As early as 2000, eight cities, including Beijing, Shanghai and Guangzhou, began piloting garbage sorting.

However progress has been rather slow. A recent survey in Guangzhou found that only 9 percent of residents sort their garbage, with some online wag suggesting "the only difference is now we have garbage bins of various colors".

But changing people's behavior is difficult and needs prompting. To ensure people get into the habit of sorting their garbage, the government needs to play a bigger role and establish a punishment and reward system, says a column in Shanghai Morning Post.

In many developed countries it is illegal to mix garbage and lawbreakers face punishments. For example, in Brussels, Belgium, over 1,000 persons were penalized for not sorting their garbage between October 2007 and November 2008.

But besides sticks, carrots are also necessary to encourage the cultivating of a new habit. In 12 sample communities in Shanghai, residents have got garbage bags with barcodes since 2013 and can get gifts such as entry tickets to cultural sites by sorting their garbage.

By the end of 2013, 2.05million households in the metropolis were required to sort their garbage. This has reduced the amount of daily garbage to 0.7 kilograms per capita from 0.82 kg, according to the Shanghai Greenery and Public Sanitation Bureau. The city aims to lower the per capita daily volume to 0.66 kg this year, the bureau said.

To this end the authorities formally implemented new household garbage reduction measures on May 1.Under the new measures, garbage will be divided into four categories: recyclable materials, hazardous waste, wet waste and dry waste. Residents will be required to sort their garbage based on these categories.

Legislation and law enforcement are indispensable if residents nationwide are to get into the habit of sorting their waste, but currently China's local governments are doing far from enough. While there is hardly any regulation that forces people to sort garbage, China City Statistical Yearbook 2012 shows that investment in fixed assets of environmental protection accounts for only 2 percent of public investment in China, of which much less is spent on garbage sorting.

How will real change in people's behavior be possible without any measures and funds in place to encourage and enforce it?