Nem que falte carvão, vamos comprar mais.

Here nem que is a fixed expression meaning even if or no matter whether. It introduces something that might happen, but that will not change the decision in the main clause.

It often gives the sentence a slightly emphatic feeling: Even if that happens, we’ll still do it.

Because nem que normally takes the subjunctive. The speaker is talking about a possible or hypothetical situation, not stating a fact.

• falta = present indicative
• falte = present subjunctive

So nem que falte carvão is the expected pattern.

Here faltar means to be lacking, to run short, or to run out.

With things, Portuguese often uses faltar where English would say something like:

• there isn’t enough charcoal
• we’re out of charcoal
• charcoal is running short

So the missing thing itself becomes the subject in Portuguese.

Because the subject is carvão, which is grammatically singular.

Carvão is a mass noun, like water or sand in English. Even though it refers to a quantity of material, Portuguese treats it as singular here, so the verb is singular too.

Because Portuguese often leaves out the article with a mass noun when speaking in a general or indefinite way.

Here carvão means charcoal in general, not a specific charcoal already identified in the conversation.

• falta carvão = charcoal is lacking / there isn’t enough charcoal
• falta o carvão = the charcoal is missing

It can mean either, depending on context.

In Brazilian Portuguese, in everyday situations like grilling or barbecues, carvão often means charcoal. If someone wants to be more specific about mineral coal, they may say carvão mineral.

It is simply omitted.

Portuguese often drops subject pronouns when the verb ending already makes the subject clear. The form vamos already tells you the subject is nós.

So vamos comprar naturally means we are going to buy.

Both are correct, but ir + infinitive is extremely common in Brazilian Portuguese for future meaning, especially in everyday speech.

• vamos comprar mais = common, natural, conversational
• compraremos mais = more formal or more written

So this sentence sounds very normal in Brazilian Portuguese.

Yes, in isolation it can.

Vamos + infinitive can sometimes be a suggestion, like let’s buy more. But in this sentence, because of the full context and structure, it is most naturally understood as we are going to buy more.

If it were meant more as a suggestion or encouragement, intonation would help a lot in speech.

Mais means more, and Portuguese often leaves the noun understood from context.

So vamos comprar mais means we’re going to buy more (charcoal).

You could also say vamos comprar mais carvão, but it is not necessary if the meaning is already clear.

Because nem que falte carvão is an introductory subordinate clause, and Portuguese normally separates that kind of clause from the main clause with a comma, especially when it comes first.

So the comma helps show the structure:

• Nem que falte carvão, = subordinate clause
• vamos comprar mais = main clause

They are related, but not identical.

• se = if; neutral condition
• mesmo que = even if; clear concession
• nem que = also even if, but often with a stronger, more emphatic, sometimes more determined tone

Compare:

• Se faltar carvão, vamos comprar mais. = If charcoal runs out, we’ll buy more.
• Mesmo que falte carvão, vamos comprar mais. = Even if charcoal runs out, we’ll buy more.
• Nem que falte carvão, vamos comprar mais. = Even if charcoal runs out, we’re still going to buy more.

So nem que often sounds a little more forceful.