Jeg skyller emballagen, når den er beskidt.

Because emballagen is the definite form: the packaging / the container.

In Danish, definiteness is often added as an ending on the noun:

• en emballage = a package / a piece of packaging
• emballagen = the package / the packaging

So the sentence is talking about a specific item or the packaging in question, not packaging in general.

Danish usually puts the at the end of the noun instead of using a separate word.

So:

• en bil = a car
• bilen = the car

The same pattern gives:

• en emballage
• emballagen

A separate word like den can also appear before a noun, but usually when there is an adjective or extra emphasis:

• den beskidte emballage = the dirty packaging
• den emballage can also mean that packaging

Because emballage is a common-gender noun, an en-word.

In Danish:

• common gender nouns usually take den
• neuter nouns usually take det

So:

• emballagen → den
• if it were a neuter noun, you would normally use det

That is why den er beskidt means it is dirty.

This is a very common question.

• når = when / whenever
• hvis = if

In this sentence, når sounds natural because it describes a real or regular situation: whenever the packaging is dirty, I rinse it.

So the idea is more like a habit or rule:

• Jeg skyller emballagen, når den er beskidt. = I rinse the packaging when/whenever it is dirty.

If you said hvis, it would sound more purely conditional:

• Jeg skyller emballagen, hvis den er beskidt. = I rinse the packaging if it is dirty.

That is not wrong in many contexts, but når is often preferred for repeated, expected situations like this.

Yes. Skyller is the present tense of skylle.

• at skylle = to rinse
• jeg skyller = I rinse / I am rinsing

In this sentence, it is understood as a habitual action, not necessarily something happening right this second.

So Danish present tense often covers ideas that English expresses with both:

• I rinse
• I’m rinsing

Context tells you which meaning is intended. Here it clearly sounds like a routine.

Skylle usually means rinse: quickly running water over something, often to remove residue.

Vaske means wash: more general or more thorough cleaning.

So in a recycling context, skylle emballagen is very natural, because the idea is often just to rinse the packaging before sorting or throwing it away.

Because når den er beskidt is a subordinate clause.

In Danish main clauses, the verb normally comes in second position:

• Jeg skyller emballagen

But after a subordinating word like når, the clause has normal subject-verb order:

• den er beskidt

So:

• Jeg skyller emballagen, når den er beskidt.

If you put the når-clause first, then the main clause changes word order:

• Når den er beskidt, skyller jeg emballagen.

That inversion in the main clause is very important in Danish.

Because når den er beskidt is a subordinate clause, and many Danish writers put a comma before that kind of clause.

So this is a very normal way to write it:

• Jeg skyller emballagen, når den er beskidt.

You may also see Danish written without that comma, depending on comma style:

• Jeg skyller emballagen når den er beskidt.

Both can be accepted, but the version with the comma is very common in teaching materials and formal writing.

Yes, Danish adjectives do show agreement, but in this sentence the form is simply beskidt.

Here it means dirty, and it is used after er:

• den er beskidt = it is dirty

A useful comparison is the plural:

• de er beskidte = they are dirty

So learners often notice that the plural form changes to beskidte.

It can do both, depending on context.

In a sentence like this, especially in a recycling context, emballagen often means the packaging/container in question. English might sometimes prefer a more specific word such as:

• the bottle
• the carton
• the container

But Danish often uses emballage more broadly when talking about sorting, recycling, or rinsing packaging before disposal.