China's eastern city Shanghai has become the center of a major policy change impacting the lifestyle of almost every resident. In July, the local government enforced a new garbage sorting rule. Residents are now required to sort trash into four categories. One month in, we look at how the system works and how people are adapting. In this first episode of our series Trash Redefined, CGTN's Yang Chengxi looks into the reasons behind setting up four waste categories.

These four bins and Shanghai's new garbage-sorting rule has become the latest internet meme and a lively conversation piece for many Chinese people. Kids are no exception. August is all about summer vacation, but the learning doesn't stop. Educational materials have been handed out across the city's kindergartens, elementary and middle schools.

YANG CHENGXI SHANGHAI "By now almost everyone here knows what the four bins are for: recyclables, hazardous waste, household food waste, and the rest goes to residual waste and many people have also wondered: why these four categories? What's the science behind it?"

To better explain this, we need to go back in time. China started treating domestic waste in the 1990s, and the volume has grown steadily every year. In the past five years, over 90 percent of new trash has been processed, the percentage reached 97.7 percent in 2017. That's good, right? Not exactly.

Because more than half of it has simply been buried. Many of China's existing landfills are nearing full capacity, and the rotting food waste inside releases odors and threatens to contaminate groundwater.

Alternatively, burning trash for electricity has gradually become more popular. But problems arise when dry, burnable garbage mixes with wet household food waste, which in Shanghai accounts for some 60 percent of all domestic trash.

LI CHANGJUN RESEARCHER, FUDAN UNIVERSITY "Food waste can lower the temperature of the incinerator, making the whole process not work well."

A lower burning temperature generates less electricity, creates more leftovers and more harmful gases. That's why it's now upon the government to single out household food waste from incinerators. When it's separated from other waste, factories use bioprocesses to break it down into either compost or electricity-generating methane gas.

There's an extra benefit too. Experts say this process means fewer greenhouse gas emissions, since garbage burials account for 5 percent of all man-made methane releases into the atmosphere.

QI YUMEI SHANGHAI LANDSCAPING & CITY APPEARANCE ADMINISTRATIVE BUREAU "By the end of this year a higher percentage of trash will be burned. By the end of 2020, Shanghai will no longer send unprocessed trash to landfills."

That's why everyone, especially younger generations, is advised to embrace a new garbage sorting lifestyle, says professor Zhang Yong, one of the co-authors of Shanghai's educational materials.

PROFESSOR ZHANG YONG EAST CHINA NORMAL UNIVERSITY "When children have a sense of the importance of garbage sorting, they will easily embrace the practice as part of their lives. Some kids now even get on their parents' cases about correctly sorting garbage just like their parents tell them to do their homework!"

The government says 46 Chinese cities will start similar garbage-sorting practices next year. Experts say raising awareness and informing people are the keys to getting them on board.

By now many Shanghai residents understand why they should sort garbage, but are they good at it? In the next episode, we'll look at how the four categories are giving many people just a little bit of a headache.

YCX, CGTN, SHANGHAI.