A controversial waste incinerator project in Guangzhou that was postponed for a year after mass protests, returned to the official agenda on Tuesday.

At a press conference in Panyu district, urban planners announced five possible locations for the incinerator: at Huijiang, Xikengwei, Sansha, Basha or Xinlian'er villages, according to the People's Daily.

Selection criteria included hydrology, traffic and power systems, said Guo Chang'an, general engineer of the Guangzhou Urban Planning and Design Survey Research Institute, at the conference.

A landfill needed to be at least 500 meters from homes, Guo said. But for an incinerator, he said, there was no minimum distance under current regulations. The distance between residential buildings and an incinerator should be farther than a landfill, Dong Jinshi, director of Beijing Kaifa Environmental Protection Technology Consulting Center, told the Global Times on Wednesday.

"It's at least five kilometers in Beijing," he said.

Experts' and residents' suggestions would also be factored into the weighing of the location of the plant, Guo explained.

A November survey found more than 97 percent of 1,550 residents opposed the incinerator, according to the Guangdong Provincial Public Opinion Research Center.

Burying or burning garbage seems easy and effective, Dong said. In fact, it causes all kinds of unexpected harm, he warned.

"Garbage sorting is of vital importance to garbage incineration," he said. "But in China, we still haven't got a proper garbage sorting system."