Oltre a essere riciclabile, il sacchetto è compostabile.

Because oltre needs the preposition a here.

The pattern is:

• oltre a + infinitive
• oltre a + noun

So:

• oltre a essere riciclabile = in addition to being recyclable
• oltre al prezzo = besides the price

Without a, the sentence would sound wrong in standard Italian.

Here oltre a means in addition to, besides, or as well as.

So the structure is adding one quality to another:

• oltre a essere riciclabile = besides being recyclable
• il sacchetto è compostabile = the bag is compostable

It introduces an extra piece of information, not a contrast.

Yes, it can be used with both.

With a noun:

• Oltre al sacchetto, serve anche una scatola.
  • Besides the bag, a box is also needed.

With an infinitive:

• Oltre a essere leggero, è anche resistente.
  • Besides being light, it is also durable.

So in your sentence, essere is an infinitive after oltre a.

Because after oltre a, Italian normally uses the infinitive.

That is why you get:

• oltre a essere riciclabile

not:

• oltre a è riciclabile
• oltre a sia riciclabile

This is similar to English besides being recyclable, where being is a non-finite verb form rather than a full conjugated verb.

Yes, you may see oltre ad essere as well.

Both are used, but oltre a essere is very common and perfectly correct.
The d in ad can appear before a vowel for smoother pronunciation:

• oltre a essere
• oltre ad essere

In modern usage, many speakers prefer not to add extra d unless it really helps the sound. So oltre a essere is a very natural choice.

Because they describe a quality of il sacchetto.

• riciclabile = recyclable
• compostabile = compostable

They are adjectives ending in -bile, a very common ending in Italian for words meaning able to be ... or capable of being ....

Other examples:

• lavabile = washable
• leggibile = readable
• bevibile = drinkable

So the sentence is literally describing the bag with two properties.

Yes, adjectives in Italian must agree with the noun they describe.

Here:

• il sacchetto = masculine singular
• so the adjectives are singular too: riciclabile, compostabile

These particular adjectives have the same singular form for masculine and feminine:

• il sacchetto è compostabile
• la busta è compostabile

But in the plural they change:

• masculine/feminine plural: riciclabili, compostabili

For example:

• I sacchetti sono compostabili.
• Le buste sono compostabili.

Because Italian often places an introductory phrase first and then gives the main clause.

Structure:

• introductory phrase: Oltre a essere riciclabile
• main clause: il sacchetto è compostabile

This is normal and clear. The subject of essere riciclabile is understood to be the same as the subject of the main clause: il sacchetto.

Italian often leaves that subject understood in the first part when it is obvious from the main clause.

Yes. Italian allows some flexibility.

For example:

• Il sacchetto, oltre a essere riciclabile, è compostabile.

This means the same thing, but it puts il sacchetto first. That can make the sentence feel a little easier to process, especially in writing.

The original version is still very natural, especially in informative or packaging-style language.

Yes. They are related, but not identical.

• compostabile means it can break down in composting conditions and become compost
• biodegradabile means it can be broken down by biological processes, but not necessarily in the way or time needed for composting

So something can be biodegradabile without necessarily being compostabile.
That is why labels often use these words carefully.

Yes, sacchetto usually means bag or small bag, depending on context.

It is a diminutive form related to sacco. In everyday use, sacchetto is common for things like:

• shopping bags
• food bags
• small plastic or paper bags

Depending on context, English might translate it as bag, sachet, or small bag, but bag is usually the most natural translation here.

Yes. Both are good ways to think about the structure.

• besides being recyclable
• as well as being recyclable
• in addition to being recyclable

All of these match oltre a essere riciclabile quite well.

The important grammar point is that Italian uses:

• oltre a + infinitive

where English often uses:

• besides/in addition to/as well as + -ing form

Absolutely. It sounds very natural in product descriptions, environmental messaging, and packaging language.

Italian often uses concise adjective-based wording for this kind of information:

• riciclabile
• compostabile
• biodegradabile

So the sentence has a very typical informational, eco-label style.