[Digestion] Nitrogen Emissions from Biogas

[Tom Miles]

We have had an inquiry from a concerned farmer in Washington state (US)
about the promotion of biogas digesters for dairy use.  His impression is
that "Such a  dairy waste water and solids treatment system is a prolific
emitter of N20."
 
His question:"Does anyone have any citations for N20 emissions from a 2000
cow dairy manure digester? How does such a digester compare to say a 100 mw
coal plant?"
 
How can nitrogen emissions from digestors be captures for use in
agriculture?
 
Where can we find answers to these questions?
 
Thanks
 
Tom Miles