Manure Takeaways
Takeaways are key points detailed and referenced in the Manure & Other Outputs section
The Manure Problem
Nutrient pollution (excess nitrogen and phosphorus) from concentrated manure is one of the central negative externalities of factory farming; nutrient pollution is one of the largest environmental problems in the U.S. and globally.
Factory farming has transformed manure from a high-value product to one that is regularly viewed as a waste product that must be disposed of.
This is mostly due to the massive amounts of manure generated by huge numbers of confined animals in small geographical areas.
Because of high manure transport costs, there is not enough cropland within economically feasible distances; the comparative convenience and predictability of chemical fertilizers further lowers manure’s value.
Manure storage facilities (lagoons, pits, etc.) disperse manure nutrients through both planned and catastrophic releases and through ammonia volatilization; manure is often land-applied as a quasi-legal method of dispersal into waterways via runoff.
Despite decades of research, regulations, and incentives, nutrient pollution from factory farm manure persists; the eutrophication of the nation’s waterways and ammonia pollution (including deadly PM2.5 pollution) are central costs of the factory farming system.
Along with nutrient pollution, the range of manure pollutants includes pathogens, antibiotics, hormones, heavy metals, and GHG emissions.
Total Nutrient Amounts
The amounts of nutrients in all farmed animal manure are ~75% of the totals in all chemical fertilizers.
The amounts of nutrients in factory farm manure are ~40% of the nutrients in chemical fertilizer. (Some manure is generated on rangeland or pasture.)
The cropland that has manure applied is less than one-tenth the size of the cropland that receives chemical fertilizers; a large portion of that manure is applied in addition to full applications of chemical fertilizers.
Almost 80% of applied manure is spread on land that is controlled by factory farm producers; generally, their purpose in owning or controlling the land and growing crops (usually corn) is to have a place to get rid of the manure.
Manure Pollution Amounts
Broadly estimated, ~90% of the nutrients in manure are dispersed into the environment rather than effectively applied to crops.
About a third of the nitrogen in factory farm manure volatizes into ammonia within hours or days of excretion causing significant damage to air quality as well as plant life and waterways due to land deposition.
After all the planned and unplanned runoff, leaching, and volatilization, a very small share of nitrogen in manure is applied to crops; broadly estimated, ~10% of manure nitrogen generated on factory farms is effectively applied to crops.
Nutrient runoff and volatilization from systematic manure over-application on crops add to the pollution.
Total Manure Amounts
Animals raised for food generate approximately 1.2 billion tons (2.5 trillion pounds) of manure per year, about 6 times as much as total human waste.
Animals on factory farms generate approximately 740 million tons (1.5 trillion pounds) of manure per year, about 4 times as much as total human waste.
A typical pig factory farm generates about 900 tons of manure per week, about equal to the weekly human waste from a city of 80,000 people.