Thanks for the input and questions, everyone. I'll try to address everything the best that I can.

As far as the consumption of paper pulp goes, this sort of analysis is out of my area of expertise. I can say, however, that based on my observations of paper pulp products in comparison to ordinary paper, molded-pulp products appear to be about 1.5 to 2 times as thick as their paper/cardboard counterparts. Molded products are notably less dense, however, so the overall consumption of pulp in a molded process to produce a reusable cup would probably be about 1.5 times the amount of pulp use in making a comparable, single-use paper cup.

The pulp would come from the same sources as the recycled paper that is used to make post-consumer recycled paper. It's all pulped anyway for recycling, we're just looking at a different process to manufacture.

I imagine that the molding process is more energy intensive than your standard pressing, die-cutting and rolling process used in normal paper cups, but I couldn't say by what factor. The important part here is that, once you've moved into molding pulp, the additional energy of adding more material, such as to make a thicker wall in a reusable cup, would not be significant.

Of course, you could make a thin-walled version that is not as robust and not intended for reuse. In such a case, you could leave the cup uncoated to make it recyclable. I don't think that ordinary paper pulp could stand up to this, but there are "paper" products made from sugarcane fibers (a byproduct of sugar refining that is normally thrown away) that can stand up to a single use of liquid. They are biodegradable, but probably not commercially recyclable (they might be recyclable by the manufacturer, however).

Once you're talking multiple uses, however, there are presently no reasonable ways to recycle a cup once it's coated. There are probably ways to separate wax or other materials from paper pulp or polymeric materials that are reagent or enzyme consumable are a possibility, but are presently too expensive to use in recycling. There are, however a number of starch-based coatings that offer the possibility of multiple uses that still preserve the ability of the cup to biodegrade.

Of course, biodegrading requires that the consumer neither throw the cup away nor put it in a typical recycling bin (the current downside to the starch-based disposable utensils that are ubiquitous in Norther California). This is the main reason why I included the requirement that the cup be surrendered to Starbucks to get a free coffee. Once the cup has been returned, Starbucks can ensure that the cup is properly disposed of; i.e. sent to a commercial composting facility.

In the case of biodegradable polymer coating, it is possible to even coat the outside, making the cup able to stand up to a limited number of full washes with hot water.

Jazz78: Your ideas and analysis are very interesting. A combination of our two ideas might at least make my concept on par with typical paper cups as far as material consumption.

Aiyo: Part of the reason for the placement of the lid well below the rim is to capture coffee that sloshes out of the holes so it doesn't become a full-on spill. This removes a lot of the need for a closure mechanism, which I wanted to avoid including because they practically double the amount of material used in making the lid. I realize that the openings are still an escape for heat, and a closure would prevent this. Ultimately, I determined that this would not be worth the material usage. After all, the cup is better insulating than a rolled paper cup anyway.

I hope this helps. Let me know if there's any further clarification needed or any more comments.

-Mike