Anaerobic Lagoon - Introduction

Introduction

Beginning in the 1950s with poultry and then later in the 1970s and 1980s with cattle and swine, the United States has turned to the Concentrated Animal Feeding Operation as a way to more efficiently produce large quantities of meat. This switch has benefited the United States consumer by increasing the amount of meat that can be grown thereby decreasing the price of meat. However, the increase in livestock has generated an increase in manure. In 2006, for example, the United states produced 133 million tons of manure. Unlike manure produced in a conventional farm, CAFO manure cannot all be used as direct fertilizer on agricultural land due to the poor quality of the manure. Moreover, CAFOs produce a high volume of manure. A feeding operation with 800,000 pigs could produce over 1.6 million tons of waste a year. The high quantity of manure produced by a CAFO must be dealt with in some way, as improper manure management can result in water, air and soil damage. As a result, manure collection and disposal has become an increasing problem.

In order to manage their waste, CAFOs have developed Agricultural wastewater treatment plans. To save on manual labor, many CAFOs handle manure waste as a liquid. In this system, the animals are kept in pens with grated floors so the waste and spray water can be drained from underfloor gutters and piped to storage tanks or anaerobic lagoons. Once at a lagoon, the purpose is to treat the waste and make it suitable for spreading on agricultural fields. There are three main types of lagoon: anaerobic, which is inhibited by oxygen; aerobic, which requires oxygen; and facultative, which is maintained with or without oxygen. Aerobic lagoons provide a higher degree of treatment with less odor production, though they require a significant amount of space and maintenance. Because of this demand, almost all livestock lagoons are anaerobic lagoons.