Compost C:N

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Composting is not a widely practiced management technique on feedlot operations, but can have very beneficial results when employed. This BMP primarily applies to operations already composting; however, we strongly encourage non-composting operations to compost their manure to create a more stable and usable end product.

The Problem
Background
Experimental Methods
Results and Cost Analysis
The Solution

The Problem

The C:N ratio of compost dictates how much N will volatilize from the compost pile as ammonia. In general, a C:N ratio above 20:1 will lead to a decrease in ammonia emissions. The high the ratio of C:N, the lower the ammonia volatilization will be. The problem is that in general, livestock compost is somewhere around 12:1 C:N. This means that a carbon source needs to be added to compost to minimize mmonia volatilization. The type of carbon added to the pile is also important and will equally effect the amount of ammonia emitted from a compost pile.

Background

Of the total nitrogen entering manure storage as compost or manure stockpiles, 20 to 50% is lost as ammonia volatilization, and the rest is converted to products of nitrification/denitrification or immobilized. Some nitrous oxide losses occur during nitrification and incomplete denitrification, but these are less than 5% of the total nitrogen loss (19). Paillat et al. (30) found that the ammonia flux in compost piles is related to the biodegradable nitrogen present and the nitrification and immobilization of ammonia, which depends on the C:N ratio, the carbon biodegradability, and microbes present in the pile. Less biodegradable carbon sources, like sawdust, were found to increase ammonia emissions, thus the choice of added carbon source to a compost pile needs to be considered as it will determine the rate of ammonia emissions. Additionally, proper management of pile moisture and air circulation will determine the rate of temperature increase and subsequent ammonia volatilization. In general, aeration and a reduction in pH will decrease ammonia emission, while an increase in temperature and a low C:N will increase ammonia. Even though the majority of ammonia is emitted from compost piles within the first 10 days of composting, tunring will produce a spike in ammonia as the inner layers of the compsot are exposed to ambient air.

Experimental Method

Method. Coming Fall 2008......

Results and Cost Analysis

Results. Coming Fall 2008......

Cost Analysis. Coming Fall 2008.....

The Solution

Proper management of compost piles will help minimize ammonia volatilization, and produce a very good compost product. By increasing the amount of C in the compost by adding available materials like straw bedding, disposed feedstuffs, or crop resides, the C content of the compost can be easily increased with little cost input.