Express delivery, also known as express delivery or express delivery, refers to a new mode of transportation in which logistics enterprises (including freight forwarders) deliver documents or parcels entrusted by users quickly and safely from the sender’s door to the recipient’s door (hand delivery) through their own independent network or through joint venture cooperation (i.e. networking).
Express delivery can be divided into broad sense and narrow sense. In the broad sense, express delivery refers to the delivery of any goods (including bulk cargo); in the narrow sense, express delivery refers to the urgent delivery service of business documents and small pieces. The object of this textbook research and analysis is mainly the express industry in a narrow sense. According to the standard of service, express delivery generally refers to express delivery service completed within 48 hours. From the definition of express delivery, the following three characteristics of express delivery can be summarized:
From the economic category, express delivery is a branch of the logistics industry, and the research of express delivery belongs to the category of logistics.
From the perspective of business operation, express delivery is a new mode of transportation and an important link in the supply chain.
From the nature of operation, express delivery is a new service trade with high added value.
Taking the water system as a whole, according to the geographical distribution of towns and industrial and mining enterprises along the coast of the water system, as well as the self-purification capacity, pollution capacity and pollution status of the water system, comprehensive prevention and control measures are taken to prevent and control water pollution. It includes various engineering technology means and management measures, which have the characteristics of integrity, comprehensiveness and regionality.
Comprehensive prevention and control of water pollution is a comprehensive application of various measures to prevent and control water pollution. Prevention and control measures involve two types of engineering and non-engineering, mainly:
(1) Reducing the discharge of wastewater and pollutants, including saving production wastewater, stipulating water quota, improving production technology and management system, increasing the reuse rate of wastewater, adopting new technology without pollution or less pollution, and formulating material quota, etc. For water-deficient cities and industrial and mining areas, regional recycling water and wastewater reuse systems should be developed.
(2) Developing regional water pollution prevention and control systems, including formulating urban water pollution prevention and control plans, river basin water pollution prevention and control management plans, implementing the total amount control system of water pollutant discharge, developing sewage after proper manual treatment for irrigation farmland and reuse for industry, establishing sewage reservoirs without polluting groundwater, and low water. Periodic storage of sewage reduces sewage discharge load and conducts controlled dilution during flood period.
(3) Develop wastewater treatment technologies with high efficiency and low energy consumption to treat wastewater.
Comprehensive prevention and control of pollution refers to the comprehensive use of various measures to prevent and control water environmental pollution from the whole point of view. It is very necessary to implement comprehensive prevention and control of water pollution, because China is a country with relatively scarce water resources, and there are two manifestations: one is resource-based water shortage, the other is water-quality-based water shortage. For a long time, the purification treatment of sewage outlet based on point source control can not effectively solve the problem of water pollution. Comprehensive prevention and control of water pollution must be carried out from the overall point of view of the region and water system in order to fundamentally control water pollution and solve the problem of water shortage caused by water quality.
Why do this
The necessity and urgency of comprehensive prevention and control of water pollution are embodied in two aspects: first, the contradiction between water resources shortage and unbalanced supply and demand is prominent, and the serious pollution of water environment makes this contradiction more prominent and urgently needs to be solved;
Why is it so urgent?
Secondly, the purification treatment of sewage outlets based on point source control can not effectively solve the problem of water pollution. Comprehensive prevention and control of water pollution must be carried out from the whole region or water system, and the tail control of point source control should be transferred to the source control in order to control water pollution fundamentally.
The basic principle of sewage prevention and control is the combination of prevention, treatment and management.
Through effective control and preventive measures, the amount of pollutants discharged by pollution sources can be reduced to the minimum.
(1) For industrial pollution sources, the most effective control method is to promote cleaner production. Cleaner production refers to the advanced production technology with the smallest utilization of resources and energy and the least pollution emission. The main technical routes adopted in cleaner production include: reforming raw material selection and product design, replacing toxic and harmful raw materials and products with non-toxic and harmless raw materials and products; reforming production process to reduce consumption of raw materials, water and energy; adopting recycling water system to reduce wastewater discharge; and recycling the usefulness of wastewater. Composition, reduce the concentration of wastewater, etc. Cleaner production advocates life cycle analysis and management of products rather than end-treatment.
(2) For domestic pollution sources, effective measures can be taken to reduce their emissions. Such as promoting the use of water-saving appliances, improving people’s awareness of water-saving, reducing water consumption, thereby reducing domestic sewage discharge.
(3) For agricultural pollution sources, in order to effectively control non-point pollution sources, we must start from “prevention”. Promoting scientific fertilization and rational use of pesticides in farmland can greatly reduce the residual fertilizers and pesticides in farmland, thereby reducing the amount of nitrogen, phosphorus and pesticides contained in farmland runoff.
Through various measures to control pollution sources and polluted water bodies, the pollution sources can achieve “standard discharge” and the water environment can achieve the corresponding water quality function.
It is very difficult or almost impossible for pollution sources to achieve zero discharge. Therefore, it is necessary to properly treat polluted (waste) water to ensure that the discharge standards set by the state or local authorities are met before it is discharged into the water body. Great attention should be paid to the relationship between industrial wastewater treatment and municipal wastewater treatment. For industrial wastewater containing acid, alkali, toxic and harmful substances, heavy metals or other special pollutants, local treatment should be carried out in the plant to meet the discharge standards to the water body or the water quality standards to the urban sewer. Those industrial wastewater similar in nature to municipal domestic sewage can be treated together with municipal sewage as a priority. It is not only unnecessary but also uneconomical to set up sewage treatment facilities separately. The design of urban sewage collection system and treatment plant should not only consider the need of water pollution prevention, but also the need to alleviate the contradiction of water resources. In areas where water resources are scarce, the treated municipal wastewater can be reused for agriculture, industry or municipal administration and become stable water resources. In order to meet the needs of wastewater reuse, its collection system and treatment plant should not be too centralized, but should be close to the reuse target.
In addition, according to the characteristics of water pollution, we should actively take physical, chemical, biological engineering and other means to control pollution, so that the deteriorated aquatic ecosystem can be gradually restored.
Strengthen the supervision and management of pollution sources, water bodies and water treatment facilities in order to promote treatment. Pipe also plays an important role in water pollution control. Scientific management includes regular monitoring and inspection of pollution sources, water treatment facilities and sewage treatment plants, and regular monitoring of water environmental quality to provide basis and information for environmental management.
