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Waste separation is the process of separating waste into different waste materials, often referred to as waste fractions. Waste separation is an integral part of SWM. In keeping with the circular economy principles and the waste management hierarchy P.1, the objective of waste separation is to separate items and materials of value from the main bulk of waste which can be repurposed, reused, recycled or treated. Separation and subsequent recovery, treatment and recycling reduce the amount of waste for disposal and thus increase the lifespan of landfills.
Waste can be separated at different stages along the SWM chain. When separated right after generation it is referred to as ‘Waste Segregation’. In this case, the segregated waste fractions have never been mixed with other waste. When waste fractions are extracted from mixed waste, it is referred to as ‘Waste Sorting’.
Waste segregation should be prioritised over waste sorting as segregated waste is higher quality and therefore facilitates recovery rates by reducing the complexity and cost of waste treatment and recycling (section T ) and providing safer and cleaner working conditions for SWM workers X.4.
Waste segregation is essential when dealing with specific wastes such as medical waste W.1, hazardous waste W.2 or e-waste W.7, given their high potential health hazard. If such specific wastes are not rigorously separated from regular domestic solid waste, their hazardous nature contaminates all the waste they come into contact with. Consequently, all the waste must be considered and handled as hazardous. Medical waste illustrates the problem: of the waste generated in health care centres, the largest waste fraction consists of unproblematic and harmless waste comparable to household waste; only a small amount is toxic or infectious. However, if these different fractions are stored together as mixed waste, the whole amount of waste must be considered toxic or infectious and would require special handling and treatment. This is also the case if some waste containing infectious or hazardous substances is mixed with waste from other sources (e.g. households, restaurants and markets.
Waste segregation ensures that items of value are kept separate at an early stage and are not contaminated by other waste. This allows much easier and cost-efficient processing in the next waste handling steps.
Waste can be segregated by using different containers/bins for the different fractions that are to be segregated. The bins are located in households or at a communal and public level. When waste has been segregated it is essential to follow up with a separate waste collection (section T ) and to prevent segregated waste from being mixed with other waste again.
To further facilitate and maintain the segregation of waste, it is essential to clearly mark the different segregation categories with, for instance, colour codes, symbols and short words. The same marking must then be applied throughout the SWM service chain, from waste storage to collection and transport vehicles, and at the various facilities such as transfer stations (C.5), processing facilities and disposal sites.
As opposed to waste segregation at source, waste sorting is the process of extracting specific waste fractions from mixed waste during the different stages of the SWM chain. Waste sorting and the subsequent use and treatment of the sorted fraction reduces the amounts of waste requiring disposal and allows the recovery of recyclables and organic materials. Waste sorting can happen at multiple stages: during collection and transportation, at waste transfer stations, at treatment facilities or even at disposal sites. Waste sorting at disposal sites is often practised by informal waste pickers, however, this is undesirable due to the high occupational health risks X.4 associated with this practice. In some cases, segregated waste may also require waste sorting, for instance, to further separate individual material types for further treatment or handling by the recycling sector. An example is the sorting of plastic types (e.g. PET, or HDPE) before sales to the recycling sector or for further processing. Sorting may even be a necessary pre-processing step in treatment facilities to, for example, remove undesired non-organic materials before organic waste treatment at the facilities. High-quality waste segregation minimises the need for further sorting. Mixed waste sorting is undesirable as it is a time-consuming task, requires numerous staff members to work in challenging conditions and typically results in materials of lower quality compared to waste segregation at source. Waste segregation should always be prioritised over waste sorting.
2-bin system: the most basic waste segregation is a separation into two main fractions: organic and non-organic materials (also referred to as ’wet’ and ’dry’ waste separation). Dry non-biodegradable waste is collected and then undergoes an additional sorting step to recover valuable recyclable materials such as plastics, metals, or glass. Such intermediate sorting may be conducted at Transfer Stations C.5 or disposal sites U.9 before disposal. Segregated organic ’wet’ waste can be further processed, for instance, to recirculate nutrients and carbon for the growth of plants (T.1 and T.2) or to produce alternative protein sources such as black soldier fly larvae T.4. Segregated biodegradable waste can also be used to produce biomass-based energy such as biogas T.3. High-fibre materials may be suitable to produce biomass-based fuels for cooking or heating T.5. If organic waste is treated for agricultural use ensuring source-segregation and minimal impurities is essential. When used, the presence of non-organic waste in the products may jeopardise the health of soil and farmed animals.
