I don't think you quite understood zwon's comment... There are 36^10 words composed of exactly 10 characters from [0-9a-z]. "Limiting" the number of characters to between 8 and 12 increases the number of combinations to 36^8 + 36^9 + 36^10 + 36^11 + 36^12, which adds up to 4873763581670522880 words.

Assuming an average of 10 characters per word (which is low, as there are many more 12-character combinations than 8-character combinations, but I'm not going to bother calculating the actual average length), plus a separator to divide them, that makes 4873763581670522880 * 11 = 53611399398375751680 bytes, or about 46.5 exabytes (or 48.8 million terabytes, if you prefer that unit).

Personally, I don't know anyone who has a few exabytes of spare disk sitting around to store all those words.

There's also the minor detail that, if you're generating a billion words per second, it would take 154 years to create all the 8-12 character combinations, even without writing them to disk.