What do broiler farms look like?
Prior to the 1920's, most farms kept chickens for dual-purposes (meat and eggs). In the 1920's, broiler chickens were developed. By the 1950's broilers surpassed dual-purpose farm chickens as the primary meat bird in the U.S. At the same time, the industry became vertically integrated, meaning the same company controls the chickens through all stages of life. Farmers that raise broiler chickens are contractors for these companies. Much of the broiler production in the U.S. is in the southeastern states but there are also significant broiler areas in the Northeast and Midwest. Recommended: Common poultry terms and definitions.
Broiler chicken housing tends to look similar across all regions. Most buildings are much longer than they are wide. A typical building has an insulated roof and a way to provide ventilation to the chickens. Some buildings use natural ventilation, controlled by curtains. Some use mechanical ventilation and some use both. There will usually be one or more metal feed bins next to the building and a wide door at one (or both) ends for access by equipment to clean out the building. Photos 1-4 below show a variety of broiler chicken housing.
Photo 5 shows a broiler breeder house. This farm houses adult chickens that produce fertilized eggs. The eggs are incubated, hatched and the chicks are placed in buildings like those shown in Photos 1-4.
What about the inside?
In broiler houses, chickens live on the floor. All the chicks in the house (flock) are brought in at the same time and all are sold at the same time, a few weeks later. The floor can be dirt (most common) or concrete and is covered with bedding - a common choice is pine shavings. The bedding usually remains in place for more than one flock - a practice referred to as 'built-up' litter. Litter is the term for the bedding + manure + feathers mixture.
The decision to clean out the litter depends on the cost and availability of bedding, the ability of the operator to manage ammonia and moisture levels, and the amount of time before a new flock arrives.
How do broiler farms manage the manure (litter)?
A broiler chicken takes only 5 weeks to grow to market weight. A typical broiler house will have 20-30,000 birds and can raise 5-7 flocks per year. A broiler chicken will produce 2-3 lbs of manure in its life. A rule of thumb is that a farm can expect around a ton of litter for each 1000 birds sold each year.
Broiler litter is a solid manure and can be collected and stored as such. The mixture of bedding and manure (litter) makes broilers different than other major animal agriculture sectors. For the most common dairy, beef, layer, and pig systems, the largest variable is the amount of solids versus water. Broiler housing introduces a third variable in the form of bedding.
Each farm varies in their litter management. A common practice is to remove the "cake" - a crusted layer - from the litter and add a little bit of new bedding in between each flock. Other farms condition or mix the litter and reuse all of it. Most remove all of the litter each year and replace with new bedding.
When a house is cleaned out, the manure can be taken directly to a field and spread. If the timing is such that a field is not available, the litter is either stockpiled (short term) or added to the manure storage. Broiler litter can be stored outdoors or under a roof - the rules in some areas may require covered storage. All litter storage areas need to be designed to prevent clean water from contacting the manure as much as possible so that any stormwater runoff is captured.
Are there other ways to manage broiler litter?
As with most manure, the primary use for broiler litter is as a crop fertilizer. The most common alternative to spreading "raw" litter on fields is to compost it. Composted litter can still be spread on fields, or reused as bedding in the broiler house, but is also marketable for other uses like golf courses or gardens.
Composting broiler litter requires less additional carbon than manure from most other animal species. This is because some carbon has already been added in the form of bedding. Another unique consideration in composting broiler litter is moisture. Litter tends to be very dry and requires a lot of additional water for proper composting.
Another option for managing broiler litter includes options referred to as "thermal conversion technologies". These include processes like gasification (Photo 2, below), pyrolysis, and combustion (Photo 3, below). All of these processes produce heat along with a range of products including bio-oils and These processes also produce biochar and ash, which are very nutrient dense. It is more economical to transport these concentrated nutrients than to transport raw manure, making this an option in areas where there are concerns about the excess nutrients accumulating in soil.