Utilization Of Municipal Solid Waste Compost As Bedding Material For Cattle Feedlots

C. M. Zehnder, A. DiCostanzo, K. Thate, R. Gilland, M. J. Murphy and T. R. Halbach

Copyright ©  2009  Regents of the University of Minnesota. All rights reserved.

Introduction

Municipal solid waste compost (MSW) results from the process of breaking down the organic components of garbage, such as paper, food scraps, and yard waste. This process helps reduce the load on landfills while enhancing utilization of normal household trash. More than 50% of normal household trash consists of organic waste (vegetable and food scraps, paper, straw, coffee grounds, egg shells, leaves, sawdust, weeds, wood, ash, and plant trimmings) that can be composted. Currently, MSW compost can be used as a soil amendment for farm fields, roadsides, lawns, nurseries, and golf courses.

Cattle can be bedded comfortably on MSW compost.

Alternative uses for MSW compost are possible because some MSW compost contains low concentrations of regulated elements (Chart 1) and can be provided in large and consistent quantities. One such alternative is to use MSW compost as bedding in cattle feedlots. Currently, paper or crop residues are widely used for cattle feedlot bedding materials. However, because of increased interest in recycling paper products in recent years, paper is no longer affordable for cattle feedlots. Similarly, some costs associated with harvesting, storing, and processing cornstalks or other crop residues for bedding may be eliminated if MSW compost emerges as an acceptable bedding alternative.

A study was conducted by the University of Minnesota to determine the impact of using MSW compost as bedding on cattle health, tissue element residues, and the environment. It was also intended to help formulate general guidelines for the use of MSW compost as a cattle-bedding alternative. The study involved bedding two pens over two consecutive cattle feeding periods (summer and winter) with either MSW compost or cornstalks. Bedding use, feed intake, and manure output were measured and sampled to gauge flow of nitrogen and phosphorous and concentrations of regulated elements. A selected sample of cattle were also monitored for regulated element concentrations in their blood and feces (throughout the feeding period) and in their kidneys and liver (at harvesting), as well as for polychlorinated biphenyl (PCBs) concentrations in their perirenal fat (at harvesting).

The objective of this fact sheet is to provide general guidelines on the use of MSW compost as an alternative bedding material. Where required, information on effects of MSW compost feedlot bedding on cattle health and performance, on dry matter, nitrogen and phosphorous fluxes and on the concentration of regulated elements in cattle tissues is provided.

1. Use of Consistent, High-Quality MSW Compost

The low regulated element concentration and relatively high water absorbing quality of MSW compost make it a suitable alternative to cornstalks or paper for livestock bedding. Under current regulations (Minnesota Pollution Control Agency Chapter 7035.2836), MSW compost can be categorized as Class I or Class II material. Class I MSW compost cannot exceed the regulated element concentrations listed on a dry weight basis as mg/kg (ppm) in Chart 1 or those in the Code of Federal Regulations, title 40, sections 503.10 to 503.18 as amended. Currently, because the study from which these recommendations are derived used Class I MSW compost, feedlot operators wanting to use MSW compost as a bedding material must be certain that it meets at least these regulations. MSW compost bedding should be processed so that the material has an approximate dry matter (DM) level of 80%. Using MSW compost that is drier than 80% DM may result in dusty conditions that will affect cattle health.

Chart 1. Maximum concentration of regulated elements in Class I MSW compost and average concentration of regulated elements in MSW compost produced at Truman, MN, in 1996.

2. Use MSW Compost in Yearling Feeding Programs

In the trial conducted by the University of Minnesota, a veterinarian examined the cattle at the start and end of each feeding period, and reported no abnormal observations. Nor did bedding cattle with MSW compost affect blood concentrations of macro-elements, electrolytes, glucose, or liver and kidney enzymes.

