In considering the coffee printer, it's important to note that this is a speculative design, but that does not mean that there isn't room for criticism, even in the concept stage. Chief among the design's defects is that the ink color and quality are limited by the materials on hand, and who knows if the ink will stay on the page for as long as other inks? The coffee scent may remain, though some users will appreciate that familiar, earthy aroma.
Cost may in fact be an issue, as one batch of coffee grounds may not produce much ink. That is, if you can even get the ink loaded: Loading the ink is a precarious process, involving manual labor, time and possible spills.
Is this sort of a machine even viable? The current design depicts the printing process as something like "drawing" with a coffee-filled cartridge. Obviously, that is not a way to produce crisp text and clear images, nor would it be pleasant to move the cartridge manually to draw on 10 or 20 pages. But even if a more conventional printer design were adapted to accept this kind of ink, your ink supply is still tied to your coffee or tea consumption. You also won't be able to print in other colors, including black, without incorporating dyes.
There are already many other alternative, environmentally friendly types of ink out there, including vegetable-oil inks and metal-free inks. Inks derived from vegetable oil are often considered eco-friendly and sustainable because they don't produce VOCs and come from several different types of crops.
Soy ink is a widely used alternative to traditional inks, many of which are derived from petroleum. Developed by the Newspaper Association of American in response to the oil crisis of the late 1970s, soy ink hit the market in 1987 and now occupies 22.5 percent of the U.S. printing market [source: TreeHugger]. It's considered cost competitive and is used by up to 90 percent of American newspapers, particularly for color printing [source: Schmidt].
There are also various soy-based options for home and office printers. In fact, soy ink has become so successful that the National Soy Ink Information Center, which disseminated information about the benefits of this greener ink, closed shop [source: NASIC]. However, be careful: Some inks that claim to be soy ink actually only have a small percentage of the stuff in them; the rest is usually petroleum-based ink.
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