Draft:Animal Agriculture Waste Management

Introduction

With almost 2 million farms in the United States, the US is the largest food-producing nation in the world. Furthermore, agriculture has served as America’s main food source for many years. In addition to providing food for the nation, agriculture also creates about $190 billion per year, more than 50% of which can be attributed to animal agriculture specifically . Animal agriculture includes the rearing of livestock (cattle, sheep, swine, goat) and poultry for export and local sale. As a result of the vast expanse of farmland and farm activities, there has also been a growing concern for the increasing volume of animal waste being produced from these farms. Animal agriculture waste can be defined as any waste material that comes from the animals that are being raised on a farm. This includes livestock excreta, bedding material, feathers, dead carcasses, and other debris. When considering animal agriculture, Concentrated Animal Feeding Operations (CAFO) produce more waste than traditional or organic animal farms. A traditional farm allows free-range grazing of the animals and, therefore has limitations on how many animals are allowed on the farm at a time so that each one has enough space to graze as they wish. On the other hand, a CAFO keeps many more animals together in small living spaces, utilizing antibiotics to guard against the increased risk of infection and, therefore, allows for a lot more animals to be held in the same space at once. This consequently means that a lot more waste is being produced.

Waste products from livestock farming may impact the rest of society by crossing over into human food and water sources. This process then has the potential to cause significant harm to humans due to the increased likelihood of transmitting zoonotic diseases such as Salmonella and Ebola. Livestock waste mismanagement can also result in excess release of greenhouse gases such as methane into the atmosphere which will lead to a worsening of the greenhouse effect that has had a large effect on our environment.

Animal Waste Management Practices

Animal Waste Management practices vary depending on the specific orientation and needs of the farm in question. These waste management practices address varying issues such as wastewater run-off, waste storage, waste treatment, and waste usage. The farmer can choose which method suits his/her farm best after considering local regulations, overhead cost, the type and amount of volume to be managed, and how close the farm is to ground or surface water. In general, the approach to animal waste management is similar in farms worldwide, and these methods are outlined in this article.

We can divide the method of livestock waste management by the type of waste that needs to be discarded. Traditionally, only carcasses would be separated from the rest of the waste. However, more advanced methods of waste management involve the separation of liquid waste from solid waste as well. Traditional methods of solid and liquid waste management include:

1.     Dung Cake: Collection of animal excreta which is then allowed to be sundried and can later be used as a form of fuel. This method is mainly used in underdeveloped countries.

2.     Dumping: This method is an older method of waste management in which the waste is dumped into a heap or pit that is located on the farmland.

3.     Composting: This is the aerobic degradation of animal waste by accelerated bio-oxidation, which is facilitated by the intermittent turning and aeration of the organic waste material until it becomes a fine, odorless material that can then be used for fertilizer.

Advanced methods of animal agriculture waste management include ammonium recycling in the case of liquid waste. However, solid waste may be disposed of by the following advanced processes:

1.     Biogas production: Production of environment-friendly fuel through the method of anaerobic digestion of animal residues and other agricultural waste material. Biogas usually consists of 55-65% methane, 35-45% carbon dioxide, 0.5-1.0% hydrogen sulfide and traces of water vapor.

2.     Rotatory drum composting: This method involves placing the waste material into a drum which is mounted on four metal rollers attached to a metal stand which is then rotated twice a day. This process tends to decrease the composting time drastically to 2-3 weeks.

3.     Vermicomposting: In this process, earthworms are allowed to consume the organic waste matter, after which the excrete pelleted material called “vermicompost”. In addition to the worms providing extra protein, vermicompost also contains plant growth-regulating substances.

4.     Pyrolysis: Anaerobic chemical decomposition of animal waste by heating it in a reactor at 400 to 1472 degrees Fahrenheit.

5.     Soldier fly breeding: Treatment of animal waste material with the black soldier fly larvae. Even though the flies themselves only live for a few days, their larvae tend to live for several weeks and are able to digest a large amount of waste in the process.

6.     Litter management: In some cases, poultry litter (excreta, bedding, wasted feed and feathers) may be repurposed and fed to cattle as it may be a source of nutrients and essential minerals. Another option for the management of litter would be combustion which tends to be the most economically viable route because of the potential to generate power from the combustion process.

Disposal of carcasses is traditionally carried out by three main methods: burial (the most common method), burning (ideal for infection-ridden animals), and electrical incineration (ideal for large numbers of carcasses). On the other hand, a more advanced method is composting the carcass, which allows for the production of nutrient-rich soil that may be utilized on the farm after about 90 days.

Conclusion

Livestock waste management is important for the control of zoonotic diseases and for the betterment of the environment. There are various methods of livestock waste management, which are outlined above. The method that is used for discarding animal agricultural waste should be carefully thought about by the farmer to ensure that he/she is using the best method for their needs on the farm. Properly managing waste decreases the likelihood of negative impacts on the environment, such as wastewater runoff into surface or groundwater sources, which is a means of the spread of infection to the general public. Livestock waste management is also important to decrease the effect of greenhouse gases and encourage the repurposing of animal waste to make compost, which can then be used as fertilizer.