How to grow climate friendly food at home

Were you as shocked as I was to hear that growing your own food at home has six times the GHG emissions as conventional agriculture? Surely it does not have to be like this? I looked at the study behind the news [1]. (It came out in January and I do not understand why it has hit the news again now.) The good news is, the main sources of emissions from home grown produce are easily avoided, with a bit of care. 

Compost heaps were one of the main sources of GHG emissions from urban gardens - but good practice can minimise this.

Climate change stories to be cheerful about

It has been a very difficult year for several reasons. But it was not all bad. To cheer us up over the holiday, here are my favourite good news stories from 2020 - including coal consumption down, renewables up, beavers for flood management, hope for the survival of coral, help in eating more plant proteins, and changes to our travel behaviour.

Food and climate change without the hot air by S L Bridle – review

Published by UIT Cambridge Ltd. Available free in electronic form or currently £15.99 from Blackwells. 

I really like this book. It works on many different levels in different ways, for different sorts of people. I recommend it to all my family and friends, not just the geeky ones.

How is a house like 3/4 of a cow?

One way to decarbonise our home heating is to use anaerobic digestion (AD) to process biomass (such as grass) into biogas. So we can grow grass as cattle feed or to heat our homes. How do cows and houses compare in terms of grass demand? Here is a back of the envelope calculation - and the conclusion is: one house is about 0.75 cows. Based on this (rough) figure, if we repurposed all our land that currently supports sheep and cattle to grow grass for biogas, we could supply about 13 million households, a little less than half the current number in the UK (27 million) [1].

The grass these cows are eating could be used to heat our homes instead.

Some facts about food waste

Michael Gove has announced that we could divert 250 million meals per year to the most needy in society [1]. Is this a lot? There are 67 million people in the UK (approx). If we each eat 2 meals per day, that comes to 49 billion meals per year. The quoted 250 million meals is 0.5% of consumption. That seems a very low level of wastage to me, though we should still redistribute it if that is practical. We waste a lot more food at home. Here are some more facts about food waste.

Should chicken be taxed higher than beef?

Meat production on farms is responsible for a sizable proportion of our greenhouse gas emissions - both directly from the animals and from producing the feed. Eating less meat is good for us in other ways too, and most of us eat much more than we need. But how to change our habits? One way is to tax meat consumption. How much should such taxes be? A comment piece by Simon Fairlie in the Guardian [1] references two conflicting sources. One, from Oxford University suggests 40% on beef and 8.5% on chicken [2]. The other, from Sweden's University of Agriculture, suggests 40% on chicken and only 28% on beef [3]. This was a surprise - I have always understood beef was much worse than chicken because cattle (and sheep) belch methane. Putting a cash value on environmental impacts is never easy but how can there by such widely differing estimates for similar products?

How much difference can we make if we change our diets?

Our food choices make a big difference to carbon emissions. In particular the amount of meat and animal products we eat is important. How much do we need to change to make a difference? I have been looking at data from the National Diet and Nutrition Survey [1] to see what we eat and where the carbon impact is. I have also derived an alternative diet which is not meat free but still saves a third of a tonne per year in greenhouse gas emissions.

How bad is bottled water, really?

I have been asked to look at the relative carbon emissions from tap water versus bottled water. Many people seem to think that our mains water supply is a significant source of greenhouse gas emissions. It is not, at least in the volumes we use for drinking. However bottled water certainly is - partly due to the bottle and partly due to the distance it is transported. The greenhouse gas emissions for bottled water are 200 - 600 times as much as tap water.

Here are some summary figures.

Water	gCO2e/litre
Tap water	0.5
Bottled water best case: from local source in 1.5 litre bottles, 50% recycled plastic	118
Bottled water worse case: from a distant source such as San Pellegrino, in 0.5 litre bottles, virgin plastic	322

For comparison, a typical UK resident will generate about 30kg CO2/day so one litre of bottled water per day could be 1% of this.

The Beef Carbon Project - still plenty of room for improvement.

The Carbon Project is a massive undertaking by McDonald's to reduce the carbon footprint of their beef supplies in the UK and Ireland. It caught my attention because it was a finalist in this year's BBC Future Food Awards. They have reduced the carbon emissions from beef production by an average of 23% across 130 participating farms over 6 years. That is not enough to make me eat beef with abandon but it is certainly worth having. However what struck me in the report was that the worst farms generated 3-4 times more emissions than the best farms. This suggests there is a great deal more room for improvement.

