OK, just had a wonderful meal of spicy pot-roast brisket and a couple of whiskys, so I'm up for another go (trouble is I don't actually understand the original question!)
100 litres
is a cubic capacity, or measure of volume (the volume of 100 litres of water), how much it weighs depends on the density of whatever your 100 litres consists of. If it was 100 litres of water, it would weigh 100 kilograms (about 220 pounds) and occupy the same volume that about 22 gallons of water does.
However, your compost is almost certainly lighter than water, so will weigh less than that but 100 litres of anything will always occupy 100 litres of space.
If you want to know how much it weighs, I have to refer you back to the bathroom scales, although i'm not sure what use that information would be to you!
(Not sure I'm feeling quite as wonderful now!!
)