Since the invention of the light bulb by Thomas Edison in 1879, electric lighting has become an essential part of everyday life, lighting homes, offices and factories, streets and pavements, sports grounds and parks.

Each of these situations requires different light quality. For example, office lighting must be similar to natural daylight, and lighting along pavements must be bright enough to see, yet subdued enough not to disturb adjacent householders. Many different types of light bulb have been developed for all these applications and some examples are provided in Table 1. Light bulbs are generally inexpensive and when they fail are disposed of and replaced with a new one.

Table 1 Different types of lighting

TYPE OF LIGHT	APPLICATION
Tungsten and carbon filament lamp	Standard household light bulb
Fluorescent tube	Long, thin tube, usually used in the workplace, schools and kitchens
Low-energy light bulbs	Used in homes and offices as a replacement for standard light bulbs
Sodium lamps	Mainly used in street lighting

In a standard light bulb, the electrical current flows through a tightly wound tungsten metal coil. Tungsten has a high resistance to this current, i.e. it does not allow the current to pass easily through it. This resistance causes a build up of energy within the wire which is dispersed as light and heat energy. To prevent the wire combusting, the surrounding glass bulb is filled with a mixture of nitrogen and argon which are two gases that do not burn.

Fluorescent tubes work on much the same principle. However, instead of a coil, the filament consists of two wires running the length of the tube. The wires do not touch but heat up and energy is discharged into the gas that surrounds the wires. The gas emits ultraviolet light, which reacts with a special mercury coating on the inside of the tube, making it glow brightly.

Low-energy light bulbs are essentially miniature fluorescent tubes, mainly for use in the home. Although the initial purchase price is higher, they last much longer than ordinary household bulbs.

Electrical energy is produced by the combustion of fossil fuels which results in the emission of carbon dioxide to the atmosphere. Carbon dioxide is the major contributing agent in global warming. Therefore, reducing energy consumption and the subsequent release of carbon dioxide can only reduce manmade influences on global climate change.

All waste exerts an impact on the environment through disposal to landfill. The quantity of discarded light bulbs and tubes takes up considerable space in landfill sites and presents physical hazards. To add to this, the dispersal of leachate from landfill sites into the surrounding environment presents further risks.

Although they save energy, fluorescent tubes and energy-saving bulbs are particularly undesirable in landfill sites as they contain mercury. Mercury powder is used to coat the inside of the tube and is therefore released when the tube is crushed. Mercury can have a severe effect on the health of humans and animals affecting the nervous system, lungs and kidneys.

Over 350 million light bulbs are manufactured in the UK every year. In 1994 this figure was broken down into:

• 286,341,000 tungsten filament bulbs
• 61,180,000 fluorescent tubes
• 5,664,000 other tubes.

In addition, a large number of bulbs and tubes are imported each year. In 1994 over 40 million fluorescent tubes were imported into the UK, bringing the total tube sales in the UK to 85 million (Riley 1996). An estimated 80 million spent fluorescent tubes are sent to landfill every year, equating to 3000 tonnes of waste, of which 4 tonnes is mercury, and the contents of a single tube can pollute up to 30,000 litres of water (Wastes Management 1999; Materials Recycling Week 2001). Some 5% of discarded tubes in the UK are estimated to be recycled (Materials Recycling Week 2001).

Sales of low-energy light bulbs are increasing with heightened public awareness of the financial and environmental benefits. Not only do low-wattage bulbs use less energy than a standard 60 watt light bulb but, on average, a low-energy bulb also lasts approximately 8,000-10,000 hours; around 10 times longer than an ordinary light bulb.

Although fluorescent tubes and energy-saving bulbs contain mercury, they are not classed as special waste under the Special Waste Regulations 1996. However, those companies dealing with lighting waste must hold a Wastes Management Licence.

Many waste management companies realise the environmental impact of mercury-waste and do not accept fluorescent tubes in their landfill sites. The landfill tax (currently £12 per tonne) also encourages those disposing of waste to seek ways of minimising waste being landfilled. Although there is no legal obligation to collect and recycle these tubes, a recycling network has been established and this alternative option is being favoured over landfill.

Legislative measures to phase out certain types of lamp have already been proposed by the European Commission. High-energy fluorescent lamps, which make up approximately 15% of the lighting market, are comparatively inefficient and a deadline will be fixed for their replacement (set at one year after the implementation of the Directive). This strong measure is thought to be more effective than energy-efficiency labelling that allows the consumer to choose which light to buy (Environment Business News Briefing 1999).

Reducing the number of bulbs that are thrown away each year is the second benefit of energy-saving bulbs, the first benefit being the reduction in use of fossil fuels. However, the environmental impact of the mercury content can only be eliminated by using an alternative method of lighting.

One alternative would be to use natural daylight for offices and schools, etc. Simple steps such as keeping blinds open and windows clean will maximise the amount of natural daylight entering the room. Taking this one step further, systems have been developed which channel sunlight into corridors and rooms via a series of super-reflective pipes. These tubes work by intensifying the sunlight shining into clear plastic domes fitted to the ends of the pipes situated in the roof. The pipes run all the way through the building to the room where the light is required. It is estimated that these pipes can save more than 75% of the electricity used to light the room conventionally, as well as the large amount of spent light bulbs and tubes that would be discarded. Although this technology has not yet been widely adopted, it does provide an effective option to the use of electrical lighting during the day.

