Nie tyle wyrzucamy obierki, co je kompostujemy.

This is a fixed Polish pattern used to correct, refine, or shift the emphasis from one idea to another.

Nie tyle X, co Y means something like:

• not so much X as Y
• rather than X, Y
• it’s less a matter of X and more of Y

So:

Nie tyle wyrzucamy obierki, co je kompostujemy.

means that the speaker is saying:
We don’t exactly throw the peelings away; rather, we compost them.

The point is not that the first part is 100% false, but that the second part is the more accurate or more important description.

No. In this sentence, co is not the relative pronoun what/that.

Here it is part of the fixed expression:

nie tyle ..., co ...

So you should learn the whole structure as a unit. In this pattern, co works more like a conjunction linking the corrected or preferred second idea.

A learner might expect co to mean something like what, but here that would be misleading.

The subject is built into the verb endings.

• wyrzucamy = we throw away / we are throwing away
• kompostujemy = we compost / we are composting

The ending -my shows 1st person plural, so Polish does not need an explicit subject pronoun like my.

You could say My nie tyle wyrzucamy obierki, co je kompostujemy, but that would add extra emphasis to we. In normal speech, Polish usually leaves the subject pronoun out unless it is needed for contrast or emphasis.

Obierki means peelings, peels, or scraps from peeling vegetables or fruit, depending on context.

For example, it often refers to things like:

• potato peelings
• carrot peelings
• apple peelings

The singular obierka exists, but in everyday use obierki is very commonly used in the plural, because peelings are usually thought of as a collection of small scraps rather than one single item.

Obierki is the direct object, so it is in the accusative case.

However, for many non-masculine-personal plural nouns, the accusative plural looks the same as the nominative plural. That is what happens here.

So:

• nominative: obierki
• accusative: obierki

They look identical, even though the grammatical case is different.

This is very common in Polish and can be confusing at first, because English learners often expect the object form to look visibly different.

Je means them. It refers back to obierki.

So the second part literally means:

• co je kompostujemy = but rather we compost them

Polish often repeats the object with a pronoun in the second clause, especially when the object was already mentioned and the speaker is contrasting two actions done to the same thing.

It helps make the sentence flow naturally and clearly:

• Nie tyle wyrzucamy obierki, co je kompostujemy.

Without je, the sentence would still be understandable:

• Nie tyle wyrzucamy obierki, co kompostujemy.

But that sounds less natural to many speakers because the second verb no longer has its object explicitly stated, even though it is understood from context.

Usually it comes before the verb, as in:

• je kompostujemy

That is the most natural placement here.

Polish object pronouns are often unstressed and tend to appear before the verb, especially in neutral word order. You may sometimes see other placements in more marked or stylistic sentences, but for a learner, je kompostujemy is the safe and normal pattern.

They are imperfective because the sentence describes a general habit, regular practice, or ongoing way of dealing with peelings, not a single completed event.

• wyrzucać = to throw away, imperfective
• kompostować = to compost, imperfective

In English, this is often translated with the simple present:

• We throw away...
• We compost...

or as a general statement:

• Rather than throwing peelings away, we compost them.

If you were talking about a single completed action, a perfective verb might be more likely, depending on the context.

Sometimes yes, depending on context, but the structure itself is a little softer and more nuanced than a blunt contradiction.

Nie tyle X, co Y often means:

• not so much X as Y
• more Y than X
• better described as Y than as X

So it can imply that throwing away is not the best way to characterize the action, because composting is the more accurate or more important description.

In real-life use, many speakers would understand it very close to:

• We don’t throw them away; we compost them instead.

But grammatically the structure is often about reframing, not just simple negation.

Yes. Nie tyle ..., ile ... is also a very common pattern.

So you could say:

• Nie tyle wyrzucamy obierki, ile je kompostujemy.

This is very similar in meaning to the version with co.

Broadly speaking:

• nie tyle ..., co ... is very common and natural
• nie tyle ..., ile ... is also correct and often sounds a bit more formal or more explicitly comparative

For many learners, the safest approach is to recognize both as standard patterns meaning roughly not so much X as Y.

Yes, wyrzucać / wyrzucić often means:

• to throw out
• to throw away
• to discard

In everyday contexts, it is often used for garbage, leftovers, unwanted objects, and similar things.

With obierki, wyrzucamy obierki naturally suggests putting the peelings in the trash / getting rid of them as waste.

Polish does not have to add do kosza every time. If the context is clear, wyrzucać by itself is enough.

You could also say:

• wyrzucamy obierki do kosza = we throw the peelings into the bin

But the shorter version is perfectly normal.

Because in the first clause the noun obierki is introduced directly, and in the second clause Polish naturally refers back to it with the pronoun je.

This is similar to English patterns like:

• We don’t throw the peelings away; we compost them.

English also prefers a pronoun in the second clause rather than repeating the peelings again.

So the Polish sentence mirrors that kind of discourse pattern:

• first mention: obierki
• later reference: je

The given word order is very natural:

• Nie tyle wyrzucamy obierki, co je kompostujemy.

Polish word order is flexible, but not random. Here the sentence flows well because:

1. Nie tyle introduces the contrastive pattern
2. wyrzucamy obierki gives the first idea
3. co introduces the corrected/preferred second idea
4. je kompostujemy completes it naturally

You might see other versions for emphasis, but they would sound more marked. For a learner, the original sentence is a very good model to copy.