Sources of waste: where to collect?[edit | edit source]
Depending on the geographical dispersion, degree of contamination and heterogeneity, it is possible to distinguish four types of plastic waste: industrial waste, commercial waste, agricultural waste and municipal waste.
Industrial waste[edit | edit source]
"Identified, unmixed, not polluted" We call "industrial waste" the waste produced by plastics processing companies, but also the leftover waste generated from the use of these plastics in the packaging industry, construction, ... These wastes have not yet been integrated into the consumption cycle. The plastics processing companies generate internal plastic waste which may be:
- Purges, which are usually in the form of large blocks of several kilos. These residues result from the discharge of injection or extrusion apparatuses. This can occur for various reasons: stops, maintenances, changes of molds or dies, changing of the coloring for the plastics. These plastics are not always top quality. They can particularly contain a large proportion of lubricants.
- Injecting carrots and grapes: this is the material that fills the injection channels (see Chapter 5). They are recovered during the demolding of the injected parts. They weigh, at most, a few tens of grams.
- Parts with defects which can therefore not be sold.
The combination of these residues may represent 10% of the production.
The large processing companies usually have their own recycling channel (primary recycling). Those that can not afford this prefer outsourcing this activity by giving or selling it to workshops capabale of recycling them. They are generally interested in rebuying the then recycled plastics.
Note: Purged blocks are very difficult to break apart. They require cutting beforehand which few companies bother to do. It can therefore be interesting to get them at a low price and recycle them. The processing companies are not the only producers of industrial waste. Other companies use plastics too. Their activities can generate large quantities of waste. As an example, we can take the manufacturers of window frames. They buy extrusion PVC profiles from processing companies. They then cut to them to size in order to make the chassis. They thus generate clean and well identified waste that can be easily collected and recycled. The packaging and conditioning sectors are also a good sources of waste. Industrial wastes are an often forgotten source of plastics. It offers however many advantages:
- Deposits already identified;
- Regulated supply;
- Clean and unmixed waste;
- Collection integrated within the undertaking;
- Collection points geographically well defined;
Commercial waste[edit | edit source]
"Identified, mixed" Commercial waste is waste from workshops and shops. After an inventory of these institutions, it is possible to identify the types of plastic waste they generate. A collection system can then be introduced within these institutions.
There are two types of commercial waste:
|department stores (packaging),enterprises (pipes, films, ...), plumbing (PVC pipes) ...||hotels (containers, ...), restaurants, bars (vials, bottles, ...), service stations, garages (drums), hairdressers (bottles), hospitals, pharmacies, ...|
|Advantages: regular supply, established collection points, easy sorting, light wash||Advantages: regular supply, established collection points, easy sorting|
Table 3.1: Commercial waste types
Agricultural waste[edit | edit source]
Farming and forestry activities also consume plastics for construction (irrigation pipes, stakes, tarps, ...) or for packaging (jerry cans, feed sacks, plastic film, ...). The deposits are often more distant, but this source should not be overlooked. With a good sensibilisation, farmers can store their plastic waste. We can then collect the waste once or twice a year.
Municipal waste[edit | edit source]
"Unidentified, mixed, fouled" Waste plastics from municipal waste is usually the most important deposit. The deposit is directly linked to the consumption of the target population, for two reasons:
- A resident can generate up to 1 kg of waste per day if his means is high, but this value is less for a person of limited means (less than 0.5 kg per day);
- also, depending on the living standard, the plastic content in the waste represents 3 to 8% (by weight). Also, the amount of plastic waste generated per person per year can vary between 5 kg and 25 kg. These wastes are usually heterogeneous, dispersed, and very heavily fouled. They consist primarily of packaging films, bags, bottles, ...
Their supply is however regular. We can recover plastics from municipal waste:
- directly from the consumer (least fouled)
- from streets and parks (very fouled)
- from sorting centers (very fouled)
- from dumps (very fouled)
Sorting centers are usually micro-or small businesses that collect the household waste for conversion into compost. They often do a brief sorting of these wastes in order to extract the metals and plastics. If the metals are sometimes recovered, plastics are often placed together. They can represent significant deposits.
In addition to the regular supply, it is important not to overlook the waste generated by certain events such as local festivals, sidewalk sales, events, ... during which fouled waste plastics that are relatively well identified are discarded.
Evaluation of a deposit[edit | edit source]
The goal of a deposit evaluation is to determine the potential waste plastics that are available for a project: location, quantity, quality, renewal, ... The evaluation result is an indispensable step for the selection and design of a recycling system. It helps to know the amount of waste that can be treated, the types of plastics to recycle, the collection system to implement, the choice of machines, the necessary investment, the required amount of labor, ...
|Deposit evaluation campaign||Choices of approach|
Table 3.1: Specifics in evaluating a deposit for choosing an approach in recycling.
