Method for making environment-friendly carbon source by straw bio-fermentation and application

Abstract

The application discloses a method for preparing an environment-friendly carbon source by straw bio-fermentation and application, and the environment-friendly carbon source comprises the following raw materials in parts by mass: 40-60 parts of straw, 15-25 parts of special tree branches, 10-16 parts of edible fungus waste fungus bags, 2-4 parts of odor-removing agents, 6-8 parts of zeolites, 6-8 parts of graphite, 2.2-2.6 parts of compound fermentation bacterial liquid and 60-80 parts of water. The application can realize comprehensive development and utilization of crop straw, reduce straw burning phenomenon, has important significance of energy saving and environmental protection, can avoid the problems of pollution to the environment and degradation difficulty caused by the waste fungus bags, improve the utilization rate of the waste, can effectively protect resources, and achieves the purpose of carbon comprehensive.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of environment-friendly carbon source, in particular to a method for preparing environment-friendly carbon source by straw bio-fermentation and application. BACKGROUND

[0002] Every year, a large amount of wheat, corn and other straws are burned in the field during summer harvest and autumn and winter, which produces a large amount of heavy smoke, causing air pollution and endangering human health. When the straws are burned, the pollution indexes of sulfur dioxide, nitrogen dioxide and inhalable particulate matter in the atmosphere reach the peak value, among which the concentration of sulfur dioxide is 1 times higher than usual, and the concentrations of nitrogen dioxide and inhalable particulate matter are 3 times higher than usual. Therefore, improving the comprehensive development and utilization of crop straws and their utilization rate is crucial for the development of society and technology in China. Combining straws with bio-fermentation to decompose carbon sources can be used for nitrogen and phosphorus removal in wastewater to ensure the effect of wastewater treatment.

[0003] The existing carbon source agents are directly put into wastewater for treatment of nitrogen and phosphorus, and provide energy required by microorganisms.

[0004] However, most of them are directly put into wastewater, and since there is no carrier, in the initial stage of purification, they can flow with water and cannot provide a good growth environment for microorganisms, which leads to a long growth and culture period of microorganisms and an unobvious effect of nitrogen and phosphorus removal in the short term. SUMMARY

[0005] The present application aims to provide a method for preparing environment-friendly carbon source by straw bio-fermentation and application, to solve the problems in the background art.

[0006] The technical solution of the present application is as follows:

[0007] According to one aspect of the present application, an environment-friendly carbon source is provided.

[0008] The environment-friendly carbon source comprises the following raw materials in mass fraction:

[0009] 40-60 parts of straws, 15-25 parts of special branches, 10-16 parts of edible fungus waste fungus bags, 2-4 parts of odor removal agents, 6-8 parts of zeolite, 6-8 parts of graphite, 2.2-2.6 parts of compound fermentation bacteria liquid, and 60-80 parts of water.

[0010] Further, the straws comprise the following raw materials in mass fraction: 8-12 parts of corn straws, 8-12 parts of soybean straws, 12-18 parts of wheat straws, and 12-18 parts of rice straws.

[0011] Further, the edible mushroom waste bag is one or a mixture of several of mushroom bags or wood ear fungus bags, and the odor-removing agent is phenylethanol.

[0012] Further, the composite fermentation bacteria liquid is activated and expanded by Lactobacillus casei, Lactobacillus bifidus, Bacillus, Enterococcus faecalis and Bacillus licheniformis.

[0013] Further, the zeolite is one or a mixture of several of chabazite, calcium zeolite, mica zeolite and sodium zeolite, and the special tree branch is one or a mixture of several of camphor tree, willow, white poplar and pine.

[0014] According to another aspect of the present application, a preparation method of the environment-friendly carbon source is provided, comprising the following steps:

[0015] Step S101: according to the above quality parts, the required raw materials of the environment-friendly carbon source are weighed;

[0016] Step S103: corn straw, soybean straw, wheat straw, rice straw, special tree branch and edible mushroom waste bag are sequentially added into a pulverizer for pulverization and mixing to obtain a mixed material A;

[0017] Step S105: water is further added into the mixed material A for sufficient mixing and stirring to obtain a slurry, which is sterilized and cooled for standby;

[0018] Step S107: the composite fermentation bacteria are added into the cooled slurry for mixing and stirring again, and then the slurry is sealed in a fermentation tank for fermentation to obtain a fermentation liquid;

[0019] Step S109: the fermentation liquid is filtered through a 300-400 mesh sieve to obtain a filtered fermentation liquid;

[0020] Step S111: the zeolite is pulverized and screened, and the zeolite powder, phenylethanol and graphite are sequentially added into the filtered fermentation liquid for mixing and stirring for 10-15 min to obtain the environment-friendly carbon source.

