Shaked From:

While I can’t answer your questions completely, I can at least give a partial answer.  Most inks are now soy based and are not toxic.  If there is metal in paper it is coming from the pulping process as an unintended side effect.  The biggest danger from paper comes from bleaching with chlorine.  When you burn chlorine bleached paper without an extremely hot, high oxygen fire, you can get dioxins, which are carcinogenic.  I don’t think newsprint is bleached this way, but the advertising inserts sometimes are.

Paper is primarily cellulose fibers which are separated from lignin in the pulping process.  This means the cellular structure of the original material (you can make paper from more than just wood) is gone.  I have not looked at charred paper under a scanning electron microscope, but I imagine that the resulting images would look quite different.  The activity of biochar is dependent on surface area, which includes internal surface area of the ground biochar.  I would also guess, again without proof, that most of the powdery paper biochars’ would have high surface area, but no internal surface, making them more like 1:1 clay (kaolinite) in activity rather than like 2:1 clays (montmorillinite or smectites) which have separable layers and a lot higher cation exchange capacity. 

In terms of CO2 making biochar from paper makes sense.  Paper does not recycle well, it only downcycles.  High quality depends on fiber length, which is why softwoods like pine make better paper than hardwoods like oak.  When you take use paper and remake paper you shorten the fiber length so you can only use it for lower grade material.  After a few cycles it does not work anymore and has to go in compost or the soil.  (Cradle to Cradle, by Bill McDonough and Michael Brungart, is excellent on this subject.)  Sadly we tend to landfill the material and in an anaerobic environment it eventually gives off methane.  So charring the newspaper is probably good for CO2, saving more carbon for the long term.  As for the quality of biochar it makes, I will let others, like Hugh McLaughlin or Steven Joseph answer that part.

Wayne