The following paragraphs describe the general approach for a detailed campaign relative to all possible sources of supply. When the outline of a project is already defined, it is not necessary to take into account all these steps. We leave the choice to the reader to refer to the third parties concerning his project.
Choosing a prospecting area[edit | edit source]
Above all, it is important to choose the geographical location in which plastics will be collected wisely. It is certain that one project is not another. Some constraints can directly define the collection area. Similarly, the objectives to attain for the project will be decisive. Also, for a plastic recycling project of which the objective consists to cooperating with a plan of waste managament in a neighborhood or village, we must ensure a large coverage of the generated waste in that zone. On the contrary, if the intention is to manufacture recycled plastic objects of quality, the project initiator will choose highly industrialized areas or areas with a high income where the quantity and quality of waste plastics are generally higher. However, some criteria must determine the selection of an area:
- We preferably select areas closest to the center of recycling. Indeed, transport of waste plastic is expensive. This is due to their low density: 100 to 400 kg/m³. The volumes to move thus become great quickly. At the transport level, the ideal location of the recycling center is obviously the center of the surveyed area.
- The amount of plastic waste generated by a household is related to its consumption, thus its purchasing power. We thus find more plastic waste in dumpsters of rich neighborhoods than in poor neighborhoods.
- The larger the area, the greater the collection system that needs to be set up. Initially, it is better to limit oneself to a small area, and then expand.
- Wherever possible, we try to integrate industrial areas. These indeed produce waste, but may also consume our recycled plastics.
Characteristics of the studied area[edit | edit source]
Once the prospection of the area is finished, a preliminary investigation is necessary to prepare the sampling campaign. This gathered information makes up a kind of identity card of the studied area. Amongst this information we find:
- The size of the area Szone(km²), preferably evaluated using a map;
- The number of inhabitants in the area Nzone;
- Population density Pzone, deduced from the first two numbers by the formula:
[math]P\lt sub\gt zone\gt /sub\gt =N\lt sub\gt zone\gt /sub\gt /S\lt sub\gt zone\gt /sub\gt (inhab./km²)[/math]
- The climate of the region. This affects the drying conditions: the number of days of sunshine, average temperature, rainfall, humidity, winds, ... All these data are used for choosing one or
another drying technique.
- The main economic activities in the area: trade, agriculture, livestock, industries ...
- A description of the habitat: rural or urban zones? The type of accommodation: detached house? buildings? farm? ...
- Events and seasonal activities.
Events are special days during which the quantity of generated waste may be larger than usual: fairs, sidewalk sales, local events, festivals, ... During a characterization campaign, we will not include these events. It is however important to identify them because they can require waste collections. Some regions enjoy seasonal activities. This is particularly the case in tourist areas where the influx of tourists during holiday periods increases the waste production (which may be significantly higher). It is then necessary to distinguish tourist periods from other periods.
Note: Where too are great differences within the study area occur, it is preferable to divide it into smaller areas (subareas). Each sub-area is characterized in the same manner as a zone. This can happen in the following situations:
- Two areas where living standards are significantly different;
- An industrial zone located next to a residential zone;
- A permanent market integrated into a residential area, ...
Inventory of sources of waste plastics[edit | edit source]
Once the identity card of the zone is established, we can consider the possibilities to supply the waste plastics. This is done by making an inventory of the available sources. For each, we must collect a representative sample which, after characterization, evaluates the potential in recyclable plastics in the zone.
a. industrial waste The enumeration of plastic processing companies must be well beyond the borders of the targeted area. Indeed, they may play a determining role in the project: outsourcing of their internal waste, sale of used equipment, purchase of recycled plastics, ...
For each, we collect the following information:
- The type of plastic that they process: PP, PVC, HDPE, LDPE, ...
- The used processing techniques: injection, extrusion, blow molding, filming, ...
- Manufactured articles: catch basins, chairs, films, bags, shoes, ...
- Production (t/month).
We will also ask them the following questions:
- Does their activity generate waste?
- If so, what ? Purges, injection carrots or grapes, defective parts, ...
- Do they recycle their internal waste (primary recycling) ?
- Are they interested to outsource this activity (or a part thereof)?
- If so, which? How much plastic does that represent ?
We will also use this meetup to inquire about their interest on working with recycled materials from the treatment center established by the project (see chapter 6).
Besides the plastic processing companies, it is important to also identify all other companies with activities that generate waste plastics and fall into our line of work.
- What types of waste do they produce? How much? What do they make ?
- Would they agree to work with a recycling center? Under what conditions? Would they agree to establish a selective collection system for these wastes in their company?
b. commercial waste On a campaign evaluation, it is not possible to go around all of the businesses in the area in question. We rather evaluate this waste deposit using the following methodology:
- Determine the businesses that are most likely to generate waste plastics, and group them by category. For each category, describe the types of waste likely to be produced.
