They break down proteins to generate energy, and do not produce much heat. They also produce some very smelly byproducts that can make a compost pile stink like rotten eggs or sour milk. These smells often attract scavengers. Compost that contains meat can attract mice, skunks, buzzards, and even bears.
The power conditioner provides protection against surges in power just as a surge protector does, but a power conditioner also maintains a continuous voltage fed to the computer during temporary voltage reductions, such as a brownout.
And you should know that the battery acts as a power conditioner itself - all the power from the power supply goes through the battery, if it's in place. Actually, a power conditioner, or UPS, is nothing more than a big battery with an alarm on it. So. leave the battery in.