Abstract: The waste incineration program were protested against by local people and environmental protection activists in G city. Disputes over waste incineration technology continuously remains among experts and lay people in the anti-incineration campaign. The main technological controversies focus on its public health risks, noxious emissions and the operating environment. Different narratives and knowledge were produced in the debate by both sides. In their anti-incineration activism, the local activists are not protesting against the incineration irrationally. Rather, they integrated scientific discourses, data collected, local knowledge and experiences, developed their own expertise and became "lay experts". The role of “lay experts” challenges the dichotomy of “expert” and “lay” in STS studies. Their expertise provides an essential local perspective to environmental decision-making.