How does waste affect our environment?

Introduction

We discard many things every day ranging from ordinary rubbish to old newspapers, packaging, cleaning materials and many different kinds of junk. Large quantities of pesticides and fertilisers are also leached into the environment from farms, for example. Large volumes of the gaseous, liquid or solid wastes produced by manufacturing and other industrial processes are also quite legally released. These emissions are only partially controlled by pollution control methods. Some of this industrial waste is discharged into the environment in substantial quantities.

So what is the impact of all this and to what extent is it harmful to our health and environment? Do the various substances break down into simpler forms over time or do they remain largely unchanged? The answers to these questions require a large amount of scientific data and information on health, risk and safety. In this resource we begin to consider a few aspects of these broader questions and how green chemistry provides ways for us to improve our record on protecting the environment.

This is an example of principle 6 of green chemistry.

Activity 1: Rubbish, junk and refuse - solid wastes

Municipal solid waste

The Department for Environment, Food and Rural Affairs (DEFRA) gathers data each year on the quantities of municipal solid waste (MSW) generated throughout England and Wales. This type of waste is what goes in your dustbin or the local tip, and it consists of everyday items such as product packaging, garden rubbish, furniture, clothing, bottles, food scraps, newspapers, electrical appliances, paint and batteries to name but a few. Municipal waste makes up 7% of the 420 million tonnes of waste generated each year.

Around 28 million tonnes of municipal waste was generated in 2000/2001. This was an increase of 689 000 tonnes on the same period 12 months earlier. Around 78% of the waste generated in 2000/2001 was deposited in landfill sites – essentially burying it. This was 2% down on the previous twelve months, but recycling, composting or incineration with power generation all only increased very slightly. 

Table 1 gives a breakdown.

Table 1 Treatment of municipal waste (Figures taken from the Digest of Environmental Statistics published by DEFRA on their web site at www.defra.gov.uk (accessed August 2005))

Activity 2: How can packaging materials be formulated in ‘greener’, more environmentally friendly ways?

Commercial packaging seems to be everywhere in the western world. Our food, drinks, clothing, medicine, furniture, computers, cleaning materials, publications etc all come packaged in some form. The main function of packaging is to protect the contents from damage. The final package often incorporates several types of packaging materials to ensure that the product can be transported easily. One problem with packaging material is that by its nature it is designed to be thrown away once the product is put into use. If it is not possible to redesign the product to eliminate the packaging or to recycle the packaging, then the best alternative is to ensure the packaging does no harm to the environment once it is discarded.

Most packaging is not harmful to the environment in terms of toxicity. However, because many common packaging materials do not degrade easily once they are discarded, they keep on adding to the large volume of solid waste that we produce. If packaging can decompose quickly it will be recycled naturally. For example, some companies are designing plastics that will break down through the action of microbes (bio-degradation) or light (photo-degradation) into harmless products.

It is estimated that the equivalent of 1.5 billion dustbins of packaging waste is produced in the UK each year, most of which ends up in landfill sites. Industry and commerce generate 150 million tonnes, and households about 3.2 million tonnes of packaging waste a year. Since much packaging ends up as litter on streets, it is a very visible form of waste.

In the USA it is estimated that approximately a quarter of landfill space is occupied by discarded packaging. In England and Wales, packaging accounts for about a third by weight of household waste.

In this activity you will investigate some of the different types of packaging materials used to protect products and note how some are able to decompose by enzyme action.

You will need to obtain samples of typical packaging materials used for cushioning such as shredded paper, bubble wrap, polystyrene packing (including pellets and moulded blocks), similar materials made of starch, and any other types of packaging you can find. Think about the similarities and differences you observe in these materials. Based on your observations of these, and any other knowledge you may have of packing materials, compile a brief list of ideal properties of packing materials.

Comparison of enzyme action on different packing materials

One of the characteristics of packaging that designers evaluate is biodegradability, a property that indicates the ease with which micro-organisms and other natural agents can break down these materials into the chemicals from which they are made. This process can vary greatly in the time required, from a considerable length of time for some substances to almost immediately for others. However, biological catalysts, called enzymes, can speed up the process considerably. Enzymes control nearly every metabolic process of living things. For new synthetic materials it is less likely that enzymes will be found in nature that can act upon them.

