Pining for a Way to Save the Planet? Try a 3D Printed Christmas Tree That Soaks Up CO2 Pining for a Way to Save the Planet? Try a 3D Printed Christmas Tree That Soaks Up CO2 BARCELONA, Spain — Spanish architects have created a stylish 3D-printed Christmas tree that can absorb carbon dioxide. The high-tech tree was invented by External Reference, an architecture studio based in Barcelona. The faux fir tree can neutralize carbon dioxide, nitrogen, oxygen and other gases. The tree was made with a 3D printer using a chemical product containing minerals that are 100% natural and capable of absor...