Water full of organics that is stagnant for more than a few days will become aneorobic and bacteria that produce toxins will begin to grow. Leaving compost uncovered can make it too wet in some climates and also lead to anaerobic conditions. Plant-based compost with adequate oxygen should never smell bad. If you put in a ton of new material it may smell like ammonia for 1 week but that is the only acceptable smell. Ammonia is naturally converted by bacteria to useful nitrogen for plants.
The water has nutrient value but I would not directly put it on any plants due to toxins. Especially not food crops.
Given how long it was stagnant, I would throw it out unless you are very short on chlorine-free water. I would maybe use that water for wetting a compost pile that is not used for growing food.
Hey thanks. That is quite informative and shows how much more I need to learn. My compost bin is a large 64 gallon covered trash barrel, and I try to only put shredded greens or decayed fruit in it, along with the leaves, and have had plenty of the former from a surplus food distribution we have been blessed to do.
However, mixing is done by pitchfork, which gets difficult once a lot gets in it, while due to the weather in MA, and the compost barrel not being able to get much sun then it is frozen for much of the year, and takes about two years to decompose enough that I would mix some into the garden soil. The latter has never been tested (I should have a basic tester soon) and i use bagged manure and some Hyponex 10-10-10 All-Purpose Fertilizer , and it has produced a lot, thanks be to God.
But I guess I will dump the water. Feel free to post on the garden thread, which could use your knowledge.