[0021] Further, the sterilization temperature in step S105 is 100-110°C, and the sterilization time is 16-20 min.

[0022] Further, the fermentation temperature in step S107 is 28-33°C, and the fermentation time is 2-3 days.

[0023] According to another aspect of the present application, an environment-friendly carbon source carrier is provided, comprising a main body, wherein the main body comprises active carbon balls one, the circumferential surface of the active carbon balls one is provided with active carbon balls two at equal intervals through connecting rods, two adjacent active carbon balls two are connected through fixing rings, and the active carbon balls one, the connecting rods, the active carbon balls two and the fixing rings are all provided with placing holes, and the placing holes are provided with fiber fillers.

[0024] The application also provides the use of the above-mentioned environment-friendly carbon source for soaking the carrier of the environment-friendly carbon source, and the carrier is soaked in the environment-friendly carbon source as a whole, and is particularly suitable for use in the removal of nitrogen and phosphorus in sewage.

[0025] In the application, the raw material components are described as follows:

[0026] Straw: It is the general term for the stem and leaf part of mature crops. It usually refers to the remaining part of crops such as wheat, rice, corn, potatoes, rape, cotton, sugarcane and other crops after harvesting seeds. More than half of the products of photosynthesis of crops exist in straw, which is rich in nitrogen, phosphorus, potassium, calcium, magnesium and organic matter, and is a renewable biological resource with multiple uses. It is characterized by high content of crude fiber and contains lignin and other substances. After biological fermentation, polysaccharides, alcohols and other substances can be converted, which can be used as a carbon source for the removal of nitrogen and phosphorus in sewage, and resources can be reasonably utilized;

[0027] Branch: It refers to the branches growing from the trunk or large branches of a tree; in particular, it refers to the branches growing from the trunk. After biological fermentation, it can be used as a carbon source for the removal of nitrogen and phosphorus in sewage, and resources can be reasonably utilized to reduce the cost of sewage treatment;

[0028] Edible fungus waste bag: The use of plastic bags for cultivating and producing edible fungi is a production method developed in recent years for the development of edible fungi. The plastic bags used for such cultivation have gradually developed into special bags for edible fungi, providing great convenience for the widespread development of the edible fungus industry. Now, almost all artificially cultivated edible fungi use plastic bags for cultivation. The natural degradation of the waste plastic bags not only pollutes the external environment, but also wastes resources. Through biological fermentation, organic matter can be decomposed and fermented into carbon sources, which can reasonably utilize waste resources, reduce the cost of sewage treatment, and avoid pollution of the external environment caused by waste;

[0029] Zeolite: It is a kind of mineral, which has different size cavities in the crystal lattice, and can absorb or filter molecules of other substances of different sizes. It is often used as a molecular sieve in industry to purify or separate mixed components such as gas separation, petroleum purification, and treatment of industrial pollution;

[0030] Graphite: It is a crystalline carbon. Hexagonal system, iron black to dark gray. Soft, with a smooth and slippery feeling, can conduct electricity. Chemically inert, corrosion resistant, not easily reacted with acids, bases, etc. In the air or oxygen, it can burn and generate carbon dioxide. Strong oxidizing agents can oxidize it to organic acids. Used as an anti-friction agent and lubricating material, made into crucibles, electrodes, dry batteries, pencil leads. High-purity graphite can be used as a neutron moderator in nuclear reactors;

[0031] Phenethyl alcohol: colorless viscous liquid, found in natural plants such as apple, almond, banana, peach, pear, strawberry, cocoa, honey, etc. It has a sweet and sweet rose-like floral fragrance. It is recommended to be used in honey, bread, apple, rose flower fragrance, etc.

