Can a fridge and an oven be good neighbours?

Surprisingly, the answer seems to be yes. In our kitchen the oven and fridge are built in side by side. The oven is a gas fan oven and as well as the fan in the oven it has a case fan which is supposed to keep the case cool, so it should not be heating the fridge too much. However, I have never been entirely convinced that having them next to each other is a good idea. Being temporarily in the possession of some electricity consumption loggers I monitored the electricity used by our fridge and oven, and the fridge temperature, over a day when we used the oven to cook a roast dinner. The charts below show what happened.

Efficiency of different ways to cook potatoes

In my book I reported on my experiments to see how much energy was used cooking potatoes either by boiling in a saucepan or baking them in an oven. (The oven took 6 times as much energy as the hob.) Recently I posted about cooking with the microwave - when it is more efficient than the hob and when not. A reader queried on how pressure cookers compared, so I borrowed one from a friend and did some more experiments. Finally, I tested out an electric steamer which we sometimes use (though mainly for greens) and a microwave. Here are the results.

Carbon emissions from freezing your garden produce

Gooseberries, tomato sauce etc. store well in the freezer

If you have an allotment or a large vegetable patch in the garden you probably store some of the produce in your freezer to eat later in the year. Eating fresh food in season saves energy and carbon emissions but people have been preserving food in various ways for millenia. These days freezing is the method which is easiest and most widely used. Is the extra energy use an issue - or not?

Do microwave ovens save energy?

I used to think that cooking with a microwave uses less energy than cooking on a hob but in practice this is not always the case - it depends on what you are cooking. In comparison to a gas hob, the microwave oven can also cost more and generate more carbon emissions even when using the same amount of energy, because gas is cheaper than electricity and is less carbon intensive. Of course the microwave can be more convenient, even when it is less efficient. I've been investigating which jobs the microwave is good for and why it isn't as efficient as you might think.

Food waste is a waste, even if we make it into biogas

 I read recently about a second installation which will be injecting biogas generated from food waste into the gas grid for general use. (Food Waste Biogas for Grid Injection Contract in UK) This is excellent news, as it increases flexibility in how we can use biogas. In this case as in others, the gas is generated by anaerobic digestion of organic waste. That means it is processed by bacteria in large tanks, a little like huge compost bins except temperature controlled and without air. The bacteria produce gas which is a mix of methane and carbon dioxide plus some smelly stuff so it has to be cleaned up before it can be injected into the grid. There is also a lot of sludge left over which can be spread on agricultural land as fertiliser.

Sadly, however, there is no way that recycling food waste for energy will contribute more than a fraction of our energy usage and it doesn't make it OK to waste food because it took a lot more energy to grow and deliver that food than we can recover from recycling it.

How much energy do you save by putting a lid on a saucepan

Someone tried to tell me the other day that putting lids on saucepans doesn't actually save any energy. I had to admit that when I did my experiements for the book, since I had been concentrating on comparing cooking on the hob and in the oven I did not actually test the effect of lid on/lid off. So I did another experiment today and here are the results.

Zero carbon tea

A friend of mine asked for advice on how to run a zero-carbon cafe at a fair in Cambridge on June 10-11th. "Do you realise how much energy it takes to boil water?" I asked. "We'll use small cups," she said. We are looking at three different methods: pedal power, sunlight and biomass.

Baking bread at home uses more energy

My friends rave about home-made bread (I have a gluten free diet and, whatever they may tell you, gluten free bread is never as good). I won't argue about the taste. However, if you are worried about climate change or energy security you should consider that baking bread in an oven at home typically uses much more energy baking in a factory.