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Climate Change & Waste Management

Introduction

The environmental and health impacts of improperly managed waste are key concerns for our society. If not properly managed, waste can cause a variety of impacts. One of these impacts is the threat of climate change. Buried or landfilled waste produces carbon dioxide and methane, both greenhouse gases, which when emitted will enhance the natural greenhouse effect. Protecting the environment over the long term is the major challenge for waste management design professionals today. This fact sheet looks at the influence of waste on the climate, and ways to both improve the efficiency with which resources are used and to reduce the impact on the environment of waste disposal - sustainable waste management.

Emissions from Waste

Emissions from waste arise through both its incineration (burning) and landfill (burial). Burning waste releases carbon dioxide to the atmosphere. Municipal landfill gas composition is controlled primarily by products of microbial reactions in the landfill. Solid waste initially decomposes aerobically; the primary gas product is carbon dioxide. As the oxygen is used up, anaerobic micro-organisms predominate. These bacteria continue to produce carbon dioxide, but the process proceeds into second-stage anaerobic decomposition, where both methane and carbon dioxide are produced at approximately a 50-50 ratio. Methane is a much more potent greenhouse gas than carbon dioxide, trapping more infra-red radiation.

Global emissions of methane from landfilled waste have been estimated at approximately 40 million tonnes per year. In the UK, almost half the emitted methane comes from landfilled waste. Carbon dioxide emitted from waste disposal is not considered to represent a man-made source of greenhouse gas, because the process returns recently photosynthesised carbon back to the atmosphere, which has been stored as biomass. (This may be contrasted with the burning of fossil fuels, where carbon is released back to the atmosphere after underground storage, as coil, oil or gas, for hundreds of millions of years.) 50% of landfill emissions, however, include methane, a more potent greenhouse gas. Consequently, the conversion of atmospheric carbon dioxide to atmospheric methane through the waste life cycle will have a man-made influence on the natural greenhouse effect, and global climate.

Sustainable Waste Management

The increasing concern about the environmental impacts of landfilling has caused many to investigate alternatives to landfills. Increasingly, the integration of waste management planning and practices is occurring with an aim to making them more sustainable. Integrated or sustainable waste management attempts to segregate the various components of the waste stream and to manage those portions of the waste stream in an environmentally sound and economically efficient manner. Integrated waste management considers the following practices for waste management: 1. Waste reduction; 2. Recycling; 3. Composting; 4. Incineration; 5. Landfilling.

Source reduction is the design, manufacture, purchase, or use of materials (such as products and packaging) to reduce the amount or toxicity of trash generated. Source reduction can help reduce waste disposal and handling costs because it avoids the costs of recycling, municipal composting, landfilling, and combustion. It also conserves resources and reduces pollution.

Recycling is the process by which materials are collected and used as raw materials for new products. There are four steps in recycling: collecting the recyclable components of municipal solid waste; separating materials by type (before or after collection); processing them into reusable forms; and purchasing and using the goods made with reprocessed materials. Recycling prevents potentially useful materials from being landfilled or incinerated, thus preserving our capacity for disposal. Recycling often saves energy and natural resources. Composting, a form of recycling, can play a key role in diverting organic wastes from disposal facilities.

Waste incineration and landfilling play a key role in managing waste that cannot be reduced or recycled. Incineration in specially designed facilities reduces the bulk of waste and provides the added benefit of energy recovery. Source reduction and recycling can remove items from the waste stream that may be difficult to burn, cause potentially harmful emissions, or make ash management problematic. Landfilling is, and will continue to be, a major component of waste management. The portion of waste requiring incineration or land disposal can be significantly reduced by examining individual contributions to garbage and by promoting the wise use and reuse of resources.

How You Can Help?

Reduce waste production

1. Reduce the amount of unnecessary packaging.
2. Adopt practices that reduce waste toxicity.

Reuse materials

3. Consider reusable products.
4. Maintain and repair durable products.
5. Reuse bags, containers, and other items.
6. Borrow, rent, or share items used infrequently.
7. Sell or donate goods instead of throwing them out.

Recycle waste

8. Choose recyclable products and containers and recycle them.
9. Select products made from recycled materials.
10. Compost yard trimmings and some food scraps.

Energy from Waste

Potential benefit may be gained from waste if heat and/or power can be recovered through its combustion (burning). There are two basic techniques for recovering energy from household waste in conjunction with combustion. The mass burn process involves waste being incinerated, with the heat released used to raise steam. This is then fed to district heating or used to power a turbine for electricity generation. Ferrous metals can be recovered for recycling from the residue. Residues amount to 20% of the original input and therefore require much less landfill space. Tight controls exist over the use of this residue ash for construction or other uses. The other system is a two stage 'refuse-derived fuel' process. Incoming waste is shredded and screened to remove the incombustible part, including metal for recycling. The products are a fuel fraction which can be burned in industrial boilers; either on site or at a distant location; and a reject fraction which must be landfilled.

Anaerobic Digestion is an additional method that creates energy from waste without the use of a combustion process. This process converts the organic part of household waste, producing a 'biogas', for use as fuel, a liquid which can be used as a fertiliser and compost suitable for use as a soil conditioner. The process deals only with biodegradable matter; plastic, metal, glass and all other non-organic materials have to be separated from the organic matter before treatment. This technology is relatively unproven and on a small scale. However, it may form some part of an integrated processing facility.

Conclusion

Emissions from incinerated and landfilled waste - carbon dioxide and methane - contribute to the man-made enhancement of the natural greenhouse effect, and possibly to global warming. Much of the billions of tonnes of waste burnt or buried each year could be recycled as secondary raw materials for industry and as energy for homes and factories, schools and hospitals. Integrated or sustainable waste management offers a framework for reducing the amount of waste we produce and minimising the environmental impact of the waste that will still remain.