Temperatures, measured at the three sets of doors for the month of September 2005 varied according to the number of large sows or mass of pigs added (see Table 1). When a 500-600-lb. sow was added, temperatures dropped for about four days. When piglets, finishing pigs and an occasional sow were added, the composting process tended to be fairly uniform, they reported. Compost exiting the effluent door was combed with a simple rake to separate bones to be recycled.

A second test period was conducted during the month of November 2005. The temperatures were considered to be ideal for rapid composting of mortalities. The sole temperature drop noted for the period occurred when a 530-lb. sow was added to the composter.

Composting temperatures were recorded in a third test period, Dec. 1-31, 2005, when outside temperature drops during two periods, Dec. 9-14 and Dec. 18-22, resulted in moderate temperature declines at the effluent door.

On average, temperatures inside the composter remained above 131° F and the quality of the compost was normal. The temperature drops during the two cold spells surprisingly resulted in the highest internal temperatures during testing.

“Generally, the composting process is capable of performing between temperatures from -13° F and 86° F,” the report stated, if the Biovator is exposed to the external climate. Composting will continue year round if the Biovator is sheltered from the environment in extreme climates.

Four samples were collected at each opening, each week, and sent to a laboratory to test moisture content of the compost and processed material.

At door 1, the moisture content range was 47.6 to 71.3%, at door 2 it was 45.5 to 66.3%, and at door 3, moisture ranged from 30.8 to 56.5%. A fourth sample, collected at the basin before transferring the material to long-term storage, ranged from 31.8 to 61.1%.

The Quebec Ministry of Agriculture required a list of physical and chemical parameters compiled from 15 samples collected between June and October 2005 (summer) and 12 samples collected between November 2005 and January 2006 (winter). Table 2 reinforces the wide variability resulting from the samplings, leading the company to note: “Only long-term averages of the product could be used as reliable data for estimation of fertilizer values of the compost.”

Noteworthy in this project, the compost had high total organic matter and high levels of nitrogen, phosphorus and potassium.

The ministry also required microbiological and pathogenic parameters to be measured, including salmonella, E. coli, enterococcus, clostridium perfringens, yersinia enterocolitica and cryptosporidium. Of the 15 summer samples, all recorded the presence of enterococcus, three contained clostridium perfringens and one had salmonella. In the dozen samples collected during the winter period, the presence of enterococcus was the only pathogen present.

In general, the report indicated the composting process was effective in the elimination of all microbiological and pathogenic parameters except enterococcus.

The long-term test results show the Biovator preferred compost-to-mortality weight ratio is 0.83. In other words, when the ingredient recipe is followed — mixing mortalities, wood shavings and recycled compost (including bones), the horizontal, in-vessel composter will convert 2.2 lb. (1 kg.) of mortalities into 1.83 lb. (0.83 kg) of compost after a 10-14-day process.

Naturally, the moisture content, the density of product and the outside temperatures influence the final compost product.

The company estimates that the capacity of the mid-sized Biovator in this study would be 154-176 lb. of mortalities mixed with 38-44 lb. of wood shavings/day, producing 128-146 lb. of compost in the summer (using the weight ratio of 0.83). In the winter, this unit could process 165-187 lb. of mortalities mixed with 46-53 lb. of wood shavings/day to yield 137-157 lb. of compost.

The driving mechanism for the Biovator consists of a 1-hp, 110-120 v. motor, two gear boxes with heavy-duty bearings, plus sprocket and chain. Prices start at US$25,000 and increase depending on capacity. Additional costs would include a concrete pad and cover for compost storage.

For additional information, contact The Puratone Corporation, Niverville, Manitoba at 800-340-4421, or 204-371-0115 (Canada) or Seven Star Enterprises at 507-381-1556 (U.S.)

View both tables in a printable Word document