Concentrations of some regulated elements found in kidneys and livers harvested from cattle in a selected sample at the end of each feeding period are listed in Chart 2. Kidneys of cattle bedded with MSW compost had greater concentrations of copper and lead. Lead concentration in the livers of these cattle was greater than those of cattle bedded on cornstalks. In spite of these differences, tissue concentrations of both copper and lead fell within the normal ranges observed in healthy cattle (Chart 2). Accumulation of copper and lead in tissue likely resulted from MSW compost being inhaled or consumed. Further evaluation of concentrations of these elements in feces indicated that some cattle within the selected sample were deliberately consuming some MSW compost. This resulted in concentrations of lead and copper in feces that were similar for cattle on either bedding system before the study began, but increased more for cattle on MSW compost with extended exposure to MSW compost. PCBs were not detectable in fat samples from cattle bedded with either material.

Chart 2. Composition of selected regulated elements in livers and kidneys (dry weight basis) of a selected sample of cattle bedded with MSW compost or cornstalks.

All these observations, taken together, support the conclusion that cattle bedded on MSW compost were healthy throughout the study. Also, although some MSW compost may be consumed or inhaled, concentrations of regulated elements in kidneys and livers did not increase beyond normal concentrations. In fact, when making a statistical comparison of daily gains, cattle bedded on MSW compost consistently had faster rates of gain than those bedded on cornstalks.

Because the use of MSW compost was only tested on yearling feedlot cattle (i.e., short feeding period), further testing is required to determine the effects of bedding with MSW compost for longer feeding periods. Therefore, we recommend utilization of MSW compost only in yearling feeding programs (150 days or less; bedding with MSW compost for longer periods of time may result in greater accumulations of regulated elements in cattle tissues).

3. Recommended Bedding Rates for MSW Compost

In the University of Minnesota study, MSW compost was used in pens measuring 75 by 112 ft with 3808 ft2 under cover. Cattle were stocked at 50 ft2/head in the summer and 61 ft2/head in the winter. Pens were bedded as required by precipitation, cattle comfort, and pen cleanliness. The decision to bed was left to the feedlot operator and resulted in 1.25/week or 1.5/week bedding episodes during the summer and 1.8/week or 2.75/week bedding episodes during the winter for MSW compost or cornstalk bedding, respectively. Bedding was added to the middle third of the pen in sufficient amounts to make a 3- to 4-inch bed. Cattle were then permitted to spread the material.

Bedding use differed by type of bedding and season (Chart 3). Overall, four times more MSW compost than cornstalks was used to bed the same number of cattle. As expected (because of cold weather and precipitation in the form of snow or rain), more bedding was needed during the winter than during the summer, but the use rate increased more for MSW compost (three times) than for cornstalks (two times).

Chart 3. Bedding use rates, manure output, and nitrogen and phosphorous composition

Concentrations of nitrogen and phosphorous differed for MSW compost and cornstalks, but were unaffected by season. The contribution of nitrogen or phosphorous to the feedlot corresponded to bedding use rates — it was higher for MSW compost pens and was more prominent in the winter (Chart 3).

A measure of bedding absorbency was calculated by the following ratio: (manure weight minus bedding weight) divided by bedding weight. This ratio indicated that cornstalks were four times more absorbent than MSW compost. This ratio was not affected by season.

Suggested guidelines for MSW compost bedding rates are to use approximately 4 lb/head/day in the summer and 14 lb/head/day in the winter. Use rate guidelines for cornstalks are 1 and 3 lb/head/day for summer and winter periods, respectively. Use rates may vary widely between feedlots. Feedlot managers will need to adjust bedding rates according to facilities, environment, and cattle comfort.

4. Manure Output and Concentrations of Elements when Using MSW Compost

The amount and type of bedding material used in a feedlot can alter manure output and composition and must be addressed when considering bedding options. Manure concentrations of nitrogen and phosphorous were considered important in evaluating manure elements because nitrogen and phosphorous loading limits must be observed when incorporating cattle manure on farm fields.

