Sources <- c(
                "Coal burning plant",
                "General plant",
                "coalescent plantation",
                "Charcoal burning plant"
        )
Registry <- seq(from = 1100, to = 1103, by = 1)

df <- data.frame(Registry, Sources)
 grep('(?i)(?=.*\\bplant\\b)(?=.*\\bcoal\\b)', df$Sources, perl=T, value=T)