XXX fertilizer is an organic degradation that can produce non-smelly waste and increase the plant growth.
Is "non-smelly" appropriate?
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If you mean that the waste has no smell at all, then you can use the word odorless.
If you mean that the waste doesn't have a rank smell, then you can use something like pleasant-smelling – if it has an odor that is pleasant. Otherwise, you might have to explain what you mean another way:
XXX fertilizer is an organic degradation that can increase the plant growth without producing the unpleasant smells of other organic waste.