Chapter 9. When Manure is not Manure
Sometimes, CAFO proponents attempt to downplay the insufferable odor of CAFO waste by saying “manure is manure.” They argue that manure has been around for 10,000 years, so people who cannot tolerate being around CAFO manure should not live out in the countryside. That argument ignores the fact that liquid manure that is stored in a CAFO lagoon or pit undergoes radical transformation during storage, which completely alters its chemical nature and creates compounds that are not only foul-smelling but toxic.
The toxic compounds are created through a process of putrefaction caused by the lack of oxygen in the manure storage reservoir. Manure that is held in a CAFO’s liquid storage reservoir begins to decompose, but because the liquid-manure environment lacks sufficient oxygen for complete decomposition, the system becomes anaerobic (without oxygen) and the manure putrefies. During the putrefaction of manure, more than 300volatile organic compounds of varying degrees of toxicity are produced.
Two of the more commonly known toxic compounds produced during liquid manure putrefaction are ammonia and hydrogen sulfide. Ammonia is an irritant that affects the eyes, nose, skin and respiratory tract. Long-term exposure to low levels of ammonia can lead to respiratory and pulmonary disease.
Hydrogen sulfide, which has the characteristic smell of rotten eggs, is a neurotoxin. At high concentrations, hydrogen sulfide will cause rapid unconsciousness and death through respiratory paralysis and asphyxiation. That is why when CAFO ventilation systems fail, the confined animals – and even CAFO workers – can quickly be overcome and die from hydrogen sulfide poisoning. Exposure to low levels of hydrogen sulfide has been associated with headaches, nausea and respiratory infections.
Other airborne emissions from CAFOs include odor, dust, allergens, and a wide variety of volatile organic compounds. Also, significant amounts of the greenhouse gases methane and nitrous oxide are created during liquid manure putrefaction.
The decomposition of animal manure under natural conditions is completely different from what happens to liquid manure in a CAFO. For example, when an animal deposits manure on the soil surface in a pasture, the manure lands on top of billions (literally) of soil organisms. The soil organisms quickly begin decomposing the manure. Unlike the anaerobic conditions in a CAFO liquid manure pit, the decomposition by soil organisms is an aerobic process; that is, it occurs in the presence of oxygen. When oxygen is present, the manure decomposes into carbon dioxide, water and humus. Putrefied compounds are not produced. The aerobic decomposition of manure in a pasture is an odorless process.
Likewise, when manure is properly composted, it undergoes aerobic decomposition, and the finished compost is odorless and rich in humus-like compounds which, when used as a soil amendment, enrich the soil and sequester carbon. When hogs or other livestock are raised in deep-bedded hoop houses, the manure and bedding mixture they leave behind is normally composted, which is why properly managed hoop houses are not an odor problem.
Approximately 50 million tons of livestock manure are produced annually in Iowa.vi With that amount of manure, it is easy to see that systemic problems in how manure is managed can produce a large degrading influence on water quality, air quality and the overall quality of life in rural areas.