Hi, im gonna start my first compost bucket and for browns i grab a box full of cardboard from my local market. To make the cutting process easier, i leave them in a bucket of water; this morning i notice a soap or detergent like smell in the water and some cardboard smell more than others. After inspection, all of them used to contain food related items no soap or anything like that. Is my first time doing this so i dont know if it is normal, the last thing i wanna do is add something harmful to my plants.

I've never added cardboard to compost... I have lined my garden paths with it b4 covering with woodchips...
The only problem I ever noticed was that there was a lot of plastic tape to take back up later.

Food boxes are often wax coated... I always found them desirable for getting a fire going when the wood was damp...

Soap is said to promote plant growth, causing algae blooms when it washes into streams...

How it affects the compost, I couldn't say...

I could imagine there may be something added in the making of the cardboard. What, who knows.

A wide variety of chemicals are utilized by the paper industry, which would include making cardboard.

See here: https://en.wikipedia.org/wiki/...

Al

I occasionally add cardboard to my compost but I've never noticed a soapy smell. But I don't soak it either. I wouldn't worry about it unless you have other reasons to think it might be contaminated.

More information: Don't use cardboard that has a lot of printing, color glossy printing, a plasticky coating or that appears to be contaminated. Greasy cardboard board shouldn't be used. Be sure to remove any parts that are not cardboard (labels, windows, etc) and peel off any tape.