In the the University of Minnesota study, manure output was similar for both bedding systems, but, as expected, was twice as high during the winter when analyzed on an as-is basis (Chart 3). However, when analyzed on a DM basis, more manure dry matter was removed from the MSW compost pen in the winter. This was expected because more MSW compost was used for bedding, and winter use was greater than summer use. Although manure nitrogen or phosphorous concentration was higher from the cornstalk pens, the total amount of manure nitrogen or phosphorous removed was similar for both bedding systems and averaged 0.26 lb nitrogen or 0.08 lb phosphorous per head per day (Chart 3). Manure nitrogen or phosphorous concentration decreased during the winter season, but total manure nitrogen or phosphorous output was not affected by season (Chart 3). Reference values for nitrogen and phosphorous output provided by the Midwest Plan Service Livestock Waste Facilities Handbook (MWPS-18, 1985) for 1,000-lb beef steers are 0.34 and 0.11 lb/head/day, respectively.

As was mentioned, manure output (on an as-is basis) was similar for MSW compost and cornstalk pens. However, more bedding material was used when bedding with MSW compost. Therefore, one would have to assume greater manure output from pens bedded with MSW compost. This assumption was corroborated when measured on a DM basis in the winter. Also, because manure output (as-is) did not differ, one would have to conclude that more run-off, fermentation and volatilization occurred from pens bedded with the MSW compost, although visual observations of areas adjacent to pens did not reveal obvious signs of run-off. This discrepancy will be investigated further.

Table 1 was generated using nitrogen and phosphorous output based on using either bedding material to determine the land required to apply manure, given a 100-head pen, a 120-day feeding period, and various nitrogen or phosphorous soil needs. The minimum acreage required for N application needs is 52 acres (assuming 100% nitrogen utilization), while minimum phosphorous application needs limit manure use to 112 acres.

The use of a feedlot as an intermediate step to manage MSW compost reduced concentrations of regulated elements between 19% and 68% (Table 2). The greatest reductions were observed for lead, mercury, zinc, and cadmium. The concentration of lead dropped from 343 to 116 mg/kg. Also, the mercury concentration dropped from 4.33 to 1.88 mg/kg. It is important to remember that concentrations were reduced because of their dispersion in bedding soiled with feces, urine, and precipitation. Total amounts of elements removed from the lots were not reduced.

Manure outputs of nitrogen, phosphorous, or regulated elements will vary due to diets, facilities, environmental conditions, bedding materials used, management practices, and potential run-off, fermentation or volatilization. Therefore, feedlot operators will need to determine their manure element output, especially nitrogen and phosphorous, on an individual basis.

MSW compost offers a quick and convenient bedding alternative

5. Economics of Using MSW Compost to Bed Cattle Feedlots

Feedlot managers interested in using MSW compost as bedding will recognize that the absorbency of MSW compost is about four times less than that of cornstalks. Thus, a greater bedding tonnage is required per feeding period. However, utilizing MSW compost reduces or eliminates the costs of harvesting and storing cornstalks or other crop residues. Also, leaving crop residues in the field retains their value as fertilizer. Considering these costs and use rates, Table 3 was generated to provide ranges for the value of MSW compost. Because of relatively lower use rates in the summer, MSW compost is a more valuable alternative in the summer than in the winter. When cornstalk costs are $15/ton, the value of MSW compost is $5/ton in the summer and $3/ton in the winter. These values range to $17/ton and $10/ton, respectively, when cornstalks cost up to $50/ton. The costs of harvesting, storing, and processing bedding material are listed in the worksheet on page 7. Feedlot managers interested in using MSW compost as bedding can enter their own costs to estimate the value of MSW compost in replacing traditional bedding material for yearling cattle feedlots.

Authors

C. M. Zehnder, Department of Animal Science
A. DiCostanzo, Department of Animal Science
K. Thate, Prairieland Solid Waste Management, Truman, MN
R. Gilland, Gilland Feedlot Inc., Morgan, MN
M. J. Murphy, Department of Veterinary Diagnostic Medicine
T.R. Halbach, Department of Soil, Water and Climate

Acknowledgments

The authors thank Western Lake Superior Sanitary District for financial support of this publication, the Office of Environmental Assistance and Prairieland Solid Waste Management for financial support of the research, and Gilland Feedlot, Inc. for their time and effort in support of this research. Research was conducted under Minnesota Agricultural Experiment Station project no. 16-044 supported by the College of Agriculture, Food and Environmental Sciences. For a complete copy of the research manuscript please contact A. DiCostanzo in the Department of Animal Science, University of Minnesota.

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