Ripping it up is as secure as the obfuscation you can apply to the task.
A shredder is actually not a very secure method, unless your total shredded quantity is high. Re-assembly is just a jigsaw puzzle & the puzzle pieces are all in the same box. Forensics experts are well-practised at this.
Let's say, just for example, you have a small 2" square post-it note with a phone number on it, which you wish to destroy.
If you tear it in half, each half contains not enough information to be useful to any 'spy', so let's take this further.
First tear it in half right across the numbers, so one half has the top of the numbers, the other has the bottom of the numbers.
Take one half & tear it into sections small enough that there's only one or two of your half numbers on each piece.
Walk round the office & drop pieces in different bins as you go.
That ought to be sufficient obfuscation for one half.
Put the other half in your pocket & take it home.
Repeat the same tear & redistribute as you did in the office; some bits in the regular trash, some in the recycle, some in the green compostibles bin, assuming you have all 3 types.
Alternatively, throw out a random ⅓ of the pieces each week for 3 weeks, into the same bin.
That ought to reduce the chances of finding & re-assembling all the pieces to as close to zero as possible.
You could, of course, first write random letters over it and scribble over that, which will increase the complexity still further.
This is a method I also use for expired credit cards...using scissors, of course.
Though the method is not 'quick' it requires very little effort overall.