Sunday, February 12, 2012

Cooking with gas

With all the protests against fracking, it's easy to get the idea that cooking with gas is bad. First, most household gas in South Africa is liquefied petroleum gas (LPG), which is not produced using fracking. Second, in the long term, we should be looking at biogas as an option for cooking. Why? Because electrical ways of producing heat are wasteful. For heating water or heating the air in winter, you can use a heat pump, but for concentrated heat for cooking, a heat pump is way too slow.

Back to fracking: it’s idiotic to scrape the bottom of the barrel for the last drop of fossil fuels. They will run out anyway, and climate science indicates a need to look at alternatives. So why try to extract gas from environmentally sensitive water-poor land with technology that carries serious risks?

Some people are  pushing induction cookers as an alternative, citing numbers that show them to be by far the most efficient form of cooking. These numbers are a bit misleading because they don’t take into account the extremely low efficiency of coal power generation, by far the most common source of electricity in South Africa. A typical coal power station has an efficiency of around 30%, and you lose about 10% more in power transmission, so you have to start counting the energy efficiency at your stove at about 27% (not taking into account the energy cost of mining and transporting the coal, but gas also has a production and transport cost we are not taking into account).

LPG is a very efficient fuel if we must burn something to make heat. However, if you buy an LPG stove, take care to get one that can be rejetted for natural gas, since biogas is closer to natural gas. LPG sold in South Africa is a mix of propane and butane, and has a very high energy density, higher than natural gas, which is mostly methane. Natural gas and LPG are fossil fuels, and switching to a more efficient one is only a step: we should ultimately aim to stop burning all fossil fuels. In the meantime, though, LPG is a better alternative than a wasteful electric stove.

If you are buying a gas stove, what should you look for?

First, quality materials. Look for cast-iron pot stands. The kind that look like plastic-coated wire don't last long. A stainless steel outer case is good, though no substitute for quality working parts. Ask a person who repairs appliances (ideally someone who doesn’t sell new ones) which brands have best after-sales service, parts availability and general reliability.

Now the critical question: how well does a gas stove work? Many people will tell you that they are great for stove-top burners, with their near-instant heat adjustment, but a gas oven is no good. I’ve previously had a gas stove nearly 100 years old with a very good oven, so it really depends on how well the stove is designed. My shiny new stove has a gas oven, and I’ll report results here shortly (see a hint in the picture).

Watch this space.

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