Bad Smell from Composting Manure
Bad odors are a common problem for people who live near livestock farms. The bad smell is mainly produced by the livestock manure. Composting tends to make the smell worse. In Japan, there are 1500 to 2000 complaints about odor from livestock production. About one-fifth of these complaints are concerned with bad odors produced during composting.
Microorganisms Which Can Reduce the Smell of Livestock Manure
Bad odors from livestock manure are a problem in every country in Asia where livestock are raised intensively. A variety of different methods have developed to solve the problem. Some of them are rather expensive, such as a closed composting facility with partial ventilation. A cheaper approach which holds considerable promise is the use of microorganisms which remove or reduce the bad smell. In fact, many commercial preparations are already being used for this purpose by livestock farmers in Japan. Their widespread use of these products reflects more the desperation of farmers to solve the problem, than the effectiveness of such products. Usually it is not clear what microorganisms these products contain, or how they work. In practice, they often seem to have little effect.
There has been a lot of research in Japan and elsewhere into microorganisms which reduce bad-smelling compounds in raw or composted livestock manure. Most of these have focused on microorganisms which reduce volatile fatty acids.
Reducing the Level of Ammonia and Sulfur
In recent years, scientists at Japan's National Institute of Livestock and Grassland Science have been searching for microorganisms which can reduce the level of ammonia or sulfur compounds.
They have isolated many microorganisms which grow in compost and manure, and which take up a high level of nitrogen. One strain of Bacillus provisionally described as Bacillus sp. TAT 105 has a high tolerance for ammonium nitrogen. Very similar to Bacillus pallidus, this bacterium is a heat-loving (thermophilic) species which thrives at a temperature of around 65oC. In tests, compost treated with the bacterium emitted less ammonia and had a higher total nitrogen content than the control.
Further tests are now in progress, with the eventual aim of developing an effective biological additive for practical use by livestock farmers.
Composting of Livestock Manure
Livestock farms in Japan often treat their solid wastes by composting them. Most cattle and swine manure is composted, and then applied to cultivated fields. Generally in the treatment of livestock wastes, the manure is mixed with a bulking agent such as sawdust or rice straw. This makes the material more porous, so that it is easier to aerate.
The compost mixture is then heaped into a pile. It soon begins to ferment. During the initial stage of composting, the organic matter tends to break down very rapidly. The temperature of the compost soon rises to 60-80oC. (This is hot enough to cause a burn if skin is exposed for more than a few seconds!!!)
In order to keep the composting material in an aerobic condition, the pile is periodically levelled, mixed again, and reformed into a pile (turning). In some composting facilities, forced aeration or continuous stirring is used rather than turning.
Composting and drying the materials reduced their original volume and weight considerably. Furthermore, the nutrient content has become stabilized and improved. Composting has the further advantage that it sterilizes weeds and pathogens originally in the manure. After several months of composting treatment, the result is a dry, powdery, odorless organic fertilizer.
Index of Images
Figure 1 Electron Micrograph of the Bacillus (X 10,000)
Figure 2 Pile of Livestock Manure Being Composted, Japan. Note Steam Being Given off As the Warm Compost Comes into Contact with Cold Air.