Greenhouse gas emissions from rearer-finisher farms

This chart shows minimum, maximum and average greenhouse gas emissions from rearer-finisher farms. They breed their own cattle and raise them all the way to slaughter. Dairy beef farms have slightly lower carbon emissions because they raise cows that are not wanted from the dairy industry. The emissions from raising the mother count towards dairy products rather than beef. 

The method used to calculate emissions is approved by the Carbon Trust.

Living on one acre or less - review

This is a guest post from my sister who lives in Wales. I asked her to review this one as she has personal experience of the topic. 

Living on One Acre or Less, by Sally Morgan, from Green Books

I am a smallholder just starting our third year in a new life and so I’ve read a few books like this prior to starting out and many more detailed books since.  I can honestly say that this is probably the best book of its type that I’ve read.

Are healthy diets bad for the environment?

Have you seen the headlines recently?

• Vegetarian and 'healthy' diets could be more harmful to the environment, researchers say (Science Daily)
• Lettuce is ‘three times worse than bacon' for emissions and vegetarian diets could be bad for environment (Independent)

Could this really be?

The main difference between the current and healthy diets was in the amount of sugar and fats consumed.
These reports are based on research from Carnegie Mellon university published in the journal Environment Sciences and Decisions [1]. I found that paper shocking but not for the reason in the headlines. The paper actually evaluates the impact of switching to a more 'healthy' diet that is not particularly vegetarian. In fact the 'healthy' diet has more calories from animal products rather than less. But the main difference between the current and healthy diets is in the amount of sugar and fats consumed. The healthy diet has 400 less calories/day from 'added sugars' (equivalent to 25 spoons) and another 400 less calories/day from fats and oils. What I find most shocking is that people are eating this in the first place.

Replacing bacon with lettuce would give you vitamin A poisoning.
By the way, I can believe that lettuce might be higher in carbon emissions than bacon, but this is completely irrelevant. If you wanted to cut down on bacon you would be ill advised to replace this with lettuce. To get the same calories as 100g bacon you would need to eat 3.6 kg lettuce and you would have just consumed 53 times the recommended daily allowance of vitamin A. You could die of liver failure.

Could the UK be self sufficient in tea?

We now grow tea in Scotland [1]. We have heard about climate change hitting coffee production [2] - well speaking as a tea drinker I don't much care about that but if I had to reduce my tea intake I would be seriously upset. It doesn't bear thinking about. So here is a back-of-the-envelope calculation for how much land it would take to grow all our own tea.

Why we need to eat less meat

The Chatham House report that just came out [1] says that most people underestimate greenhouse gas emissions from agriculture, particularly livestock agriculture. So here is a chart comparing emissions from a serving of beef, pork, chicken or eggs with a litre of diesel, running a freezer or a dishwasher. You may be surprised.

Greenhouse gas emission from meat in comparison with other everyday energy use

Meat emissions from [2], Protein content and fuel emissions from [3]

Freezer is typical class A, Dishwasher is typical 1.7 kWh/run

Time for change - but not too much at once

On holiday in Finland

The New Year is a time when many people resolve to change their lifestyle in some way - perhaps to be more fit and healthy, or to save money for a special purchase, or to reduce your carbon footprint. As a member of Transition Cambridge and Cambridge Carbon Footprint I know some people with what I consider to be quite extreme lifestyles, such as being totally vegan or living with hardly any heating (from choice not from necessity). On the other hand, I have found it relatively easy to make changes to my lifestyle - a bit at a time. For example I now take exercise most days, we eat vegetarian or vegan often, and although we are in the house all day we run it cooler during the day than in the evening. So here are some suggestions for fun and healthy ways to reduce your energy use and carbon emissions in small doses.

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?

How green is my charcoal barbecue?

The barbecue season has started. In my book I looked at cooking on the hob and in the oven but I didn't think of barbecues. You might think that using charcoal on your barbecue is carbon neutral because charcoal is made from wood which is renewable fuel. This is not entirely true because of greenhouse gas emissions (a) during manufacture of the charcoal and (b) in transport.  So how does cooking on the barbie compare with, say, under a grill in the kitchen?

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.