Odpady komunalne obejmują odpady zmieszane i bioodpady.

Because the subject, odpady komunalne, is plural.

• singular: odpad komunalny obejmuje...
• plural: odpady komunalne obejmują...

So obejmują is the 3rd person plural form of obejmować (to include / to comprise / to cover).

Because Polish adjectives must agree with the nouns they describe.

Here:

• odpad = singular, masculine
• odpady = plural
• komunalny = singular masculine adjective form
• komunalne = plural form matching odpady

So:

• odpad komunalny = one municipal waste item / one municipal waste type
• odpady komunalne = municipal waste

The same thing happens in odpady zmieszane:

• zmieszany → singular masculine
• zmieszane → plural, matching odpady

Because in Polish, repeating the noun often makes the sentence clearer and more natural in formal language.

So:

• odpady zmieszane i bioodpady = mixed waste and bio-waste

If you said only zmieszane i bioodpady, it would sound incomplete or awkward, because zmieszane is an adjective and the noun it describes would be missing.

You could sometimes omit repeated words in conversation if the meaning is obvious, but in official or informative language, Polish often keeps the full phrase.

It is in the accusative, because it is the direct object of obejmują.

However, this is one of those places where the form looks the same as the nominative.

Why?

Because:

• odpady is a non-masculine-personal plural noun
• for this type of noun, nominative plural and accusative plural are often identical

So:

• nominative: odpady zmieszane
• accusative: odpady zmieszane

Same surface form, different grammatical function.

That is a very common difference between Polish and English.

In English, waste is often treated as an uncountable mass noun:

• Municipal waste includes mixed waste and biowaste.

In Polish, the equivalent idea is very often expressed with a plural countable form:

• odpady komunalne

So even though English may use singular-looking waste, Polish naturally uses odpady.

This is normal and not something you should try to translate word-for-word.

The singular forms are:

• odpad → odpady
• bioodpad → bioodpady

But in real usage, the plural is much more common when talking about waste categories in general.

For example:

• Ten odpad należy segregować. = This waste item / this piece of waste should be sorted.
• Bioodpady należy wyrzucać do brązowego pojemnika. = Biowaste should be thrown into the brown bin.

So yes, singular exists, but the plural is often the more natural form in this topic.

Here obejmować means to include, to comprise, or to encompass.

So odpady komunalne obejmują... means that municipal waste consists of or includes the listed categories.

Be careful: obejmować can also mean to embrace / hug in other contexts.

For example:

• Plan obejmuje trzy etapy. = The plan includes three stages.
• Objął ją ramieniem. = He put his arm around her.

So the meaning depends on context.

In Polish, bioodpad / bioodpady is commonly written as one word.

This is normal with many modern compounds using bio-, such as:

• biożywność
• biopaliwo
• biodegradowalny

So:

• bioodpady = biowaste / organic waste

You may also see slightly different terminology depending on the context, but bioodpady is standard and common.

A rough English-friendly pronunciation is:

o-bay-MOO-yon

A bit more carefully:

• o as in off (shorter)
• bej sounds roughly like bay
• mu like moo
• ją is nasal; in slow learner-friendly approximation, it can sound a bit like yon

Stress in Polish is usually on the second-to-last syllable, so here the stress falls on mu:

o-bej-MU-ją

Yes, Polish word order is more flexible than English, though the original version is the most neutral and natural in an informational sentence.

Neutral order:

• Odpady komunalne obejmują odpady zmieszane i bioodpady.

Possible variations:

• Odpady zmieszane i bioodpady obejmują odpady komunalne.
  This changes the meaning, so it is not equivalent.

• Odpady komunalne bioodpady i odpady zmieszane obejmują.
  Grammatically possible in a very marked or poetic sense, but unnatural here.

A more realistic alternative might be:

• Do odpadów komunalnych należą odpady zmieszane i bioodpady.

That means roughly the same thing: Mixed waste and biowaste belong to the category of municipal waste.

So yes, Polish allows flexibility, but not every reordering keeps the same meaning or sounds natural.

Sometimes, but not in the same register.

• odpady is more formal, technical, and official
• śmieci is more everyday and conversational

In a public-information, legal, or administrative sentence, odpady is the better choice:

• odpady komunalne
• odpady zmieszane
• bioodpady

If you said śmieci komunalne, it would usually sound less official and less standard in this kind of context.

So for waste-sorting vocabulary, it is best to learn odpady as the standard term.

Because Polish has no articles like English a / an / the.

So:

• Odpady komunalne can mean municipal waste or the municipal waste, depending on context.
• bioodpady can mean biowaste or the biowaste category, depending on context.

Polish expresses definiteness through context, word order, and situation rather than articles.

Yes. In this sentence, i simply means and:

• odpady zmieszane i bioodpady = mixed waste and biowaste

It joins the two items in the list.

A small pronunciation note: i is pronounced like ee in see.