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Horizontal Composter Handles Mortalities

Article-Horizontal Composter Handles Mortalities

The medium-sized Biovator was tested for compliance with Canadian regulations at a 1,250-sow farrow-to-finish unit. Handling the inevitable mortalities on any hog farm creates both a practical and a biosecurity challenge. In some herds and regions, the problem has been exacerbated by higher-than-normal mortalities caused by porcine circovirus associated disease (PCVAD). Canada's third-largest pork

The medium-sized Biovator was tested for compliance with Canadian regulations at a 1,250-sow farrow-to-finish unit.

Handling the inevitable mortalities on any hog farm creates both a practical and a biosecurity challenge. In some herds and regions, the problem has been exacerbated by higher-than-normal mortalities caused by porcine circovirus associated disease (PCVAD).

Canada's third-largest pork producer, The Puratone Corp. of Niverville, Manitoba met those challenges by developing a horizontal, in-vessel composter known as the Biovator. The company wanted an alternative to traditional composting, incineration or commercial rendering and, more importantly, to comply with Canadian federal regulations administered by the Ministry of Agriculture.

Tested in Quebec

Puratone set up a test project at a 1,250-sow, farrow-to-finish site utilizing a medium-sized Biovator (30 ft. long and 4 ft. in diameter).

The mortality composter is basically a long, rotating stainless steel cylinder that turns mortalities and a carbon source, such as wood shavings, into harmless compost. Smaller, 18-ft. versions and larger, 42 ft. versions are also available.

The insulated cylinder has three openings. The first set of doors is for loading mortalities, wood shavings and recycled compost. The second set of doors allows operators to measure temperatures and compost mass. At the end is the effluent door, which spills into a recuperation basin for long-term storage.

The objective of the Quebec project was five-fold:

  • To develop the compost recipes and mortality-carbon source mixing ratios;

  • To establish optimum operating temperatures, moisture levels and drum rotation frequencies and speeds;

  • To validate effectiveness in summer and winter periods;

  • To monitor specific bacteria and pathogen levels in the end product, and

  • To comply with Quebec law and regulation for the disposal of swine mortalities.

Dead animals were added to the load cell with a tractor front-end loader, five days a week. Weekend mortalities were added on Mondays. Animal weights were verified. Wood shavings, serving as the carbon source, were added to cover mortalities with 6-8 in. (150-200 mm) of material. Therefore, the ratio was 2.2 lb. (1 kg) of mortality to 1.5 lb. (0.7 kg) of dry wood shavings. No water was added.

Compost bones collected at the end of the cylinder were recycled with mortalities and new wood shavings at a rate of 2.2 lb. of mortality to 0.55 lb. new wood shavings and 0.97 lb. of the recycled matter.

The goal was to reach temperature above 100.4° F (38° C)to initiate the composting process. In cool/cold weather (below freezing), a 60,000 Btu/hour heater was necessary to achieve the desired temperatures on start up.

Temperatures and humidity levels were obtained five days a week and agronomic and pathogenic samples were collected every 14 days for specific periods.

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Internal Temperatures

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.

Moisture Content

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%.

Ministry Requirements

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.

Weight:Compost Ratio

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.)

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