Functional zoning of water environment is the basis for comprehensive prevention and control of water pollution
According to the current functions of water environment and the needs of economic and social development, the functional zoning of water environment is based on surface water environmental quality standards, which is the basis of water source protection and water pollution control. For example, the surface water environmental quality standard divides the water area control functions into five categories: Class I is mainly applicable to source water and national nature reserves; Class II is mainly applicable to primary protection areas of centralized drinking water sources, precious fish protection areas, fish and shrimp spawning grounds; Class III is mainly applicable to centralized drinking water sources II. Class IV is mainly suitable for general industrial water use and recreational water areas where human body does not contact directly; Class V is mainly suitable for agricultural water use areas and waters where general landscape requires.
Principles and methods
The principles of division are as follows: priority protection of centralized drinking water source areas; water body should not reduce its current use function, taking into account planning function; water areas with multiple functions should be classified according to the highest function; professional water standard requirements should be considered as a whole; consideration should be given to each other between upstream and downstream areas, with due consideration to potential functional requirements; and rational use of water body itself. Net capacity and environmental capacity; Consider the combination of land industrial rational layout; Consider the impact on underground drinking water sources; Practical and feasible, easy to manage.
Functional zoning method: according to the principle of adapting measures to local conditions and seeking truth from facts, according to actual measurement, empirical analysis and administrative decision-making.
Controlling pollution and protecting water sources according to functional areas.
(i) The level of protection shall be defined according to the functions of the waters and the requirements for water pollution control shall be put forward. For example, special protected waters refer to the first and second categories of national Surface Water Environmental Quality Standards (GB3838-2002). No new sewage outlets shall be built for such waters. Existing sewage discharge units shall be strictly controlled by local environmental departments in order to ensure that the water quality of accepted waters meets the water quality standards for specified purposes; and key protected waters shall be protected. It refers to the third class waters stipulated by GB3838-2002, and the first class discharge standards stipulated in the Comprehensive Sewage Discharge Standard (GB8978-1996) are applied to the sewage discharged into the waters.
(ii) The total amount control shall be implemented according to the functional areas. The so-called total amount control refers to the maximum allowable emission of some kind of pollution in order to maintain the environmental target value of an environmental functional area. Therefore, water environmental functional zoning is the basis for implementing total water pollution control.
Formulating comprehensive prevention and control plan of water pollution
Main contents and working steps
(i) Based on the investigation and evaluation of water environment, the main problems of water environment are analyzed and determined.
(ii) Division of water pollution control units. According to the analysis conclusion of water environment problems, considering the administrative division, water area characteristics and pollution source distribution characteristics, the source area and receiving water area are divided into water pollution control units.
(iii) Put forward environmental objectives and demonstrate accessibility. At the Fourth Session of the National People’s Congress, the strategic goal of environmental protection across the century was clearly put forward, which is the basis for the goal of comprehensive prevention and control of water pollution. Environmental objectives should include the total amount control objectives of major pollutants and the specific objectives of various sub-items of comprehensive water environment improvement. It is necessary to demonstrate the accessibility of environmental objectives.
(iv) Determine the amount of major pollutant reduction and the proportion of reduction allocation.
(v) To formulate a comprehensive water pollution prevention and control plan and implementation plan.
(vi) Support and guarantee for the implementation of the plan. Including: analysis of sources of funds, formulation of annual plans, implementation of pollutant discharge declaration and registration and pollutant discharge permit system proposals, as well as the necessary technical support.
Several principles that must be adhered to in formulating comprehensive water pollution prevention and control plan
(i) Focusing on economic construction is conducive to the coordinated development of economy and environment.
(ii) Take rational development and utilization of water resources as the core, focusing on the whole process control. By changing the mode of economic growth and promoting cleaner production, pollution can be eliminated in the process of economic reproduction.
(iii) Overall planning, highlighting key points, adapting measures to local conditions and stressing practical results.
(iv) adhering to the principle of comprehensive improvement. Systematic analysis of the planning scheme is needed to achieve overall optimization.
Emission permit system, transition from concentration control to total quantity control
Practice has proved that in carrying out this system, we must follow the following five requirements in the light of China’s current technological level and management system.
(1) Determine the total amount control target from the actual point of view. When it is difficult to determine the environmental capacity of the receiving water body for discharging pollutants, according to the principle of the total amount control plan put forward by the State Environmental Protection Administration in December 1995, the total amount of discharged major water pollutants in 1995 can be regarded as the target total amount, and the proportion of reduction can be determined according to the actual technical and economic level of the region, and allocated to the main body. Pollution sources.
(2) Choose the target of issuing certificates. The main target of issuing permits is the large polluters in the region. A city can catch more than a dozen or dozens of households. It is necessary to select the key control points through investigation and evaluation of pollution sources. For example, Anyang City put forward that we should do a good job of 2, 5 and 8, and control 8 and 9, that is, we should catch 20, 50 and 80 large polluters in batches, and control 70%, 80% and 90% of the city’s water pollution load.
- Control the total amount of sewage. Measure according to local conditions and control the total amount of sewage.
- Strengthen environmental supervision and management after issuance of certificates.
- Pay attention to practical experience and constantly improve the level. In order to implement the sewage discharge permit system, we should first carry out pilot projects, sum up experience and gradually popularize it.
- But we should also pay attention to the new problems in the process of implementation, such as the paid transfer of pollutant discharge indicators and the trading of pollutant discharge rights.
- Comprehensive Prevention and Control of Water Pollution in Township Enterprises
- The discharge of industrial wastewater from township enterprises was only 3.9 billion tons in 1997.
Housing provident fund refers to the long-term housing savings deposited by state organs and institutions, state-owned enterprises, urban collective enterprises, foreign-invested enterprises, private enterprises in cities and towns, other urban enterprises and institutions, private non-enterprise units, social organizations and their working staff on an equal basis.
In 2011, the Ministry of Housing and Urban-Rural Construction is jointly working with various departments to study and revise the Regulations on the Management of Housing Provident Fund, and to liberalize the provisions on individual withdrawal of provident fund for housing rent payment. In 2013, some cities introduced measures to allow workers suffering from major diseases or their immediate relatives to withdraw provident fund for emergency relief.
In 2014, the three departments issued a document to cancel the housing provident fund personal housing loan insurance, notarization, new housing evaluation and compulsory institutional guarantee and other fee items, so as to alleviate the burden of loan workers.
In 2015, the Regulations on the Management of Housing Provident Fund (revised draft for examination) intends to stipulate that the deposit ratio of workers and units of housing provident fund shall not be less than 5% or more than 12%. From February 21, 2016, the interest rate of employees’housing provident fund account deposits has been adjusted to the benchmark interest rate of one-year fixed deposits. The interest rate after the increase is 1.50%.
