Moisture content is not relevant to C:N ratio. I can take wheat straw (a high C material) and soak it in water but it will not change its C:N. I can cut alfalfa (a high N material) and dry it and it will not appreciably change its C:N. The actual color of the material is also irrelevant. Coffee grounds are brown yet are considered an N material. As most of us have no analytical abilities to determine C:N ratios of any particular material we have to rely on published information to get C:N.

"So here is my question. Given that I have a hard time finding carbon sources, what if I dehydrated or dried out my kitchen scraps. Would they then become low nitrogen, high carbon?"

Simply, no. Drying sources of Nitrogen will not change the C:N ratio. What the C:N ratio of any material is depends on several factors. Freshly fallen tree leaves will have a C:N ratio of 40:1 while leaves laying around for months will be closer to 80:1. The wheat straw Lloyd referred to can be a source of Nitrogen if cut while still green and before the seed heads develop or a Carbon source if used after harvesting the seeds, ie. wheat berries.

Straw (in the context of grains) by most definitions refers to the stalks left after the seed has been removed. If one is cutting their crop prior to full maturity they are likely doing so to make "green feed" and we don't call that stuff "straw".

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

Hay, on the other hand (foot?) is green grass which is higher in N. Unfortunately it has a ton of seeds in it (which are nutritious), whereas straw is the stalks leftover after removing the wheat seeds, so it's actually better for composting as far as seed sprouting is concerned.

Hay is probably listed at Wikipedia too but I'll let you look it up. :-P

If a material is used for composting (human intervention), then seed content as it relates to sprouting is not necessarily relevant. Composting tends to make most (not all) seeds non-viable either through the thermophilic process or turning (destroying said sprouts). What is "better" for composting has more to do with what one needs. If they need to increase the carbon side then "hay" would not normally* be the best choice. As an aside, threshing does not usually remove all the seeds therefore seeds will be present even in straw.

Getting back to the point, moisture content nor color play a part in determining the C:N ratio of materials.

*old weathered hay could very well be a not bad C component. It ain't always a black/white issue.

@kcandmilo, there are as many opinions on this as composters. My simplified view: browns and greens are simplified terms, don't take them too literally. Browns for compost terms tend to be brown - like dried fallen leaves. Greens tend to be green like green grass. Since a lot of materials (like grass and leaves, really, any type of leaf or blade) will tend to be wetter when they are 'greener', there also tends to be a relationship, but they're not the same thing - it's actually that the contents that makes a material 'green' can break down and disappear as they dry out. Grass and leaves that are thoroughly dried out will tend to browns - but it doesn't work with everything, dried apples are still greens.

To be a bit mroe technical: most of what we call browns have high cellulose and/or lignin content, the pulpy and hard parts of plants; they break down differently. Greens have more nitrogen and simple sugars - like most fruits, or green leafy plants (lettuce, etc). For the water part, greens just tend to come in forms with lots of waters, browns have less (in the actual cell content).

But don't worry about it - while it doesn't hurt to know some of this, it still needs experimenting.

Thank you all. That really helps. Armoured, thank you, that really helped me understand the process and understand that the material needs to have carbon content to begin with. The nitrogen could be lowered by the process of decay, but the carbon, as far as I understand remains as it is, and so the ratio might change, but I can't inherently change nitrogen rich plant into carbon rich plant matter. The point you made about high cellulose/lignin content really does help me understand what constitutes the carbon, and how greens and sugars have more nitrogen. That also helps understand why excess of nitrogen rich materials would get slimy and stinky.

Thank you all again, I guess shredded cardboard and sawdust will continue to be my sources of carbon and I have to consider my kitchen scraps greens, no matter how long I dry them out before adding to the pile!

(I was joking to my son who studies physics that he should have been able to break this down for me, and he laughed and said, ah mom, you need a chemist for this! If you want to hear about electromagnetism, I could help you, but I don't know much about the carbon and nitrogen cycles! Sheesh!)

KC

@kcandmilo, glad that helped. Really, the browns and greens (and carbon and nitrogen) terms as used in composting are just shorthand - almost everything has carbon (including chlorophyl), including fats; simple sugars like glucose are just carbon and hydrogen and oxygen, too. Cellulose and lignin are longer and harder to break down polymer versions. Nitrogen is more predominant in proteins, but even in 'greens' the percentage of nitrogen might be fairly low.

So anyway don't worry about the terms unless they help you. If you think 'leaves, wood, cardboard, dry pulpy plant stuff' for browns it'll be pretty close. And even if 'wet' isn't correct for greens, it's not a bad shortcut - if you think 'wet inside' like most plants. But again, they're just terms to help simplify stuff; if they don't help, ignore them.

"Too much nitrogen in my compost: smells, rotten garbage issues."

No ... too much WATER in your compost.

You can get a smelly bin from straw and paper if it's wet and anaerobic. You can have a properly decomposing bin that is also high nitrogen if you control the moisture better.

Coffee grounds are a rather weak green. They would compost by themselves pretty well except that the fine grind causes them to clump so they really need to be mixed with other materials for best results.

tox, really? I have LOADs of coffee grounds! And I have a friend who has a cafe, so can get bucket loads! Tell me what I can do with a couple of gallons of grounds!

@tox: I've noticed the coffee clumping depends a lot on the grind; my espresso pucks are solid and then dust when broken up.

@kcandmilo - what do you use your compost for? You could just add coffee to your garden or lawn as a mulch, or mix it with other mulch. In a lot of cases, the coffee would be close enough to 'soil' - and when it isn't, earthworms would mix it up without any extra effort. At fall / beginning of winter it'll have time to break down on the ground anyway.

Now, a note of caution: you probably shouldn't add a foot thick around sensitive plants. But within reason used coffee grinds shouldn't harm much if spread around in off-season. If I had a lot of coffee grinds I'd spread 'em around pretty much anywhere. As it is I've occasionally tossed small amounts in the yard; they're always indistinguishable within a few days.

All good stuff in armoured's post above.

If you do want to put large amounts into the compost, mix or layer them with other compostables - this time of year, leaves would be dandy.

Oh, I use compost mostly in my veggie beds, but this is the first year I'm trying out two new methods for me, a tumbler and a bin from the city. Actually 3, I also have a new worm bin in a plastic rectangular bin! In my old house, where I had neither a shortage of leaves nor a huge wildlife problem, I just dumped everything in a pile and turned it over and let time and nature do the balancing for me. We did get rats and raccoons though, and here since i live along a creek with all kinds of critters running up and down the banks, I want to keep the balance really carefully in the tumbler and bins!

KC