[0032] Lactobacillus casei: belongs to the genus Lactobacillus, is a gram-positive bacteria, does not produce spores, has no flagellum, is not motile, and can ferment various sugars. It has the effects of regulating intestinal flora, enhancing immunity, protecting gastric mucosa, improving intestinal function, relieving constipation, preventing and treating diarrhea, promoting digestion, anti-tumor, antioxidant, etc.

[0033] Lactobacillus plantarum: has the effects of regulating intestinal flora, enhancing immunity, protecting gastric mucosa, improving intestinal function, relieving constipation, preventing and treating diarrhea, promoting digestion, anti-tumor, antioxidant, etc.

[0034] Enterococcus faecalis: gram-positive, hydrogen peroxide-negative coccus. It originally belongs to the genus Streptococcus and can form a biofilm on the intestinal epithelial cells to protect the intestinal epithelial cells from harmful substances. Enterococcus faecalis has nutritional effects.

[0035] Bacillus licheniformis: Bacillus licheniformis has rod-shaped cell morphology and arrangement, and can adjust the imbalance of intestinal flora to achieve the purpose of treatment. It can promote the body to produce antibacterial active substances and kill pathogenic bacteria. It can produce active substances and has a unique biological oxygen scavenging mechanism, which can inhibit the growth and reproduction of pathogenic bacteria.

[0036] Bacillus: a family of bacteria that can form spores. It includes Bacillus, Lactobacillus, Clostridium, Desulfotomaculum, and Sporosarcina. They have strong resistance to external harmful factors, are widely distributed in soil, water, air, and animal intestines, and release high-activity decomposition enzymes while proliferating. They can decompose large molecules of organic matter, organic sulfur compounds, and organic nitrogen that produce foul-smelling gases, greatly improving the environment of the place. They can also synthesize various organic acids, enzymes, physiological active substances, and other nutrients that are easy to use.

[0037] Enterococcus faecalis: gram-positive, hydrogen peroxide-negative coccus, one of the main flora in the intestinal tract of humans and animals, which can produce natural antibiotics, is beneficial to the health of the body; It can also produce bacteriocins and other bacteriostatic substances to inhibit the growth of pathogenic bacteria such as Escherichia coli and Salmonella, improve the intestinal microenvironment, and inhibit the reproduction of urease-producing bacteria and spoilage bacteria in the intestinal tract, reduce the content of intestinal urease and endotoxin, and reduce the content of ammonia and endotoxin in the blood. A kind of probiotic is widely used in the fields of medicine and food engineering. In addition, Enterococcus is a kind of microorganism normally existing in the digestive tract, which has strong tolerance and colonization ability in the intestinal mucosa, and is a kind of facultative anaerobic lactic acid bacteria. Compared with anaerobic and culture preservation conditions, Bifidobacterium is more suitable for production and application, and can decompose part of the protein into amide and amino acid, and make the fiber soft.

[0038] Compared with the prior art, the beneficial effects of the present application are:

[0039] (1) Through the recycling of straw, special tree branches and edible fungus waste bag, the comprehensive development and utilization of crop straw can be realized, the phenomenon of straw burning can be reduced, which has important significance of energy saving and environmental protection, and the pollution, degradation difficulty and utilization rate of waste can be improved, the resources can be effectively protected, and the purpose of carbon comprehensive can be achieved;

[0040] (2) The environmental protection type carbon source is temporarily adsorbed by the activated carbon ball one and the activated carbon ball two, and the fiber filler can adsorb a large amount of the environmental protection type carbon source, wherein the fiber filler can be extracted from straw, so that the cost of purification can be greatly reduced. By putting the fiber filler into the sewage, the microorganisms can be provided with a place for rapid reproduction and growth. The nitrogen and phosphorus and other eutrophic pollutants in the water can be consumed by the rapid growth of the microorganisms, the treatment efficiency is improved, and the treatment cost is reduced. When the internal carbon source is consumed, the main body can be taken out, treated and purified, and then the fiber filler and the environmental protection type carbon source are added again, so that the main body can be utilized again, and the cost of sewage purification is greatly reduced;