- Select a few traders and undertake with them a campaign of selective collection of their waste plastics. It doesn't do any good to work with too many businesses: three to five are usually sufficient. After having well explained the aim of the campaign to the traders, we suggest them to put aside all their plastic waste which they obtain in a certain period of time. A fortnight is recommended. After this period, we harvest the waste and store it in bags on which we note the name of the business and the waste class.
- Weigh all the bags and note down the weight category in a table. When a sample of a class seems different, it is better to discard it rather than wanting to integrate it at any cost. Indeed, it may distort the results, more than provide interesting information.
- For each category, estimate the number of businesses present in the area of prospection.
- Calculate the quantity of waste available by category and then sum them up to get the total weight of the of commercial waste in the area to study.
- The sensibilisation of the traders in the project area is essential. The quality of samples collected is dependant on it. It is particularly important to emphasize that only the commercial waste must be preserved. They do not need to add any other waste. Some people have a tendency to insert all waste they find in order to show that they are able to raise significant quantities of waste. These laudable intentions may distort the data.
- Be wary of waste from hospitals and pharmacies. These may have contained drugs or other substances, and thus need to be handled with care. It is best to check with doctors and pharmacists, and to establish with them a list of "recyclable" waste. Other waste will be
not be collected.
- If the area is not too large, a systematic count of businesses may be achieved by walking the streets. When the area is too large, this work becomes too complex. We prefer to select only a few areas (preferably on the map), and counting the businesses in these neighborhoods and extrapolate the data for the entire area.
Example of a reminder table:
|Category||Type of waste||Sensibilised shops||In the zone|
|Service stations||Oil cans||4||24||6||4||24|
|Hairdressers||bottles (shampoo,lacquers, dyes, ...)||3||0.3||0.1||27||2.7|
|Cafes||bottles, racks, tables, chairs, ...||5||2.5||0.5||46||23|
Table 3.2: Example of a summary evaluation campaign (15 days)
Example: Estimated number of shops in an area of Kinshasa (2003) The study area comprises three communes of Kinshasa: Lemba, Ngaba and Makala. Living standards and activities of these three municipalities are very different, the area has been divided into three sub-areas corresponding to the three municipalities. Given the importance of sub-areas, only a few representative neighborhoods of the sub-areas were studied.
After having sensibilised some traders, a campaign of selective waste collection was undertaken over a period of 15 days. This has allowed to determine the amount of plastic waste produced by each category of businesses in each sub-area.
The results are extrapolated to the entire sub-area using an equal factor regarding the surface cover per subarea and those of the studied neighbourhoods.: [math]Q\lt sub\gt subarea\lt /sub\gt =Q\lt sub\gt sensibilized\lt /sub\gt _X_N\lt sub\gt neighbourhood\lt /sub\gt _X_S\lt sub\gt subarea\lt /sub\gt /S\lt sub\gt neighbourhood\lt /sub\gt [/math] with:
- Qsubarea (kg): quantity of plastic waste produced in the sub-area;
- Qsensibilized(kg/com.): quantity of waste plastics per sensibilised businesses;
- Nneighbourhood: number of enterprises in the studied neighbourhood(s);
- Ssubarea(m²): surface area of the sub-area (calculated from the map);
- Sneighbourhood(m²): surface area of studied neighbourhoods (calculated from the map).
All results are noted down into a table:
|Category||Sensibilised||In the neighbourhood||In the subarea|
|Area 1||Neighbourhoods 1 and 2 (12%)|
|Total of area 1||120.3|
|Area 2||Neighbourhood 1(13%)|
|Hospitals||2.5||2||5.0||15||37.5||Total area 2||115.4|
|Area 3||Neighbourhood 3 (15%)|
|Total Zone 3 55.1|
|Total in all zones||280.8|
Table 3.3: Evaluation of waste products in 3 commercial communes in Kinshasa
We take note that no service stations are installed in the two studied districts of Lemba (subarea 1). However, there are 6 in the municipality of where 2 were sensibilised (4kg/station). The results could of been directly placed in the last columns of the table. The same applies to hospitals in area 3. In total, the amount of commercial waste produced in the three municipalities has been estimated at 280.8 kilograms over a period of 15 days, or 561.6 kilograms per month.
c. agricultural waste When such sources of waste presents themselves, we will apply the same evaluation methodology as for commercial waste. We however choose a longer period (2 to 3 months) and a number of larger enterprises.
d. municipal waste Before evaluating the municipal waste deposit in a targeted area, we first need to know what is currently happening with this waste by asking the following questions:
- Is there a collection system set up? If so, what type (see Selective collection systems)? Is it structured? What is the frequency of collection? What type of transport ?
