I would like to know how many consonant clusters can a human being utter in any language.
Unknown, possibly unlimited!
In languages with a "classical" consonant-vowel distinction, the longest clusters I know of are eight consonants long, such as Georgian gvprtskvni "you are peeling us". Whether this is truly a consonant cluster or not is debatable, and depends on your definition of "consonant"—it's not as straightforward as you might think! But you'll often find this particular word cited as an example of the longest possible clusters.
Some Salishan languages (spoken in the Pacific Northwest) go even farther, forming words, phrases, even sentences with no "vowels" at all. At this point the idea of a "syllable" starts to break down; the classic example is Nuxalk clhp'xwlhtlhplhhskwts' (
/xɬpʼχʷɬtʰɬpʰɬːskʷʰt͡sʼ/ in IPA), "he had previously had, in his possession, a bunchberry plant". Since this word has no "vowels" at all in it, you could presumably have a Nuxalk speaker repeat the word over and over to get as long of a consonant cluster as you wanted (again depending on your definition of "consonant").