Depends what the gerbils are bedded on, but yes, probably. Sawdust, wood shavings, MegaZorb, newspaper -- all of that is compostible. So are all raw veg and fruit bits, toilet rolls (the cardboard bit), eggshell boxes, paper bags, old paper towels, natural fabrics like cotton & wool and eggshells are ok, too (says our council). Toilet rolls, Fabric/paper ideally shredded or ripped to small pieces first.
Must not put in faeces or cooked food (health and vermin hazards respectively). Mind you, I cast bread crumbs in mine, anyway.
These are options, assuming you have a garden:
- have a condensed pile in messy corner of the garden you just keep adding stuff to it.
- have some type of container that doesn't decompose or decomposes slowly. We used a concrete coal bunker for a few years, more recently DH built a wooden frame bin (it will slowly rot, but takes years).
- A lot of councils flog Tardis-shaped plastic bins for a subsidised price. They have a lid and no bottom, you just put stuff in top.
Whatever sort you have, it's optimal if you shift the whole thing once a year; there will be rich soil out the bottom, and the area underneath will be ultra fertile the next year.
There are kitchen composters too for people w/out gardens (Google it).
Councils collect compostible materials in some areas for as little as £30/yr, providing you with a storage bin, too. Advantage of council scheme is you can throw all cooked waste food in there, the Council Compost heaps get hot enough to cook any would-be vermin.
Ahem....You can accelerate decomposition by adding human urine to the top. Otherwise you will need to throw in some water ocasionally anyway.