From July 1, 2017, all the national housing provident fund management centers will handle the transfer and continuation of housing provident fund in different places through the platform according to the requirements of the “Operation Rules for the Transfer and Continuation of National Housing Provident Fund in different places” issued by the Ministry of Housing and Construction. All national housing provident fund management centers will “network” through a unified platform for the transfer of housing provident fund business in different places. According to incomplete statistics, more than 20 cities, such as Beijing, Shanghai, Fuzhou and Guangzhou, have access to the transfer platform of the National Housing Provident Fund. On May 15, 2018, the Beijing Housing Provident Fund Management Center issued the Notice on the Cancellation of Copies of Identity Certificates as Requirements for the Collection of Housing Provident Fund and the Processing of Loan Business.
Housing accumulation fund refers to the long-term housing reserve deposited by state organs, state-owned enterprises, urban collective enterprises, foreign-invested enterprises, private enterprises in cities and towns and other urban enterprises, institutions, private non-enterprise units, social organizations and their employees.
The definition of housing provident fund includes the following five aspects:
(1) Housing provident fund is only established in cities and towns, but not in rural areas.
(2) Only on-the-job workers can establish the housing provident fund system. Urban residents without jobs and retired workers do not implement the housing accumulation fund system.
(3) Housing provident fund consists of two parts, one part is deposited by the unit where the staff and workers work, the other part is deposited by the individual staff and workers. The personal deposit of employees shall be withheld by the unit and deposited into the individual account of housing accumulation fund together with the deposit of the unit.
(4) The long-term nature of housing provident fund deposit. Once the housing provident fund system has been established, the staff and workers must pay in accordance with the regulations uninterruptedly during their working period. Except for the retirement of the staff and workers or other circumstances stipulated in the Regulations on the Administration of the Housing Provident Fund, they may not suspend or interrupt it. It embodies the stability, unity, standardization and mandatory of housing provident fund.
(5) Housing provident fund is the personal housing reserve fund which is specially used for housing consumption expenditure stored by workers according to regulations. It has two characteristics:
First, the accumulation, that is, housing provident fund is not an integral part of workers’wages, not in the form of cash, and must be deposited in the housing provident fund management center in the entrusted bank to open a special account management.
Second, the special purpose of housing provident fund, the storage period can only be used for purchasing, building, overhauling self-housing, or paying rent. Employees can withdraw the housing provident fund in their accounts only when they retire, die, lose their working ability completely and terminate their labor relations with the unit or move out of their original residence city.
According to China’s regulations, enterprises should deposit housing provident fund for employees, regardless of state-owned enterprises and private enterprises.
The part of housing provident fund paid by enterprises and institutions does not belong to the attributes of total wages, but belongs to the expenditure of the nature of enterprise cost and expense. According to the Notice of the State Administration of Taxation on Deduction of Enterprise Wages and Salaries and Workers’Welfare Expenses (State Tax Letter 3), the term “total salaries and salaries” referred to in Articles 40, 41 and 42 of the Implementation Regulations of the Enterprise Income Tax Law of the People’s Republic of China refers to enterprises in accordance with document No. 3 of the State Tax Letter  Article 1 stipulates the total wages and salaries actually paid, excluding the social insurance premiums and housing provident fund such as the employee welfare premiums, the employee education funds, the trade union funds, the old-age insurance premiums, medical insurance premiums, unemployment insurance premiums, industrial injury insurance premiums and maternity insurance premiums borne by enterprises.
(1) Guarantee, the establishment of the staff housing accumulation fund system, for the staff to solve housing problems faster and better provide security;
(2) Mutual assistance, the establishment of housing provident fund system can effectively establish and form a mechanism and channels for housing workers to help workers without housing, and housing provident fund in terms of funds to help workers without housing, reflecting the mutual assistance of housing provident fund for workers;
(3) For a long period of time, every working worker in a town must pay the individual housing accumulation fund from the date of taking part in the work to the time of retirement or termination of labor relations; the unit where the worker works should also pay the housing accumulation fund for the worker’s subsidy according to the regulations.
(1) Generality, urban employees, regardless of the nature of their work units, family income and whether they have housing, must deposit housing accumulation fund in accordance with the provisions of the Regulations;
(2) Compulsory (policy nature). If a unit fails to register the deposit of the housing accumulation fund or to set up an account of the housing accumulation fund for its employees, the management center of the housing accumulation fund has the power to order it to do so within a time limit. If it fails to do so within the time limit, it may be punished in accordance with the relevant provisions of the Regulations and may apply to the people’s court. Enforcement;
(3) Welfare, apart from the housing provident fund deposited by employees, units should also pay a certain amount of money for employees, and the interest rate of housing provident fund loans is lower than that of commercial loans;
(4) Returnability, the retirement of employees, or the complete loss of labor capacity and termination of labor relations with the unit, the removal of household registration or outbound settlement, etc., the housing provident fund deposited will be returned to the individual employees.
It refers to the state in which personal casualties or property losses can be controlled at an acceptable level in the course of traffic activities. Traffic safety means that the possibility of loss to people or things is acceptable; if this possibility exceeds the acceptable level, it is unsafe. As a dynamic open system, the safety of road traffic system is not only restricted by internal factors of the system, but also disturbed by external environment of the system. It is closely related to human, vehicle and road environment. Any unreliable, unbalanced and unstable factors in the system may lead to conflicts and contradictions, resulting in unsafe factors or unsafe states.
(1) Traffic safety is a state under certain dangerous conditions, and it is not absolutely free from traffic accidents.
(2) Traffic safety is not an instantaneous result, but a description of the process or state of the traffic system in a certain period or stage.
(3) Traffic safety is relative and absolute traffic safety does not exist.
(4) For different periods and regions, the acceptable level of loss is different, so the criteria for measuring the safety of the transportation system are different.
Raising the level of road traffic safety is a matter of great benefit to the country and the people. Many experts and scholars have carried out extensive and in-depth research in this area. Traffic accident prevention is one of the main tasks of traffic safety and an important part of traffic engineering research. From the point of view of traffic engineering, it is considered that the prevention of traffic accidents should start from three aspects: laws and regulations, education and engineering, and from the point of view of people, vehicles, roads and environment, which constitute the four elements of road traffic, it is also considered that the prevention of traffic accidents should start from these four elements.
Improving Transportation Legal System
Strengthening the construction of road traffic safety laws and regulations system is a direct and effective measure to improve the overall level of road traffic safety. At present, the content of our country’s road traffic safety regulation system has been covered in a number of different laws, regulations and other traffic management normative documents, and it plays an active and important role in our country’s road traffic operation practice. With the development of the times, the legal system should be amended and adjusted accordingly.
Strengthen Traffic Safety Education
(1) Carry out traffic safety propaganda
Traffic safety propaganda is an important way to publicize and educate the masses. In carrying out propaganda activities, we should attach importance to achieving practical results and link traffic safety with everyone’s vital interests so as to arouse people’s attention to traffic safety. We should adopt propaganda forms popular with the masses, incorporate them in people’s daily work and life, and in cultural entertainment. At the same time, propaganda activities must mobilize the strength of society to the greatest extent possible, and strive for the depth and breadth of propaganda to ensure the quality of propaganda.
