Based on the traditional calculation method of trash cans, this paper puts forward the configuration method of classified trash cans, including the judgment method of trash can configuration ratio, the correction method of configuration ratio to trash can demand and the community structure. Based on the actual data of Beijing, this paper calculates the number of garbage bins in six typical communities (schools, residential areas, office buildings, shopping malls, business districts and hotels) under different classification rates. The results show that the ratio of recyclables, kitchen waste and other garbage bins in residential areas is1:1:1; For schools, office buildings, shopping malls and business districts, when the classification rate is lower than 50%, the allocation ratio of the three garbage bins is 1:0: 1, and when the classification rate is higher than 50%, the allocation ratio is 2:1:1; The proportion of classified garbage bins in hotels has changed greatly. The allocation of schools, office buildings, shopping malls and business districts increases with the improvement of classification rate, while the allocation of residents and hotels has not changed much.
Garbage classification; Trash can; Configuration; analog computation
Urban trash can is the infrastructure for citizens to throw garbage. Determining the number of trash cans is one of the first problems to be solved in municipal waste management. As early as the 1960s, some scholars studied it, but it still attracts much attention [1-2]. The main reason is that with the improvement of public awareness of environmental protection, people put forward higher and higher requirements for garbage management, and the number of garbage bins itself has become one of the necessary parameters for the modeling and research of urban garbage system [3-4].
In the whole garbage delivery, collection, transportation and treatment or disposal system, the setting of garbage bins not only affects the delivery effect of the front end of the garbage system [5-6], but also affects the collection and transportation efficiency of the middle and back end of the garbage system [7-9]. For cities that implement garbage classification management, it is necessary not only to clarify the total amount of garbage bins, but also to solve the problem of the allocation ratio of classified garbage bins. The allocation of classified garbage bins has become an important part of the whole garbage classification management system.
Since 2000, Beijing has vigorously promoted the construction of garbage classification system in the city. By the end of 2006, there were 1827 communities with garbage classification conditions [10]. The classification of residential areas involves many types, including residential areas, institutions, primary and secondary schools, hotels, office buildings and so on. At present, there are three kinds of domestic waste in Beijing: kitchen waste, recyclable waste and other waste. Most of the trash cans in different types of communities are 1: 1: 1, and the influence of garbage components and community categories is not considered in detail, which leads to insufficient or idle trash cans to some extent.
The number of garbage bins classified by the city is first determined by the garbage classification method implemented by the city and the output of various garbage components [1 1- 13], and the number of garbage bins required for all kinds of garbage calculated from this can be regarded as the theoretical calculation value. The actual demand is often much larger than the theoretical calculation value. The reason for this difference is that the allocation ratio of sorting trash cans and the structural characteristics of residential areas have important influence on the actual demand, but the existing research rarely considers the influence of these two factors, which leads to the disconnection between theoretical calculation and practical application. In this paper, the influencing factors of trash can configuration are comprehensively considered, and the configuration method of trash can in garbage sorting community is put forward. Taking Beijing garbage sorting demonstration community as an example, the configuration of trash can is actually estimated.
1 Configuration method of trash can in garbage sorting community
1. 1 theoretical calculation of trash can configuration
In principle, the number of trash cans is the total amount of garbage divided by the amount of garbage that can be loaded in a single bucket. However, the number of trash cans is also affected by the number of garbage removal. The more times you clean it, the less trash can you need. Considering these two factors, the number of trash cans can be expressed as:
Where n is the number of trash cans set; W is the weight of garbage; ω is the number of times the trash can has been cleaned; ε is the packing density of garbage; B is the volume of a single trash can; ζ is the filling coefficient of the trash can, which indicates the filling degree of the trash can during transportation, and usually takes 0.75 ~ 0.9 [14].
When the garbage is put into different categories, the number of garbage bins required for each category should be the total amount of garbage divided by the amount of garbage that can be contained in a single bucket, and calculated by formula (1) respectively. However, since the garbage sorting rate is not always 100%, it is necessary to consider the size of the garbage sorting rate when actually calculating the number of trash cans in an area, that is,
Where γ is the garbage classification rate, which indicates that the classified collection amount of a certain garbage component accounts for the percentage of the total amount of the component.
