Increase in Manure Removal Rate

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For this BMP, we looked at increasing the frequency of manure removal rate in dairy freestall barns. We looked at increasing the rate of vacuum manure removal from twice daily to three times daily.

The Problem
Background
Experimental Methods
Results and Cost Analysis
The Solution

The Problem

In dairy barns, ammonia volatilization occurs soon after manure is deposited on the barn floor. Urine urea nitrogen mixes with the urease enzyme in feces and rapidly hydrolyzes to form ammonia gas. The rate of the reaction is a function of mixing time, temperature, relative humidity, and pH of the manure, but is relatively fast taking anywhere from 2 to 10 hours for peak ammonia volatilization to occur (9, 10). Since dairy barns are continuously supplied with both urine and feces on a regular basis, they are hot spots for ammonia volatilization.

Background

The easiest and most effective way to reduce ammonia volatilization from barn floors is by removing manure, which is the source of ammonia emission, at frequent intervals. In dairy systems, there are three types of housing: drylot, freestall, and mixed. For this BMP we are addressing mixed and freestall barn dairy systems. Freestalls are where animals are housed in open barns with the ability to move freely in open alleyways between bedded cubicles provided for resting, and the feeding area. Manure is deposited in the alleyways, which are usually flushed, vacuumed, or scraped concrete, and is removed regularly. Since the fresh manure deposition is frequent and mixing rate is increased in these areas, the ammonia volatilization rate is very high in freestall barns. On average, about 16% of the total nitrogen excreted by cows is lost from the freestall area (19), most of that as ammonia.

Studies have found that manure removal systems that don't completely remove manure, but rather just spread and distribute manure over the barn floor surface, were not as effective as systems that completely removed the manure (20, 21). This is important to note when evaluating different removal systems and their effectiveness. However, reductions in ammonia volatilization have been seen with more frequent removal of manure from alleyways under various removal techniques (flush and scrape) (20).

Experimental Methods

Method. We looked at increasing manure removal rate with a vacuum system. The current practice at the sample dairy was vacuum manure removal from freestall barn alleyways twice daily at 0500 and 1400 h. The BMP treatment increased that rate to three times per day (0500, 1400, and 2200 h) in the sample pen. In order to determine what the optimal scrape time should be, we first sampled for one day with no scraping. This 0 vacuum rate also acted as a control against which additional treatments were measured against. We then sampled for one day at the current scrape rate of two times a day, and one day at the increased rate of three times a day.

Results, and Cost Analysis

Results. Coming Fall 2008....

Cost Analysis. Coming Fall 2008....

The Solution

Coming Fall 2008....