- Where is the collected waste brought to ? Are they sorted in a recovery center for composting or other? Are they dumped in a municipal landfill or is it illegally dumped ?
- Is there a lot of garbage on the highway ?
After finding answers to these questions, it may be useful to sketch the transfer of the waste stream on paper to design a strategy for estimating the amount of available plastic waste. There is no universal strategy, every situation is different. However, some guidelines can be followed:
- To the extent that their activity is structured, it is always preferable to work with people already active in collecting garbage. In fact, they perform a collection directly from the consumer (upstream collection) with whom they generally maintain a relationship of confidence. After explaining the project in detail, it is possible to conduct a campaign evaluation with some of these collectors. This campaign will run for a fortnight and will consist of asking them to separate the plastic waste from the garbage they collect. After the campaign, the plastics will be weighed and the data will be entered in a table similar to that of the commercial waste. Extrapolating this to the entire area is done using an estimation of the areas covered by the collectors.
- Where there is no sufficiently structured collection system, it is possible to realise a sensibilisation campaign among the locals. To do this, simply select a few neighborhoods in the area and proceed in the same way as for commercial waste, motivating people to separate plastics and other wastes.
- The evaluation of waste lying in the streets is very difficult or impossible their waste flows are so irregular and heterogeneous.
- Direct evaluation in the landfill is always inadvisable because the waste released there are often very fouled and the hygienic condition for working here is precarious. However, when there is no alternative, this evaluation is relatively simple. It consists of determining the percentage of plastics contained in the garbage and assessing the amount of waste that is sent daily to the landfill. The product of these two results gives the amount of plastics available
every day: [math]Q\lt sub\gt discharge\lt /sub\gt =%\lt sub\gt plast.\lt /sub\gt _X_M\lt sub\gt discharge\lt /sub\gt [/math]
- Qdischarge (kg/day): quantity of daily available plastic waste
- %plast.: percentage by weight of the plastics contained in the garbage
- Mdischarge (kg/day): daily quantity of garbage sent to through the discharge
Sampling will be performed to characterize the identified plastic.
Characteristics of collected waste[edit | edit source]
Once samples are collected and gathered, we must determine what their main characteristics are to determine the proportion of recoverable material in these wastes. This characterization is done for each category of collected waste.
To do so, various data can be found on collected batches, namely:
- The degree of fouling: this is the proportion of matter other than the recyclable plastic that the waste contains: labels, metal components, plastics of a different nature than the object, ... It is found by removing these unwanted bodies, weighing them and calculating their proportion by weight (see chapter 2).
- The degree of soil: this is determined by weighing the samples before and after the washing (see chapter 2). Knowledge on the levels of fouling and soil of a batch of plastic allows the calculating of the amount of potentially recoverable plastics. For plastic bottles for which the degree of fouling is equal to 5% and the degree of soil is 10%, we know that for a kilo collected only 855 g. can potentially be recovered (0.95 x 0.90 x 1000g.)
- The types of plastics: these are determined by the recognition criteria described in chapter 2. Thus, for each collected sample, we determine the percentage of each major category of plastics (PP, HDPE, LDPE, PS, PVC) and the proportion of other plastics for which recovery will probably not be considered.
Besides these three types of important data, other characteristics may be determined. This is the case with the percentage of matter which can not go through a grinder and therefore requires a preliminary cut up. In the case where there is already a grinder, it is obtained by weighing the parts that are larger than the mouth of the grinder and dividing the obtained weight by the total weight of the sample. Otherwise, we will consider the waste that can not go through a rectangular hole (cut from a sheet of cardboard, for example) of 150 x 150 mm, corresponding to a typical opening of a grinder with a capacity of 150 kg/h as ungrindable.
[math]Plast.\lt sub\gt to be cut up\lt /sub\gt (%)=Plast.\lt sub\gt ungrindable\lt /sub\gt (kg)/Sample(kg)_X_100[/math]
Vials and bottles are generally regarded as belonging to this category. Indeed, their rounded shape makes sure they are not driven by the grinder knives. They therefore require a preliminary division. Another interesting fact is the drying time (in the sun, for example) of washed plastic matter. It allows to evaluate the drying area to be foreseen and, if it shows that solar drying is not possible, allows to explore other drying techniques (see chapter 4). All these characteristics need not be determined for the entire collected batch. Smaller samples, but as representative as possible, may do the trick. Finally, all results will be placed in an overall table that will highlight the intresting deposits of plastics, to dimension the approach of recycling to be put in place (machines, human resources, consumables, ...) and to budget the project (see chapter 6). This approach seems long and tedious. It is however necessary if one wants to adopt a work strategy to implement into his recycling project, notably regarding the balance of material flows and economic prospects. Furthermore, characterization is not only useful for the evaluation phase, but also duting the production to reevaluate the operation of a certain deposit!
