While I take the point that a compost heap is a source of growth materials in the agricultural sense, it is nonetheless a pity that such an analogy should be used.
We toss unwanted, decaying food, leaves, cow manure, horse dung and other unsavoury materials on to the heap to rot, and therein lies the ugliness of the analogy.
And that is the point - the inherent ugliness of the metaphor.
With a bit of ingenuity, anything can be turned into an analogy - but this one is only one step away from saying that the Bible is like a sewage farm, which is an even uglier metaphor, and really smacks of considerable disrespect verging on total contempt.
If you said such a thing about the koran, they would be declaring jihad against you. Fortunately, the Bible is big enough and mature enough to be able to shrug off such unpleasantness, and the readers of the forum are sufficiently sensible not to be crying for your blood (metaphorically speaking, of course).
I personally have studied it for an very long time, and would never dream of likening it to a compost heap. It is far too wonderful a thing for me to even begin to consider expressing such an opinion.
Yes, the opinion is clever - and that is its only virtue - but is demeaning to something really wonderful and far beyond human ability to construct or generate.
I suppose we could say that a star is just a lump of hydrogen and helium - and that would be true in the main: but go out there and look at them, and feel a little foolish when you recall the words of the Psalmist:
8. 3 ¶ When I consider thy heavens, the work of thy fingers, the moon and the stars, which thou hast ordained;
4 What is man, that thou art mindful of him? and the son of man, that thou visitest him?
19.1 The heavens declare the glory of God; and the firmament sheweth his handywork.
And Daniel:
3 And they that be wise shall shine as the brightness of the firmament; and they that turn many to righteousness as the stars for ever and ever.
It's similar here:
Proverbs 30:5 Every word of God is pure:[like a compost heap???] he is a shield unto them that put their trust in him.
Hebrews 4:12 For the word of God is quick, and powerful, and sharper than any twoedged sword, piercing even to the dividing asunder of soul and spirit, and of the joints and marrow, and is a discerner of the thoughts and intents of the heart. [like a compost heap???]
1 Peter 1:23 Being born again, not of corruptible seed, but of incorruptible, by the word of God, [like a compost heap???]which liveth and abideth for ever.
Psalms 119:9 BETH. Wherewithal shall a young man cleanse his way? by taking heed thereto according to thy word.[to that compost heap???]
And the most respect-engendering one of all:
Psalms 138:2 I will worship toward thy holy temple, and praise thy name for thy lovingkindness and for thy truth: for thou hast magnified thy word above all thy name.
A bit of respect, chaps, wouldn't go amiss here.