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As demand for meat and dairy products increases across the world, much attention has landed on how livestock impact the environment, from land usage to greenhouse gas emissions.
Now researchers at Georgia Institute of Technology and the Centers for Disease Control and Prevention are highlighting another effect from animals raised for food and the humans who eat them: the waste they all leave behind.
In a paper published November 13 in Nature Sustainability, the research team put forth what they believe is the first global estimate of annual recoverable human and animal fecal biomass. In 2014, the most recent year with data, the number was 4.3 billion tons and growing, and waste from livestock outweighed that from humans five to one at the country level.