[0041] (3) By means of biological fermentation technology, the macromolecular substances in the straw, tree branches and edible fungus waste bag can be decomposed into small molecular substances, a plurality of organic acids, enzymes, physiological activities and other nutrients can be synthesized, the microorganisms can be conveniently reproduced and grown, the sewage can be rapidly purified and treated, the organic matter, organic sulfur compound and organic nitrogen which produce foul-smelling gas can be decomposed, the effect of sewage purification is improved, and the odorless agent is a kind of odorless gas which can effectively prevent air pollution in the process of putting. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 It is a structure schematic diagram of the main body in the application of the environmental protection type carbon source;

[0043] Figure 2 A flow chart of a preparation method of an environment-friendly carbon source is shown in the figure.

[0044] Figure 3 A data chart of three comparative examples of the environment-friendly carbon source in application is shown in the figure.

[0045] In the figure: 1, main body; 2, activated carbon ball one; 3, connecting rod; 4, activated carbon ball two; 5, fixing ring; 6, placing hole; 7, fiber filler. DETAILED DESCRIPTION

[0046] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0047] According to one aspect of the present application, an environment-friendly carbon source is provided.

[0048] The environment-friendly carbon source comprises the following raw materials in mass fraction:

[0049] 40-60 parts of straw, 15-25 parts of special branches, 10-16 parts of edible fungus waste fungus bag, 2-4 parts of odor removal agent, 6-8 parts of zeolite, 6-8 parts of graphite, 2.2-2.6 parts of compound fermentation bacteria liquid, and 60-80 parts of water.

[0050] The straw comprises the following raw materials in mass fraction: 8-12 parts of corn straw, 8-12 parts of soybean straw, 12-18 parts of wheat straw, and 12-18 parts of rice straw.

[0051] In order to more clearly understand the above technical solutions of the present application, the above solutions of the present application will be described in detail below through specific examples.

[0052] Example 1

[0053] An environment-friendly carbon source comprises the following raw materials in mass fraction:

[0054] 40g of straw, 15g of special branches, 10g of edible fungus waste fungus bag, 2g of odor removal agent, 6g of zeolite, 6g of graphite, 2.2g of compound fermentation bacteria liquid, and 60g of water.

[0055] The straw comprises the following raw materials in mass fraction: 8g of corn straw, 8g of soybean straw, 12g of wheat straw, and 12g of rice straw.

[0056] The preparation of the environment-friendly carbon source comprises the following steps:

[0057] Step S101: According to the above mass fraction, the required raw materials of the environment-friendly carbon source are weighed;

[0058] Step S103: Corn stalks 8g, soybean stalks 8g, wheat stalks 12g, rice stalks 12g, special branches 15g, and edible fungus waste fungus bags 10g are sequentially added to the pulverizer for pulverization and mixing to obtain a mixed material A;

[0059] Step S105: 60g of water is further added to the mixed material A for sufficient mixing and stirring to obtain a slurry, which is sterilized and cooled for later use;

[0060] Step S107: 2.2g of compound fermentation bacteria liquid is added to the cooled slurry for mixing and stirring again, and then the mixture is sealed and fermented in a fermentation tank to obtain a fermentation liquid;

[0061] Step S109: The fermentation liquid is filtered through a 300-400 mesh screen to obtain a filtered fermentation liquid;

[0062] Step S111: 6g of zeolite is pulverized and screened, and 6g of zeolite powder, 2g of phenethyl alcohol, and 6g of graphite are sequentially added to the filtered fermentation liquid for mixing and stirring for 10-15 minutes to obtain the environment-friendly carbon source.

[0063] Example Two:

[0064] An environment-friendly carbon source comprises the following mass fractions of raw materials:

[0065] 50g of straw, 20g of special branches, 13g of edible fungus waste fungus bags, 3g of odor removal agent, 7g of zeolite, 7g of graphite, 2.4g of compound fermentation bacteria liquid, and 70g of water.

[0066] The straw comprises the following mass fractions of raw materials: 10g of corn stalks, 10g of soybean stalks, 15g of wheat stalks, and 15g of rice stalks.

