Tuesday, September 6, 2016

Reducing our climate impact by eating less dairy

Some years ago we became concerned about our dairy consumption level.  When we did our first carbon audit, food was the biggest contributor to our carbon footprint (responsible for about 30% of our carbon emissions or 1.4T CO2e per year each).  The planet can only cope with 1.2T CO2e per person per year, so obviously that number needed to come down a lot if we wanted to do right by our vulnerable neighbours in places like Bangladesh.

Dairy was the biggest contributor within that, coming in at around 0.45T CO2e.  The obvious question was, how could we reduce this?


Reducing butter consumption

Initially, I was reluctant to reduce my consumption of milk, cheese, yoghurt etc.  On medical advice I eat two servings of such dairy products every day: I spend most of my day lying down, so I'm at high risk for losing bone density and developing osteoporosis.

However, after a couple of years we realised that we were also eating a lot of butter.  Butter isn't important for bone density, so would we reduce our greenhouse gas emissions by drastically reducing our consumption?

First I did a comparison of the greenhouse gas emissions associated with butter and margarine:


emissions for a 500g package/kg CO2e

butter margarine

fat 6.50 1.95


make packaging 0.09 0.05


dispose packaging 0.01 0.04








total 6.60 2.04



It was clear there'd be significant savings, especially as we were eating a surprising 20kg of butter and ghee per year between the two of us!

Since 2011, we've saved butter for contexts where we really benefit from its delicious taste.  Hot crumpets are always served with butter, shortbread and Russian fudge are made with it and dry curries and pancakes are fried in ghee; otherwise, we generally use margarine.

Overall, we've replaced about 3/4 of our butter with margarine, saving us around 70kg CO2e each.  That's a 5% reduction in our food-based emissions and just under a 2% reduction in our total emissions :-)

NB Obviously milk and butter are produced together.  As their greenhouse gas emissions come primarily from the raw milk production rather than later processing, it's not really correct to speak of them as having separate emissions.  However, we were consuming far more butter than could be made from the cream taken out of the milk we drink (you can typically make around 1.5kg of butter and 96L milk from 100L of raw milk - source), so that butter was causing greenhouse gas emissions in excess of those associated with producing the milk we drink.

Reducing yoghurt and custard consumption
Recently I've begun to wonder if I can do better.  Martin has many vegan friends who are adamant that humans don't need to consume milk past infancy: are they right?  Could I get the calcium that is so important for my under-used bones without consuming dairy?

As I've looked into it, I've come to the conclusion that the vegans' claim is only sort-of right.  If you look at traditionally-available foods, your best sources of calcium are dairy, fish bones, egg shells and tofu-like products.  There are also trace amounts in figs, oranges, hard water, peanuts etc., but there's no way you could get enough calcium just eating those foods.  But, unless you lived in Asia, until our current era of globalisation and food-fortification, there was no way adult humans could meet current calcium RDAs without consuming animal products.

However, I do have ready access to tofu and soy products.  Could I substitute them for some of my remaining dairy consumption and so reduce my greenhouse gas emissions without compromising my bones?

For years, I've had a dairy snack for morning or afternoon tea every day: yoghurt in summer and custard in winter.  Could I find palatable and nutritionally-equivalent tofu puddings to replace them with?  Turns out I could :-)

For the last month or so, I've replaced my custard with a simplified version of tofu-fa - a popular Chinese dessert.  It's a thick curd which gives off whey when you put a spoon in it - a lot like junket - but it tastes best warm.  In the summer I'm considering eating a cold tofu pudding that has the consistency of thick Greek yoghurt and has a refreshing lemony taste.*  Nutritionally, it turns out both puddings are pretty similar to the custard I've been eating until now, although neither are as nutrient-dense as the yoghurt.

* click here to jump to recipes for the two puddings.


g protein/serve mg calcium/serve
my tofu-fa derivative 7.0 223
custard 8.5 188
cold tofu pudding 9.0 176
yoghurt 12.8 469








To make up for the minor decrease in total calcium intake this will give me, I've moved from snacking on roasted chickpeas to roasted soybeans.  That's been enough to make up the difference, and doesn't cause any noticeable increase in greenhouse gas emissions.  I'm not going to bother compensating for the minor decrease in total protein intake I'll have as I'm pretty sure I'm already eating a little more protein than I need.

So, I've found a nutritionally-equivalent non-dairy alternative, but will it result in a substantial decrease in greenhouse gas emissions?



kgCO2e/serve
my tofu-fa derivative 0.08
custard 0.28
cold tofu pudding 0.39
yoghurt 0.42

Making this change means I'll reduce my 'dairy-snack' greenhouse gas emissions from around 110kg CO2e per year to 80kg CO2e per year.  That takes under 1% off my greenhouse gas emissions, which feels like too small a difference to be worth bothering with.  It turns out that tofu, whilst causing much lower carbon emissions than meat, causes higher carbon emissions than I would have expected.

If I ate the tofu-fa pudding year-round, however, the emissions come down to 25kg CO2e per year.  That takes 2% off my personal greenhouse gas emissions or 1% of our collective emissions.  It'd also save a little money (the tofu-fa pudding is about the same price as my custard but cheaper than yoghurt), but take about 15 minutes more work per week in the winter and 20 minutes in the summer (as yoghurt is faster to make than custard so the comparison's different).

That could be worthwhile.  I need to think about it some more, but I'll certainly keep on making tofu-fa pudding in the meantime.

If you'd like to try the puddings for yourself, here are the recipes.

