Monday, 27 February 2012

Challenging misperceptions around clean energy

Which are the greater threat, heavy metals or greenhouse gases? 

Most people are happy to agree that LED lighting is clean, efficient and the way forward - when the balance of quality, performance and price becomes acceptable for mainstream customers in our high streets and retail parks.  Until then, we can get along with the current generation of energy-saving lights, known as compact fluorescent lamps (CFLs).  In recent years they have been given away by energy companies, and sold for pennies in supermarkets, under the Government's Carbon Emissions Reductions Target (CERT) programme.  Those days are gone, however, as you will know if you have had to buy any CFLs recently - they cost anything from £2 to £6 each, which is pretty much what they should cost - they last many years and save many times their own cost in electricity over their lifetimes .

There are some downsides with CFLs:

  • they can take a long time to reach full brightness
  • their colour rendition is usually less attractive than that of old-fashioned tungsten incandescent bulbs and halogen lights
  • their brightness can fall substantially over their lifetimes
  • they contain traces of mercury and, at the end of their life, they need to be disposed of through suitable recycling facilities.
These issues have led some green campaigners to argue that we should not have banned traditional bulbs, or subsidised distribution of CFLs in recent years, because it was the wrong technology: instead, we should have waited until now - or even until 2014, when the performance and price of LED lighting will really be ready to compete with incandescent bulbs.  Their feeling is that long warm-up times and poor quality light from CFLs have turned consumers against low-energy lighting, so that the adoption of great LED lights will be held back by people's bad experiences of CFLs.  

More concerning, they oppose CFLs because of the presence of trace amounts of mercury in these bulbs.  Some bulbs will be broken in the home, exposing families to traces of mercury vapour, and many will be disposed of through household waste, potentially venting their heavy metal waste to our atmosphere or soil.  In response to this, should we all be so concerned about mercury in our CFLs that we insist on keeping our incandescent lightbulbs, stockpiling them from online retailers before they run out forever?  Well, NO.  That would be a disproportionate reaction to a misunderstood threat.

The US Environmental Protection Agency (EPA) website sets out the origins and consequences of mercury contamination, here.  The principal manmade source of mercury contamination is from burning coal.  The coal is burned in order to generate electricity, to power our homes and businesses.  In Britain today, lighting accounts for about 20% of electricity demand (source).

Here's a decent analysis of the mercury released through using a traditional, incandescent light and an energy-saving compact fluorescent lamp.  The CFL contains about 5 milligrams of mercury.  Generating the power to run it for its typical lifetime of 7,500 hours releases a further 3.5mg mercury.  That gives a maximium total mercury release of 8.5mg, if the bulb is not properly recycled when it stops working.  

How about the old-fashioned, tungsten incandescent lamp?  It will only last 1000 hours.  Powering a succession of these bulbs, with the same brightness as our CFL, for 7,500 hours will release 13 mg mercury from coal.  From this, we can conclude that (a) it's important to recycle CFLs (and all fluorescent lights) properly and (b) old-fashioned lightbulbs cause much more mercury to be released into the environment than CFLs, through their inefficient use of electricity.

Emissions of carbon dioxide and other greenhouse gases are much more significant for our future wellbeing than traces of mercury.  Dr James Hansen of NASA has written, in "Storms of my Grandchildren" (2009), that the greenhouse gases emitted from a large coal-fired power station over its operating lifespan of around 25 years will be responsible for driving 400 species to extinction, through climate change.  

CFLs have been available for about 20 years and, by using them since the mid-nineties, we have reduced emissions of both mercury and carbon dioxide from Britain's power stations.  They have been unarguably a good thing in the battle against manmade global warming.

There is no doubt that LEDs are a cleaner, greener, brighter solution for the future of lighting but they are only now beginning to challenge CFLs as the low energy lighting solution of choice, in terms of performance, quality and cost.  I have adopted LED lighting in my home as widely as I can but the great majority of my lights are compact fluorescents and I still depend on these to keep my energy bills and carbon footprint low while providing warm, welcoming lighting in almost every room of the house.  The LEDs to replace these are nowhere near competitive yet and I shall be loving my CFLs until the new lighting technology can beat them on performance, quality and total lifetime cost.  


Emma said...

A good thorough write up. And think you're right on with the energy debate.

Just wanted to query the mercury assumptions: If in the UK 36% of our electricity comes from coal, then surely the mercury footprint of 'old bulbs' should be 4.6g? Making it a lot less then that of a CFL?

However, not disagreeing that we have to look at how much carbon such replacements have made.

CFLs were a great stepping stone technology, as long as people are ready to see that they were only ever a stepping stone, not a final solution...

Archipet said...

Thanks for posting your comment, Emma. You are right to question the relevance of US mercury emissions from power generation to the use of CFLs in UK. UK coal generated just 68 TWh electricity last year, compared with 1,971 TWh reported for USA in 2006, in the Practical Mechanics review that I linked to.
The National Atmospheric Emissions Inventory reports great reductions in our mercury emissions over the past 40 years:

However, my aim in this piece is to challenge the way people perceive risks. While mercury pollution is undeniably A Bad Thing, it is nowhere near as great a threat to us and our descendants than that of manmade climate change, driven principally by fossil fuel combustion. Greenhouse gases act globally, rather than locally, and the beneficial role of CFLs in reducing CO2 emissions from lighting in emerging economies is likely to be much greater even than it has been here in the past 20 years. Of course, the world's poorest people are typically deprived of any electric lighting at all. Decentralised energy programmes like Solar Aid across Africa and Sunlabob in Laos are essential in providing these people with access to clean, safe lighting for the very first time and LEDs are the technology of choice right now because of their high efficiency.

Back home, consumer acceptance of LED lighting hinges on the balance of performance, quality and cost. I await the future LEDs with the brightness and colour of halogen lights, more lumens/watt than CFLs and - crucially, lower lifetime ownership costs than either of these current technologies. Until then, compact fluorescent lamps will remain the energy-saving lightbulb of choice for many domestic applications.