I have one of these and it’s a beast:

AmazonBasics 24-Sheet Cross-Cut Paper, CD, and Credit Card Shredder with Pullout Basket https://www.amazon.com/dp/B00HFJWMV4/ref=cm_sw_r_cp_apip_o9FQf3hoAifOg

“Shredding by hand” is no such thing in my experience. It’s a huge pain to tear boxes up into small pieces, and even pieces just a few inches long can clump together in the pile and protect each other.

I gave up and got a machine. The output is so fluffy and light and packed with surface area for microbes to colonize. Works amazingly great.

The kids also like helping put pieces through the machine. Despite its power it is constructed in a really safe way. There’s no way anything the size of a finger could reach the blades. The in slot is long and slightly bent and will accommodate the 24 sheets of paper it’s rated for but only barely. A piece of cardboard is a snug fit but they go through easily enough. I’ve done probably 100 boxes at this point.

Yes, this Amazon Basics one is a beast. It’s rated for 24 sheets of paper at a time and it has made short work of a ton of cardboard for me. It will do two layers of cardboard at once!

AmazonBasics 24-Sheet Cross-Cut... https://www.amazon.com/dp/B00HFJWMV4?ref=ppx_pop_mob_ap_share

I’ve been using this one for a couple years. Works great for cardboard.

AmazonBasics 24-Sheet Cross-Cut Paper, CD, and Credit Card Shredder with Pullout Basket https://www.amazon.com/dp/B00HFJWMV4/ref=cm_sw_r_cp_apip_qRbrJxXvNMeIc