If I had only a single item for compost,alfalfa would be near the top of the list. It has suficent N to do quite well without addition of other materials but you can combine enough additional N&C to make a full bin. Ordinarly,alfalfa is cut and baled long before it has seed on it. Are you certain it is pure alfalfa? If the animals that refused it are horses,cows,sheep,goats or rabbits,it is not alfalfa. Thousands of bales are sold every year that are not. It is easy to identify by sight and smell if you are familiar with it.

Have rabbits here. I buy compressed bales of alfalfa. The compression causes lots of powdered alfalfa that is definitely green manure.

Definitely green! Can use alfalfa straw as a mulch but place thinly to avoid composting or lay it thick making certain it doesn't get too wet. I'm referencing gardening on this note.

Alfalfa will go to seed, but it's nominal and never a problem. Toss it in the compost and forget about it. Excellent nitrogen source.

Probably moldy alfalfa. Sometimes it gets wet & goes bad. A friend with horses passes it on to us & our gardens love it!

Yes treat as grass clippings -- can be used as sheet mulch right on top of beds if you're not using them this fall. Rich & heats up quickly. Can get smelly if wet & in one spot not balanced with browns such as paper or cardboard.

I've never had it reseed in my gardens & wouldn't hesitate to use it.

If you're growing in the beds spread it very
t... h...in...ly

What does that Alfalfa hay smell like? Good Alfalfa hay should have a pleasant fresh cut grass like odor while spoiled hay will have a musty smell.
Alfalfa hay that animals won't eat is still good in the garden because it has a fairly high protein content that is converted into Nitrogen in the soil. Alfalfa hay is always a "green" because of that.
The Alfalfa hay should not have seeds, although there may be "weed" seeds in the bale, but it can be composted and will be similar to fresh grass clippings. You can also use it as mulch although a half bale will not go very far.

Here is a link that might be useful: About Alfalfa hay

Thanks all! Sorry about the late reply, I was on my first retirement trip to Yosemite (before the shut down!) and the area. Just got back!
I'm glad to hear it's a green, cause I don't have many! Mostly kitchen scraps and leaves right now.
I'll tuck the alfalfa in the shed to add N from time to time, and maybe mulch the asparagus bed. Nancy