Made up of oxygen, hydrogen, and carbon, cellulose is actually the most abundant organic compound on earth — it’s more commonly referred to as a dietary fiber. You can find it naturally in virtually all fruits and vegetables. Cellulose also shows up in foods as an additional “filler” ingredient. It's often used to thicken ice creams, to keep powdered drinks from absorbing unwanted moisture, or to stand in for another ingredient that would add calories where there were already plenty. That’s the appeal of adding cellulose to something like a burger. Because it’s both indigestible and has no real nutritional value, it can be added to the mix without compromising taste.
So, while fillers like cellulose might not be the first thing you expect to find in your burger, we’ll take a little wood pulp over the infamous “yoga-mat chemical” any day.