Skip to main content
Printable page generated Thursday, 24 Jun 2021, 21:36
Use 'Print preview' to check the number of pages and printer settings.
Print functionality varies between browsers.
Printable page generated Thursday, 24 Jun 2021, 21:36

Study Session 8  Solid Waste Reduction, Reuse and Recycling

Introduction

In every aspect of human life unwanted materials are generated and then discarded simply because they are considered to be wastes. Think about preparing a meal; there will be vegetable peelings and fruit cores, there may be skin and fat trimmed off fish and meat, and, if canned or bottled ingredients are used, there will be the empty bottles and cans. Households, businesses, industries, the healthcare system and public organisations all produce wastes that need to be processed. In Study Session 7 you learned about the different types of wastes, and in this study session you will learn how the waste hierarchy can be applied to help reduce, reuse or recycle the solid wastes that we produce.

Learning Outcomes for Study Session 8

When you have studied this session, you should be able to:

8.1  Define and use correctly each of the terms printed in bold. (SAQs 8.1 and 8.2)

8.2  Use the waste hierarchy to identify the best ways of dealing with different wastes. (SAQ 8.2)

8.3  Give examples of how people and organisations can reduce waste. (SAQ 8.3)

8.4  Explain the benefits of separating solid waste. (SAQ 8.4)

8.5  Explain the processes for composting and for producing biogas from organic wastes. (SAQ 8.5)

8.1  The waste hierarchy and the ‘3 Rs’

  • Think back to Study Session 1. What do you remember about the waste hierarchy?

  • The waste hierarchy lists the different ways of dealing with wastes, starting with the most beneficial and working down to ‘disposal’, which is the worst way of getting rid of waste.

Many versions of the hierarchy have been published, but they all present the same message. The version of the hierarchy used in this module is shown in Figure 8.1. Reduction, reuse and recycling were first defined in Study Session 1 and are explained more fully in the following sections. The fourth option, recovery, is also explained here. The final option, disposal is about finding a place to get rid of wastes that cannot be treated by any of these alternatives. Waste disposal is the topic of Study Session 10.

Figure 8.1  The waste hierarchy.

8.2  Waste reduction

At the top of the hierarchy is waste reduction. This is the best option because the most effective way to limit the health effects and environmental impacts of a waste is not to create waste in the first place. Making any new product requires materials and energy. Raw materials must be extracted from the Earth and processed, and the product must be manufactured, packaged and transported to wherever it will be sold. Each of these stages may produce solid waste as well as liquid wastes and air pollutants. If we can find ways of making a particular item whilst producing less waste in the process, this is one of the most effective ways to reduce pollution, save natural resources, protect the environment and save money. Industry has a major part to play in waste reduction. If more efficient manufacturing processes were adopted, greater quantities of products could be made without increasing the use of raw materials. Industry can also work to incorporate less material into its products – so for example, an item could be packaged using less cardboard than before.

Waste reduction is also important at household level. In Ethiopia a number of waste reduction initiatives have been put in place in big cities like Addis Ababa and Mekelle by informal organisations and private sector enterprises. These initiatives frequently involve several different stakeholder groups including urban Health Extension Workers (HEWs), civil society, private sector enterprises and organised women’s development groups. The local kebele administration and appropriate experts from the Woreda Health Office and Greenery and Beautification Office are also likely to be involved. The Ministry of Health has produced some teaching aids and promotional materials aimed at educating communities on how to reduce and minimise waste at household level. Educational campaigns can raise awareness of the individual economic incentives, and can also be used to reduce the stigma attached to working with waste.

Part of your role as an urban WASH worker may be to help educate householders, through home visits and at community gatherings, about better ways to manage their domestic waste. This can result in behavioural change among the community members and increase their active participation in waste reduction (and reuse) at the household level.

There are many possible ways of reducing the amount of waste produced at home that could be suggested to householders. These include educating and encouraging them to:

  • Buy products that use less packaging. Buying in bulk, for example, can reduce packaging and save money. Where households cannot afford to pay large sums of money up front, it may be possible for neighbours to club together and buy a large quantity of a basic foodstuff between them.
  • Make use of reusable rather than disposable items. For example, use refillable containers where possible; washable rather than disposable nappies; cotton handkerchiefs rather than paper tissues; rechargeable batteries and refillable ink pens.
  • Use their own shopping bags, preferably made of cloth or other recycled material rather than plastic bags.
  • Minimise food scraps or feed these scraps to animals, if appropriate.
  • Repair and maintain items such as clothing so that they last longer.

