Answer: We would prefer to say that blood is necessary to satisfy justice, not to "appease" God. It is not a matter in which God's character has to be appeased in any way, it is simply a matter of "a life for a life" to balance the scales of justice.
Lev 17:11 tells us that life is in the blood, "For the life of the flesh is in the blood: and I have given it to you upon the altar to make an atonement for your souls: for it is the blood that maketh an atonement for the soul."
The Scriptural principle regarding the need for blood to be shed is found in Hebrews 9:22 - "And almost all things are by the law purged with blood; and without shedding of blood is no remission."
Because Father Adam was a perfect man and then he sinned, his penalty was death: Romans 6:23, "For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord."
Since the penalty of sin is death, only by a sacrificial death of another perfect man could sinners (Adam and all his children) be released from the death penalty. A perfect man (Jesus) had to take the place of the perfect man (Adam) who sinned.
God is perfect, and His standard is righteousness and absolute justice. In order to deal with us, He provided his only-begotten Son, Jesus, to come to earth as a perfect man to pay the corresponding price to ransom Adam who fell — a perfect life for a perfect life. Once Jesus' ransom merit is paid to the Father on behalf of the world, they will have the opportunity to come back into harmony with God in his kingdom.
We are told in Acts 4:10-12, "By the name of Jesus Christ of Nazareth...whom God raised from the dead...there is none other name under heaven given among men, whereby we must be saved." All people are born sinners (passed on to them from their father Adam). The only possible way to come out from the condemnation of death is through Jesus Christ — a perfect man who gave his life for the perfect man Adam. Romans 5:15: "For if through the offense of one many be dead, much more the grace of God, and the gift by grace, which is by one man, Jesus Christ, hath abounded unto many."
It is because Jesus paid the ransom [corresponding price] for Adam and his whole race that all mankind will, in Christ's kingdom on earth, be brought to a full knowledge of God and given a full opportunity of recovery from sin and death. 1 Timothy 2:4-6, "Who will have all men to be saved [out of condemnation], and to come unto the knowledge of the truth. For there is one God, and one mediator between God and men, the man Christ Jesus; who gave himself a ransom for all, to be testified in due time."
So all mankind have a wonderful hope, because of Jesus Christ, of being raised to life and have the opportunity to live forever in a perfect earth.
But many times it is overlooked that the Scriptures teach two different kinds of salvation. In the familiar "Lord's prayer" in Matthew 6:10, Jesus prayed, "Thy kingdom come. Thy will be done in earth, as it is in heaven. "There will, therefore, be a kingdom on earth as well as one in heaven.
Christians who have fully consecrated their lives to God, willing to sacrifice their present lives to do the will of God, are promised a heavenly salvation if they are faithful, and they will be Christ's church. The rest of the world will be raised to life in the kingdom on earth. The kingdom on earth will be restored to perfection, being ruled by Christ and his church.
1 John 2:2 says, "And he [Jesus] is the propitiation [satisfaction] for our sins [the church's]: and not for our's only, but also for the sins of the whole world." Romans 8:19 is another scripture which tells us there will be two salvations. "For the earnest expectation of the creation [the whole world] waiteth for the manifestation of the sons of God [the church to be completed]." Once all the church are completed and resurrected in heaven, then the kingdom on earth can begin when the whole world will be blessed.