kitchen waste, commonly known as food waste, is a kind of domestic waste formed by residents in the process of daily consumption, which is easy to rot and deteriorate, emits stench, and spreads bacteria and viruses. The main components of kitchen waste include rice and flour food residues, vegetables, animal and vegetable oils, meat and bones, etc. From the chemical composition, there are starch, cellulose, protein, lipids and inorganic salts.

sources and characteristics

kitchen waste is the most important kind of food waste, including food processing leftovers (kitchen waste) and edible residues (feet) produced in families, schools, canteens and catering industries. Its composition is complex, mainly composed of oil, water, peel, vegetables, rice flour, fish, meat, bones, waste tableware, plastics, paper towels and other substances. The amount of kitchen waste in China is very huge, and it is on the rise rapidly.

Food waste has obvious harm and duality of resources, and its characteristics can be summarized as follows:

1. The water content is high, reaching 81%-95%.

2. The salt content is high, and some areas contain pepper and acetic acid.

3. High organic matter content, protein, cellulose, starch, fat, etc.

4. It is rich in nitrogen, phosphorus, potassium, calcium and various trace elements.

5. There are pathogenic bacteria and pathogenic microorganisms.

6, perishable, deteriorated, smelly, breeding mosquitoes.

classification

according to different sources, kitchen waste is mainly divided into catering waste and kitchen waste. The former is produced from the leftovers of restaurants, canteens and other restaurants, which has the characteristics of large quantity, many sources and wide distribution, while the latter mainly refers to the leftovers discarded by residents in their daily cooking, and the quantity is not as large as that of catering waste.

treatment method

now, the kitchen waste is uniformly treated by the solid waste treatment method. The treatment methods mainly include physical method, chemical method and biological method. Specific treatment technologies include landfill, incineration, composting, fermentation, etc. In short, its resource reuse shows a diversified trend. The following methods are mainly introduced according to different application scopes and actual situations.

1 physical separation treatment

mainly adopts a series of ways to realize the separation of various components in the garbage and then recycle them uniformly. On the one hand, this method makes the best use of everything, on the other hand, it minimizes the possible pollution caused by garbage. However, due to its high cost, except for a few developed countries, most countries do not use this method.

2 crushing and direct drainage method

As early as the 1941s, the United States has successfully developed a personal household food waste processor. The specific principle is: the food waste packed in the liner is crushed by a high-speed blade, and then the mixture is flushed to the sewer, thus solving the trouble of residents discarding and storing kitchen waste. At the same time, Japan has also developed a kitchen waste processor very early, and some of them are even equipped with an ozone deodorizer to remove various odors generated by kitchen waste.

3 landfill method

The landfill method of kitchen waste is an anaerobic digestion method, which can decompose the organic matter into CH4 and completely dispose of the waste. This technology is convenient and will not leave the problem of residue disposal. However, although this method can deal with kitchen waste well, it aims at eliminating the waste and cannot realize the recycling of kitchen waste.

4 Anaerobic treatment

is the most environmentally friendly and profitable method at present. The investment is large, and very few people produce biogas through anaerobic fermentation.

Because kitchen waste contains all kinds of animal meat, if it is used as feed, cannibalism can easily lead to foot-and-mouth disease and various diseases, which will spread to human beings and cause harm; Landfill is easy to produce a lot of leachate and pollute groundwater because of its high water content; When making fertilizer, the smell is overflowing in the production process, which affects the surrounding environment; Anaerobic treatment can produce a large amount of biogas. Biogas is a clean and renewable energy source, which can be used for power generation and fuel. Because the system is completely closed and has no odor, anaerobic treatment of kitchen waste is the future development direction.

5 microbial treatment

is the process of decomposing and utilizing the organic matter in kitchen waste through the metabolic growth activities of microorganisms. Fermentation methods mainly include solid fermentation and liquid fermentation. Because solid-state fermentation has the characteristics of low energy consumption, short cycle and high yield, solid-state fermentation is mostly used now. Solid-state fermentation can be divided into single-strain solid-state fermentation and mixed-strain solid-state fermentation. Now, mixed-strain solid-state fermentation technology is mostly used: that is, kitchen waste is fermented by two or more bacteria, and a large number of cellulases are produced to degrade fibers, and at the same time, nutrients such as carbon source and nitrogen source are fully utilized to synthesize single-cell bacterial protein, so as to improve the nutritional value of protein feed. Solid-state fermentation has the advantages of good palatability, high protein digestion and absorption rate, and it also avoids the problems of incomplete utilization of nutrients in traditional kitchen waste. It is an important method to reuse the feed resources of protein, a living organism of kitchen waste.

6 composting method

The kitchen waste contains more organic matter, higher nutrient elements and a reasonable ratio of carbon to nitrogen, which is suitable for the growth and metabolism of microorganisms and is a good raw material for production. The basic technology of kitchen waste composting can be divided into two types: anaerobic fermentation composting and aerobic fermentation digestion. Among them, thermophilic aerobic composting is a common method at present, which can complete the ripening process of material compost in a short period. The high temperature produced during composting can obviously inhibit harmful bacteria.