The concept cars of the coffee cup world (images)

What can be done to solve the problem of the 58 billion coffee cups that are thrown away each year? In a pro-sustainability move, coffee giant Starbucks has thrown its weight behind the Betacup Challenge, a design competition dedicated to building a more sustainable coffee cup.

Entries in the competition run the gamut from practical to ridiculous, a mix of reusable cups and sustainable disposable cups.

This one, called the "Cococup," suggests that coconut hull could be used as a naturally sourced, biodegradable material for coffee cups. If thrown away into special "Cocobins," the designer foresees them as recyclable, too, easy to break down and reconstruct into new cups.

The Cococup wasn't the only Betacup Challenge entry inspired by the coconut's potential role as a naturally grown drinking vessel. This one, called the "Grown Coco-Cup," goes a step further by suggesting that it would be possible to grow coconuts in the shape of coffee cups.

"(The) idea is simple to cultivate a novel coconut breed with less flesh and let the fruits grow in pre-cup-forms, like bulbs in bottles," the designer wrote. "Such novel coconut plantations can replace monocultures in the third world, maybe also beside established coffee plantations."

One of the most popular entries in the Betacup Challenge is the "Mille Mug," a collapsible, reusable mug. Its creator envisions incentives like "badges" on the mug for every 100 times used, or using a barcode to build in a Starbucks loyalty program.

Unlike many of the concepts entered in the Betacup Challenge, the Mille Mug has already been physically constructed. Its creator has even put a video online.

Here's another collapsible cup, but this one is a little more off-the-wall: "Made from heat-resistant elastic rubber," this collapsible coffee cup claims to use 75 percent less paper and requires 90 percent less shipping space than a traditional paper coffee cup. Plus, the creator claims it'll be reusable.

That's ambitious. But could you really imagine rushing to the office with it?

One entry in the competition was not a cup at all, but a cleaning device designed specifically for reusable coffee cups. "I believe the majority of coffee drinking people would use a travel mug in their coffee routine if only the inconvenience of having to wash it after every time of use was removed," the designer wrote in his Betacup Challenge entry.

These would, ideally, be installed in coffee shops. "Just bring a travel mug to the nearest coffee shop, have it cleaned and filled with coffee, and then carry on with the day," the designer suggested.

Here's one of the wackier ideas: A firm called Tallac Design has designed a cup called the "Bucky Air," an inflatable (!) cup that it says will use 8 grams of material in contrast to the 20.45 used in a traditional paper coffee cup. The designers envision the cups as "dispensed from a filling station that inflates, pressure tests and heat seals each cup."

Bucky Air cups would be constructed from a single recyclable plastic, or alternately, the design team suggests that special "cause recycling" bins be placed inside each Starbucks so that cups could be turned into something for charity: water jugs, for example, or plastic lumber for construction.

One entry in the Betacup Challenge suggests reusable polypropylene coffee cups that can be discarded at collection centers "where people have finished consumption and normally want to throw away the cups." They'd then be washed professionally and returned to stores for another use.

This would be a tough infrastructure move for a brand like Starbucks, which in a major city would pretty much need to install these on every corner. Do we really need Starbucks to be any more ubiquitous?

We're all for dreaming big, but a Wi-Fi-enabled, collapsible stainless steel coffee cup with a solar-powered Twitter stream and automatic Foursquare check-ins might be taking things too far.

Hey, to each his own.

Many of the entries in the Betacup Challenge suggest that it's going to be difficult for people to give up their disposable coffee cup habits altogether, and seek a biodegradable alternative. This one might be the most unusual of the bunch: it's made out of...coffee.

"If we look for a biodegradable material in coffee shops, the very first material that we see is the used coffee powder," the designer explained on the contest entry. "It can be formed and also works as an insulating container. So there is only a covering layer needed to gain water resistance properties."

The designer envisions coffee cup makers in each Starbucks to press coffee and soy wax into cups and then fill them. The machinery has not yet been designed.