8.3  Waste reuse

Reuse can be defined as using a waste product without further transformation and without changing its shape or original nature. This is the second option in the waste hierarchy. Different types of solid wastes can be reused, such as bottles, old clothes, books and anything else that is used again for a similar purpose to that originally intended. Reuse means that less solid waste is produced. It brings other benefits by taking useful products discarded by those who no longer want them and passing them to those who do. 

  • Suppose you are attending a meeting of a women’s development group and one of the participants asked you to explain what is meant by reusing waste. How would you explain the concept?

  • You could first explain that reuse means using something without changing its shape or original nature. You could then list some examples, such as bottles that can be refilled, old clothes that can be passed to neighbours and carrier bags that can be used more than once.

The informal waste management sector does a lot to promote reuse and recycling. Individuals (known as korales) buy reusable bottles and jars and recyclable materials from householders and sell them on to small shopkeepers and merchants (Figure 8.2). Bjerkli (2005) estimated that around 5000 korales were working in Addis Ababa.

Figure 8.2  Collecting and selling reusable plastic bottles.

8.4  Benefits of reducing and reusing solid waste

Waste is becoming a bigger problem in urban areas each year. Households are producing more waste, so disposal sites are filling up and new sites are further away from residential areas. Where waste is collected and transported to a disposal site, this is becoming more expensive. Where householders have to dispose of waste themselves, they have to spend more time doing this. Anything that reduces the amount of waste that has to be disposed of helps to reduce these problems. Some other advantages of waste reduction and reuse are summarised below.

Community benefits

Reuse can be very helpful for disadvantaged people who cannot afford to buy new goods. These could include clothing, building materials, and business equipment. Reuse centres that collect and distribute reusable goods can also provide community benefits by engaging in job-training programmes and general training for the long-term unemployed, disabled people and young people.

Economic benefits

By reusing materials rather than creating new products from raw materials, there are fewer burdens on the economy as a whole – especially if reuse results in a reduction in raw material and product imports. Reuse is an economical way for many people to acquire the items they need. It is almost always less expensive to buy a used item than a new one.

Environmental benefits

Reusing something uses little or no water, energy or other resources and is unlikely to cause pollution. As well as these benefits, reuse eliminates the environmental damage that would have been caused if the item had been disposed of, rather than reused. In contrast, manufacturing a product from raw materials (and, to a lesser extent, recycling) consumes resources, causes pollution and generates wastes.

8.5  Waste recycling

Recycling waste means that the material is reprocessed before being used to make new products. The reprocessing activities can have an impact on people’s health and the environment, but these impacts are usually lower than those from making the product from new, raw materials. Recycling means treating the materials as valuable resources rather than as waste. It has many benefits but it is important to have a market for the end product, otherwise the process will not be economically sustainable.

The options for recycling depend on the type of waste. For example, waste paper can be broken down to its fibres in a process called pulping. The pulp is cleaned and then formed into new paper to be used for printing or packaging. Waste metals and glass can also be recycled by melting them down into new raw materials. Sheet metals can be beaten and reformed into new products (Figure 8.3). Plastic bottles can be ground down and used to make plastic rope or plastic coating for electric wires. For some wastes, recycling involves complex technical processes and requires specialised machinery, but others can be recycled more simply and on a small scale. All types of organic waste can be recycled by composting, which can be carried out at home or on a larger scale. Composting is described in Section 8.5.2.

Figure 8.3  Large metal containers can be cut and reformed into new products like these sieves and stoves.

8.5.1  Waste separation

It is difficult to recycle materials once different wastes have been mixed together, so the first stage of the recycling process is to separate the materials into different categories. This is called waste segregation or separation at source and should be done by the householder when the waste items are finished with and discarded. Waste is separated by placing the different categories of waste into different bags or containers.

The degree of separation required will depend on the recycling opportunities that are available, but it is important to separate ‘dry’ and ‘wet’ materials. The simplest method of separation is to keep food waste separate from the remaining materials so that the food waste can be composted or used to make biogas (see Sections 8.5.2 and 8.6). If korales are active in the area, they may ask householders to keep all their recyclable materials (paper, metals, plastics and glass) together, or ask for just one or two materials to be separated.

