I have no idea what the ratio or carbon and nitrogen is for chaff. I have read that the chaff can be slightly waxy and tough to break down so you want to use other brown with it to speed up the process. Honestly using that much liquid as your N source sounds like a terrible idea. It will evaporate fairly quickly if the pile does heat up. I have also never composted in a plastic bag not sure how that will work.

Composting takes place all the time in nature, no matter what the ratios are.

I always think that composting is like making cornbread.

The recipe say, "if mixture is too dry, add a little water. If mixture is a little too thin/runny, add corn meal."

If the compost pile is approximately the consistency of a wrung-out sponge, not too wet & not too dry, it'll compost nicely.

Like John, I never have tried to compost in a plastic bag, but it sounds like it could be difficult, since microbes need oxygen/air.

I'm afraid a plastic bag would suffocate your micro-herd!

Plus...how would the excess water drain?

seems like it could turn into a big ole stinky anaerobic mess.

You might try poking holes in the sides & bottom, or you could use a 5-gallon bucket with holes in the bottom & sides, or make a compost cage from livestock wire (fencing).

This year, I'm using some huge tree-sized nursery pots, & it seems to be working.

Have fun!

Attempting to make compost in a plastic bag would result in an anaerobic (the absence of air) mix that smells really vile unless a lot of holes where punched in the bag. That would allow any excess fluid to flow out that might result in a mix that is too dry.

Used coffee grounds have a C:N ratio of 20:1 but we cannot assume that for the chaff. Maybe you state universities Cooperative Extension Service would have that information.

To get a mix that will compost you need just enough moisture to dampen the dry material, not enough liquid to float that material.

kimmq is kimmsr

You'd think someone would publish the CN ratio of coffee chaff, what with the amount of roasting and composting we do these days.

I'm not sure how you determined a 4:1 ratio of chaff to urine, but if you really wanted to calculate it, you would need to know the mass of nitrogen per volume of urine and make the calculations based on that. It's a little more complicated than calculations for mixing solid greens and browns for which the CN ratio is known. I don't even think I've seen a CN ratio for urine, but the N content is probably around here someplace.

HOWEVER...my biggest concern about your proposed method of chaff + urine is that there will be too much salt in the product. I would encourage mixing the chaff with other materials to compost and don't depend on urine for the entire N supply. If you want to do slow cold compost, you could certainly moisten the pile of chaff with urine to get things started and let it draw N from the air after the first flush of N is gone (no pun intended...OK it was intended :-).

This thread:

http://forums2.gardenweb.com/discussions/1597896/urine-as-fertilizer?n=69

has some good numbers and calculations in it. Basically I came up with about .05 lb N per gallon for urine. That thread quoted .02 probably using different source numbers for the urea content or the percentage of solids as a starting point. Urine is mostly water, and %N is based on the dry weight which is only about 5% of the total.

Playing around with all this can give you an idea what will happen if you try to compost browns using only urine. Let's say you have some material that's C:N ratio is 50:1. If you have 50 lb of this you have 1 lb of nitrogen in it and to bring it to a 25:1 ratio you need another lb of N. 1 lb of N x 1 gal urine/0.05 lb N = 20 gal urine. That's an awful lot for a 50 lb compost pile. It couldn't even be added all at once as the pile wouldn't soak it up, it would be too wet and it would rapidly go anaerobic and lose most of that N as ammonia.

If you have a lot of coffee chaff, consider trench or sheet composting.

I'm pretty sure coffee chaff has little nitrogen. It is the shell around the seed. The seed itself (the coffee bean) has plenty, but the husk around it does not. At least grass chaff is considered a low quality nutrition source for animals. That's because the protein content is low, and it's the proteins that carry the nitrogen.

Be aware (though it is evidently never discussed), that the urea in urine, which carries the nitrogen, decomposes (urea hydrolysis). So "fresh" urine is optimal. Best I can tell, at normal temperatures and pH, urine loses about half it's nitrogen to ammonia volatilization in a week or so, if left in an open container. Coming up with gallons of urine in a week or so is going to be a major challenge, at least for one person.

Aha, I never thought of searching the web for the protein content of coffee chaff.

It appears the average nitrogen content of protein is about 15% (it varies by type of protein), and when that is multiplied by 5% protein gives 0.75% N.

Note, however, there are various parts of the bean that come off at different times. On the plant it looks like a little cherry and there is a hull or husk that comes off during initial processing to reveal the bean. Most of us never see coffee berries, only beans. I wonder if the 'husk' referred to in your protein content reference is that outer layer removed during initial processing, or the chaff, which is a thin papery inner layer that comes loose during the roasting. Chaff is also referred to as husk (see the third link below)

https://en.wikipedia.org/wiki/Coffee_production

https://en.wikipedia.org/wiki/Coffee_roasting

http://www.rountoncoffee.co.uk/coffee-chaff-ideas/

That last link says chaff can be composted or used as bedding for chickens. I think if it was high enough in protein to be usable as a feed ingredient, we'd be hearing about that, but I've only heard of it being composted.

Also if you scroll down a bit on that page there is a whole thing about mixing it with sawdust as feed for a briquetting machine to make sawdust/chaff fuel bricks. Which smell like coffee!

you can look any thing up on this data base https://phyllis.nl/Browse/Standard/ECN-Phyllis#coffee%20husks

Coffee chaff C/N ratio on the data base is 41.65 /.53 or 79/1 approx