1.2 Parameters for determining the allocation ratio of classified trash cans
According to the formula (1), the theoretical distribution numbers of recyclable garbage, kitchen garbage and other garbage can be calculated respectively, and the proportion between them can be obtained. Due to the different garbage production and removal time of these three different sources, a variety of distribution ratios will be obtained through the formula (1), and the direct application of this proportion form will bring great inconvenience to management. From the actual situation at home and abroad, although the proportion of trash cans is different, there are often only a limited number in the same area. Therefore, it is necessary to put forward a judgment method or parameter to simplify the calculated theoretical proportion into several simple proportional forms according to the set principle for practical application.
For the convenience of comparison, the ratio of the theoretical quantity of three kinds of trash cans is expressed by two parameters (α, β), namely
Where N 1, N2 and N3 respectively represent the number of recyclable garbage bins, kitchen waste garbage bins and other garbage bins. In the estimation of the actual number of trash cans, these two parameters will be used to determine the allocation ratio of trash cans. (Source: Internet)
In addition, the number of trash can configuration groups calculated according to the trash can configuration ratio sometimes produces decimal points, which need to be used to round off the values. For example, suppose that the configuration ratio of three kinds of trash cans is actually n 1:n2:n3, then the number of groups of classified trash cans GR = (n1+N2+n3)/(n1+N2+n3). If gr has decimal places, the actual total number of trash cans NR = [Int(gr)+1] (n1+N2+n3), where int (gr) represents an integer to GR.
In the allocation of classified garbage bins in actual residential areas, besides the quantity and cost of garbage generated in this area, the influence of residents' characteristics on the allocation of garbage bins should also be considered comprehensively. The quantity and composition of garbage are the same, and the types of residential areas are different, such as residential areas, shopping malls, commercial areas, schools, etc. The specific configuration of garbage bins should also be different. Here, the concept of "configuration coefficient (λ)" is used to reflect this difference, that is
Na=λNr，(4)
Where Na is the actual number of trash cans in the community, and the distribution coefficient λ should be determined according to the actual situation of the community.
2 Beijing classification community classification trash can configuration estimation
2. 1 waste composition and formula coefficient values
For the convenience of calculation, the whole city of Beijing is simplified as a model community with 6,543,800 people, and all the parameters of this community are obtained according to the actual data of Beijing. Demonstration communities include all kinds of major social activity places, namely residential areas, shopping malls, hotels, commercial areas, schools and office buildings. The garbage they produced accounted for 24.60%, 14.77%, 6.03%, 9.57%, 29.80% and 15.24% of the total garbage entering the landfill respectively, and the per capita garbage output was.
Table 1 Output of Domestic Waste from Different Sources
According to the definition of classification rate, the data in table 1 is the removal amount of each garbage component when the classification rate of model community garbage is 100%. When the sorting rate is 0, all garbage will be mixed, collected, transported and treated. At this point, only other garbage will be removed. For the convenience of calculation, it is assumed that the classification rate of kitchen waste and recyclable waste is the same, so the removal amount of each waste component under other waste classification rates can also be calculated. According to the formula (1), when calculating the theoretical configuration of each component trash can, the parameter values are shown in Table 2.
Table 2 coefficient values of theoretical calculation formula of trash can
Note: a. Volume density data are from the literature [15-16]; B, introducing the coefficient of variation of bulk density and peak volume of garbage to eliminate the error caused by average value [14]; C. For residential areas, 240L is selected for the calculation due to the concentration of garbage throwing time, and 120L is selected for other areas as the volume of a single trash can.
2.2 Determination of theoretical demand and allocation ratio of classified trash cans
According to the data in table 1 and table 2, the theoretical demand (N 1, N2 and N3) of six recyclable garbage sources, kitchen garbage and three other garbage bins in the model community can be calculated by formula (2), as shown in table 3. Thus, the values of decision parameters α and β are calculated according to formula (3), as shown in figure 1. When calculating the theoretical demand of trash cans, the garbage classification rate (γ) is 50%.
