Cockroach — the most hardworker for food waste?

When we think about cockroach, we might relate to words like dirty, disease vector… negative emotions attached with them. However, things exist for a reason! Now in China, they found a way to use them as an efficient way of transforming foodwaste into protein!

山东章丘养殖蟑螂吃餐厨垃圾：设置三重防逃逸体系-中新网

300,000,000 cockroach consumes 10tons of food waste per day (at the time of this news)!

But why do we consider using cockroach? First, they have very fast reproduction rate and high survival rate comparing to some other insects. Also, they are not picky eater and non-selective to the types of food waste. It is valuable protein source if used properly, therefore high conversion rate and recovery of nutrients in the environment and decrease the burden of loaded amount of waste. They can be used as feed after sanitasation processes and convertion to powder form. The powder could be sterilized and hydrated, which will be easily used in feed.

But why do we select this method but not other ways, e.g. anaerobic digestion for biogas production, landfilling, combustion? Well, we know that even with the production of usable energy in anaerobic digestion system, it requires large space for storage, which makes it less efficient. In terms of combustion, it requires large amount of energy input, which is less sustainable system and relies heavily on external system. Landfilling is known to be bad for the environment and it requires long degradation period. However, using cockroach biodegradation method could be threatening to biodiversity in the environment if any leakage happens. To solve this problem, they utilised multi-layers of barriers to prevent cockroach escaping from the enclosed space, which include concrete, water, fish, and temperature (during winter).

What are the benefits of using cockroach to degrade organic waste? First of all, their stomach contain potent enzymes to digest any potential harmful bacteria and pathogens, which has advantage over the use of fly larvae composting. Alos, cockroach could be used as medicine if used in powder form, and the use of cockroach in feed can boost immune system of the feeding animals (e.g. chicken in the experiment mentioned in http://www.yogeev.com/article/76292.html), which will decrease the current phenomenon of overuse of antibiotics in animal rearing. At the same time, it is efficient way of handling solid food waste fraction and good nutrient recovery and conversion.

There are many advantage of using cockroach composting method but how does the process work actually? First of all, food waste are shreded into small fractions to easier transportation and digestion. Then, food waste fractions are then transported to feeding area (in the higher and upper area) through pipe. The amount of feed used are calculated to be optimal but not maximun to avoid leftover food in the feeding area. Then cockroach start consuming feed from the inner to outer layer with organised order without chaos. This is one feeding event.

Then when cockroach close to the end of their life cycles, they approach to the lower end of the area, where they wait till the end of their lives. When they die, they will be cleared out from the lower end of the area and sent to further processing. The cockroach will then be sterilized, grounded into powder and hydrated. And the hydrated powder could be used in feed depending on the regulation.

Is it cost effective? In terms of recycling nutrients, reducing waste volumn, producing protein from organic waste, then yes it is for sure effective and advantagious comparing to many other organic waste handling methods. However, at the moment, only food waste from restaurants are used and recycled for the waste input in China, and one of the main reason is due to the lack of seperation of organic waste in households. Therefore, even though with all those advantages mentioned, more approaches should be promoted for recycling organic waste accompanied by this organic waste treatment method.

In the bigger picture, the usage of cockroach in feed has high potential in big scale rearing, for example it has implemented in Shandong, China. In the future, it is expected to have this implemented in all the large cities in order to deal with the rising amount of organic waste.