(2) Strengthen traffic safety education
Traffic safety education, like other cultural knowledge, should be carried out systematically from the early childhood. Before high school, every stage of education was listed as a compulsory course, which enabled students to establish the concept of traffic legal system, traffic safety, traffic ethics and safety prevailing concepts from the beginning of education. To educate the society, we should adopt different ways and methods according to different objects, and carry out targeted education.
Improve vehicle safety performance and maintain good vehicle condition
To improve the safety performance of vehicles, we should take active safety measures and passive safety measures.
(1) Active safety measures
1) Improve side and front vision, install reversing lights and alarms to prevent traffic accidents caused by blind areas.
2) Improve the perspective performance of windowpanes to prevent traffic accidents caused by rain, snow and frost.
3) Take anti-glare measures to improve the illumination of headlamp in order to prevent traffic accidents caused by glare and insufficient illumination of headlamp.
4) In terms of power performance, the overtaking acceleration capability should be improved and the drive anti-skid system (TCS) should be installed.
5) In the aspect of stability, we should improve the stability and portability of operation, such as installing electronic stabilization program (ESP).
6) In braking aspect, the auxiliary braking system, ABS anti-lock braking system, retarder and braking system fault alarm system are installed to improve the anti-skid performance of tires, so as to ensure safety.
7) In terms of accident prevention measures, we should also improve the recognition performance of vehicles, including rear, signs and driving directions, in order to prevent accidents.
8) Active anti-collision warning system is adopted. When the vehicle encounters danger, the driver can be reminded in time. If the driver fails to take measures in time because of his errors, the system can automatically take measures to avoid danger (such as deceleration, bypass, etc.).
(2) Passive safety measures
1) In-car measures
In-car measures mainly include increasing occupant space as much as possible, i.e. the strength of the car body, in order to reduce the deformation of the collision, using toughened glass or partition glass to reduce the injury of the occupant caused by the accident, enlarging the area of the steering wheel to make it elastic, and making the switches, knobs and handles inside the car as round as possible. Sliding and soft; door and roof have enough strength to protect the safety of passengers and facilitate rescue. In addition, fire prevention performance, safety belt and airbag play an important role in occupant safety protection.
2) Outside measures
Extravehicular measures mainly refer to minimizing injuries when crashing bicycles and pedestrians, such as bumpers should be as smooth and flexible as possible, movable rearview mirrors and fenders, and protective nets connected with trailers, etc., which will have certain effects on the protection of the weak traffic.
Strengthen the Construction of Road and Traffic Safety Facilities
(1) Improving road conditions
Considering from the aspect of road alignment design, we should strictly follow the horizontal and vertical curves of the designed road to make the curves and ramps conform to the technical standards of highway engineering. The safety of various alignment combinations should be fully considered.
(2) Improving road safety facilities
Road safety facilities mainly include partition belts, safety fences, traffic signs, markings, sight guidance facilities and anti-glare facilities. For urban traffic, pedestrian overpasses, underground passages, traffic safety islands, etc.
(3) Implementing traffic control
Traffic control can be divided into traffic signal control and traffic regulation control. Traffic signal control refers to the establishment of traffic lights at road entrances and intersections to reasonably control the driving of vehicles. Traffic regulation control includes setting up one-way traffic section, turning lane, bus lane, etc.
(4) Establishment of Traffic Information System
Traffic information is also known as traffic information. In order to ensure the safety and rapidity of vehicles traveling on automobile lanes or urban trunk roads, public security and management departments should report traffic congestion, weather, road ahead or temporary traffic control to drivers in time so that drivers can change their countermeasures in time.
(5) Establishing Emergency Rescue System for Accidents
The monitoring and forecasting system estimates possible accident areas according to abnormal weather conditions, adopts information collection and liaison system, and assigns special personnel to monitor and make preparations. When an accident occurs, advanced communication equipment and means should be used to quickly and reliably contact the relevant departments to deal with the accident in a timely and effective manner so as to ensure road safety and smoothness.
(6) Improving the Road Traffic Environment
The improvement of road traffic environment mainly includes two aspects: on the one hand, improving road environment, making drivers have good driving sight distance and constantly changing visual effect, improving the monotonous environment which makes drivers tired and irritable; on the other hand, improving traffic flow environment, keeping good density as far as possible, and avoiding as possible. No mixed traffic flow.
Not every gas in the atmosphere absorbs intensely long-wave radiation from the ground. The greenhouse gases in the earth’s atmosphere are called greenhouse gases, mainly carbon dioxide (CO2), methane, ozone, nitrous oxide, freon and water vapor. They absorb almost all the long-wave radiation emitted from the ground, and only a very narrow region absorbs very little, so they are called “window region”. It is through this window that the earth returns 70% of the heat from the sun to the space in the form of long-wave radiation, thus maintaining the ground temperature unchanged. The greenhouse effect is mainly due to the increase in the number and variety of greenhouse gases by human activities, which makes the 70% value decrease and the remaining heat makes the earth warm.
What is greenhouse gas?
However, although CO2 and other greenhouse gases have a strong ability to absorb long-wave radiation from the ground, their amount in the atmosphere is very small. If the atmospheric state of pressure as a atmospheric pressure and temperature of 0 C is called the standard state, then the whole atmosphere of the earth is compressed to this standard state, its thickness is 8000 meters. At present, the content of CO 2 in the atmosphere is 355 ppm, or 355 parts per million. Converting it to the standard state, it will be 2.8 meters thick. This is 2.8 meters thick in the atmosphere of 8,000 meters thick. Methane content is 1.7 ppm, corresponding to 1.4 cm thick. The ozone concentration is 400 ppb (ppb is one thousandth of ppm), which is only 3 mm thick after conversion. Nitrous oxide is 310 ppb, 2.5 mm thick. There are many kinds of freon, but the most abundant Freon 12 in the atmosphere is only 400 ppt (ppt is one thousandth of ppb), converted to the standard state of only 3 microns. This shows that there are few greenhouse gases in the atmosphere. It is also for this reason that human release without restrictions can easily lead to rapid global warming.
History of development
As early as 1938, British meteorologist Carlinda pointed out that CO2 concentration had risen by 6% since the beginning of the century after analyzing sporadic CO2 observations around the world at the end of the 19th century. He also found that there was a warming tendency in the world from the end of last century to the middle of this century, which caused great repercussions in the world. To this end, Kellin of Scripps Oceanographic Research Institute established an observatory in 1958 at an altitude of 3,400 meters in the Maunaroya Mountains of Hawaii, and began the precise observation of atmospheric CO2 content. Because Hawaii is located in the middle of the North Pacific Ocean. Therefore, it can be considered that it is not affected by terrestrial air pollution and the observation results are reliable.
