Vegans are said to emit 60% more methane gas than meat eaters because of their diet and are therefore among the main causes of the greenhouse effect, according to an article published on social media. Experts at the University of Munich respond to this claim with some scientific facts.
ASSESSMENT: Human digestion is not one of the main causes of the greenhouse effect – whether you eat vegan or not.
FACTS: After carbon dioxide, methane is the second most important anthropogenic – i.e. man-made – greenhouse gas contributing to climate change. Annual global methane emissions are approximately 600 million tonnes.
The largest methane sources are (in millions of tons per year; database 1992):
- Wetland agriculture (225)
- Cattle / animal agriculture (115)
- Energy (110)
- Forest fires (40)
- Garbage dumps (40)
Human digestion contributes only minimally to methane emissions compared to these factors. “Not even half of all humans produce methane at all, and if they do, then only a few micrograms per second,” says Jia Chen, Professor of Environmental Sensors at the Technical University of Munich.
As an example, we assume that each person produces an average of 10 micrograms of methane per second. This corresponds to 310,536,000 micrograms per year, or 0.31536 kilograms. For 8 billion people, this would be 2,522,880 metric tons per year, significantly less than, for example, emissions from landfills (40,000,000 metric tons).
According to a report by Deutsche Umwelthilfe, German agriculture emitted around 1,268 kilotons of methane in 2012. This accounts for around 53 percent of Germany’s total emissions. According to the study, the majority of this methane is released in livestock farming.
Sources
Article University of Oxford: http://dpaq.de/ro028
Methane, plants and climate: http://dpaq.de/PtyBU
Study on methane sources: http://dpaq.de/XBOAo
Article in the “Abendzeitung”: http://dpaq.de/G3nue
Report of Deutsche Umwelthilfe: http://dpaq.de/GTpsf