If waste is not separated at the source, it ends up at a disposal site where all the waste is mixed up so separating the different types becomes much more difficult and hazardous. In many developing countries, including Ethiopia, collecting waste for recycling is often conducted by the informal sector. Such work can be done in a very labour-intensive, unsafe and polluting way, and for very low income. Often young children are employed as collectors. Part of a WASH team’s job is to help put the recycling industry on a more formal basis. This is another aspect of waste management that requires collaboration among stakeholders, including the informal sector and other concerned partners, to help improve the working conditions and provide protective equipment and training to the korales and other waste collectors.

It is possible to set up a more formal scheme to collect recyclable materials where the collectors provide separate receptacles for recyclable and non-recyclable wastes. Although separation has the advantage of promoting recycling, it also has the disadvantages of higher collection costs and needing special equipment and additional workers to collect each type of material. Therefore, in most urban and peri-urban areas, recycling collections are carried out by the informal sector.

Once separated materials have been collected from householders by the korales or by the more formal sector, they are passed on to merchants and eventually to the industrial operations that transform the wastes back into useful raw materials or products. Much of this part of the recycling chain falls outside the work of a local WASH team, but team members can still help people to become more aware of the importance of waste recycling and encourage them to separate materials for collection.

8.5.2  Composting

Composting is the process where biodegradable organic wastes (food and garden waste) are converted into compost in a natural biological process. Composting can be done by individual householders and community groups or on a commercial scale. On the larger scale, the waste from an entire town or city could be composted if sufficient land, labour and equipment is available. The benefits of composting are not only the reduction of waste, but also the production of compost which is a valuable soil improver. Soils treated with compost are better able to withstand droughts and are more fertile because plant nutrients are returned to the soil, which reduces the need for manufactured fertilisers. It is possible to add a certain amount of animal manure to residential waste for composting, which may help with other waste problems in the community and adds to the amount of useful soil improver that is made.

  • Refer back to Table 7.1 in Study Session 7 and estimate what proportion of the municipal waste from urban areas can be composted.

  • According to the data in Study Session 7, municipal waste contains 44% food waste and 12% garden waste making a total of 56%, so more than half of the waste can potentially be composted.

As an urban WASH worker you may be required to help individuals or communities set up and operate composting processes (Figure 8.4). The stages in the composting process are outlined below.

Figure 8.4  The composting process.
  1. Separation of compostable materials: It is important to begin with an uncontaminated input to the process. Nearly all organic wastes can be composted, but if a composting pile attracts rodents and other scavenging animals it may be better to exclude meat products and cooked food from the process and just collect garden waste and raw vegetable waste.
  2. Grinding or shredding: To speed up the composting process it may be necessary to shred the raw waste before placing it in the compost pile. Shredding is normally required if a significant proportion of the waste has particles greater than about 50 mm. On a domestic scale this can be achieved simply by cutting up the waste into smaller pieces.
  3. Blending or proportioning of materials: Composting works best with the right mixture of wastes so that the moisture content and the proportions of the chemical elements carbon and nitrogen are suitable. Generally, the ideal mix for composting is three parts (buckets, for example) of ‘brown’ waste (such as leaves, hay, straw, eggshells, shredded paper, card and woody material), with one part ‘green’ material (such as grass, food waste and animal manure). ‘Brown’ waste contains a higher proportion of carbon and ‘green’ waste, contains more nitrogen and has a higher moisture content. Thus the ratio of brown waste to green waste is 3:1.
  4. Composting: Composting is normally carried out in a pile. For larger scale composting processes, piles are in the shape of long rows of waste, normally with a triangular cross-section (Figure 8.5). The ideal pile is 1.5–2 m wide and about 1.5 m high. The length of the pile is determined by the space and the amount of waste available. On the domestic scale the pile will be much smaller, forming a rounded heap. The pile can be built up as waste becomes available, but it is important to have enough material present to allow the biological processes to take place reasonably quickly, so as a guide a domestic compost heap should be at least 1 cubic metre to start the process.
Figure 8.5  Composting process: mixed waste is piled in long rows.

