Theoretically, livestock manure – and human waste – in the U.S. could meet half of the nation’s agricultural needs for phosphorus, and more than 100 percent of its needs for nitrogen.
A Cornell study, published April 15 in Nature Sustainability, found that animal and human waste could significantly reduce producers’ dependence on synthetic fertilizer, which experts and advocates have pointed to as a major source for greenhouse gas emissions.
But the study merely puts to paper what livestock producers and manure applicators have been insisting for years – that manure is anything but a “waste” product. The benefits of manure have been proven in various studies for years, but most data points to manure only being applied to about one-tenth of fields for major U.S. crops.
While acceptance – both by producers and the public – is one hurdle, the study identifies another: moving manure (and human waste) is complex for both economic and environmental reasons, and the location of the waste and where the nutrients are needed don’t often add up. For example, the Northeast and part of the West were found to possess excess nutrients, while the Midwest and southern Great Plains have a deficit of nutrients.
However, the study analyzed both the sources and the locations of the waste produced and where it was needed, and found that roughly 37 percent of recoverable nitrogen and 46 percent of phosphorus could be used locally, and more than half of the remaining surplus nutrients could be redistributed to nearby regions with low economic and environmental costs.
The problem, says study author Chuan Liao, is “a coordination problem, not a resource problem.” The constraints alone are not enough to justify manure and human waste going to – to put it plainly – waste, says Liao.
Liao says an ideal solution begins with a decentralized system and a focus on local processing.
Read more about the study in the Cornell Chronicle, or read the full study here.
