Praise be to Allah the Lord of the Worlds.
Allah the Almighty has forbidden the blood poured forth due to sustaining a wound or slaughtering and the like. He, the Exalted, says: "Say: "I find not in the message received by me by inspiration any (meat) forbidden to be eaten by one who wishes to eat it, unless it be dead meat, or blood poured forth, or the flesh of swine,- for it is an abomination - or, what is impious, (meat) on which a name has been invoked, other than God’s". But (even so), if a person is forced by necessity, without wilful disobedience, nor transgressing due limits,- thy Lord is Oft-forgiving, Most Merciful." {Al-An`am, 145}.
According to scholarly consensus, the blood poured forth is impure and forbidden to be sold or benefitted from. However, scholars have disagreed about the cause for this forbiddance. The majority of the Malikies, Shafies and Hanbalies said it is the impurity of the blood. Al-Shirbini said, "The blood of the animal, even that coming from its liver or spleen, is impure because Allah the Almighty says: "Forbidden to you (for food) are: dead meat, blood,…." {Al-Ma`ida/3}. I.e. the blood poured forth." {Moghni Al-Mohtaaj, 1/232}.
Al-Dasookhi, a Maliki scholar, said: "The blood poured forth due to a wound or slaughtering is impure." {Al-Shareh al-Khabeer Wa Hashiyat Al-Dhosookhi, 1/57}.
Ibn Qhoddamah, a Hanbali scholar, said, "Three types come out of an animal whose meat is lawful: one of them is impure, and that is its blood." {Al-Moghni, 2/67}.
Hanafie scholars said that the cause for the forbiddance of selling blood and the invalidity of the sale contract is that the blood has no monetary value. Al-Khasani, a Hanafi scholar, said: "The sale contract of the dead meat and the blood isn`t valid because it is of no monetary value." {Bada`I Al-Sanai`, 5/141}.
In conclusion, the sale contract of an Udhiyaah`s blood, or other, is invalid, and, in principle, it must be gotten rid of. However, if the party, deputized to do the slaughtering, collected the blood and delivered it to the fertilizer factories-for processing and manufacturing fertilizers-in return for a certain amount of money, then that may be permissible if the money was taken against leaving that blood and not as part of a sales contract in the jurisprudential sense. Scholars have called this "Return for giving something up"." It was stated in the Shafie book [Hashiyat Al-Baijoori, 1/144]: "It is permissible to receive money in return for giving something up."
It is worth pointing that the money collected from the above transaction should be distributed among the poor and needy since it is not permissible to make money out of selling blood as it is forbidden to sell part of an Udhiyyah. And Allah the Almighty knows best.
