When explaining the rules of a city recycling center (la déchetterie), you will often need to state what can or must be done with different materials. To do this, use the passive voice with modal verbs.
Must Be / Can Be Done
In English, we say "must be sorted" or "can be reused." In French, the structure is identical: conjugate devoir (must) or pouvoir (can), follow it with the infinitive être (to be), and add the past participle of the action verb.
Because this is the passive voice using être, the past participle must agree in gender and number with the subject of the sentence. Add an -e for feminine subjects and an -s for plural subjects.
| Everything that is recyclable must be brought to the recycling center. | Tout ce qui est recyclable doit être apporté à la déchetterie. |
| This dumpster must be left near the recycling center. | Cette benne doit être laissée près de la déchetterie. |
| Bulky objects must be thrown into this dumpster. | Les objets volumineux doivent être jetés dans cette benne. |
This same pattern works perfectly for stating what is possible or permitted using pouvoir.
| Some waste can be compressed or incinerated. | Certains déchets peuvent être compressés ou incinérés. |
Negation in the Passive Voice
When you need to say that something cannot or must not be done, place your negative words (like ne ... pas or ne ... jamais) directly around the conjugated modal verb. The infinitive être and the past participle remain together at the end of the phrase.
| Aluminum cannot be shredded in these dumpsters. | L'aluminium ne peut pas être broyé dans ces bennes. |
| A bulky object must never be incinerated without being shredded. | Un objet volumineux ne doit jamais être incinéré sans être broyé. |