Why is Peter Allen, a businessman with an MBA, picking up dirty diapers from homes across the Twin Cities?

"I saw a rising trend," said Allen, who started Do Good Diapers cloth diaper delivery service in Minneapolis last October. As more parents choose cloth diapers, what was once a niche market is taking root in the mainstream.

Proponents say cloth is thriftier, gentler on the environment and better for their baby's skin and health. Parents gush over how easy it is to use the new pinless, not-your-grandma's-cloth diapers. Although an estimated 90 to 95 percent of American parents use disposables, people such as Allen believe the pool of cloth users will keep expanding.

Target.com and Costco.com carry cloth. Cloth diaper sales at Bumkins, one of the largest U.S. cloth diaper companies, have increased 30 percent or more every year for the past three years. Another major cloth diaper company, Cotton Babies, started six years ago with $100 and ran the operation out of a living-room bookshelf. Today the company has nearly 50 employees and distributes to six continents.

For the past two years, cloth diapers have been the fastest-growing category of products at Peapods Natural Toys and Baby Care in St. Paul.

"People are seeing that this is an option," said customer Jessica Griffith, who's used cloth for her 2 1/2- and 1-year-old sons. In addition to being concerned about diapers in landfills, "We were mostly interested in saving money," said the St. Paul resident. Griffith estimates that she's spent $400 total to diaper both boys. Plus, "the nicer cloth diapers have resale value, so I was able to sell some of those on Craigslist and get some of my money back," she said.

Cloth diapers vary significantly in style and cost, from $1 to $25 per diaper, so cloth runs $50 to $500 total from birth through potty-training. Parents spend up to $2,000 per baby on disposables, according to Consumer Reports.

People such as Karina Crockett, who uses Allen's diaper service instead of washing them at home, pay about the same for cloth as they would for disposables. Crockett switched to cloth because she felt guilty about throwing away diapers. "We also realized this is on her skin 24 hours a day, and we had this growing uneasiness. There's no way having scents and chlorine bleach and plastic against the skin is a good thing."

Cloth diapers are often made of cotton, bamboo, terrycloth, flannel or microfiber, and many are made in the United States. Concern over how diapers are manufactured and what's in them is also driving sales of some disposables. Seventh Generation makes disposables without fragrance, chlorine or the chemical tributyltin (TBT). Sales jumped 84 percent between 2007 and 2008.

Dr. Alan Greene, a pediatrician at Stanford University and author of "Raising Baby Green," doesn't believe there's evidence that either cloth or disposables are superior from a health standpoint, but he does encourage parents to buy diapers without TBT, chlorine and fragrance.

"From a baby's perspective, cloth diapers tend to be more comfortable when they're dry and more irritating when they're wet," he said. "But that irritation when they're wet can be a signal that helps them potty-train earlier," as much as 50 percent sooner, he said.

There's a question of whether disposables cause fertility problems for boys because the plastic raises the temperature of their testicles, he said. Some studies show it's a problem, but so far nothing conclusive has proven that link.

Calls to Huggies and Procter & Gamble, which sells Luvs and Pampers, were not returned. Some proponents of disposables say that health concerns are unfounded and that the environmental impact is even because washing cloth diapers uses energy and water.

Tina Darr, mother of 2-year-old twins and a newborn, doesn't buy it. "I haven't seen a big change in my water bills," she said. "I feel good about not putting nonbiodegradable things in the landfill that are going to take 500 years or more to decompose." Darr became such a fan of cloth that she started a business, Cloth Diapers Today, to sell her favorite styles and brands from her home in Rushford, Minn.

"The biggest thing is people's perception of what cloth is like," she said. "You have to throw out the idea of what cloth used to be like and see that it's really quite easy."

People use cloth diapers with waterproof covers or all-in-ones, which combine absorbent and waterproof materials. Many soiled diapers can go directly into the wash. Poopy diapers get shaken, scraped or sprayed off into the toilet. But that's something people using disposables are supposed to do as well -- human waste in the trash is a no-no, and the fine print on disposable packages points that out.

Elizabeth Wickoren of Blaine wished that she had known about cloth earlier, so last August she decided to get the word out by starting the nonprofit Teeny Greenies, which provides diapers to families wishing to try cloth. She has diapers out to 35 families and a growing waiting list. Wickoren is helping people in Michigan, Florida, Illinois, Tennessee, Texas and Mississippi start local diaper lending services under the Teeny Greenies name.

"There's been a perfect storm with the increase in the green movement combined with the downturn in the economy," she said. "Cloth diapers are right there in the middle -- good for the environment and good for your pocketbook."

Sarah Moran is a freelance health writer in Minneapolis.