If natural lighting alternative can not be used, purchasing narrow tubes with a lower mercury content is preferable to the larger diameter tubes. Measures taken during installation can also prolong tube life. For example, fitting a switch that starts up fluorescent tubes slowly will reduce energy consumption and increase the life span by up to 50%.

Due to the singular purpose and low costs of light bulbs and tubes, they cannot be reused in any other capacity. Often companies with a large number of fluorescent tubes in their offices have a wholesale replacement programme. The replaced tubes which are in working order can be used by other organisations, such as community and voluntary groups and there have been a number of such initiatives around the country (NHHWF 1998).

The recovery and recycling of general household bulbs is currently not standard practice. They cannot be recycled with other household glass waste due to the metal components which are difficult to separate from the glass bulb by the householder.

Until recently the same was true of fluorescent tubes, sodium street lamps and low-energy bulbs. However, in Sweden, a system has been developed for recycling these lamps into their constituent parts, all within one piece of machinery. This system was introduced into the UK in 1998 and since then, recycling fluorescent tubes and lamps has been possible. The availability of these facilities and the refusal by some landfill operators to accept fluorescent tubes, has prompted the Government to order the recycling of the one million tubes used by its offices each year.

The recycling process starts by crushing the material to produce a stream of small components. These are passed through a separation tower before the glass (coated with the mercury-containing phosphor powder), aluminium and steel are separated using a vibrating screen. The steel can be magnetically removed from the aluminium and the two metals can then be sold to the metals refining industry. The glass fraction is passed into a rotary drum feeder and then to a discharge conveyor to remove the powder coating. The contamination is carried in an air stream to a distiller for separation. The clean air is passed back into the atmosphere and the powder is heated to condense the mercury and oxidise the organic content to leave 99.99% pure mercury and phosphor powder. The mercury is sold to refiners, the glass is used to line incinerators and it is only the phosphor powder that is not reusable (a mere 1% of the total input into the system).

The recycling facilities presently available in the UK do not have the capacity to collect and recycle all the mercury-containing light bulbs that are generated each year. This results in a significant quantity still going to landfill as there is no other suitable disposal route. Incineration is not a viable option because of the volatility of the mercury and the resulting hazardous atmospheric emissions.

A larger volume of spent lamps could be recycled if the participation in collection schemes increased. Until legislation prohibits the disposal of fluorescent and sodium lamps to landfill, it will remain the preferred option and the threat of mercury-related pollution incidents will grow.

Mercury Recycling Ltd was the first UK company to establish a recycling plant for fluorescent tubes, energy-saving lamps and sodium street lamps. In 1998 it imported Swedish technology that could process approximately 2,000 tubes per hour using the method described above (see Waste Management Options: Recovery). Mercury Recycling Ltd has established a collection programme called Lampsafe. Subscribers are provided with a plastic storage container in which the spent tubes can be safely stored until the box is full. A Mercury Recycling Ltd vehicle then collects it and an empty box is deposited in its place.

Although the idea of fluorescent tube recycling originally met with scepticism, and concerns that the cost of producing recycled mercury would outweigh the benefits, it has not deterred the company. As of June 1999 the process was not profit-making, although it is hoped that it will become profitable as the company develops.In March 1999 Mercury Recycling Ltd was awarded a contract to recycle all the fluorescent tubes generated by Government offices. The company plans to expand and could eventually handle a maximum of 20 million tubes a year, thus making a significant dent in the 60 million currently generated as waste.

SOURCE: MERCURY RECYCLING LTD 1999

Whilst significant progress has been made in reducing the amount of mercury present in fluorescent lamps over the last 20 years, the scope for further reducing mercury content is limited. This is because mercury vapour has to be present in sufficient quantities to produce the UV radiation needed to create visible light.

Progress for minimising the amount of waste generated is possible through the drive toward energy efficiency. The EU has approved eco-labelling criteria for light bulbs with the life-span set at 10,000 hours for single ended bulbs and with strict controls over mercury content, (Warmer Bulletin 1999).

At the same time legislative measures to phase out certain types of lamp have already been proposed by the European Commission. High-energy fluorescent lamps, which make up approximately 15% of the lighting market, are comparatively inefficient and a deadline will be fixed for their replacement (set at one year after the implementation of the Directive) (Environment Business 1999).

The European Commission_s draft directive on waste electronic and electrical equipment (Council of the European Union 2001a) is due to become law in the UK by 2003. Most types of lighting equipment are included in the definition of WEEE , although filament bulbs are exempted. The Waste Electrical and Electronic equipment section of this guide offers more detail of the impacts of the directive, but the overall implication for lighting is that gas discharge lamps will have to be recycled, rather than landfilled. Specifically:

• gas discharge lamps will have to be collected separately
• 80% (by weight) of gas-discharge lamps will have to be recycled or recovered
• mercury will have to be removed from gas discharge lamps.

An associated directive additionally limits the amount of mercury allowable in new gas discharge lamps (Council of the European Union 2001b).