For more information on evaluating waste deposits: For people who dispose of only a minimum in equipment and knowledge regarding computing, the ModecomTM software is a useful tool to facilitate the management of the collected data of the campaign, but also during the period of production. This program, developed by ADEME (Agence de l'Environnement et de la Maitrise de l'Energie, France) for the management of domestic waste can be adapated to the projects described in this manual. It can manage the basic data and derive key information. For more information, consult the website of the ADEME (www.ademe.fr) at the section "publications". We find here the conditions of sale (price: 30,49 €) and a downloadable order form to send to the following address: ADEME 2, square La Fayette BP 406 - 49004 Angers cedex 01 France Tel: 00 33 (0) 2 41 20 41 20 Fax: 00 33 (0) 2 41 20 41 97
Collection systems[edit | edit source]
Sensibilisation[edit | edit source]
Experience has shown that the recycling of plastic waste is an activity that can be profitable. This profitability is often compromised when the recycling center must take charge of the own sensibilisation of people regarding the problematic of waste. Sensibilisation requires substantial resources that must not be neglected. Generally, it is advised to separate the two activities and to be imaginative about how to sensibilisation is done: financing research parallel to those funding the project, involvement of local authorities or associations sensitive to the environment, use of communications media (media), ...
a. Sensibilisation of collection agents The sensibilisation of collection agents is essential. They are in fact directly in contact with waste producers and thereby contribute to their sensibilisation. Moreover, they are the ones who handle the waste. They can then judge the quality of the sorting. These agents may be part of the recycling center, work for their own account or belong to an existing collection network. Their sensibilisation can be done through training sessions. They will notably learn:
- Sensibilisation of their role in industry development;
- The extent of the damage plastic waste can do to the environment, but also the benefit that be provided for it;
- To differentiate the recyclable plastics amongst each other and evaluate their quality (fouling, soil, ...);
- To sensibilise the population of the problem of plastic waste.
Do not hesitate to explain in detail the central activity, and the problems encountered throughout the recycling process, especially when the quality of the waste is also put into consideration. It is also important to perform debates to know everyone's problems and find solutions adressing everyone's interests.
b. Sensibilisation of waste producers Education and sensibilisation of the inhabitants or waste producers to separate the plastics from other waste is not done overnight. Indeed, the audience often has other concerns as sorting their daily waste. It is nevertheless important that sorting is done; the supply of plastic recycling centers depend on it. Women and children are most susceptible to environmental problems. Women are the primary concerned ones because it are them who often dominate the daily household tasks, and therefore the cleanliness and waste. Children are more engaged in separate collection from a personal motivation (see Table 3.5), which will bring them an intresting little income. Furthermore, the sensibilisation from an early age has long-term effects.
Communication channels for a good sensibilisation are numerous. The main thing is not to lack imagination. As examples, here are some ideas:
- Articles in local newspapers, posters in the streets;
- Radio and television commercials;
- Meetings in associations sensitive to the environment (including women's associations);
- Fun activities in schools (drawing contests, games on the theme of waste ...);
- Message at religious events, sporting, cultural, ...
- Organized visit to the recycling center for stressing the importance of sorting at the source, ie by the people.
During these campaigns, we seek to empower collection agents that stress the importance of their activity for the safety of their neighborhoods. Sensibilisation is an activity to be renewed perpetually. Good habits get lost quickly. It is always necessary to find new ideas.
Selective collection systems[edit | edit source]
Collection systems are "the way how waste moves from the inhabitant or producer of waste to the collection service". In the case of the collection of plastic wastes, we speak of separate collection, ie which aims to collect only certain types of waste. The selective collection can be fit into an existing collection system or, conversely, be organized in parallel to it. Before running through the different collection systems that can be implemented, it is important to make some recommendations:
- No ideal collection system exists. Each case needs to be studied to respond to the local context and project objectives. The best collection systems are those that are customised and not those who were simply copied.
- Equip adapted means. In the collection, it is indeed tempting to use so-called "modern" means but these often do not meet the conditions of countries with low and medium incomes. Also, the purchase of expensive vehicles, but immobilized ones because they are not appropriate to road conditions or because the price of maintenance is too high do not make smart investments. Instead, it is often preferable to use methods which use a greater human capital and base technologies better adapted to the conditions.
