One fundamental difference between the two is the process.
In recycling, the waste product is completely broken down to its base materials, whereas in upcycling the product is altered to make something completely new without breaking it down.is the breakdown process that leaves carbon footprints. For instance, plastic can be recycled only when it is shredded into small pieces in a shredder. The shredder machine runs on power, thus increasing the carbon footprint.
It takes less energy to upcycle the parent product than creating a new product from scratch. Upcycling also elongates the lifespan of the product before it reaches the landfill.