NASA Close to Being Able to 3D Print Trees

In a process of 3D bioprinting, researchers working fro NASA are close to have a working concept of a 3D Tree printer.

http://3dprint.com/nasa-soon-able-to-3d-print-trees/

Basically they are Printing out cells which will excrete wood. The technology could also be used some day for 3D printing meat, wool, silk, or other products.

The article says "The benefits of this technology to NASA would be that astronauts would not need to bring heavy, large pieces of wood up to space. They could bring, much lighter, smaller materials up there, and then print out the cells, which will excrete the wood they need for whatever projects is being worked on."

As far as i understand, the conservation of mass/energy applies to biological systems. If you want cells to excrete heavy pieces of lumber, I assume you will need to feed them at least the equivalent mass/energy of food. They must be planning on manufacturing culture media for these cells from the raw materials available to astronauts in space. How many liters of culture media does it take to make a 2 x 4?

Good catch, Wilsoc5.