- For reasons of workhygiene, it is better to focus on maximizing the "Upstream collection", that is to say, at the inhabitant rather than recovery in streets and landfills. Wastes have indeed less soil, and are therefore less fouled. Moreover, washing and sorting will be facilitated.
a. Selective collection inserted into an existing collection network Table 3.4 shows the most common waste collection systems (H.C. Haan, 1999). For each system, some suggestions are proposed to insert a selective plastic waste collection.
|Shared||People or waste producers can bring their waste when they so wish.|
|Deposits on specified places||Inhabitants and other waste producers deposit their waste at a specific location or a masonry enclosure where they are transported.||Possibility to limit a part of the enclosure reserved for waste plastics.||Little investments||Difficult loading. The sorting is little controlled. The plastics are often mixed with other waste, thus soiled. Theft of waste plastics.|
|Shared container||Residents and other waste producers bring their waste to the container which is frequently moved or emptied.||A container can be reserved to only hold plastic waste.||Possibility to use closed containers that limits thefts.||The sorting is little controlled. The plastics are often mixed with other waste. Fairly expensive.|
|Individual||Inhabitants and farmers keep their waste at home until the collection|
|Block collection||The garbage collector waits at the specified places where the inhabitants bring their waste to the collection cars.||The garbage collector can recover the plastics separately and encourage residents to separate their waste. For this, the vehicles must be equipped with a compartment for plastics.||Inexpensive. Good sorting control. Possibility of sensibilisation and payment.||Requires a member of the family to be on-site and thus moves itself.|
|Sidewalk collection||The waste is deposited in front of the houses and placed in a vehicle or investigated and collected by a garbage collector.||Residents can deposit the plastic waste separatly. These are separately collected.||Convenient for the inhabitants.||Storage of the waste in the street, where it fouls and mixes.|
|Door-to-door collection||The garbage collector goes to the inhabitants and waits until they bring him the waste.||The inhabitants can deliver their plastic waste separately. The garbage collector will deposit the plastic waste in a container of his vehicle intented for the plastics.||Possibility of sensibilisation and payment. No waste is stored in the street.||Requires the presence of an inhabitant. Little suitable for large buildings.|
|Collection in the dooryard or garden||The garbage collector enters the property to remove the waste.||Residents can deposit plastic waste separatly. These are collected separately.||Convenient for inhabitants. No waste stored in the street.||Requires some trust between the garbage collector and the inhabitants.|
Table 3.4: Insertion possibilities of a selective collection into existing collection systems
The "block" and "door-to-door" collection gives the best results because they bring together inhabitants and the collection agent. This may allow sensibilisation to improve the quality of the supplied plastic waste. It is not always possible to change people's habits by sensibilisation to separate the plastic waste from the other waste. Nevertheless, the collection agent can always sort the waste he picks up daily himself, and this irrespective of the collection system in place. The plastics thus recovered provide him an additional financial return.
Example of a selective collection in Cairo (Egypt) The case of the scavengers in lower Mokattam is one of the most famous in the collection. This neighbourhood of Cairo lives mainly on the collection and recycling of waste. Every day, the trash pickers go into the richer neighborhoods off the central city to collect the garbage (door-to-door, dooryard or garden collection). They divided themselves into neighborhoods buying a collection right and take the waste from their home to dispose of them. The sorting is usually a family affair. The waste is separated by the type of material (organics, wood, cardboard, paper, metals, plastics, ...) but also according to their destination. Also, the plastic waste is divided by color, objects (cans, jars, shoes, ...) and so on. Regarding these different kinds of plastics, there is a terminology that has been created. They speak not of PP, PE, PVC, ... but of hard plastics, soft, tender, ... All obtained objects are sold to recycling workshops or neighborhood intermediaries who undertake the task of recycling them. It is not uncommon for parts of this waste to be directly sold to official factories. Thus, the route from the informal sector to the formal sector is quite common.
b. selective collection established in parallel Some neighborhoods do not always dispose of domestic waste collection approaches or, if they exist, they may not be well enough structured so as to be able to introduce a separate collection of waste plastics. In these conditions, it is necessary to establish a separated collection system for plastic waste. The different options are described in Table 3.5.
