In recent years, biological breeding conversion technology, with the black soldier fly as a typical representative, is an emerging process that is considered to be able to achieve efficient treatment, resource utilization and reduction of wet waste, and the product has good economic value. It is gradually becoming a hot spot for wet waste treatment. At present, the scientific research, breeding technology, project operation and other popular science articles about black soldier flies are not comprehensive. Therefore, this column will be based on the "Laogang Solid Waste Environmental Protection Science and Technology Innovation Center Demonstration Project-Wet Waste Biorecycling Technology Integrated Demonstration" established by Shanghai Urban Investment (Group) Co., Ltd. and the established 50 tons/day three-phase solid slag aquaculture The Black Soldier Fly Demonstration Project has launched a series of popular science articles with the theme of Black Soldier Fly, mainly including basic knowledge of Black Soldier Fly, automated breeding technology, egg hatching, fresh/dry insect utilization, ecological risk control, insect sand bio-fertilization , odor pollution control and other series, providing comprehensive science popularization for the scientific understanding and engineering operation of wet waste transformed by black soldier flies.

The biological characteristics of the black soldier fly

The Chinese name of the black soldier fly The bright-spotted waterfly, the English name is black soldier fly (BSF), and the scientific name is Hermetiallucens. The black soldier fly originated in South America and mainly fed on animal feces and carcasses. It later spread and settled around the world with human activities. This insect originated in South America and later migrated around the world. It is currently mainly distributed in most areas of the tropics, subtropics and temperate zones. There are also areas where this insect lives in our country. It is currently mainly distributed in most areas of southern my country, and also in small numbers in areas with higher temperatures in the north.

The life cycle of the black soldier fly is divided into five stages of development: egg, larvae, prepupa, pupa and adult. It is a completely metamorphosing insect. It generally takes about 35 days from egg to adult. The development cycle of eggs is related to temperature. The higher the temperature, the shorter the time for eggs to hatch. There is a negative correlation between egg development and environmental humidity, and an increase in humidity will shorten the egg hatching time. When the temperature is 27°C and the relative air humidity is 25%, the egg duration is as long as 5-6 days; when the relative humidity is 50-70%, the egg duration is the shortest, less than 4 days, and when the relative humidity is 60% , the incubation time is only 3 days.

The eggs of the black soldier fly are in the shape of lumps. Each egg lump contains approximately 200-600 eggs. The color of a single egg is milky white or light yellow, and will turn yellow in the later stages of development. The growth of black soldier fly larvae can be divided into six stages, among which the 1st to 5th instar larvae are milky white in color and are called white worms. White worms are active in feeding, especially when they are 3 to 5 years old. The 6th instar larvae are black and are often called black worms. At this stage, the larvae will no longer eat, so they are also called prepupae. At this stage, the black soldier fly no longer eats and will continue to consume energy substances in the body. At this time, the larvae are suitable for harvesting as feed.

The pupa of the black soldier fly is a peripupa, with a flat body and a dark brown color. The head end is tapered and the end of the abdomen is bent at 45° toward the ventral surface. The body length of the adult black soldier fly is generally between 15 and 20 mm. The body color is mainly black, with a blue or green metallic luster on the chest, and sometimes the end of the abdomen is slightly red. The whip segments of the antennae are relatively flat, and the length of the antennae is about twice the length of the head. The base half of the foot is black, and the terminal appendages and anterior appendages are white.

The adult body is like a wasp, but has a smooth body and only one pair of membranous wings. Generally, female insects are larger than males. The black soldier fly no longer eats in the adult stage, so it will not actively invade human homes. It will not transmit diseases and is not a sanitary pest. At this stage, it mainly relies on the fat accumulated in the larval stage to survive. Under suitable conditions, after mating, females will look for dry crevices to lay their eggs.

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The main components of the black soldier fly

The black soldier fly is an edible resource insect designated by the Food and Agriculture Organization of the United Nations (FAO). Black soldier fly larvae are rich in active protein, insect fat, probiotics, antimicrobial peptides and chitin. They are the best natural health products for all kinds of animals. They are known as "animal ginseng" and can be used as a staple food or feed supplement for animals. It can help digestion, promote growth, enhance immunity, and make meat delicious. Live insects can also be used as feed additives or partial replacements, for example, replacing 10% of the feed. The cost is low, but the animal's survival rate, feed-to-meat ratio, meat texture, etc. have been greatly improved, and the breeding benefits have doubled.

Dried black soldier fly worms contain 44%-48% crude protein and 34%-35% fat. Fresh black soldier fly worms contain 17% protein and 12% fat. The calcium to phosphorus ratio is close to 2. Balanced and comprehensive nutrition, good animal palatability. Essential amino acids in black soldier flies account for more than 50% of the total amino acids. The nutritional content of black soldier flies is relatively comprehensive and contains a variety of amino acids required by animals. The content of each nitrogen-based acid is higher than that of fish meal. The total amount of essential amino acids is 2.3 times that of fish meal, and the methionine content is 2.7 times that of fish meal. The lysine content is 2.6 times that of fish meal. The total essential amino acids of the black soldier fly raw material and dry powder are 44.09% and 43.83% respectively, both exceeding the reference value of 40% proposed by the World Health Organization of the Food and Agriculture Organization, the total amount of essential amino acids/the total amount of essential poor amino acids The values ​​are 0.79 and 0.78 respectively, both exceeding the proposed reference value of 0.6.

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Raising conditions of black soldier fly larvae

< p>The cultivation of black soldier fly larvae will be affected by factors such as temperature, relative humidity, light conditions, feed moisture content, heavy metals, and symbiotic microorganisms.