Figure 1 Determination of trash can configuration ratio of different garbage sources
As can be seen from Figure 1, the variation range of α and β is very large, the distribution of data points is very scattered, and the trend of relative concentration is not obvious, which shows that there are infinite cases in the ratio of trash can configuration calculated in theory, and it is difficult to directly apply it to practice. Therefore, the practical application of trash can configuration ratio can not be completely calculated according to theory, and it needs to be simplified.
Generally speaking, no matter what type of community, other garbage will be generated, and other garbage bins need to be set up. The number of other trash cans is different in different countries. At present, Beijing is vigorously promoting garbage sorting, and setting up multiple other garbage bins will have a negative impact on the garbage sorting effect, so it is not appropriate to set up more. Considering two factors, other trash cans are set to 1. The main purpose of garbage classification is to separate recyclables, and the garbage bins of recyclables in various communities should be at least 1. The setting of the total number of a group of trash cans is subjective, which needs to consider the acceptance of residents, and cannot be too different from the total number of a group of trash cans set up in Beijing in the past. Here, the total number of a group of trash cans is set to no more than 4. The above principle can be expressed quantitatively as follows
N 1+N2+N3≤4，N 1≥ 1，N3= 1 .(5)
According to the above principles, combined with the specific values of α and β, the proportion of three kinds of trash cans can be determined. When α >; 2，β& lt； 0.3, that is, the theoretical demand of kitchen waste bins can be ignored, and the other two are similar, that is, N2=0, N 1≈N3. Substituting these two formulas into formula (5), the distribution ratio of the three types of warehouses is 1:0: 1. When α >; 2，β& gt； 0.3, the theoretical demand of kitchen waste trash can should not be ignored, that is, N2≥ 1, N 1≥N2. Substituting these two formulas into formula (5), the allocation ratio of the three trash cans is 2: 1: 1. When α
When the composition of waste is determined, the higher the classification rate of waste, the lower the proportion of other waste, and the greater the β value (kitchen waste/other) in figure 1. As can be seen from the figure 1, for schools, office buildings, shopping malls and business districts, the area I is 1:0: 1, which is also in line with the actual situation that the amount of kitchen waste generated in the corresponding area is small, and kitchen waste recycling bins may not be provided when the sorting rate is low; Zone II has a high classification rate, and the allocation ratio should be recyclable: kitchen waste: others =2: 1: 1, which means that when the classification rate is high, the allocation of the above-mentioned garbage bins that produce kitchen waste can no longer be ignored, and the demand for recyclable garbage bins has been greatly improved, so it has been increased to two. Area ⅲ is mainly residential, and the parameters under different classification rates all satisfy α < 2. The distribution ratio is recyclable: kitchen waste: others = 1: 1: 1. For hotels, when the classification rate is 20%, α=2, which is just at the critical point; when the classification rate is 50%, α=3.0, β=0.27, which are all close to the critical point. Therefore, when the sorting rate is lower than 50%, the garbage bins in the hotel can be mixed, that is, in places where kitchen waste is produced more. Recyclable ratio of trash can: kitchen waste: other = 1: 1, recyclable ratio of other places: kitchen waste: other =1:1,which is consistent with the hotel's two major activities including catering and accommodation. When the classification rate is greater than 50%,
Table 3 Theoretical configuration and discriminant coefficient values of garbage bins with different garbage sources under the condition of classification rate of 50%
As can be seen from the above discussion, different types of sources produce different garbage components, and garbage bins also have different configurations. For schools, office buildings, shopping malls, business districts and hotels, with the change of source classification rate, the configuration form of trash cans can be adjusted accordingly, and residential areas can also adopt the same method.
2.3 Revision of demand for classified trash cans
The theoretical total demand of a trash can of a production source shown in the column of "Total Amount" in Table 3 is a simple sum of the theoretical calculation values of three kinds of trash cans, regardless of the influence of the allocation ratio of three kinds of trash cans. According to the allocation ratio, the revision of the demand for classified trash cans is called revision. Table 4 is the calculation result of trash can after considering the allocation ratio. In addition, considering that the actual number of trash cans is an integer, all decimal places are treated as 1 in the calculation process. If the proportion of office buildings with a classification rate of 100% is recyclable: kitchen waste: others =2: 1: 1, and the theoretical total demand is 69, it needs 69/(2+1+1) =/kloc-. By analogy, the first revised demand values of six sources with different classification rates are obtained (Table 4).
