hops as a fertiliser

I've recently had to put hours of hard work and effort into making my newly purchased allotment plot look like an allotment plot, which I have to say I have thoroughly enjoyed and am over the moon at the results.

Unbelievably, because of the wet weather, since October 2012 I have managed to get onto the plot a couple of times to dig the soil over and prepare it ready to have veg planted into it!

I am no wanting to put fertiliser into the soil to help break it down and enrich it a little. My dad has told me to use the hops from a local brewery that they have used in the brewing process and no longer require, he uses them for his plants. I have looked on the internet for anything that might suggest using hops in vegetable plots but I have been unable to find anything. I'm worried that these may have been mixed with chemicals during the brewing process and may have a negative effect on a vegetables growth.

Does anyone use hops on their plots and is its use successful?

There is a little info in this article http://www.telegraph.co.uk/property/3354686/Bulk-organic-fertiliser.htm