According to this verse an Israelite farmer could have brought gallons of blood drained from live animals to the altar to atone for his sins.
Jewish law forbade assaulting an animal for food without slaughtering it. On this basis alone it was forbidden. It would be like tearing off a limb from a live animal and offering it to God or eating it.
You wouldn't be assaulting the animal, in the same way that someone who donates blood is not assaulted during the process. The scriptural fact, is that blood had no real value in the eyes of God until a life was taken. It was only then you could present it to God and it was only then he would look upon it as being acceptable.
(Leviticus 17:11) For the life of the flesh is in the blood, and I myself have given it on the altar for you to make atonement for yourselves, because it is the blood that makes atonement by means of the life in it.
To take this one step further the blood of slaughtered animals was not even sacred enough to atone permanently for sins.1 peter 1:18-19 For you know that it was not with corruptible things, with silver or gold, that you were set free from your futile way of life handed down to you by your forefathers. 19 But it was with precious blood, like that of an unblemished and spotless lamb, that of Christ
It required a level of sacredness that only the blood of Jesus could potentially attain to. But Jesus still had to die before God would accept his blood as being valuable enough to pay the price required to atone for sins.
It is only through the pouring out of the life blood, resulting in the death of the animal or individual, that God views as having sacred sacrificial value. You just simply couldn't offer blood up without a life having fist been taken. This also explains why eating the blood of an un-slaughtered animal found dead only resulted in ceremonial uncleanness rather than stoning to death. It also explains why you could drink the symbolic blood of Jesus before his death without breaking any laws.
(Matthew 26:27, 28) And taking a cup, he offered thanks and gave it to them, saying: “Drink out of it, all of you, for this means my ‘blood of the covenant,’ which is to be poured out in behalf of many for forgiveness of sins.