How to control or optimize or remove or deallocate unused memory in UNION's

This question about how to control or optimize or remove or deallocate unused memory in unions? We know that the union size is maximum data type descaled inside union. Suppose I declared long type then it allocates 64-bytes of memory but I used only 16-bytes in program. How to optimize the remaining 48-bytes of memory?

#include<stdio.h>
int main(){
  union data_type {
    unsigned long A;
    unsigned int B;
    unsigned short C;
    unsigned char D;
  };
  union data_type my_union;
  my_union.C = 0X09;
  printf("UNION size:%d\n", sizeof(my_union));
  return 0;
}