Composting is an aerobic process, so the pile needs to be turned regularly to introduce air. This means dismantling it, mixing the waste to introduce air and then rebuilding the pile. The first turning-over of the heap should be done after two to three weeks and then every three weeks or so. The composting process will be complete within three to six months. The composting process generates heat, so it is normal to see steam coming out of the pile.

The process is complete once the pile no longer heats up after mixing and rebuilding. The final product should be brown and crumbly and look like a good soil. If it still contains identifiable items, the process is not complete.

  • Summarise the advantages of composting.

  • Composting provides an effective and safe way of disposing of a large proportion of a community’s waste that doesn’t involve specialised or costly equipment. It provides a valuable product that can be used by the community to improve the quality of its vegetables while reducing the need to buy fertilisers. Other wastes, such as animal manure, can also be added to the composting process.

8.5.3  Recycling and composting in Ethiopia

It is very difficult to assess how much of Ethiopia’s waste is recycled or composted. As explained above, much of the nation’s recycling is done by the informal sector and so information about it never enters the official statistics. Percentage recycling rates cannot be estimated because the total amount of waste produced is unknown. Much of the waste is never collected and disposal sites do not weigh the waste that does arrive there. Bjerkli (2005) quoted government figures for Addis Ababa which suggested that about 15% of the city’s waste was recyclable, but that the recycling rate was about 5%. Around 60% could have been used in compost production, but only 5% was composted. However, these figures should be viewed with caution because they depend on the reported quantities of waste and, as noted above, it is very difficult to obtain accurate data. In addition, some reusable and recyclable wastes such as metal scraps, old clothes and shoes are not considered as wastes in the first place. The actual recycling rates, if these materials were taken into account, would probably be higher.

8.6  Energy recovery

The fourth option in the waste hierarchy is recovery. Recovery is about finding other uses for wastes that enable some value to be extracted or recovered from them, usually by using them as a source of energy.

Recovering energy from waste on a large scale using an advanced incineration plant is a high-technology, high-cost option that is common in many developed countries. However, it needs a highly developed infrastructure (a reliable source of waste, good roads, a reliable waste collection service, a power distribution grid, etc.) and large amounts of waste. This technology is currently rarely used in low- and middle-income countries, but as cities develop there is great potential for energy-from-waste in the future in Ethiopia and many other countries (Scarlat et al., 2015).

8.6.1  Biogas production

In Study Session 5 you learned about the production of biogas from excreta by anaerobic digestion using the biogas latrine. The same technology can be used to treat food waste on its own or in combination with human excreta or animal manure.

Biogas recovery from organic waste (Figure 8.6) can be done at the kebele or household scale, where the biogas can be used for cooking and heating water. The sludge from the digester can be used as a fertiliser and soil improver. Another benefit of biogas production is the reduced use of fuel wood, which improves living conditions by reducing indoor air pollution. Additionally, biogas contributes to the reduction of greenhouse gases. The use of biogas as a cooking fuel will mainly benefit women because it will reduce their overall workload by providing energy for the household without requiring labour-intensive fuel collection.

Figure 8.6 A biogas instructional poster from the Biogas Pilot Program (BPP).

Biogas production needs more equipment than composting, so it is more expensive to install. It also requires greater expertise than composting to operate and the equipment must be maintained. Small-scale biogas is well established in China and India, but this method is still relatively uncommon in Ethiopia (Rajendran et al., 2012).

To conclude this study session and provide an example of the various ways in which waste can be used, Box 8.1 describes the IGNIS programme, based in Addis Ababa. This programme included several pilot projects using many of the waste management options that you have been reading about.

Box 8.1  The IGNIS programme

The overall aim of IGNIS is to help people to generate income by recovering value from waste. This has involved the development and implementation of novel technologies and working to improve the social status and health of waste workers. Funding was provided by the German Federal Ministry of Education and Research, and the programme was run by a number of German and Ethiopian governmental agencies, academic institutions and non-governmental organisations (NGOs).

