The poo can be, but not the bedding, the bedding is better off being taken to the tip, or put in your dustbin/trashcan.
I guess as long as it doesnt hurt the worms
Maybe, Maybe not. It depends if your bedding is wet, stinky, and has a lot of food and feces in it.I would change it every week.
Compost
Fecal matter can be allowed to compost and turn into soil. Or if it is manure (cow feces), it can be applied directly to crops.
No, urine isn't very good. Although poop is a useful material in compost pile it's very stinky. -Super Llama edit: Both feces and urine are good in compost. It should be noted that the bacteria found in feces takes a great deal of time to disappear in a compost pile (at least 2 years in warm climates). Feces contains biological matter that humans do not digest, that can be further broken down in the compost pile. The urine contains nitrates and phosphates which are beneficial for plant life.
Sure y not
Feces, urine, other excrement, and bedding produced by livestock that has not been composted
If you have a small cage, change the bedding every three or four days. If you have a larger cage, change it once a week. Guinea pigs produce a lot of fecal matter which is where flies lay their eggs. If there's less feces, the flies have no home or reason to stay around. In other words, keep the area clean!
Yes, earthworms do produce and excrete feces. Some people use worms to help compost organic matter into soil since they break down minerals as they are passed through the body. Then the compost people can collect what they call "worm tea" from the bottom of the container to use as fertilizer.
By not washing your hands thoroughly after touching the guinea pig or any of it's things. Ecoli, if present, is in the feces of the guinea pig. Since it lives in the same bedding as it goes to the bathroom in, it is on the guinea pig and it's house, bowl, etc. When you touch these things it gets on your hands and possibly your clothing. By not keeping clean after you handle the guinea pig, you may rub your eyes or eat something. This takes the ecoli bacteria right from your hand into your own body system. Giving you ecoli.
The process to convert animal waste to gaseous fuel is rather simple. You would compost the feces and collect the fumes released by the process. One way would be to use two barrels. In the first barrel, you compost the feces by keeping it moist and stirring it regularly. You would use the second barrel to collect the vapors released during the composting process.
If they are on a proper diet, it is mostly un-digested fibre.
This is an indicator that the guinea pig is not getting sufficient nutrition; improve the cavy's diet to make this behavior stop.