[0067] The preparation of the environment-friendly carbon source comprises the following steps:

[0068] Step S101: According to the above mass fraction, the required raw materials of the environment-friendly carbon source are weighed;

[0069] Step S103: 10g of corn stalks, 10g of soybean stalks, 15g of wheat stalks, 15g of rice stalks, 20g of special branches, and 13g of edible fungus waste fungus bags are sequentially added to the pulverizer for pulverization and mixing to obtain a mixed material A;

[0070] Step S105: 70g of water is further added to the mixed material A for sufficient mixing and stirring to obtain a slurry, which is sterilized and cooled for later use;

[0071] Step S107: Add 2.4g of the composite fermentation broth to the cooled slurry and mix again, then put it into a fermentation tank for sealed fermentation to obtain a fermentation liquid;

[0072] Step S109: Filter the fermentation liquid through a 300-400 mesh sieve to obtain a filtered fermentation liquid;

[0073] Step S111: Crush and screen 7g of zeolite, then add 7g of zeolite powder, 3g of phenethyl alcohol, and 7g of graphite to the filtered fermentation liquid in sequence and mix for 10-15 minutes to obtain the environment-friendly carbon source.

[0074] Example Three:

[0075] An environment-friendly carbon source, which comprises the following raw materials in mass fractions:

[0076] 60g of straw, 25g of special branches, 16g of edible fungus waste fungus bag, 4g of odor removal agent, 8g of zeolite, 8g of graphite, 2.6g of composite fermentation broth, and 80g of water.

[0077] The straw comprises the following raw materials in mass fractions: 12g of corn straw, 12g of soybean straw, 18g of wheat straw, and 18g of rice straw.

[0078] The preparation of the environment-friendly carbon source comprises the following steps:

[0079] Step S101: According to the above mass fractions, weigh each raw material required for the environment-friendly carbon source;

[0080] Step S103: Crush and mix 12g of corn straw, 12g of soybean straw, 18g of wheat straw, 18g of rice straw, 25g of special branches, and 16g of edible fungus waste fungus bag in sequence in a crusher to obtain a mixed material A;

[0081] Step S105: Add 80g of water to the mixed material A and mix thoroughly to obtain a slurry, which is sterilized and cooled for later use;

[0082] Step S107: Add 2.6g of the composite fermentation broth to the cooled slurry and mix again, then put it into a fermentation tank for sealed fermentation to obtain a fermentation liquid;

[0083] Step S109: Filter the fermentation liquid through a 300-400 mesh sieve to obtain a filtered fermentation liquid;

[0084] Step S111: Crush and screen 8g of zeolite, then add 8g of zeolite powder, 4g of phenethyl alcohol, and 8g of graphite to the filtered fermentation liquid in sequence and mix for 10-15 minutes to obtain the environment-friendly carbon source.

[0085] According to another aspect of the invention, an environmentally friendly carbon source carrier is provided; please refer to [reference needed]. Figure 1 The system includes a main body 1, which includes activated carbon balls 1-2. Activated carbon balls 2-4 are equidistantly arranged on the periphery of the activated carbon balls 1-2 via connecting rods 3. This allows for convenient temporary adsorption of carbon sources and also enables the adsorption and purification of harmful substances in the water during use. Each adjacent activated carbon ball 2-4 is connected by a fixing ring 5. Placement holes 6 are provided in the activated carbon balls 1-2, connecting rods 3, activated carbon balls 2-4, and fixing rings 5. Fiber filler 7 is placed in the placement holes 6. The fiber filler 7 is extracted from straw, which can greatly reduce the purification cost, adsorb carbon sources, provide a place for the initial reproduction of microorganisms, and improve the purification efficiency of wastewater.

[0086] The environmentally friendly carbon source obtained in Example 1 was added to the wastewater of a power plant in the following manner for use in wastewater treatment:

[0087] Application Example 1: Add all the carbon source to the wastewater to remove nitrogen and purify the wastewater;

[0088] Application Example 2: Half of the carbon source was put into the sewage, and the other half was soaked in the main body 1 and then put back into the sewage;

[0089] Application Example 3: Immerse all the carbon source in the main body 1, and then release it into the sewage.

[0090] Regular sampling and analysis of bacterial concentrations in three application examples yielded the results shown in Table 1 below. Figure 3 In Table 1 and the graph, the unit for the horizontal axis is min; the unit for the vertical axis is 10. 6 cell / g.