The estimation of the final trash can needs to specify the configuration coefficient λ (Formula (4)). λ is calculated from the calculated value and the investigation value of trash cans in typical communities. In Beijing, various types of mature garbage classification communities (representing different garbage sources) are selected. In order to calculate the theoretical demand of the corresponding sources conveniently, the numerical value under the condition of 50% classification rate is taken. Here, it is assumed that the distribution coefficient is the same under different classification rates. Take the calculation of trash can configuration coefficient in residential area as an example. The actual residential area is Gong Jian Li Nan Residential Area, Xuanwu District, Beijing. The daily output of garbage in this community is 0.747t, and there are 25 240L garbage bins in the community. The daily output of garbage in the residential area of the demonstration community is 2.69t (Table 2), and the theoretical demand for garbage bins is 42 when the classification rate is 50% (Table 4). According to the definition of 2. 14, the distribution coefficient between the actual demand and the theoretical demand of garbage bins in the community can be calculated. By analogy, the allocation coefficient of trash cans from other sources is shown in Table 5. What needs to be pointed out in particular is that the school here mainly refers to colleges and universities, and its activities can be regarded as the integration of residential areas and office buildings, so the average allocation coefficient of garbage bins in schools is 3.02; In addition, due to the lack of corresponding information in shopping malls, the corresponding garbage can configuration coefficient is estimated to be 2.
Table 4 Revised values of theoretical demand of different garbage sources
Table 5 Configuration coefficient λ of trash cans from different garbage sources
According to the theoretical demand and allocation coefficient of each source trash can, the actual demand of trash cans in schools, residents, offices, shopping malls, business districts and hotels under different source classification rates is calculated respectively. The actual demand of trash cans in model communities is the sum of six, as shown in Table 6.
It can be seen that the allocation of schools, office buildings, shopping malls and business districts increases with the improvement of classification rate, while the allocation of residents and hotels has not changed much.
In the model community, there are more trash cans in schools and office buildings, the smaller ones are commercial areas and hotels, while the residential areas and shopping malls are at a medium level, which is not only related to their respective garbage output, but also affected by garbage composition and community structure. The total demand of garbage cans in model community increases with the increase of source classification rate, that is, the actual demand of garbage cans increases by about 3. 1% for every increase of source classification rate in model community.
As a microcosm of Beijing, the demonstration community can provide reference for the promotion of garbage classification in Beijing.
Table 6 Number of trash cans required by model community under different classification rates (120L)
(Source: Internet)
3 Conclusion
1) On the basis of synthesizing the traditional calculation methods of trash cans, this paper puts forward the allocation methods and corresponding calculation models of classified trash cans under different classification rates, including the indicators and methods for judging the allocation ratio of trash cans, and the correction coefficient of community structure for the demand of trash cans. This method comprehensively considers the factors that affect the configuration of classified trash cans, and has certain reference value.
2) According to the output, composition and classification of garbage in Beijing, a demonstration community including different types of garbage classification communities in Beijing was established, and the allocation ratio of garbage bins in each community was estimated accordingly. The proportion of trash cans in different communities is sensitive to the change of classification rate, and the proportion of recyclable trash cans and kitchen waste in residential areas can remain unchanged under different classification rates, both of which are1:1:1; The allocation mode of schools, office buildings, shopping malls and business districts needs to be adjusted accordingly with the change of the classification rate of tourists. When the sorting rate is lower than 50%, the distribution ratio of the three trash cans is 1: 1, and when the sorting rate is higher than 50%, the distribution ratio is 2:1:1; The proportion of classified garbage bins in hotels has changed greatly.
3) The allocation of schools, office buildings, shopping malls and business districts increases with the increase of classification rate, while the allocation of residents and hotels has not changed much. Every time the source classification rate increases by 10%, the total demand for garbage bins in the whole model community increases by about 3. 1%.
Thank you for your support and help in the classified community survey.
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