• ehopman

CO2 on the plate

Updated: Jun 7

Food, both in terms of its means of production and its worldwide consumption, is one of the major issues to tackle in a near future. The problem is even more baffling when we realise we are already producing more than we should and this global production has a tremendous impact on the environment, be it CO2 emissions, land use or freshwater consumption.

This paper will answer the following question: can we feed 10 billion people while keeping the environmental impacts as low as possible and if so, how?

The challenges at stake

Living in a Western European country prevents us from properly grasping the scale of food matters worldwide. The World Health Organization, in their latest Global Nutrition Report delivered unacceptable numbers: 22% of children under 5 are stunted, 9.7% of women aged 20-49 are underweight. Though the number of underfed children and adults worldwide is slowly decreasing in relative terms, there is still a long way to go, and the number of overweight and obese people has steadily been growing since 2000. The consequence is that for every person suffering from malnutrition, 2 are overweight or obese.

If this is the state of the world today, what will it be in the next decades? The global population is expected to reach 10 Billion by 2050, which, even with today’s efforts in improving the situation, means more humans will suffer from under or overeating each year.

World Health Organisation, 2018 Global Nutrition Report (2018).

On the resource side, if we have the capacity today to feed more humans than there are on earth, what will it be when developing countries will adapt new eating and consumption habits? Can we feed 10 Billion Europeans or North Americans? The World Resource institute showed, taking demographic as well as economic growth of countries into account, that the world will need to increase its annual calorie production by 70% by 2050. If we also consider the increase of meat consumption in developing countries, this means that there will be a dramatic increase in the meat industry.

However, environmentally speaking, types of food aren’t equal at all. How can we ensure the calorie production increases while respecting our GHG reduction targets? Should meat be prohibited? What is the optimal food diet and is it replicable worldwide?

Life cycle analysis of food

The first two questions can be assessed by properly measuring the environmental impact of various food products. One method of doing so is by measuring and evaluating the greenhouse gas emissions, the eutrophication, water use, energy use and other environmental indicators of each food product over its full life cycle. The difficulty lies in the amount of variables to look at when one wants to investigate the food industry: the type of product, the type of agriculture, the distance to the final consumer, and the type of preservation methods… Meaning that two different LCA (Life Cycle Analysis) could not be comparable because they didn’t take the same assumptions. All the results shown hereafter come from published scientific papers that explicitly cited all their assumptions.

The first type of food to investigate is meat. It is now well-known that meat is highly criticized for its environmental impact. The largest study made so far on the meat industry is probably the one performed by Battagliese et Al. (2018) on the US meat industry.

Asem-Hiablie, S., Battagliese, T., Stackhouse-Lawson, K.R. et al. A life cycle assessment of the environmental impacts of a beef system in the USA. Int J Life Cycle Assess 24, 441-455 (2019).

This graph shows the breakdown, for each metric used in the paper, of the contribution of different phases. One can observe that feeding and growing cattle (from Calf to Cow) are the main contributors in most metrics used (10 out of 12). For instance, for the Global Warming Potential indicator, which measures the emissions of greenhouse gases, almost 50% of the total emissions come from enteric CH4, emitted by the cow during its development.

As a final note, this paper calculated that one kilogram of carcass weight (meat that is eaten by consumers) emits 18.5kg of CO2 equivalent (all GHG converted to CO2). When such an assessment is done for each food type, one can properly compare them on a selected number of indicators. The World Resource Institute published such a meta-analysis and showed the following results:

World Ressource Institute. Janet Ranganathan, Daniel Vennard, Richard Waite, Brian Lipinski, Tim Searchinger, Patrice Dumas. et al. Shifting Diets for a Sustainable Food Future (April 2016).

An important note before analysing this result is that the WRI converted each food into a protein equivalent, to also answer the usual concern of proteins intake in vegetarian meals. The result of their analysis is unequivocal: meat emits more, consumes more water and uses more land than any other type of food and by a very large margin. The reasons are not technological or human-based but from the nature of the product itself: cows need space, water to produce the food they consume and emit a lot throughout their developing cycle. If turning completely vegetarian is not yet considered a necessity, simply reducing red meat intake, or replacing it with chicken, would divide one environmental impact by four.

Hence, red meat, and animal products in general, are very polluting. This can easily be understood by the fact that an animal is a very inefficient machine: it takes vegetables and transforms them into tissues, bones and muscles but only a fraction of this transformation is then extractable for human consumption (bones, waste, energy is not edible).

What is the "perfect" diet?

This will constitute the final note of the paper: now that we know the magnitude of the environmental impact of different types of food, what would be the optimal diet environmentally speaking while guaranteeing the right nutrient intake?

In 2006 Researchers in Italy made the comparison of various food diets concerning their environmental impact. Each diet was elaborated by a dietitian and have an equivalent energetic and nutrient content, but one is omnivorous, one vegetarian (eats everything except meat or fish flesh) and one vegan (no animal-based products whatsoever). The environmental impact of each diet is evaluated for two types of agriculture: conventional and organic.

To these six different dietary patterns a seventh was added, the average Italian diet, and all were then compared and evaluated based on resource usage, ecosystem impact and damage to human health.

Baroni, L., Cenci, L., Tettamanti, M. et al. Evaluating the environmental impact of various dietary patterns combined with different food production systems. Our J Clin Nutr 61, 279-286 (2007).

The same conclusion can be drawn. Within the same agricultural method, the less the amount of meat in a diet, the smaller its impact on health, resources and ecosystems combined. Here, however, conventional farming and organic are compared and one can observe the gain from shifting consuming habits while maintaining the same diets.

But the most interesting point of this study is that it shows the orders of magnitude of the changes one can expect by shifting diet. The result is interesting as it shows that taking animal flesh out of a diet (OMNIV-INT vs VEGET-INT) reduces the global impact by a much smaller margin than simply eating a healthier amount of meat (NORM-INT vs OMNIV-INT). In fact, the paper shows that eating non-organic vegetarian will yield a higher environmental impact than eating a healthy omnivorous diet.

As a conclusion, it isn’t expected from people to drastically change their eating habits and multiple studies show that people are very reluctant to make such a change. However, knowing these results, one can know that small measures can have huge results globally. For instance, the WRI estimated that reducing meat consumption by half would reduce the environmental impact (GHG emissions and land use) by half whereas taking meat out of the menu would “only” increase this reduction by 10%. The message is therefore not to stop eating meat, but to eat it more responsibly and with full knowledge of its implications on human health and the environment. The local aspect of our diet is one essential criterion to reduce the amount of CO2 on the plate. For a European, eating chicken from the farm next door will always have less impact on the environment than avocados from Chile.

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