[0091] 0 10 20 30 40 Application Example 1 1.00 1.81 2.72 5.51 6.89 Application Example 2 1.00 2.42 4.61 7.04 7.31 Application Example 3 1.00 2.11 4.3 6.33 7.12

[0092] Table 1

[0093] In summary, the carbon source provided by this invention can provide a superior breeding ground for microorganisms, which can greatly increase the reproduction rate and quantity, thereby improving the removal effect of wastewater. The rapid growth of microorganisms consumes eutrophic pollutants such as nitrogen and phosphorus in the water, improving treatment efficiency and reducing treatment costs.

[0094] It will be apparent to those skilled in the art that the application is not limited to the details of the above-exemplified embodiments and that the present application can be implemented in other particular forms without departing from the spirit or essential characteristics of the present application. The embodiments should therefore be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the above description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. No reference signs in the claims should be considered as limiting the scope of the claims with respect to the figures of the patent document.

Claims

1. An environmentally friendly carbon source, characterized by, The environment-friendly carbon source is used for sewage treatment, and contains the following raw materials in mass fraction: 40-60 parts of straw, 15-25 parts of special branches, 10-16 parts of edible fungus waste fungus bag, 2-4 parts of odor removal agent, 6-8 parts of zeolite, 6-8 parts of graphite, 2.2-2.6 parts of compound fermentation bacteria liquid, and 60-80 parts of water; the straw contains the following raw materials in mass fraction: 8-12 parts of corn straw, 8-12 parts of soybean straw, 12-18 parts of wheat straw, and 12-18 parts of rice straw, the mass ratio of the corn straw to the soybean straw is 1:1, and the mass ratio of the wheat straw to the rice straw is 1:1; the edible fungus waste fungus bag is one or a mixture of several kinds of mushroom fungus bag or agaric fungus bag; the odor removal agent is phenethyl alcohol; the compound fermentation bacteria liquid is activated and proliferated by compound fermentation bacteria species including lactobacillus casei, lactobacillus bifidus, bacillus, enterococcus faecalis and bacillus licheniformis; the zeolite is one or a mixture of several kinds of chabazite, calcium zeolite, phillipsite and sodium zeolite; and the special branches are one or a mixture of several kinds of bauhinia, willow, white poplar and pine. The whole environment-friendly carbon source carrier is soaked in half of the environment-friendly carbon source, and the other half is directly put into sewage for use in the direction of removing nitrogen and phosphorus from sewage. The environment-friendly carbon source carrier comprises a main body (1), the main body (1) comprises active carbon balls one (2), equidistant active carbon balls two (4) are arranged on the circumferential surface of the active carbon balls one (2) through connecting rods (3), two adjacent active carbon balls two (4) are connected through fixing rings (5), and the active carbon balls one (2), the connecting rods (3), the active carbon balls two (4) and the fixing rings (5) are all provided with placing holes (6) therein, and the placing holes (6) are provided with fiber fillers (7) therein. The preparation method of the environment-friendly carbon source comprises the following steps: Step S101: according to the mass fraction, the required raw materials of the environment-friendly carbon source are weighed; Step S103: corn straw, soybean straw, wheat straw, rice straw, special branches and edible fungus waste fungus bag are sequentially added into a pulverizer for pulverization and mixing to obtain a mixed material A; Step S105: water is further added into the mixed material A for fully mixing and stirring to obtain a slurry, which is sterilized and cooled for standby; Step S107: compound fermentation bacteria are added into the cooled slurry for mixing and stirring again, and then the slurry is sealed in a fermentation tank for fermentation to obtain a fermentation liquid; Step S109: the fermentation liquid is filtered through a 300-400 mesh screen to obtain a filtered fermentation liquid; Step S111: zeolite is pulverized and screened, and zeolite powder, phenethyl alcohol and graphite are sequentially added into the filtered fermentation liquid for mixing and stirring for 10-15 minutes to obtain the environment-friendly carbon source; In step S107, the fermentation temperature is 28-33℃, and the fermentation time is 2-3 days.

2. The environmentally friendly carbon source according to claim 1, characterized in that, In step S105, the sterilization temperature is 100-110℃, and the sterilization time is 16-20 minutes.

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