Production of recycled manure solids for use as bedding in Canadian dairy farms: II. Composting methods

Abstract

Recent technological advances in the dairy industry have enabled Canadian farms with liquid manure systems to use mechanical solid-liquid separation paired with composting of the separated solids for on-farm production of low-cost bedding material. However, because several approaches are available, it is difficult for farmers to select the appropriate one to achieve high quality recycled manure solids (RMS). Whereas 3 solidliquid manure separators were compared in part I of the series (companion paper in this issue), the present study (part II) aims to assess the performance of 4 composting methods (static or turned windrow and drum composter for 24 or 72 h) under laboratory conditions. Parameters evaluated included temperature, physicochemical characteristics, and bacterial composition of RMS, as well as airborne microorganisms, dust, and gases associated with composting RMS. Because each treatment attained the desired composting temperature range of 40 to 65°C (either in heaps or in the drum composter), reductions in bacteria were a better indicator of the sanitation efficiency. The treatment of fresh RMS in a drum composter for 24 h showed decreased bacterial counts, especially for Escherichia coli (from 1.0 × 10 5 to 2.0 × 10 1 cfu/g of dry matter) and Klebsiella spp. (from 3.2 × 10 4 to 4.0 × 10 2 cfu/g of dry matter). Increasing the time spent in the rotating vessel to 72 h did not result in further decreases of these pathogens. Composting in a static or turned windrow achieved similar E. coli and Klebsiella spp. reductions as the 24-h drum composting but in 5 or 10 d, and generally showed the lowest occupational exposure risk for dairy farmers regarding concentrations of airborne mesophilic bacteria, mesophilic and thermotolerant fungi, and total dust. Drum-composted RMS stored in piles exhibited intermediate to high risk. Composting approaches did not have a major influence on the physico-chemical characteristics of RMS and gas emissions. Drum composting for 24 h was the best compromise in terms of product quality, temperature reached, decreased bacterial numbers, and emitted airborne contaminants. However, because levels of pathogenic agents rapidly increase once composted RMS are spread in stalls, bacteriological characteristics of RMS along with milk quality and animal health and welfare features should be monitored in Canadian dairy barns applying recommended separation (part I) and composting (part II) systems to evaluate health risk and optimize management practices.

Production of recycled manure solids for bedding in Canadian dairy farms: I. Solid–liquid separation

“…The low DM content of RMS produced with the screw press used in this study may limit direct use of the RMS without further processing. Consequently, part II of the series (Fournel et al, 2019) compares composting methods as subsequent treatment for the production of high quality RMS.…”

Effect of different initial C/N ratio of cow manure and straw on microbial quality of compost

“…1, all mixes showed a thermophilic stage at the beginning of the process, reaching 55-64 °C. In the study by Fournel et al (2019), with temperatures from 45 to 65 °C, they were effective in the reduction of bacterial growth. In a study conducted by Lafond et al (2002) it was observed that pathogen survival was closely related to the C/N ratio.…”

Cattle barn bedding from recycled manure: some veterinary, technological and economic aspects of application

“…In general, the foreign researchers believe this practice to have several significant advantages: lower economic expenditures on bedding purchase and transportation, lower external supply dependency, weaker stresses associated with the housing systems and improved livestock health [10,12,32,33].…”

“…It is used in North America and Europe. In Russia, however, it is only starting to be introduced [10][11][12][13].…”