Either way, of course, getting more cereal into a smaller package represents a step forward. And if General Mills ends up applying the same technology to its regular-sized boxes of cereal too, that could potentially have a much larger cumulative effect on reducing packaging and trucking emissions.

Wine bottles and shoe boxes

Also showcased at the packaging exposition were new bottles from The Wine Group, which makes Walmart’s Oak Leaf wine. Launched in April, the bottles no longer include a punt – the dimple or dent at the bottom of traditional wine bottles – and they're also lighter and shorter. Those measures are expected to reduce glass consumption by 6,700 tons per year, cut cardboard and other packaging by more than 75 percent annually and yield transportation savings.

Another product displayed at the exposition was one that consumers don't normally get to see: "replenishment boxes" for shoes, which hold loose footwear before they hit the racks. Roughly 30 million of these boxes are used each year, and Walmart redesigned the boxes to use 43 percent less paper – and to standardize their size to cut transportation costs. Three box distributors in Asia are now making the redesigned boxes, Sasine said.

Efficiency has always been a consideration in packaging, he said. But many of the new advancements in reducing materials stem from computer-aided design, which has made it easier to figure out in advance how different package designs will perform, he added.