That balance should come in the form of ‘greens’ and ‘browns’. Despite the name green material isn’t always green, kitchen scraps are included in ‘greens’. Greens can be seen as things which were recently living – nitrogen rich green stuff with moisture in. So think grass clippings, kitchen scraps and the tops of vegetables (carrots, potatoes etc).
The browns are things that are more dry and carbon rich, quite often the more woody material. This includes cardboard, sticks and hollow plant stems.
Look on your compost bin more like a living breathing organism needing air, moisture and nutrients rather than a pile of dead stuff which will magically rot down. If you add moisture and nutrients from your green waste it should be balanced out with the more structural and aerating brown waste.
For added nutrition, add weeds such as comfrey, nettle leaves or chickweed - it’s a little like giving your compost bin a vitamin pill.
Also human urine is nitrogen rich so a mix of dry dead stuff (including torn up cardboard) and wee should decompose well.
To add more life to your bin grab a handful of compost from someone else’s bin and add it onto yours
To learn more about this rotten art read Nicky Scott’s How to make and use compost