From April 1958 to June 1991, the atmospheric CO2 concentration in the Maunaroya Mountains was observed. It was found that the atmospheric CO2 content in 1958 was only about 315 ppm, which reached 355 ppm in 1991. The seriousness of the problem also lies in the fact that only about half of the 5.5 billion tons of fossil fuels (about 4 tons of CO2 per ton) that humans burn annually (1996) enter the atmosphere and the rest are mainly absorbed by marine and terrestrial plants. Once the ocean is saturated with CO2, the atmospheric CO2 content will increase exponentially. In addition, they also found seasonal variations in CO2 content, with a difference of 6 ppm between winter and summer. This is mainly due to the winter drought and summer glory of vegetation on the vast continents of the Northern Hemisphere, that is, plants absorb CO2 in summer, which makes the atmospheric CO2 concentration relatively lower.
According to the determination of CO2 concentration in the air of sealed bubbles in the Antarctic and Greenland continental ice sheets, the CO2 content in the atmosphere has been relatively stable for a long time in the past, about 280 ppm. Only from the mid-18th century, before and after the Industrial Revolution began to rise steadily. That is to say, it took 240 years for human beings to increase the atmospheric CO2 concentration from 280 ppm to 355 ppm.
Methane is the second most important greenhouse gas after CO2. Although its concentration in the atmosphere is much lower than CO2, its growth rate is much higher. According to the Second Climate Change Assessment Report issued by the Intergovernmental Panel on Climate Change (IPCC) in 1996, CO2 increased by 30% in 240 years from 1750 to 1990, while methane increased by 145% in the same period. Methane, also known as biogas, is produced when organic matter decays under anoxic conditions. For example, paddy fields, compost and animal manure all produce biogas. Nitrogen monoxide is also known as laughing gas, because inhaling a certain concentration of this gas can cause facial muscle spasm, which looks like laughing. It is mainly produced by burning fossil fuels and organisms using chemical fertilizers. Although the ozone content in the atmosphere decreases in the stratosphere, it increases in the troposphere, which will be discussed later. Freon gases are compounds of chlorine, fluorine and carbon; they do not exist in nature and are entirely human-made. Because of its low melting point and boiling point, non-flammable, non-explosive, odorless, harmless and excellent stability, it is widely used in the manufacture of refrigerants, foaming agents and cleaners. Although the highest concentrations of Freon 12 and 11 in the earth’s atmosphere are very few, their growth rates have been very high in the past, both of which are 5% per year. Because of its severe destruction of the ozone layer in the atmosphere, its concentration in the atmosphere is expected to decrease gradually from the beginning of the 21st century according to the 1987 International Montreal Protocol.
It should be noted that although the atmospheric concentration of greenhouse gases other than CO2 is much lower than that of CO2, some of them are several orders of magnitude smaller, their greenhouse effect is much stronger than that of CO2. Therefore, their contribution to atmospheric greenhouse effect, according to the second IPCC Report, is only one order of magnitude lower than that of CO2. If their total contribution to the greenhouse effect of the Earth’s atmosphere is small compared with CO2 before 1960, it is not negligible that in the near future they will go hand in hand with CO2 and even exceed CO2.
April 2, 2018, DOE Labor
Biotechnology is a well-known term. The National Science and Technology Commission defines biotechnology as “biotechnology contains a series of technologies that can produce the products we need from organisms or cells, including gene recombination, cell fusion and some biological manufacturing processes.”
In fact, human beings have a long history of using organisms or cells to produce the products we need, such as tillage 10,000 years ago, animal husbandry to provide a stable source of food, fermentation technology to brew wine and make bread 6,000 years ago, fungus to treat wounds 2,000 years ago, and use in 1797. Smallpox vaccine, the discovery of antibiotic penicillin in 1928, etc.
Since human beings have been using biotechnology for so long, why has biotechnology suddenly attracted widespread attention since 1990? This is because since the 1950s, the scientific community has had a better understanding of the cells that constitute the smallest unit of organisms and the genes that control the genetic characteristics of cells, as well as the development of gene recombination and cell fusion techniques in the 1970s. Since these two technologies can enable cells or organisms to produce the substances we need more effectively, and contribute to industrial or agricultural production, a new biotechnology industry has been created since the 1980s.
Bill Gates said in 1996 that “biotechnology will change the world like computer software”. Modern biotechnology industry has been developing since 1980, and its applications include pharmaceuticals, agriculture, environmental protection, food processing, special chemicals and other industries. In the field of biomedical pharmaceuticals, 155 biotechnology drugs or vaccines have been approved by the Food and Drug Administration of the United States and used to treat diabetes, heart disease, cancer, AIDS and other diseases. In agriculture, genetic recombinant plants such as papaya, tomato, maize and soybean have been listed. These plants are characterized by strong resistance to pests and diseases, and can reduce the use of chemical pesticides.
The progress of human civilization is from the collecting society of early fishery hunting life to the agricultural society dominated by farming and animal husbandry, and then to the modern industrial society. Because of the increasing population and the over-exploitation of industrial land, the area of agricultural cultivated land has been reduced. In addition, the generation of greenhouse effect has also accelerated the extinction of species other than human beings, making the food problem become a very important core issue in the 21st century. With limited resources and unlimited human growth, some people have come up with the idea that if food could be increased by high technology, there would not be a day when food would be eaten up. Therefore, with the vigorous development of biotechnology, many things that could not be done before can be done today in the 21st century. Many impossible tasks can be accomplished through biotechnology, such as the use of smears or patches to influence body fat to achieve beauty and weight loss, or the use of Botox is an example of biotechnology.
Since human beings, people have tried to transform organisms. Traditionally, breeding and mating were used to acquire desired biological traits (such as sweet and tasty corn) and to reduce or eliminate undesirable traits (such as natural toxicity). On the other hand, food is a necessity for human growth, and the population has increased rapidly recently. In view of the shortage of food, so-called “artificial food” has begun to emerge. However, the biggest limitation of traditional breeding is that the mating varieties must be the same or similar. In order to break through this limitation, modern genetic engineering technology should be used scientifically to select the genes with some excellent characteristics of organisms accurately and transfer them to another species so that the new genetically modified organisms have the expected specific characteristics.
Data from the Food and Drug Administration (FDA) show that in 1991, Calgene applied for genetically modified tomatoes to transfer antisense polygalacturonase (PG) gene into tomatoes, delaying the maturation and softening of tomatoes. In 1994, the company’s “Flavor” (FLAVR SAVR) tomato was the world’s first approved genetically modified food. The PG gene that promotes the ripening of soft enzymes in delicious tomatoes is inhibited, so its texture is more solid, and it can reduce the damage and deterioration during harvesting, transportation and processing, thus preserving the flavor. At present, however, commercial production of tomatoes has ceased. In 1994, there were 29 applications, including soybeans, tomatoes, corn, potatoes, cotton and melons. Monsanto is one of the big companies.
