The Facts: vegan nitrogen emissions

Is it true that veganism increases the nitrogen issues?
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During elections, politicians make bold claims. Prospective Euro-MP Jessica van Leeuwen contested the validity of plant-based protein production during the recording of the VPRO-podcast Europa Draait Door.  


‘Human nitrogen emissions increase by 15 per cent when we switch to a plant-based diet. This has been shown in pigs, whose gastrointestinal system is similar to that of humans. It will likely be higher in humans. Thus, switching to plant-based does not solve the nitrogen issue.’ (Jessika van Leeuwen, BBB)


Let’s check the setting first. Van Leeuwen visited The Spot on Wageningen Campus to debate with Gerben-Jan Gerbrandy (D66) and Anja Hazekamp (Partij voor de Dieren) on the question of whether the European Agriculture policy is tenable. Hazekamp and Gerbrandy say it is not. Hazekamp denounced the unsustainable livestock and meat industry. The future is plant-based, she states. ‘We must stop wasting food on animals’  gastrointestinal system.’

Replacing animal protein with plant-based protein in the human diet ultimately lowers nitrogen emissions

Walter Gerrits, professor of Animal Nutrition

Van Leeuwen calls this a miscalculation. Animal protein is easier for humans to process, which means that switching to plant-based proteins is less efficient, hence causing a relative increase in nitrogen emissions. Van Leeuwen claims a vegan diet increases human nitrogen emissions by at least 15 per cent. Although she fails to cite her source, we may assume she is correct. Van Leeuwen is not only an Animal Science alum of WUR, but she also obtained her PhD here.

Animal Nutrition Professor Walter Gerrits agrees that switching to a plant-based diet does, in fact, lead to the loss of proteins and, as a result, nitrogen. ‘Most animal proteins are easier to digest than plant-based proteins. Nitrogen emissions through manure will certainly increase. Although I don’t know what the 15% is founded on, it seems a plausible estimate for the emission of nitrogen through urine and manure.’

However, Van Leeuwen’s conclusion is ‘rather far-fetched’. Yes, a plant-based diet causes some nitrogen emissions, but these emissions are higher if pigs convert these plant proteins into animal proteins. Gerrits: ‘How efficiently pigs store nitrogen in their bodies depends on many factors, but oscillates at around 50%. Hence, replacing animal protein with plant-based protein in the human diet ultimately lowers nitrogen emissions, even if humans require a higher protein intake as a result of this switch. It is essential to ensure your comparisons are correct in a discussion.’


Van Leeuwen focuses solely on the costs and ignores the gains, and, as a scientist, should know better. However, as a politician, she is a fast learner.

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