The two proposed sites for a new incinerator have attracted opposition from local groups concerned about the impact on the environment.
Cardiff Against the Incinerator and Stop Newport Incinerator say that a better solution to domestic waste would be to increase recycling targets.
The two bidders, Veolia and Viridor, say that the plans represent a major investment and electricity generated by the incinerator will help power local homes and businesses.
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The development has the potential to employ 55 people as well as supporting jobs during the construction phase.
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