|Door-to-door collection||Collection agents regularly visit the inhabitants or waste producers who wish to get rid of their plastic waste. These collection agents may either be employed by the recycling center or be paid by it according to weight. In some countries, the collection agents pay the inhabitants for the received plastics per kilogram.||Possibility to sensibilise the inhabitants and the waste producers. The collected plastic waste is often of good quality.||Slow job requiring a large number of agents. Requires the presence of inhabitants when the collection agents pass by.|
|Voluntary contributions||Closed containers are placed at strategic locations in the area targeted by the project: major intersections, near markets, ... The inhabitants or waste producers come to dispose of their used plastics. Containers are regularly removed or emptied.||Cheap system.||No control over the quality. Much other wastes are generally found in these containers (thus fouled). Difficult to implement sensibilisation.|
|Contribution motivated by payment by weight||Collection agents regularly visit strategic locations called "collection points". They pay the people or waste producers according to the weight of the given plastics. Often, young people perform their own collection from door-to-door and bring the received plastics to the collection points.||Control of the quality of the received plastics. The waste can be paid according to their type if they are already pre-sorted according to the type. A good sensibilisation is then required.||This system can be costly if the collection agents are not adequately trained tn the recognition and the prices of the plastic waste.|
|Sorting center||These centers typically sort municipal waste into compost. An arrangement is made with the leaders of the sorting center to ensure that they also sort the plastic waste. The collection agents regularly visit the center to collect the plastics and may also pay by weight.||The waste is already gathered in a place. Sorting centers are often interested in getting rid of this non-recycled waste.||The plastic waste is often very soiled and fouled by other wastes (metals, paper, cartons, ...)|
|Dumpsite sorting (photo 3.12)||The sorting is done when no selective collection system has been established. Sorting is then performed by people who earn their living bringing the plastic waste to the recycling center (or collection points). They are paid according to the weight of the plastics.||The waste is assembled in a place.||Precarious (unhealthy) working conditions. This system is to be avoided at all costs.|
Table 3.5: Possibilities for inserting a collection system in parallel to existing collection systems
When a voluntary contribution collection system is proposed, it is sometimes necessary to use closed containers so as to avoid any risk of theft of the plastic waste. The figure below illustrates a proposed solution for Kinshasa. This is an oil drum above which two steel pipes are welded at an angle. An opening system with a padlock allows collection agents to recover the plastic waste during their daily rounds. The cost of manufacturing this type of dumpster is 75€ (Kinshasa, 2003).
Example of payment motivated collection in Yaounde (Cameroon) In Yaoundé, specifically in the area of Etoug-Ebe, the NGO CIPRE (Centre International de Promotion de la REcuperation) has established a selective payment motivated collection system where the payment is done according to weight. Every fortnight, a dozen collection agents serve the 50 collection points located in this neighbourhood of about 100,000 inhabitants. Their role is to collect the plastic waste, pre-sorted, weigh, and package them and pay the inhabitants who bring them.
This system allows to collect ten tonnes of waste plastics per months, or one tonne per collection agent. In addition, it offers the advantage of a certain flexibility. Indeed, by adapting its compensation schedule, the IPRC can recover the plastics it wishes. So, the PE bottles are paid 25 CFA/kg (0.04 €/kg) while a kilo of PVC soles can reach 100 CFA (0,16 €). This system is not exploited to its full potential as an objective of CIPRE is to reduce the impact of plastic waste on the environment.
Example of a mixed system in Bangalore (India) India is one of the most active countries in the recycling of plastic waste. In the city of Bangalore, a dual collection system exists. First, 3000-4000 collection agents perform a door-to-door collection and buy plastic waste from the inhabitants. These buyers collect on average 10 kg of plastics per day for 25 days a month. This source collection can obtain waste quality plastics with little fouling, with an intresting market value. On the other hand, 25,000 people sort on the various dumpsites of the city. They extract 15% of the recoverable material of which 4% of plastic waste. On average, each sorter recovers 8 kg of plastic a day and works 20 days a month. The most fouled waste is resold at lower prices than those collected at the source.
'c. Frequency, transmission and transfer Besides the type of collection system in place, it is important to consider three parameters which are the frequency of collection, transport and transfer. 1. The collection frequency of plastic waste is assessed during the implementation of the collection system but must be regularly updated. It is charecterized by various factors such as:
- The quantity of accumulated waste with the inhabitants or in the reunification points. A too infrequent collection causes accumulations of waste and therefore significant nuisance: odor, visual pollution, risk of being eaten by livestock, ... this may discourage the sorting and all efforts in sensibilisation will be destroyed.
- The quality of plastics, which is directly related to the storage time of the waste sorted by the inhabitant, in the streets or in the landfills.
- Habits of the local community. In some communities, waste is collected every day. A less regular collection of sorted plastics can cause a blockage and become irreversable.
The frequency of collection is thus an excellent indicator of the quality of the collection service. It is necessary to make every effort into make it as high as possible.
2. We can not repeat it enough: "Transporting is expensive! And transporting plastic is even more expensive given their low densities (between 0.9 and 1.4, but the density in bulk rarely exceeds 400 kg/m³). It is therefore needed to be very wary about this aspect of the project. To do this, some advices may be followed:
- Shorten up the routes as much as possible, including placing the recycling center as central as possible in the area but also by organizing the pick-up smartly.
- Use of cheap transport, adapted to the local environment
- Atleast condition the waste to densify the content of the collection vehicles. For this, it is sometimes advisable to already perform an initial cut up before placing it in the vehicle.
