April 2008


Global Warming &Heating and Cooling29 Apr 2008 11:15 am

This week, my favourite little Rinnai gas heater stopped working when load shedding began on a cold night. It may use gas, but it also has an electric fan so it isn’t Eskom-proof. I’ve been looking at alternatives.

Last year at about this time, I wrote an overview of home heating options. In it, I ranked an open fireplace heated by gas 8th out of 11 options, well worse than average. This is because gas may burn cleanly, but any open fireplace loses most of its heat up the flue.

I failed to mention then that I own a Jetmaster open gas fireplace. In the past, I only used it a few times a year for ambience when we had guests, but I’ll have to use it a lot more during load shedding this winter since it’s my only heater that runs without electricity. That’s a problem, because LPG has risen in price from R367 for a 48 kg bottle when I installed the Jetmaster in 2001 to R820 now. And according to my own ranking, I’ll be using one of the least environmentally friendly options around.

When I first installed the Jetmaster, I briefly considered a wood stove, but I knew that wood burning was a source of carcinogenic particulates, and I didn’t see how wood made sense in a semi-arid country with so few trees.

I’ve learned two important things since then. First, I got a quick lesson in urban forestry a few years ago when I had to remove a giant dying oak from my garden. It broke my heart to see tons of potential firewood being carted away by a tree-feller who told me he was taking it to the dump. (The trunk and limbs were too large for me to split.) The logs would ultimately decompose, releasing greenhouse gasses without benefiting anyone. I called around and learned that some other tree-fellers cut and split the wood they retrieve to sell for firewood. In the future, I would only use a tree-feller who recycled this way.

Johannesburg is sometimes called the world’s largest urban forest. I suspect that this is hyperbole that could not be proven, but the fact is that the city creates enough firewood to heat many more local homes than it currently does. (Though not all of the homes, of course.)

The second education I received was when I began researching the latest wood stoves and fireplace inserts. They aren’t just better than open fireplaces, they are unrecognizably better. An open wood fireplace loses 90 percent or more of its heat up the chimney and releases about 50 grams of particulates per hour. Anyone who has read what I have writing about diesel emissions in the Mail & Guardian and on this website knows that particulates are a serious health risk.

But modern stoves typically emit 2 to 4 grams of particulates per hour, and some are closer to 1, that’s just 2% of the particulate pollution from a wood-burning open fireplace. And about a quarter of what a typical diesel car might produce. In addition, they retain 75 percent or more of the energy in the wood to heat the room, losing just a fraction to the flue. A free-standing stove unfortunately doesn’t suit my lounge, but the fireplace inserts are only a few percentage points less efficient and just as clean.

Perhaps most important, burning wood is widely considered to be almost carbon neutral, because a decaying dead tree would release carbon dioxide anyway, while a new tree growing in the place of the old one absorbs the greenhouse gas. Firewood from the urban forest is even closer to carbon neutral than most because it was going to be cut anyway and involves minimal transport.

Only two fireplace inserts fit my opening, but they seem like good units. I’m seriously considering the Scan DSA 3-5, which rates at 76 percent efficiency. I haven’t yet found particulate emissions data for this fireplace, but it seems similar to the DSA 4 which emits a very low 1.1 grams of particulates per hour. If I could choose among a wider range of wood stoves, I would look for one with the Swan eco-label. Among the brands in South Africa, Scan, Morsø, and Jötul all have stoves that meet the wide variety of environment criteria to earn the Swan logo. A list of Swan stoves can be found here.
These advanced, closed-combustion stoves are not cheap. Expect to pay at least R10 000, and up to R40 000 for a top-of-the-line wood burning stove. But the wood is cheap. Malcolm Sims of Cosy Heating has done calculations suggesting that gas now sells for R1.23 per kilowatt hour of energy, whereas wood is about 30 cents per kwh if burned in a 75 percent efficient stove-cheaper than electricity. (Cosy Heating sells both gas and wood heaters.) Comparing my inefficient Jetmaster with the Scan fireplace, I could heat with wood for one-tenth the price, though the Jetmaster offers greater control in adjusting the flame, which would mitigate that somewhat.

Sadly, Cosy Heating says that my Scan fireplace is out of stock because of the load-shedding rush. So for the next seven weeks we’ll be huddling next to the open gas fireplace when the lights go out, and thinking about how warm that chimney must be.

Lighting &Uncategorized09 Apr 2008 11:19 am

I just received a comment to a year-old post about compact fluorescent lamps. The reader raises concerns about mercury in CFLs. I replied to him at length with my own comment, but the information is too important to leave it buried there.

The issue of mercury in CFLs keeps rearing its head. I once read a long article in the Star that left the reader with the impression that CFLs’ negatives may outweigh their positives.

This is simply not true. If you read what the independent experts have to say, it is clear that compact fluorescents reduce the amount of mercury in the environment in the long run. One thorough article on the subject notes that:

CFLs represent between 0.006 and 0.04 percent of U.S. anthropogenic [mercury] emissions

It concludes:

CFLs prevent the emissions of substantial quantities of mercury, greenhouse gases and other pollutants; they reduce consumer energy bills; and they last far longer than incandescent alternatives. They are currently the environmentally preferable product despite their mercury content – whether they are recycled or not.

Two other web pages worth reading on the subject can be found at the Natural Resources Defense Council and Popular Mechanics.

The reason CFLs can contribute to mercury emission reductions despite containing mercury is that coal-burning power plants are the world’s largest contributor to mercury emissions. In the U.S., they are responsible for about a third of the mercury released. Since coal accounts for less than half of U.S. electricity generation and about 90 percent of South Africa’s electricity generation, it’s safe to say that more than half of all mercury released in South Africa comes from Eskom. Cut your electricity consumption and you reduce mercury pollution.

Aside from the broader environmental issue, some people are concerned about exposing their families to a source of dangerous mercury in their homes. John Balbus, M.D., the Chief Health Officer at Environmental Defense, writes

The exposure from breaking a compact fluorescent bulb is in about the same range as the exposure from eating a can or two of tuna fish.

Still, if a bulb breaks in your home, it’s worth following a few precautions such as using disposable paper towels to wipe up—not a vacuum cleaner—and washing your hands when you are finished. For more details, you can read the instructions suggested by the U.S. Environmental Protection Agency.

I don’t want to go too far in minimizing the dangers of mercury. It is a serious poison, and we should all try to reduce our contribution to mercury pollution in any way we can. Batteries are a very large source of mercury, so you should only buy watch batteries and alkaline batteries that are mercury free. (Recyclable batteries are even better, of course.)

In buying CFLs, the best recommendation is to stick with major international brands such as Osram, GE and Philips. They have to comply with EU standards that allow no more than 5 mg of mercury in a globe. Osram CFLs have 3.5 mg according to their technical marketing manager in South Africa, Wally Wilmans. Cheaper brands may have more.

There is no way to recycle CFLs in South Africa currently, but Eskom has a working group tasked with this issue. CFLs last so long that before the bulb you buy today burns out, even Eskom may have come up with a plan.