They are talking about farts from humans. That produces methane so there is a systematic attack on farms all over the world which will result in less food and widespread famine. I am being facetious but bot really because worldwide governments are imposing policies on farms that will drive crop yields waaaay waaaay down. Places like Sri Lanka already have starvation because the government mandated organic farming with no chemical pesticides or fertilizers and drove them from a net exporter of rice to a country that can't feed their own people. That situation is coming everywhere, here too. It's already being talked about.
They have been blaming the Russian-Ukraine war for those shortages but that is gaslighting. Here is an article from last November giving a different reason. Probably also false.
North American fertilizer shortage sparks fears of higher food prices Nov. 24, 2021