Heather's cold tofu pudding (based on this)

Ingredients:
2 blocks firm tofu (around 300g each)
1 cup water
1/2 cup icing sugar
2 ice cubes lemon juice (around 3 T)
2 tsp vanilla essence

Method:

Chop tofu into approx 1 cm cubes.
Place all ingredients in blender and pulse till smooth.

Gives around 4 cups (6 servings)
Store in fridge.

Heather's tofu-fa derivative (based on this; manual soy milk method taken from here and here; photos of the process below.)

Ingredients:
3/4 cup dry soy beans and 1L water OR 1L unsweetened soy milk.  If using soy milk, start at step 6.  Please be aware that your pudding will only have about half the protein of my pudding if you do this, and a little less calcium.  It will, however, be a lot smoother :-)

1 tsp calcium sulphate powder (also called 'gypsum'.  Buy from home-brew shops - I'm using this one from here - they deliver for only $3).
1 tsp potato starch (buy from Asian grocers - I expect cornflour would also work fine)
1 1/2 tsp ginger powder
1/4 cup water

3/4 cup loose packed brown sugar (or 1/2 cup white sugar or 1/4 cup honey)


Method:
1. Soak soy beans overnight
2. Drain beans then microwave two minutes.*
3. Place drained beans with 1 cup water in a blender or food processor and grind till a thick, smooth porridge forms.
4. Place a sieve over a 2L jug or bowl and line with a tea towel.  Put the pulp in the sieve.  Rinse the blender with one cup water then add this liquid to sieve.  Drain liquid through with stirring.
5. Add a third cup water and stir through pulp.  When no more liquid comes through easily, close the tea towel over the pulp and twist and squeeze the remaining liquid through.  Add further water to make up to 1L of soy milk.**  (Rinse this cloth well before washing it - otherwise you'll get tiny soy particles all through your wash.)
6. Transfer milk to 3L saucepan and bring to a rolling boil.
7. Whilst milk is heating, mix gypsum powder, potato starch, ginger and water in a large bowl (I use the same jug I used in step 4).
8. When the soya milk boils, foaming rapidly, pour into the gypsum powder mix from about 1 foot above. This action will make all the ingredients mix together well. Don’t move it or stir the mixture after pouring in the boiling soya milk. Cover it with a cloth to absorb steam and leave it for at least 30 minutes (a couple of hours is fine). The soya milk will form a milky jelly surrounded by a little milky fluid.
9. When the pudding is set, stir through the sugar.***

Gives around 4 cups (6 servings)
Store in fridge.

Reheat servings in microwave 1 min on high.

* this deactivates the enzymes in the soy beans that otherwise make some of the protein indigestible.  This is usually destroyed by boiling the soy milk or beans for at least 10 minutes, but microwaving is also effective and I find it faster and easier.
** soy milk is usually made by hand by straining all the liquid through a cloth from the beginning.  I use this method of first sieving then straining as it is considerably faster and less work.  It does result in a lot of sediment coming through into the milk.  If you want to make a really smooth pudding, strain the milk through a cloth from the beginning.
*** soy milk is very sensitive to acid.  Brown sugar and honey are both slightly acidic - if you add them to the pudding at any time before the end, the pudding will instantly curdle into unpleasant dense lumps.

Photos of making tofu-fa

Soaked soy beans

Soy beans ground to a thick, smooth porridge-like paste.
Soy pulp in the tea towel, after most of the extra water has been added.

Soy pulp after the water has been stirred through.  How wet it is at this stage depends a lot on how coarse the weave of your tea towel is.

Gathering the tea towel around the pulp, ready for squeezing.

After all the liquid has been squeezed through.  It fascinates me how much like milk it looks!
What remains after squeezing out the remaining 'milk'.  In Japanese, this is called 'okara'.  It's a good source of fibre, and still retains some protein and minerals.  So far we've used it to make patties (you can approximate the 'old bay' seasoning called for using this recipe) as well as adding it to soups.  People also use it a lot in baking, where it gives a crumbly texture that is sometimes desirable.

Tofu-fa setting, covered with a tea towel and pot lid.
 
Set tofu-fa.  Note how there's a lot of foam and some milky residue.  Real tofu-fa isn't like this it's very smooth and has a little clear liquid around it.  Mine is like this mostly because I use unusually strong soy milk (more gypsum would compensate for this, but I don't mind it so I'm not bothering), but also because I don't skim the soy milk before adding it to the gypsum solution.

Tofu-fa after brown sugar has been stirred through.

2 comments:

  1. Is all calcium in milk and soy actually bioavailable? What about in chalk? Would just grating some chalk into your curries have the same effect more cheaply and easily than trying to find a new dish that has sufficient calcium "naturally"?

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    Replies
    1. Interesting. I thought that sounded crazy at first, but it would work reasonably well. I don't think it would be palatable, but some variant of it is worth bearing in mind.

      It turns out that calcium bioavailability is mostly governed by what you're eating it with, rather than which salt etc. The very poorly soluble ones (like calcium carbonate) are just as bioavailable as the really soluble ones like calcium gluconate.

      Calcium in tofu and milk is about 1/3 available, calcium in beans other than soy is around 20% available (no one seems to know why soy is different), calcium in cabbage-related leafy veg. is around 60% available, calcium in things with lots of oxalic acid in (rhubarb, spinach etc.) is only about 5-10% available. So chalk on the dairy I'm still eating would be ideal, and chalk in bean curries wouldn't be too bad.

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