I don't find it redundant, but that would depend on what preceded it.
Is the paragraph redundant? Is it natural English?
But a report raises the alarm that disposable chopsticks pose risks of their own for consumers and the environment. Not only are disposable chopsticks extremely wasteful, they also are not necessarily sanitary.
Where has but gone, OP, please? Isn't but obligatory in the correlative conjunction, please?
'But' before 'they also' is not obligatory.