Beth Lukomski was grinning about "goodness" as she carried two white containers from Transfer Pizzeria to her car late last week.

She wasn't thinking about the south side café's pizza - which she loves - but its kitchen scraps in five-gallon buckets that she was delivering to a compost pile behind Sweet Water Organics, an urban fish and vegetable farm in the Bay View neighborhood.

The scraps eventually will help create nutrient-rich soil for growing healthy vegetables in community and backyard gardens this summer, explained Lukomski, a volunteer for the Milwaukee Community Compost Network.

Having kitchen scraps hauled for compost is good for community gardening efforts and helps the pizzeria reduce its carbon footprint, restaurateur Krys Zielinski said. The other restaurant he co-owns, Via Downer at 2625 N. Downer Ave., also is linked to the composting network.

The food residual that's composted is not prepared food, which could contain pathogens, but fruit and vegetable trimmings, eggshells and coffee grounds that otherwise would be hauled to a landfill.

LeanPath, a Portland, Ore., company that helps restaurants track garbage output to reveal potential savings, estimates average restaurant waste is 4% to 10% of total food purchases, due to overproduction, trimming, spoilage and expiration.

Scientists say the United States could save the energy equivalent of about 350 million barrels of oil a year if food waste could be eliminated instead of being processed at landfills. That includes food tossed by diners and home cooks that isn't composted because of pathogen risks.

Growing Power, the nonprofit urban farm at 5500 W. Silver Spring Drive founded by Will Allen, has been composting millions of pounds of "pre-consumer" food waste since 1999 and has several dozen pickup sites, including corporate cafeterias, a brewery, restaurants, coffee houses and produce companies. The kitchen scraps (not table scraps) are picked up free of charge and converted to compost for growing food.

The volunteer-driven Milwaukee Community Compost Network, an offshoot of the community-based Victory Garden Initiative, has been collecting food residual since 2009 and has grown dramatically with increased interest in vegetable gardening, and demand for garden soil that's not contaminated.

The volunteer network formed when two new community gardens were started - Concordia Gardens, 220 E. Concordia Ave., and Hide House Community Garden near S. Greeley St. and E. Deer Place. The first compost pile was created behind Sweet Water Organics, about four blocks from Hide House. Another compost pile is at Concordia Gardens.

"There's an energy and excitement in flipping the compost pile, and stirring it with a pitchfork to work the soil," said Lukomski, one of about 20 network volunteers who pick up food scraps each week from 13 Milwaukee establishments, including restaurants, coffee shops, an Asian market, two Outpost Natural Foods stores and Whole Foods.

Melissa Tashjian is the compost network's project manager.

"Melissa is the only person I know who could talk 20-plus people into doing this in the middle of winter," Lukomski said.

The group collects 600 to 1,000 pounds of food residual from businesses weekly, Tashjian said.

"Our main core of volunteers has been with us since we started," she said. "Mainly what motivates them is passion for their community, and being able to see sustainability and self-reliance within the community. The more volunteers you have, the more businesses you can take on."

Lukomski said the volunteer group is recruiting in Riverwest. It also is discussing a possible community drop site this summer at the South Shore Farmers Market for residents who want to contribute kitchen scraps to composting efforts.

Compost for growing food is important to gardeners because city soil may be contaminated with lead and arsenic, said Allen, of Growing Power.

Growing Power last year diverted more than 20 million pounds of food waste from landfills, according to its website. The nonprofit urban farm expects to convert 22 million pounds of food waste and carbon (wood chips, straw, hay and leaves) into 10,000 yards of compost this year, Allen said.

Growing Power expanded its composting capacity last year by leasing an unused 4-acre lagoon at the South Shore sewage treatment plant in Oak Creek from the Milwaukee Metropolitan Sewerage District.

Among Growing Power's food waste pickup sites: Lakefront Brewery (grain waste); Children's Hospital of Wisconsin; Harley-Davidson; Maglio Produce; Rishi Tea; Alterra Coffee; Stone Creek Coffee; S.C. Johnson in Racine; Johnson Controls; Rockwell Automation; Kohl's Corp.; two University of Wisconsin-Milwaukee dorms; Waukesha County Technical College; Milwaukee School of Engineering; and a Walmart store.