Cows are bad for the environment and they use up enormous amounts of resources – we need to feed them 10kg of grain to produce 1kg of meat. This is what we keep hearing from environmentalists and vegans. No wonder many people feel guilty for eating cheese and meat.
The fact is that this portrayal of the cow as a “climate killer” and a primary cause of world hunger is a very dangerous simplification. The truth is, over 1 billion small farmers around the globe live primarily off the few ruminant livestock they have – and they do not feed them any grains whatsoever. These animals – cattle, sheep, goats and camels – live off shrubs, rangeland and pasture. Even in Switzerland cows eat an average of more than 60% grass, in organic agriculture that figure stands at more than 90%. In my opinion feeding cows even as little as 10% soy and grains is too much. And certainly all feedlots where cows primarily eat soy, grain and corn are in many ways exactly the kind of environmental and ethical disaster that we have all heard about.
But lets have a closer look at farms that feed their cows 100% grass - there are still a lot of those in Switzerland. How much resources does this kind of animal husbandry use? I have outlined in previous articles that ruminants (particularly cattle) play a vital role in a sustainable corp rotation and are essential to preserving soil fertility.
But it still seems like it would be more efficient to grow potatoes for human consumption rather than grass which the cow then first has to convert to milk before humans can consume it.
Lets look at the math
I take my numbers directly out of the Swiss "farmer's bible" - the Wirz Kalender - they have no bias or distorted incentives - virtually every farmer in Switzerland uses this booklet. It is written by farmers for farmers.
Our book tells us the yield we can expect on a hectare of arable land at 500 meters above sea level (organic agriculture):
Gras/clover: 100 tons fresh (12 tons dry mass) - that yields 72,000 MJ in Energy which is available to the cow for consumption
Corn: 113 tons fresh (13.6 tons dry mass) - 88,400 MJ Energy available to the cow.
An average cow which is able to produce 5,850 Liter of milk per year will need to consume the following amount energy (MJ) in order to sustain herself, produce the milk and carry a calf for 9 months:
Total energy required per cow per year is 31,500 MJ Energy yielding 5,850 liters of milk - that makes 5.38 MJ of energy consumed per liter of Milk.
Per hectare of grass/clover we will therefore be able to produce 13,382 liters of milk.
Per hectare of corn we will produce 16,431 liters
Now lets look at how much food that yields for human consumption in terms of energy and protein. According to our helpful book, one liter of milk has 1,970 kJ of energy and an average of 3.2% protein content.
The one hectare of grass/clover will therefore yield 26,362 MJ of energy (6.3 million calories) and 428 kg of Protein. The same calculation for the corn will yield 32,369 MJ energy (7.74 million calories) and 525 kg of protein.
Obviously we also have a calf born each year and I have counted that energy into the energy per liter of milk as well - what happens to that calf afterwards is another calculation.
Now lets have a look at how much we will be able to produce if we grow either potatoes or wheat.
Wheat will yield an average of 5 tons per hectare (organic) or 25 tons of potatos.
Wheat has 8.5 MJ energy (2,031 calories) per kg and an average protein content of 14%. That yields a total 42,500 MJ of energy (10,157 million calories) and 700kg of protein.
Potatoes have 2.76 MJ energy (660 calories) per kg and an average protein content of 1.4%. One hectare of potatoes will therefore yield 68,750 MJ of energy (16,430 million calories) and 350 kg of protein.
Our book also informs us that on average 20% of our wheat and potato harvest will "not be fit for sale for human consumption" - the quality is too bad and it should therefore be used as animal fodder - so the above numbers would need to be revised downwards accordingly.
I will now roughly calculated (average between energy and protein needs) how many people one hectare of each of the above will be able to sustain for one year:
Grass/clover -> milk -> human: 26.2 people
Corn -> milk -> human: 32.2 people
Wheat -> human: 42.2 people
Potato -> human: 47.1 people
It becomes quite clear that producing milk is not nearly as inefficient a way of producing food as it has been so widely propagated (in movies like Cowspiracy).
What I have to mention each and every time I talk about this topic is that of the 4 options above, the grass/clover is the only one which builds up soil fertility rather than depleting the soil's reserves. That is why it is important to practice crop rotation where grass/clover is grown for 2 or 3 years before growing potatoes, grains and vegetables for 3-4 years.
Some vegans argue that we do not need cows in order to practice crop rotation - we could just use the grass/clover as green manure (mulching it into the soil). They are right. But it would be a hell of a waste, considering how much high-quality food those cows can produce for us out of that grass. Additionally, long-term studies by the Swiss Research Institute for Organic Agriculture has shown that when the same crop rotation with cows (the cows eat the grass and the manure is used as fertiliser) is significantly better for soil fertility than without cows (grass/clover is used as green manure). And we know that the world's soils store twice as much carbon as we have in our atmosphere. As Michael Pollan tells us, building up our soil fertility is our greatest chance to tackling climate change.
So lets feed out cows grass/clover not grains and soybeans and we will have ourselves cows that are climate heroes, not climate killers!