The choice of the vehicle is very important. There are countless projects that have opted for unsuitable transport means and of which the vehicles (often very sophisticated) are found to stop due to fuel exhaustion, breakdown, unobtainable parts, ... It is therefore essential to thoroughly research the local situation before investing. The volumes of waste to be transported and the distances are known before the evaluation of the deposit made on the area. The table below shows, in order of increase in investment cost, the various means of transport traditionally used to collect urban waste.
|Handcart||0.25 to 1 m³||~ 1 km||Everywhere||Cheap, no negative effects on the environment|
|Tricycle with pedals||1.5 m³||1 to 3 km||passable trails||Faster, no negative impacts on the environment, lifetime sometimes limited.|
|Animal-pulled cart||1.5 m³~7 km||passable trails of a with larger than 2.5m||Greater investment cost (purchase, nutrition and animal care). Little impact on the environment, except for the excrement.|
|Small motor vehicles (motorcycles, tractors, freight motorbike, ...)||1.5 to 4 m³||Up to 10km||Passable trails||Lifetime often limited because they are pushed to their maximum capacity. Fuel expenses.|
|Pick-up||3 to 6 m³||Very far||Passable roads and tracks||High investment cost (purchase, insurance, fuel, maintenance, ...)|
|Truck||Up to 12 m³||Very far||Passable roads of a minimum width||Very high investment cost, expensive and sometimes difficult obtainable spares, great delay of delivery for these parts, ...|
Table 3.6: Types of collection vehicles
Accessibility is a qualitative type of data. The streets in some neighborhoods are too narrow, congested or unpassable for large vehicles to pass. We evaluate the accessibility by identifying the streets of the area and classifying them according to their ease of access:
- For large vehicles: truck, pickup
- For light vehicles: pickup, van, small motorized vehicles, ...
- For non-motorized vehicles: freight motorbike, cart, carts, ...
- Only on foot.
3. The notion of transfer occurs when the collection system in place requires different means of transport. We then talk of different levels of collection:
- The primary collection. This is the collection at the place of waste production, notably at the inhabitants, at the enterprises, at the merchants, ... When travel distances permit and when the quantities of waste to be collected do not exceed the capacity of the used vehicle, the waste is directly transferred to the recycling center.
- The secondary collection. The distances from collection sites to landfill or recycling center is sometimes too long, notably for cart- or freight-motorbike-type vehicles. It is better to conduct a waste collection run and then transferring the collected waste into a larger vehicle which is better suited for long trips. We call these stopovers "transfer sites".
- The tertiary, quaternary, ... collection. And so, we can multiply the methods of transport and the transfer sites. The waste may also be transferred to sorting centers. The recyclable matter is then transported to the recycling centers while the leftover waste is going to the landfill.
The main thing is know whether to proceed from a primary to a secundairy waste collection and the costs of this transfer must be evaluated according to the material used in each phase.
Moreover, we must carefully determine the best method for unloading the primary vehicles and the loading of the secondary vehicles. For this, there are two ways in which to proceed:
- The direct transfer consists of simply loading the waste by hand or by using tools from the primary or secundary vehicle. This technique, unfortunately too often used, is very inefficient and not hygienic. The transfer is very slow. We are wasting time (and money) because we need to synchronize the vehicles. The environment is often polluted by any waste falling off during operations.
- The transfer at two levels consists of raising the primary collection vehicle sufficiently high so as to be able to dump the waste into the vehicle or in a secondary container using the force of gravity. This can be done by constructing ramps, pits, or simply by using the natural elevation of a slope. The transfer is so much faster and more hygienic. The economic performance is obviously much greater.
Note: A too gentle slope takes up a lot of space. A too steep slope limits the weight contained in the primary vehicle.
To learn more about waste management: H.C. Haan, A. Coad, I. Lardinois, 1999, Gestions de déchets municipaux: Engager des micro- et petites entreprises, translation by F. Weijters-Bage, SKAT, Switzerland. Book intented to managers of municipal solid waste who seek to improve their service or save money. He answers the questions "why" and "how" to engage small groups in community-based collection of solid waste from streets, households and businesses. The authors look mainly on the situations encountered in countries with low and medium incomes and derive many lessons from experiences that were made in Latin America, South-East Asia and Africa. This book can be obtained at: Intermediate Technology Publications Ltd. 103-105 Southampton Row, London WCIB 4HH, UK tel. : + 44 171 436 9761 fax. : + 44 171 436 2013 e-mail: firstname.lastname@example.org website: www.waste.nl Website of the dutch ngo WASTE; which specializes in the management of solid waste in developing countries. Some publications (in English) can be directly downloaded from the website (Integrated Sustainable Waste Management, UWEP). Others may be ordered by contacting Verele de Vreede, information officer (fax: + 31 182 5503 13 e-mail: email@example.com). The prices vary between 5 and 25 €.
References[edit | edit source]
- H. C. Haan, A. Coad, I. Lardinois, 1999; Management of Municipal Solid Waste: Hire micro and small enterprises, guidelines for municipal officials; Intermediate Technology Publications, London.
- Esha Shah Rajaram, 1997; Plastic Recycling in Bangalore - India, case study report plastic recycling, Waste Publications, Gouda, the Netherlands.