Diego Horcajada, April 2018
Nowadays it is no secret that contribution to climate change is significantly higher in animal-based diets than in plant-based diets. But how much? How would a comparison based on relative units such as grams of protein or kilocalories look?
The image below sheds light on the question. From looking at this, we can conclude beef and lamb are highly greenhouse gas (GHG) intensive, 7 times higher than eggs, pork or poultry.
Other significant criteria to compare the different product types are the energy conversion efficiency and protein conversion efficiency: Both efficiency rates are defined as the percentage of calories (or protein) used as feed that are converted to end animal product. An efficiency rate of 25% would mean 25% of calories (or protein) from animal feed input were effectively converted to end animal product calories (or protein); the remaining 75% would be lost during conversion.
So, how do different food types rank in regards to their energy and protein efficiency conversion rates?
As expected, whole milk and eggs have the highest conversion efficiency (both in energy and protein). This is logical: milk in mammals is supposed to provide the newborn with the highest possible amount of fats and proteins in order to support rapid development during the first months of life. Similarly, chicken eggs contain all the fats, proteins and many other nutrients needed to generate a whole new chick.
On the other hand, conversion efficiency rates of meats (poultry, pork, lamb and beef) are lower than milk and eggs. This is somehow logical as well as now we have to consider the total life span of the animal and all the food it eats before it is transformed into food for humans in the slaughterhouse. But it is important to notice the differences between types of meat: the energy efficiency rate of beef is half that of lamb, almost five times less than pork, and nearly seven times less than poultry.
It is becoming obvious that our society’s current heavy consumption of red meat is not only unsustainable in terms of production capacity to satisfy population growth rates but also has a tremendous negative impact on the environment.
We need a drastic change in our consumption behaviours, and we have to do it respecting the different cultural and gastronomical traditions: we cannot expect everyone to become vegan or vegetarian.
A more realistic goal to aim for is to have a more appropriate balance in our diets. For example, if we significantly reduce the amount of red meat we eat, without reducing the money we spend on it, we can enjoy higher quality meat from local farmers, with fewer hormones, less antibiotics and better animal welfare. Meat lovers can enjoy the highest quality while making a positive impact on the environment and their local economy.
So, are you willing to make the change?
- Clark & Tilman (2017). Comparative analysis of environmental impacts of agricultural production systems, agricultural input efficiency, and food choice.
- Alexander et al. (2016). Alexander, P., Brown, C., Arneth, A., Finnigan, J., & Rounsevell, M. D. (2016). Human appropriation of land for food: the role of diet. Global Environmental Change