Some of the IGNIS projects include:

  • Setting up a house-to-house collection of compostable waste and training people to make compost and to use it to grow vegetables.
  • Collecting and composting waste from street markets and employing former street children and sex workers to collect the waste, as well as to make and sell the compost.
  • Using the compost to fertilise and improve soil on deforested slopes around Addis Ababa which are prone to erosion. The land can then be planted with crops and brought back into use.
  • Addressing the health issues (malnutrition and back problems) of the korales.
  • Encouraging small-scale paper recycling factories.
  • Supporting a women’s group in recycling charcoal dust and reconstituting it to make fuel briquettes.
  • Installing pilot biogas plants that use food and kitchen waste to produce biogas for cooking.
  • Making gloves from scraps of leather and textile wastes.
(IGNIS, 2012)

The IGNIS projects demonstrate that considering waste as a resource has many environmental, economic and social benefits. They also show how integrating different approaches to waste management can maximise the benefits.

Summary of Study Session 8

In Study Session 8, you have learned that:

  1. The waste hierarchy is a guide to selecting the most environmentally sound strategies for municipal solid waste, which ranks waste management interventions according to their environmental or energy benefits.
  2. Waste reduction involves industry in designing products to reduce the amount of waste that will later need to be thrown away. At the household level, waste reduction is about people making decisions to avoid generating waste.
  3. Recycling means reprocessing waste into new material. The first step is separation of waste into different types.
  4. Composting is the process of converting biodegradable waste into compost, a soil improver. This method has the advantage of providing a safe disposal route for organic waste while producing a useful end product.
  5. Composting requires organic wastes to be sorted, shredded, blended and placed in a pile for a few months. The pile must be turned every few weeks to introduce air.
  6. Recovery means extracting (recovering) value from waste, usually in the form of energy.
  7. Biogas recovery from organic waste has the potential to provide gas for heating at the kebele or household level. It can treat residential waste along with human excreta and animal manure.

Self-Assessment Questions (SAQs) for Study Session 8

Now that you have completed this study session, you can assess how well you have achieved its Learning Out comes by answering these questions.

SAQ 8.1 (tests learning Outcome 8.1)

Composting is an example of waste recycling but it could also be described as an example of recovery from waste. Explain why this statement is true.

Answer

Composting is an example of recycling because the waste is reformed into a new material, compost, which is different from the original waste. It is also an example of recovery because the compost has value as a soil improver and has been recovered from the waste.

SAQ 8.2 (tests Learning Outcomes 8.1 and 8.2)

The waste management hierarchy is shown in Figure 8.7 below but without labels.

Add the correct terms to the five label lines on the right side of the diagram.

Figure 8.7  The waste hierarchy.

Answer

Figure 8.8  The waste hierarchy.

SAQ 8.3 (tests Learning Outcome 8.3)

Tigist is a mother of three children aged between 6 months and 5 years. Her husband has a good job and the family are well-off. Tigist does most of her shopping in the local supermarket where they give plastic carrier bags to all their customers.

Give three examples of ways Tigist could reduce the amount of waste produced by her household.

Answer

There are several possible answers but you may have thought of the following:

  • When she is shopping, Tigist could look for products with less packaging. She could buy fresh food bought loose in a market rather than packaged food from the supermarket.
  • She could take her own bags to the supermarket so that she didn’t have to use theirs and get new ones on each visit.
  • For the baby, she could use washable nappies instead of disposables.
  • She could use the clothes that the older children have outgrown for the younger children.

SAQ 8.4 (tests Learning Outcome 8.4)

In your job as a WASH worker, one of the korales has told you that they can’t collect much waste paper from a particular kebele because it is too dirty. How would you explain to the householders how and why they should separate their waste paper?

Answer

You could explain that separating wastes into different types makes it easier to reuse and recycle. Separation should be done in the home so that the different types do not get mixed up together. If householders sorted out their waste paper and ensured it was not made dirty by food and other wet waste, this would make it more usable. If it was clean, the korales could take it away so the householders would not have to dispose of it themselves. You could also explain about the social benefits to the korales and the wider environmental benefits of reducing waste.

SAQ 8.5 (tests Learning Outcome 8.5)

Which of the following statements are false? In each case explain why it is incorrect.

  • A.Biogas is produced from organic waste in an open tank called a digester.
  • B.Removing plastic from waste is important for both composting and biogas production.
  • C.Compost piles must be turned regularly because composting is an anaerobic process.
  • D.Composting and anaerobic digestion both produce material that can be used to improve soil.
  • E.Methane makes up about 60% of biogas.

Answer

A is false. Biogas is produced in a digester but the tank must be sealed, not open because it is an anaerobic process.

C is false. Compost piles must be turned regularly but this is because it is an aerobic, not anaerobic, process.