Final answer:
The liver is the organ responsible for processing alcohol in the body, metabolizing it through various reactions and preserving the health of both the liver and kidneys in the excretory system.
Step-by-step explanation:
The organ that a person's body uses to process the alcohol he or she has consumed is the liver. The liver metabolizes up to 98% of the alcohol present in the bloodstream by converting it into acetaldehyde and then into other metabolites that are easier to eliminate. Chronic consumption of alcohol can lead to serious liver diseases, which also put strain on the kidneys, with the liver and kidneys being important organs of the excretory system. Consequently, excessive alcohol consumption not only affects the liver but can also result in kidney dysfunction, highlighting the significant impact alcohol has on these vital excretory organs.