In addition, in environmental protection, some toxic industrial wastes and contaminated crude oil have been decomposed by recombinant microorganisms. In food, fermentation engineering technology has been used to produce healthy foods such as lactic acid bacteria, Ganoderma lucidum and Cordyceps sinensis. In special chemicals, recombinant enzymes have been used to produce drugs or fibers. Or use it in detergents to decompose dirt. By 2001, there were about 1500 biotechnology companies worldwide, with an annual output value of $30 billion.
The technology of gene recombination and cell fusion is the cornerstone of modern biotechnology. In recent years, many new technologies and new applications have been developed on this basis. For example, protein engineering technology can be used to improve the structure and activity of proteins, and Bionanotechnology can be used to manufacture biosensors, biochips and drugs. Transport systems, tissue engineering technology can use stem cells to repair damaged organs, and animal replication technology can use nuclear transfer to replicate animals, etc.
The development of biotechnology aims at curing diseases, improving the quality of life, providing food that is not scarce and protecting our living environment. However, if not strictly monitored during the development of biotechnology, it may cause harm to human beings or the ecosystem of the earth. Attention should also be paid to its impact on humanity, morality or ecology.
As the application of biotechnology is very extensive and closely related to our daily life, there are often related reports in general newspapers and magazines or news media, so understanding new knowledge of biotechnology should be included in our regular study.
The task of biotechnology is to explore the mystery of life and master the law of life movement.
- Genetically modified products
- Genetically modified food
- brief introduction
The application of science and technology brings convenience, but also brings unknown fears. When the technology of gene recombination is widely used in the development of biology, medicine, agriculture and industry, and may even enter more fields in the future, which deeply affects our lives, we seem to realize that this is an irresistible trend. Therefore, it is more correct to have a positive understanding of genetically modified foods, to think rationally about acceptability, and to leave the right of choice to everyone.
The so-called “genetic modification” refers to the selection of specific genes for individual traits of organisms and the alteration of their genome composition and expression. Scientists use different biotechnologies, such as restriction enzymes, to make target gene fragments, then connect DNA fragments to “vector” DNA molecules, and then transfer vectors to target chromosomes. This process is a kind of genetic engineering.
Different from the traditional breeding method, the transfer of traits is limited to individuals of the same species or similar provenances. Modern genetic engineering technology has broken through the traditional pattern of breeding. It can insert foreign genes from different provenances into plants in a “man-made” way. In addition, genes can even be derived from microorganisms or animals. Body. For example, insecticidal crystalline toxin gene (cry-gene) from Bacillus thuringiensis was implanted into maize, which can also synthesize insecticidal toxin protein produced by cry gene. Therefore, it has insect-resistant characteristics. This maize with cry gene implanted artificially can be called a GMO.
GMO (genetically modified organism) can generally be divided into three categories, namely:
Genetically modified microorganisms (and their products): including microorganisms that can be used as fermented food or as food additives such as enzymes, aminoacids, organic acids, vitamins, pigments and spices.
Genetically modified crops (and their processed products): This is the fastest growing area in GMOs. Transgenic crops such as soybeans, maize, tomatoes and potatoes have been introduced.
Transgenic animals (and their processed products): Salmon transfected with growth hormone gene, but most of them are at the research stage.
Genetically modified foods (GMF = GM foods), also known as genetically modified foods, are processed by GMO. Therefore, all foods derived from genetic recombination technology are called genetically modified foods. How does genetically modified food come into being?
Generally speaking, there are two main ways to implant functional foreign genes into plants. For dicotyledons such as soybeans, tomatoes and cotton, gene transfer is usually achieved by Agrobacterium tumefaciens. Agrobacterium crown can naturally (i.e. without any artificial treatment) infect a wide variety of plants by inserting a segment of its own DNA directly into the DNA of infected plants, so long as the oncogene in Agrobacterium crown DNA is removed, and the foreign gene to be inserted into the stem of Agrobacterium crown. Bacteria infect plants so that additional genes can be transferred to the DNA of infected dicotyledons. Cells containing additional genes in infected plants can be further screened out, and cell culture techniques can be used to produce complete plants containing additional genes. As far as monocotyledons (e.g. maize, wheat and rice) are concerned, Agrobacterium crown is not very effective in infecting them. Generally, the foreign genes to be implanted are coated on tungsten balls, and then the tungsten balls coated with foreign genes are physically introduced into plant cells, some of which have foreign bases. As part of plant DNA, these plant cells containing foreign genes can be screened out and cultured into complete beads because they fall off from the surface of tungsten particles. In addition to Agrobacterium coronatum, plant viruses are often used as vectors, but not all plant viruses have the function of vectors unless the virus can be dispersed between cells via plasmodesmata, and foreign genes must be replicated and the modified viral nucleic acid can infect plant cells. It does not cause symptoms, and the virus must be widely parasitic. Generally speaking, DNA is the main target of gene transfer. RNA-containing viruses are considered only when viruses using DNA are not effective. It is preferable for plant viruses to contain DNA rather than RNA as vectors. However, only caulimo virus and Gemini virus are known to contain DNA, among which caulimo virus and Gemini virus are used. The latter is widely favored by researchers because it can infect dicotyledons and monocotyledons and has a wide range of hosts.
Controversy over genetically modified foods
In recent years, biotechnology has been gradually applied to food production, so the derivatives of genetically modified foods have also been listed on the market. There are still many controversies about the impact of genetically modified food on human body, which requires long-term and extensive research. In order to understand the public’s knowledge and attitude towards genetically modified foods, the Department commissioned a survey on “the public’s knowledge and attitude towards biotechnology and genetically modified foods” by private companies. It is hoped to understand the public’s attitude towards genetically modified foods and their views on labeling policies, which will serve as a reference for future government to formulate relevant laws and regulations. According to.
Threats to the environment include:
(1) threats to non-target organisms and beneficial insects;
(2) reduction of biodiversity;
(3) gene drift and genetic pollution.
The main economic impacts are as follows:
Loss in the market
Although the crop itself will not move, food made from it can be sold everywhere, which also arouses many people’s concerns about genetically modified crops. In 2000, Nature magazine reported that Star Link Corn, an unauthorized genetically modified maize for human consumption, had flowed into Japan’s food distribution network. Star corn is not allowed to be eaten by humans in Japan, although it can be used as feed in the United States, mainly because it contains an insecticidal toxin called Cry9C, which is thought by scientists to cause allergic reactions after being eaten. In the past, about one third of the maize exported by the United States was exported to Japan, while the European Union purchased about 40% of the soybean exported by the United States. Consumers in these areas have doubts about the food safety of genetically modified maize or soybean, which will pose a great threat to future exports of the United States.