The best conditions for the cultivation of black soldier fly larvae

(1) Temperature: The optimal growth and development temperature of black soldier fly larvae is 27~30℃. Adults will not lay eggs below 26°C, and temperatures that are too high will cause the larvae to stop feeding.

(2) Relative humidity: The optimal relative humidity for raising black soldier fly larvae is 70%~75%. Humidity below 50% will affect the growth and development time of larvae. When the humidity drops to 30%, larvae will no longer develop into pupae. Adults need a humidity of about 60% to lay eggs.

(3) Lighting conditions: Adult courtship and mating behaviors require light intensity stimulation, and natural light is the best. However, when natural light is insufficient, iodine tungsten lamps are considered to be suitable equipment to replace natural lighting during the breeding stage, producing The number of eggs during the peak egg period is equivalent to 61% of the number of eggs laid under sunlight intensity.

(4) Feed moisture content: The average body weight of black soldier fly larvae under artificial feed conditions with 70% moisture content was significantly higher than that under 50% and 30% feed conditions. The reproduction cycle is about 10 days shorter with a moisture content of 30%, and the larvae cannot develop into prepupae under feed conditions with a moisture content of 30%.

(5) Heavy metal content: Heavy metals will affect the growth and development of black soldier fly larvae. When black soldier fly is used to treat feces containing high concentrations of Zn (≥600 mg/kg), the fifth instar larvae and pre- The weight of pupae and pupae will be significantly reduced, while the development time is extended and accumulated over generations; when the concentration of Cu2+ in livestock and poultry feed reaches 600mg/kg, the larvae development time will be significantly increased and the emergence rate will be significantly reduced; when the Cu2+ concentration reaches 1200mg /kg, the development time of the pupa will also be greatly increased.

(6) Symbiotic bacteria: In a sterile environment, black soldier fly larvae lag in growth and development and increase mortality. However, after re-inoculation with microbial cleaning solution, their growth will gradually return to normal. At the same time, insects can use bacteria in the environment as their own symbiotic bacteria to help their own growth and development.

(7) Other conditions: When the pH is between 5 and 10, the difference in the development process is not significant, and it has strong adaptability to alkaline environments; in environments with a salinity of less than 6%, black soldier flies have good performance Adaptability; at the same time, even if the mass concentration of capsaicin reaches 1%, it will not have much impact on the black soldier fly.

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Main application directions of black soldier flies

(1) Bioconversion of organic waste by black soldier flies

Black soldier flies Larvae have the characteristics of a wide diet, large food intake, low nutritional requirements, and high safety, so they have huge potential for organic waste treatment. Black soldier fly larvae are scavengers and feed on animal feces and rotten organic matter in nature, such as chicken manure, cow manure, rotten fruits, vegetables and meat, rotten seafood and dead livestock and poultry carcasses. According to incomplete statistics, there are currently 78 types of organic waste that can be processed by black soldier fly larvae (including mixed organic waste). The processing rate of black soldier fly larvae for single organic feces is 20% to 50%; the processing rate for food waste is higher, reaching 50% to 70%. Compared with other wastes, food waste is richer in nutrients and has higher bioconversion value. Using kitchen waste to raise black soldier flies has a short breeding cycle, high insect body production, high feed conversion rate and larval survival rate, and has good economic benefits. Although differences in eating habits in different regions lead to differences in the content of food waste components, research shows that black soldier flies have good tolerance to environmental conditions such as hunger, pH, spiciness and salinity, which provides a basis for the use of food waste to achieve scale. Black soldier fly breeding provides strong support.

(2) Used in the breeding industry

Black soldier fly larvae have the characteristics of high protein and high fat. Their amino acid content is similar to that of fish meal and can be used to replace fish meal as a protein additive. Researchers used black soldier flies to replace fish meal, which significantly increased the weight of broiler chickens, the dry matter intake was not affected, and the integrity of various organs and hematopoietic systems was ensured. Relevant scholars used black soldier fly meal to replace soybean meal to feed laying hens. There was no significant difference in the egg production and feed intake of the laying hens. There were no signs of death or health disorders during the feeding period, and feather and wound scores remained stable. Black soldier fly powder can be used not only for the breeding of livestock and poultry industries, but also for the breeding of aquatic products. Researchers tried to use black soldier fly prepupa meal to partially replace fish meal to feed tilapia. Based on the detection of feed intake, feed conversion rate, weight changes and other indicators, it can be concluded that up to 50% of the meal can be used Black soldier fly meal replaces fish meal without affecting feed utilization and other parameters. Some researchers used black soldier fly oil to replace soybean oil to raise carp. The results showed that 25% black soldier fly oil replaced soybean oil and the effect of carp raised with all soybean oil formula was the same.

(3) Other applications

In Europe and the United States, black soldier fly larvae have good therapeutic effects on some skin damage diseases. The broad diet of the black soldier fly gives the black soldier fly itself a strong immune mechanism. The methanol extract of black soldier fly larvae has strong antibacterial activity. It not only has a strong inhibitory effect on the growth and proliferation of bacteria, but also has the property of blocking the viability of bacteria; the ethyl acetate extract is effective in combating armor-resistant Oxycillin is effective against Staphylococcus aureus, suggesting that the black soldier fly may be a source of new antibiotics. In addition to high protein content, black soldier fly larvae also contain high fat, which makes black soldier fly larvae a biodiesel raw material with research value and practical application significance. The production of biodiesel produced by black soldier fly larvae raised on food waste has almost doubled. Using 1kg of food waste to raise 1,000 black soldier fly larvae can produce approximately 23.6 g of biodiesel. The methyl ester components of biodiesel produced from this larvae are methyl oleate (27.1%), methyl laurate (23.4%), and methyl palmitate (18.2%). Most of the properties of this part of biodiesel comply with the EN14214 standard.