Synthetic plastics and polymers often remain unchanged in landfills for decades because there are no natural decomposers with the ability to break them down. In this investigation you will investigate how enzymatic degradation affects materials.

What you will need

• Eye protection
• Samples of typical packaging materials used for cushioning such as shredded paper, bubble wrap, polystyrene packing, including pellets and moulded block, and starch-based packaging granules
• Six 100 cm³ beakers
• Dropping pipettes
• Access to a top pan balance
• A 24-well plate
• Glucose test strips
• A little amylase
• Distilled or deionised water
• Iodine solution (0.01 mol dm^-3 in potassium iodide)

Safety

• Wear eye protection

What to do

1. Weigh two pieces each of samples of paper, polystyrene pellets and starch pellets. Trim each as necessary so that each sample is of approximately equal mass.
2. Take six 100 cm³ beakers and place a piece of each sample into each.
3. Label the beakers so that one piece of each sample is Group A and the other Group B.
4. Break up the samples into small pieces.
5. Add 10 cm³ of distilled or deionised water to each beaker and stir thoroughly. Make a note of any changes that occur in the samples.
6. To each sample in Group B add a small amount (about 0.05 g) of amylase powder and stir. Allow the sample to stand for 10-15 minutes.

Starch test

This test is based on the principle that iodine reacts with dissolved starch to produce a dark blue colour.

7. Use a 24-well plate to carry out the tests described below.
8. Using a pipette, transfer approximately 2 cm³ of the liquid for each of the six samples to separate wells in well plate. (Be sure to rinse your pipette well after each transfer to avoid cross-contamination of samples.)
9. To each of the samples in the well plate, add 4-5 drops of iodine solution and mix by gently shaking the well plate.
10. Note any colour changes in each, let samples stand for 10 minutes and make final observations.

Test for glucose

11. With a clean 24-well plate, repeat step 8 above.
12. Using glucose test strips measure the glucose concentration of each sample and record it.

Discussion and questions

Activity 3: Using the web to investigate toxic wastes

The principles of green chemistry relevant to this material deal with returning safe substances to the environment. The solid wastes we considered in the first two activities are mostly non-toxic. The major problem they present is that they take up an increasingly large amount of space in landfills and represent an inefficient use of the Earth’s resources. The toxic wastes released into the environment by various industrial operations present a much greater threat. In this activity we will attempt to find out how great this problem is.

The Pollution Inventory (PI) is published by the UK Environment Agency and is an annual record of pollution in England and Wales from regulated activities. It records the release of toxic chemicals into the air, discharged into rivers or the sewerage network, or disposed of as waste on land. The PI includes three years of data from major industrial sites and is being gradually extended to cover sewage treatment works and sites licensed to work with radioactive substances. Interestingly, during the year 2000, the chemical industry has shown some of the greatest reductions in emissions. In fact for most chemicals the trend over the past three years is for a reduction in pollution.

The Pollution Inventory currently contains details on large industrial sites, with the greatest potential to cause pollution, as designated in the Environmental Protection Act 1990. The smaller, less hazardous, but more numerous, processes are regulated by Local Authorities. Many other sources of pollution are not included, such as the significant contribution made from transport. For further details on national pollution levels to air visit the UK National Air Quality Information Archive (formerly the National Atmospheric Emission Inventory) www.airquality.co.uk (accessed September 2002), published by DEFRA and the Department of the Environment (DOE). Indications of the levels of pollution to air from sources not included in the PI are indicated in the Figure 1 which can also be found at www.environment-agency.gov.uk (accessed September 2002).

Notes on Figure 1

• VOCs are volatile organic compounds.
• PM₁₀ refers to particulate matter in the air with an aerodynamic diameter of less than 10 µm.
• Dioxins are a group of 210 similar chlorinated organic chemicals produced naturally from volcanoes and forest fires and from the by-products of smelting, bleaching of paper pulp and manufacture of some herbicides and pesticides. Dioxins may cause adverse health effects.

Figure 1 Emissions to Air from Agency-regulated industrial processes, other sources and road transport, 1990 to 2001 (Reproduced with permission of The Environment Agency)

Discussion and questions: the pollution inventory

Discussion and questions: pollution Inventory data by region

Table 2 shows the total amounts of toxic pollutants released in each UK region for 2000.

Table 2 The total amounts of toxic pollutants released in UK regions in 2000