For farmers growing organic crops, if they are cross-pollinated or mixed with genetically modified crops, they will suffer serious marketing problems due to poor quality, especially maize and sugar beet, which are cross-pollination plants. In this way, farmers who produce organic agricultural products will have to temporarily withdraw from the organic product market, and their income will drop sharply before they get organic certification again.
Bio Engine Composting Part 2
Classification by type of fermentation plant
According to the type of fermentation device, there are vertical composting fermentation tower, horizontal composting fermentation drum, silo composting fermentation tank and box composting fermentation tank.
1 vertical compost fermentation tower
Vertical composting fermentation tower usually consists of 5-8 layers. The composting material enters the tower from the top of the tower. In the tower, composting moves from the top of the tower to the bottom of the tower through different forms of mechanical movement. Generally, after 5 to 8 days of aerobic fermentation, the compost is moved from the top of the tower to the bottom of the tower to complete a fermentation. Vertical composting fermentation tower usually has a closed structure. The temperature distribution in the tower gradually increases from the upper layer to the lower layer, that is, the lowest layer has the highest temperature. In order to ensure the activity of microorganisms in each layer for high-speed composting and maintain the optimum temperature and ventilation volume of microorganisms in each layer of the tower respectively, the oxygen supply of the tower device is usually forced ventilated by a fan, and the air is quantitatively ventilated into the tower through the vents of different heights installed on the side of the tower body to meet the micro-generation. The demand for oxygen.
Vertical composting fermentation tower usually includes vertical multi-stage cylinder type, vertical multi-stage landing gate type, vertical multi-stage blade scraper type, vertical multi-stage movable bed type, etc.
2 horizontal composting fermentation drums
Horizontal composting fermentation drum is also called Danot type. The main equipment is a horizontal drum with a length of 20-35 m and a diameter of 2-3.5 M. In the fermentation device, waste is raised along the rotating direction by friction with the inner surface of the cylinder, and falls down by means of self-weight. By rising and falling repeatedly, the waste is evenly turned over and contacted with the air supplied, and fermented by microorganisms. In addition, because the cylinder is oblique, when the waste lifted along the rotating direction falls by its own weight, it gradually moves to one end of the outlet of the cylinder, so that the rotary kiln can automatically and steadily supply, transport and discharge compost. The processing conditions of the device are summarized as follows:
The ventilated air temperature is normal in principle. For a 24-hour continuous operation device, the ventilation rate is 0.1 m3/(m3.mm), and the rotating speed of stirring in the cylinder should be 0.2-3.0 r/min. If the whole fermentation process is completed in this device, the residence time should be 2-5 days. The filling rate of cylinder is generally as follows: waste volume in cylinder/cylinder capacity is less than capacity. The average temperature of compost in the whole fermentation process is 50-60 when the device is used, and the maximum temperature can reach 70-80 high. When the device is used for one fermentation, the average temperature is 35-45, and the maximum temperature can be about 60 high.
3 silo type compost fermentation silo
Silo-type compost fermentation silo is a single-layer cylindrical (or rectangular) fermentation silo, the depth of fermentation silo is generally 4-5 M. The upper part is provided with a feed inlet and a scraper diversion device, and the lower part is provided with a screw discharger. Most of them are made of reinforced concrete. High-pressure centrifugal fan was used to supply oxygen in fermentation chamber to maintain aerobic fermentation of compost in fermentation chamber. Air generally enters the fermentation bin from the bottom of the silo, and composting material enters from the top of the silo. After 6-12 days of aerobic fermentation, the compost with initial maturity was discharged from the bottom of the silo through the discharger. According to the movement form of compost in fermentation bin, silo fermentation bin can be divided into static and dynamic.
(1) Silo-type static fermentation bin.
The device is a single-layer cylinder with stacking height of 4-5 M. The compost enters the silo through the distributor from the top of the silo. After 10-12 days of aerobic fermentation, the compost is discharged by the screw discharger at the bottom of the silo. Because there is no repetitive cutting device in the warehouse, the raw materials are compacted and lumpy, the ventilation performance is poor, the ventilation resistance is large, the power consumption is large, and the product is difficult to homogenize. However, the device occupies a small area and has a high utilization rate of fermentation bin, which is its advantage. The structure of this device is simple, so it is widely used.
(2) Silo-type dynamic fermentation silo.
The silo-type dynamic fermentation silo is a single-layer cylindrical silo with a stacking height of 1.5-2 M. During the operation of the dynamic fermentation bin, the crushed wastes sorted by the pretreatment process are transferred to the middle of the top of the tank by the feeder, and then uniformly distributed by the feeder to the tank. The screw drill located in the rotating layer stirs the wastes in the tank by revolution and rotation, so as to prevent the formation of grooves, and the shape and arrangement of the screw drills can pass through. Maintain a uniform distribution of air. Waste falls from the top down in the pond by gravity. Rotary cutting screw device with revolution and rotation is installed at the bottom of the pool. Whether the upper rotating layer rotates or not, the product can be discharged from the bottom of the pool. The air required for aerobic fermentation is forced into the bottom of the pond through the air distribution board. In order to maintain the aerobic environment in the pond and promote fermentation, forced ventilation from the bottom of the pond was adopted by blower. By measuring the temperature and gas concentration in each section of the pool, the air quantity supplied to each section can be adjusted and the rotation period of the bridge tower can be controlled to change the overturning frequency. The period of one fermentation is 5-7 days. In the composting process, the helical blades cut off the raw materials repeatedly, and the raw materials are pressed on the helical surface, which is easy to produce compacted lumps, so the ventilation performance is not very good. In addition, it also has some shortcomings, such as uneven residence time of raw materials, uneven product shape and not easy to seal. Its advantage is that the height of the outlet and the residence time of the raw material can be adjusted.
4 Box composting fermentation tank
There are many kinds of box-type composting fermentation ponds and their applications are very common. The main classifications of box-type composting fermentation ponds are as follows:
(1) Rectangular fixed plough-shaped overturned fermentation tank.
The box-type composting fermentation pool is equipped with plough-type upside-down mixing device. The device acts as a mechanical plough to dig waste. It can regularly agitate and move materials several times. It can keep the ventilation in the pool, make the materials evenly disperse, and also has transportation function. It can move materials from the feed end to the discharge end, and the materials stay in the pool for 5-10 days. The air is forced to ventilate through the air distributor at the bottom of the pool. Fermentation tank adopts conveying mixing device, which can increase the height of material accumulation.
