Here’s how kitchen waste becomes organic material

WITH Shanghai’s first garbagemanagement regulations taking effect on July 1, when trashsorting will become a norm, there is much concern over how this sorted-out garbage will be processed.

A team from Shanghai Ocean University has come up with a solution — a machine that can “eat” kitchen waste and produce organic material for fertilizers or feedstuff without polluting the environment.

The machine, which is 1.5 meters long, 70 centimeters wide and 1.4 meters high, can take in 120 kilograms of waste at a time and after four hours of processing, it can let out about 60kg of brown organic matter and steam without causing a stink.

Liu Haiquan, an associate professor at the university and leader of the team, told Shanghai Daily that the initial aim for developing the machine was to make use of offcuts in the food-processing industry, such as rotten vegetable leaves and fish scales, to produce additional value.

“But when we learned that Shanghai plans to sort out garbage and process different kinds of waste separately, we found that our machine could be used on a larger scale,” he said.

According to Liu, processing of kitchen waste has been a problem due to the low efficiency and the bad odor and secondary pollution it generally causes. “The high content of salt and oil in kitchen waste makes it difficult to process and it also easily produces stink and polluted water, which can harm the environment again.”

To solve such problems, his team has developed a kind of liquid with several carefully selected bacteria, which can accelerate the process of fermentation without giving out unpleasant smell. They have also installed a device in the tank of the machine, where the waste is put, to extract air, thereby further speeding up the fermentation process.

They have tested the machine with waste from the university’s canteens and it was successful.

The researchers have also used the organic material produced by the machine as fertilizer for plants in their lab, which has proved to be effective in promoting their growth. Liu said they can also be used to produce feedstuff for animals, such as crayfish.

They are now looking for partners to test the machine outside the campus.

Liu added that the team can customize the machine according to the area it serves and even modify the formula of the bacteria liquid to handle cuisines in different areas of China, where salt and oil content may vary.

“Stinky odor from garbage bins in restaurants or communities is a common occurrence if the waste is not cleared on time. But with our machine, you don’t have to wait for the garbage truck to take the stuff away, you can process it in the restaurant area or community immediately,” said Liu.

“The organic matter produced by the machine does not have any odor, so you don’t have to worry about when the garbage truck will come.” According to Liu, it costs less than 1.6 yuan (23 US cents) to process a kilogram of kitchen waste with the machine, which itself costs around 80,000 yuan depending on the size.