3-bin system: improved segregation uses three categories of separation: organic waste, recyclables and residual waste. This setup helps to keep valuable recyclables cleaner and easier to sort at a later stage.
Segregation in more than 3 fractions: segregating additional waste categories, such as different types of plastics, metals, glass or cardboard, is possible but increases the complexity of separate collection and transport. It can be difficult and requires behaviour change X.6 for waste generators.
Collection frequency: different waste segregation categories may have different generation rates, so they can be collected at different frequencies. Organic waste must normally be collected most frequently due to its rapid decomposition and resulting smell and attraction for animals. Collection approaches can vary according to how and from where segregated waste is collected (section C ). If collected from communal storage, it is feasible to send vehicles dedicated to one or several waste categories. If collected directly from households, collections should ideally happen several times a week, if not daily. In this case, the different categories of segregated waste can be collected in one go. There are positive examples from door-to-door collections as operators observe each household’s quality of segregation and can build up relationships with the different households. Operators can sensitise households about the importance of SWM and, if necessary, can directly correct waste segregation or instruct households on correct waste handling.
Waste segregation and behaviour change: to facilitate the segregation of waste, raising awareness and introducing the concept of source-segregation in the communities is both a key factor for success as well as a challenge. Source-segregation fails if communities do not comply with the planned segregation practices and do not segregate waste correctly or at all. In these cases, a later sorting of waste within the SWM service chain is the only remaining option. However, this approach is commonly ineffective and costly and compromises occupational safety X.4. Awareness and sensitisation campaigns might be insufficient to introduce waste segregation to communities and behaviour change interventions will be required X.6.
Waste segregation in humanitarian settings: waste segregation is particularly important in humanitarian settings for the reasons mentioned above: it reduces waste amounts and provides opportunities to boost local economies. Nevertheless, efficient waste segregation strongly relies on the participation X.2 and correct practices of individuals and households as well as on functioning and intact services and infrastructure. As waste segregation might be new for targeted communities in humanitarian settings, behaviour change X.6 may be even more challenging. It is therefore not usually feasible during and shortly after emergencies. In such settings, community members might be traumatised, busy with their day-to-day survival struggles and unlikely to be willing and able to consider specific and new waste-handling practices. In protracted and development settings, the likelihood of successfully implementing waste segregation is much higher.
Prerequisites for waste segregation include relatively stable living conditions, correspondingly adapted SWM services and infrastructure, a local link to the recycling sector and the possibility of processing recovered materials on-site. While the latter can be applied with simple means for biodegradable waste and the production of compost T.1, it can be more complex for recyclables. Successful waste segregation is also based on thoroughly trained staff. If staff are not sensitised about the importance of safe waste handling and resource recovery, there is a risk that source-segregated waste is mixed again during collection and transport. Given the challenges of waste segregation, it might be expedient for humanitarian settings to limit waste to only two (organics/non-organics) or three (organics/residual waste/recyclables) segregation categories.
Once waste segregation can be implemented in humanitarian settings – for instance in stable contexts where communities are ready to apply new disposal practices – the segregation of organic waste is advantageous in all cases. Even if agricultural reuse is of limited interest, removing organics helps to significantly reduce waste amounts, largely reduces odour nuisances and limits the attraction of animals. For all other segregation categories, SWM actors need to thoroughly assess P.3 the market interest for recoverable items and materials, as well as the feasibility of processing recovered materials in humanitarian programmes. It is unreasonable to create segregation categories for materials which are neither of value nor can be processed by humanitarian actors. The required storage for these materials until there is market demand might be too expensive and space-consuming. SWM actors also need to consider that local small-scale scrap dealers might not be aware of all potentially re-saleable recyclables as they are likely to focus only on the most valuable materials. If scrap dealers work together and pool their collected materials, the trading of less valuable recyclables may become profitable. Another approach to ensure higher prices is to pre-treat recyclables and facilitate their transport, for instance, through the hydraulic pressing of metals to compact batches or the shredding of plastic containers to allow a denser filling of transport bags. Before incorporating these processing capacities, it is advisable to consult recycling stakeholders to ensure that the quality requirements for handling recyclables are being met.
