Many times the instuctions for sacrifices were to burn such things as kidneys and parts of the liver. These two organs are there for filtering out impurities. Figuratively speaking, the sinful things in our lives at repentance are "burned away". This would be like the "aroma pleasing to the Lord". When we repent, we die to sin.

Interestingly the first animal sacrifice was done by God as a covering for Adam and Eve. Lots of connections with the animal sacrifices "covering" the sin temporarily. Praise God, Jesus covers our sins completely! But He is very clear what He expects from us. Once we repent, we turn our back on what we were before.

1 Cor 6:11
And that is what some of you were. But you were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and by the Spirit of our God.

To repent means to turn around completely and go the other way....God's way!