizzas, saving money for a house of his own that would generate no bills. When he was laid off by the pizza parlor in 2000, he was done with jobs.

"I have not paid a utility bill in 10, 12 years," Willoughby said. "I do not have a job. You don't need a job. There's enough work to do."

He moved into a camper van on a lot a friend bought for him for $7,000. Eventually, he bought a dome kit for $350, plus shipping.

Willoughby estimates that he lives on perhaps $4,000 a year, mostly money from repair jobs. Last week, he applied for Social Security, which he figures will give him a few hundred dollars a month.

With a steady income, he intends to spend it building a larger solar array and better batteries to power and heat his house. Most of the gizmos he needs, he has already built. He can always get by with less.