In humanitarian settings, the highest priority for recovered materials is always to hand them over to the local recycling sector. Even if recovered materials are handed over for free, SWM actors still financially benefit from the reduced amount of waste to be disposed of and the corresponding cost savings. Priority must also be given to the handover as the establishment of a parallel processing system by humanitarian or development actors leads to competition with the local private sector and a distortion of markets X.5. In almost all cases, this competition will be to the disadvantage of the private sector, as works conducted by humanitarian or development actors are not business-oriented and benefit from indirect subsidies. The second priority, in the absence of private-sector activities, is for humanitarian and development actors to consider the processing of recovered materials themselves, such as plastic downcycling T.8. The output of such activities needs to be balanced with the likely lack of expertise amongst actors and the potential occupational X.4, public health and environmental risks.
For waste originating from in-kind distributions such as food packages and food containers W.5 there are good examples in humanitarian settings of waste segregation and the ‘take-back’ of distribution packaging by communities to the next distribution. In-kind distributions should ideally be designed to minimise waste generation and facilitate reuse and recycling. In some cases, in-kind distribution organisations also use returned packaging material and food wraps for upcycling T.7 projects. These workshops can provide income, and the creative work might be a welcome distraction for affected communities. The distribution of new items or food must not be contingent on the return of packaging waste though communities seem to get used to storing packaging waste in their homes and bringing it back when new distributions take place. These recovered waste materials are then ready to be safely disposed of or can be used for recycling T.6, upcycling T.7 or downcycling T.8.
In humanitarian settings, waste is generated from activities linked to humanitarian and development actors (e.g. in-kind distributions, food assistance, general operation) and from market-available consumer goods. For the latter, avoiding and reducing waste is more complex or potentially even impossible compared to waste generated by humanitarian actors. In both cases, reducing waste must be considered with the highest priority P.1.
Potential activities and priorities to implement waste segregation in humanitarian settings include:
In humanitarian settings and in low and middle-income countries, valuable waste materials are likely to be recovered by the informal sector. Informal removal is usually limited to the most valuable and accessible materials and can happen directly at the household, communal and public storage levels as well as on informal disposal sites. Informal workers should not have access to controlled disposal sites and landfills U.9. SWM interventions must not create competition with the informal sector as it is a last-resort opportunity for income generation for the poorest of the poor. Instead, informal workers should be integrated into interventions X.2 or at least strengthened so that their working conditions are improved, occupational health and safety X.4 maintained and child labour prevented X.1. Informal workers might remove the most valuable materials before SWM providers can collect them. It is also possible that official operators remove valuables during collection or transport. While the practice of the official operators in particular may be condemned by SWM providers, it is recommended that SWM providers do not prohibit it. Removing valuables from waste might be a welcome side income for official SWM operators and is an essential livelihood for informal workers. In both cases, SWM providers still benefit from the handling of reduced waste amounts. For organisations, the financial value of the removed items might anyway have been limited.
Waste separation, whether ‘Segregation’ or ‘Sorting’, is represented in this Compendium with the specific symbol. When associated with storage technologies, the symbol represents waste segregation at source. Further along the waste service chain, the symbol represents waste sorting. Sorting can be associated with collection and transport, treatment or even disposal. Sites of combined waste sorting and waste transfer are commonly referred to as Material Recovery Facilities (MRF). After the sorting at the MRF, the different waste fractions are further transferred to treatment, processing or disposal.
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