(2) Fan bucket overturned fermentation tank.
This kind of fermentation tank is horizontally fixed. It is equipped with a dumper to mix the waste so that the humidity of the waste is uniform and in contact with the air, which promotes the rapid decomposition of compost and prevents the generation of odor. The residence time is 7 to 10 days. The frequency of dumping waste is once a day as the standard. The number of dumping can also be changed depending on the material properties. The fermentation plant has several characteristics in operation: the fermentation tank is equipped with a mixer and an overturning car mounted on the truck conveyor. When the waste is overturned, the overturning car runs on the fermentation tank. When the overturning operation is completed, the overturning car returns to the movable car. According to the handling capacity, sometimes the traveling crane structure can not be installed. Vehicle conveyor; When the material in the pond is overturned, the mixer is lifted by rope traction or mechanical piston tilting device, and when it is overturned again, the mixer can be put down to start mixing; In order to transfer the overturning vehicle from one fermentation pond to another fermentation pond, the track conveyor and crane can be used to scrape out the conveyor and belt conveyor. Feeder or swing conveyor, compost is agitated by mixer, conveyed by vehicle conveyor at the end of fermentation pool, and finally scraped out of the pool by scraper conveyor placed on movable car. Several specific stages of fermentation process are controlled by a compressor, and the required air is blown in from the bottom of fermentation pool.
(3) Crane overturned fermentation tank.
This kind of fermentation tank is usually used for secondary fermentation. The compostable materials which have been crushed and sorted by the pretreatment equipment or which have been fermented once are sent to the fermentation tank by the conveying equipment, and the compostable materials which are fed into the fermentation tank are piled up in the designated box fermentation tank by the shuttle conveying equipment. During accumulation, air is supplied from suction trough, and hopper crane is used to overturn material and perform vaccination operation at the same time.
(4) Horizontal blade fermentation tank
The agitator blade is attached to the mobile device and then moves. Because the mixing device can move horizontally and vertically, the mixing device moves the mixing material repeatedly vertically and transversely at the same time. Because stirring can be used throughout the fermentation tank, the fermentation tank can be designed very wide, so that the fermentation tank has greater processing capacity.
(5) Horizontal scraper fermentation tank.
The main component of the fermentation tank is a flaky scraper driven by gear and rack. The scraper swings from left to right to stir waste, returns from right to left without load, and then swings from left to right to push a certain amount of material. The amount of material pushed by the scraper can be adjusted. For example, when stirring once a day, adjustable push volume is required for a day. If the treatment capacity is large, the fermentation tank can be designed into a multi-stage structure. The pool body is a sealed negative pressure structure, so the odor does not escape. The fermentation tank has many ventilation holes to maintain aerobic condition. In addition, sprinkler and drainage facilities are installed to regulate humidity.
The type of composting equipment used and the corresponding composting process usually depend on the following factors:
- Types of solid waste;
- Establishing natural conditions of composting plant site (distance from residential area, topography, wind direction, etc.);
- Control level of secondary pollutants (leachate, odor gas) in composting process;
Investment and operation cost of plant construction.
Because of the superiority of geographical location, stacking composting can be widely used in rural areas and small towns. However, in some densely populated rural areas, farms, aquaculture farms, urban suburbs and other areas, the composting process with high efficiency for odor gas and leachate treatment should be chosen first.
Trend of development
The Seattle Solid Waste Utilities Bureau first implemented the Masterminer Program in the United States in 1986, marking the beginning of household composting, which mainly uses composting technology to treat yard waste and food waste. In 1995, 41% of Seattle households implemented household composting, diverting about 8 300 tons of yard waste, 82% of which was used for yard greening. There are studies. In the Mississauga area of Ontario, roadside collection, centralized composting and household composting cost $140 t-1, $190 T-1 and $50 t-1, respectively. Moreover, household composting can reduce the amount of household garbage by 3%-5%. Compared with centralized and large-scale composting systems, household composting has significant advantages: low cost and reduction of solid waste sources. In Seattle, there are two types of household composters for food waste: earthworm boxes and conical buckets. In the past, earthworm boxes were commonly used. Now, conical barrels are popular. The height of conical barrels is about 0.9 M. There is a basket with a height of 0.46 M. It can accommodate food waste produced by a family of three within 6 to 9 months. There are two kinds of household composters for yard waste: 0.34 m3 and 0.59 m3. Wood, recycled polyethylene and stainless steel are used to make household composters.
Composting toilets are suitable for places without or without water, such as large-scale composting toilets for parks, highways, stations, etc., and small-scale composting toilets for ships, etc. The commercial composting toilets are divided into self-contained and centralized ones, which can be operated intermittently or continuously, and are made of glass fibre and polyethylene. The self-contained composter is located next to the toilet, while the centralized composter is located next to the basement or building. Intermittent composting toilets contain more than one compartment. When one compartment is full, they are transferred to another compartment. Its advantage is that there is only one compartment in the composting toilet which can run continuously without contamination by fresh manure. Fresh manure and decomposed quasi-manure are mixed together.
Small Capacity Reactor Suitable for Field Operation
Because of the economic, odor control and site reasons, composting systems with large reactors, forced ventilation static stacking and strip stacking are greatly limited. Therefore, a portable, small-capacity reactor composting system suitable for field operation emerges as the times require. For example, Mulch Co. of County, UK, has built two mobile composting systems (30.584-38.23 m3 in volume) similar to rolling containers, with bucket loaders for feeding and cranes for lifting containers when discharging, and materials poured out from the back door of containers. Temperature and oxygen content are controlled by computer. Although this kind of system has only appeared for a few years, it is receiving more and more attention and application from small sewage treatment plants, food industry, catering industry, communities, schools, hospitals, research institutes and business groups. At present, it is mainly used for food waste treatment. The small capacity reactor composting system on the market includes box system, mixing bin and rotary digester, etc. But at present, the most commonly used one is box composting system. The system can be operated intermittently or continuously. It has the advantages of good process control, low investment and operation cost, simple equipment, easy operation and assembly, etc. But its greatest advantage is that it is easy to operate and assemble. Organic waste treatment technology is provided for groups or units that do not have enough space. Currently, 50 and 25 box composting systems are operating in the United States and Canada, respectively. A typical box-type composting system has a treatment scale of 1-40 t/d-1. It consists of several boxes, two of which are used as biofilters. In order to facilitate field operation, the mixing equipment and reactor are connected with the trailer.
In a word, the source of solid waste is more and more dispersed, and the amount of solid waste is also more and more, so the application scope of composting equipment will gradually expand. For different solid wastes, different composting equipments need to be adopted and developed. With the development of solid waste composting, household composters and small-capacity reactor composting systems emerge as the times require. On the one hand, home composters have been reduced from the source.