ANAHEIM, CALIF. — In the year since stepping down as co-chief executive officer of Whole Foods Market, Walter Robb has joined the fight against food waste. Mr. Robb recently became an investor and board member of FoodMaven, an online marketplace for otherwise wasted food.

Based in Colorado Springs, Colo., FoodMaven sells local and oversupplied food from distributors, manufacturers and producers to food service buyers at a discount.

"Forty per cent of the food produced in the United States is lost," Mr. Robb said during a presentation at Natural Products Expo West, held March 8-11 in Anaheim. "We're not talking about the stuff off of the salad bars at Whole Foods at the end of the day. We're talking about the way that systems are set up between supply and demand."

Mr. Robb said he partnered with Patrick Bultema, co-founder and c.e.o. of FoodMaven, because he believes there is "no scalable solution at this present time" for rescuing wasted food in the United States.

FoodMaven was built on a mission to reclaim the estimated $200 billion per year in revenues from lost food and currently serves hundreds of suppliers and buyers in Colorado with plans to roll out to metro services areas across the United States. In January, FoodMaven announced it had closed an $8.6 million Series A financing led by members of the Walton family to scale its footprint and impact.

"While there’s a lot of talk about farm to table, the truth of the matter is there isn’t a system for it." — Patrick Bultema, FoodMaven

"A third of what's going into landfills is food waste," Mr. Bultema said during the presentation. "And with all this food being thrown away, 42 million Americans are food insecure."

Mr. Bultema pointed to several reasons why food is wasted. He referred to one reason as "an abundance expectation" among grocery shoppers that is pressuring suppliers to produce more than what is needed.

"From the farm to the packing shed to the distributor all the way to the big grocery distribution centers and stores, there’s an enormous amount that gets lost that’s really the oversupply in this quest to always have everything all the time," Mr. Bultema said.

And then there are the imperfect or outdated items that are tossed in favor of higher-quality fare. Distributors or retailers may "get fussy" and dump product that doesn't meet cosmetic standards if there is already too much supply, Mr. Bultema said.

Another issue driving food waste is the local food movement, he said, noting that local growers often struggle to gain access to the market.

"While there’s a lot of talk about farm to table, the truth of the matter is there isn’t a system for it," Mr. Bultema said. "They may have a great sourcing relationship with a Whole Foods store, but if they have another 20% or 30% of the crop, oftentimes they have no place to go with that crop."

For producers and distributors, FoodMaven retrieves, stores and sells lost or local product to restaurants and institutional kitchens, helping to increase profits by eliminating waste costs and recuperating otherwise lost revenue. Food that doesn't sell rapidly may be donated for hunger relief. FoodMaven operates on a "zero-landfill policy," Mr. Bultema said.

"I think we all have to vow to do better at making sure we're good stewards of food," he said. "I'm so grateful to have folks like Walter leaning in and such a growing amount of awareness on the issue."