A great alternative to Yesterdays News is pellets for wood stoves- commonly sold under brands such as “Stove Chow”, etc. It usually labeled as “hardwood pellets” and you do not want stove pellets with accellerants (although I have never personally seen any for sale). They can be hard to find as they are considered a seasonal product- but I paid less than $6 for 40lbs. I bought them at a local home improvement store- Home Depot and other local store. The brand I have now is Greenway and it is 100% natural, 100% hardwood.
Stove pellets work great for odor control and they are extremely absorbant. a 40lb bag last me 2-3 months for 1 bunny. The pellets are maybe a little bigger around than Yesterdays News- but that should make no difference to the bunny. Since they are seasonal- I bought 6 bags in February or so- and I still have 3 full bags stored on a high shelf in my garage. And they are so cheap it is not too expensive to stock up on them when they are available.
I would probably not add baking soda to your bunnys litter box- as bunnies have such furry feet if they get any baking soda (wet or dry) on their feet they might groom it off. It could possibly make them nauseous- but even if it does not it contains a lot of salt which your bunny does not need.
I know alot of BinkyBunny members use Stove Pellets (at least those of us that can find them) and there have been no reported problems and I think they have comparable odor control to Feline Pine or Yesterdays News.
When you store them or buy them- you have to make sure the bag is dry as if the pellets get wet they turn to mush as they would in a litterbox. That is why I bought all my other bags at another store other than Home Depot- as they store theirs on a pallet INSIDE the store- Home Depots was on a pallet in the garden center and exposed to weather. And although the bag was fine- I did not want to stock up on bags that had been exposed to the weather (so I bought them from a local home improvement chain called Menards).
This is by far one of the best money saving tips that I have gotten for my bunny- and I have not sacrificed quality to save money.