Serving up Wood

Whole wheat flowers, vegetables, fruits have enough fibers + all the vitamins, minerals and micro-elements  that comes with them (and human body can process).Does wood provide you with all that. I don't think so. ;)

Beavers will never forgive us :D

I'm a little uncomfortable with the "obvious assumption" that  no-nutritive-value ==> bad-for-you. As far as I know my Metamucil doesn't have any nutritive value either. (And a "fiber" ingredient is important to many gluten-free flour replacements.) I'd prefer to eat real foods that integrated fiber, but getting fiber by itself instead doesn't seem like the worst thing to me...

The difference is in cellulose content. From wikipedia: 

Cellulose is the structural component of the primary cell wall of green plants, many forms of algae and the oomycetes. Some species of bacteria secrete it to form biofilms. Cellulose is the most common organic compound on Earth. About 33% of all plant matter is cellulose (the cellulose content of cotton is 90% and that of wood is 40–50%).[4][5]

For industrial use, cellulose is mainly obtained from wood pulp and cotton. It is mainly used to producepaperboard and paper; to a smaller extent it is converted into a wide variety of derivative products such as cellophane and rayon. Converting cellulose from energy crops into biofuels such as cellulosic ethanolis under investigation as an alternative fuel source.

Some animals, particularly ruminants and termites, can digest cellulose with the help of symbiotic micro-organisms that live in their guts. Humans can digest cellulose to some extent,[6][7] however it is often referred to as "dietary fiber" or "roughage" (e.g. outer shell of maize) and acts as a hydrophilic bulking agent for feces.

http://en.wikipedia.org/wiki/Cellulose

Hmmm cotton... may be next time, when i'm mixing my dough I'll drop my  t-shirt into the bowl :D

More interesting reading : 

http://www.chem.cmu.edu/groups/collins/res/dyes.html

Wood pulp consists of two polymers, primarily cellulose, the material used for making white paper, and 2–6% colored lignin. Bleaching seeks to remove the lignin from the cellulose. Worldwide, the P&P industry is currently using chlorine dioxide as its principal bleaching agent. Chlorine dioxide oxidatively breaks lignin away from the solid cellulose in two forms, little fragments and big fragments. The fast majority of lignin solubilized by bleaching is in the form of little fragments. These are than digested by bacteria and other organisms in artificial oxidation lakes before the effluent is ejected to a natural water body such as a river, lake or ocean. However, the big lignin fragments where the color resides are too large to be digested by the microorganisms. The color is recalcitrant and ends up staining natural waterways and changing the flux of light absorbed by aquatic ecosystems.