This study investigates the degradation of antibiotics during the composting of dairy manure solids and biosolids, revealing that 90-95% of antibiotics are eliminated within four weeks. Different composting treatments were tested, which showed significant reductions in concentrations of various antibiotics such as florfenicol, sulfadimethoxine, sulfamethazine, and tylosin. The findings suggest that the compost produced under these conditions poses minimal health risks when applied to the environment.

1. Antibiotic
Degradation during
Dairy Manure Solids
and Biosolids
Composting
A. I. Bary*, S.M. Mitchell*, J.L.
Ullman, C.G. Cogger*, A.L. Teel*,
R.J. Watts*
*Washington State University
University of Florida
1

2. Introduction
• 5-90% of human
and animal
administered
antibiotics are
excreted
unchanged.
• 0.1 – 240 mg/kg
(ppm) in manure

3. • 250 different antibiotics available
• 17 different classes
• Antibiotics within a class have similar core
chemical structures, antibacterial properties, and
environmental fate and transport behaviors
• Three antibiotic classes were investigated in this
research
• amphenicol, macrolide, and sulfonamide
3
Introduction

4. 4
Chemical properties Structures
Amphenicol – Florfenicol
Water sol. = 5,900 mg/L
Log Kow = -0.12
Macrolide – Tylosin
Water sol. = 100,000 mg/L
Log Kow = 1.6
Sulfonamide – Sulfadimethoxine
Water sol. = 343 mg/L
Log Kow = 1.63
Sulfonamide – Sulfamethazine
Water sol. = 1,500 mg/L
Log Kow = 0.89
• Antibiotic chemical structures and
properties affect how the antibiotics
degrade and move in the environment.
Introduction

5. • Degradation half-lives in water are higher
compared to degradation half-lives in waste.
5
Antibiotic degradation half-lives (days) reported in current publications
Water Soil Manure Composting
Florfenicol No degradation 2-30 d 4 d No data
Tylosin No degradation 30 d 6 d 19 d – Turkey litter
20-44 d – Cattle manure (windrow)
4-10 – Horse manure
Sulfadimethoxine No degradation 40 d 2 d No data
Sulfamethazine No degradation 60 d 5 d No degradation – Turkey litter
27-237 d – Cattle manure (windrow)
Introduction

6. 6
Feedstocks
1. Fresh, de-watered dairy manure solids
2. Fresh, anaerobically digested and de-watered
biosolids
3. Ground Douglas fir was used in a 3 to 1 ratio (by
volume) with biosolids
Methods

7. • Four composting treatments were tested:
• aerated manure
• non-aerated manure
• aerated biosolids/wood-product (1:3 by vol.)
• non-aerated biosolids/wood-product (1:3 by vol.)
7
aerated
manure
non-aerated
manure
aerated
biosolids/wood
(1:3 by vol.)
non-aerated
biosolids/wood
(1:3 by vol.)
aerated
manure
non-aerated
manure
aerated
biosolids/wood
(1:3 by vol.)
non-aerated
biosolids/wood
(1:3 by vol.)
Methods

8. • 1/3 of the feedstock for a batch was added to a
manure spreader
• 1/3 of the antibiotic solution in water was spread
evenly on the feedstock
• Method was repeated
8
Methods

9. • Manure spreader was turned on and the feedstock was
mixed.
• Mixing with the manure spreader was repeated, and
time zero samples were collected.
9
Methods

10. • Aeration pipes were placed into the bins
• Plenum chamber material (coarse wood) was added
• Bins were filled with the antibiotic-fortified feedstock
• Temperature probes were placed at two depths
• Air was turned on (30 s on, 1 hr off)
10
Methods

11. Results: Temperature
11
20
30
40
50
60
70
80
90
0 5 10 15 20 25 30
Aerated manure
Non-aerated manure
Aerated biosolids/wood
Non-aerated biosolids/wood
Temperature(°C)
Time (days)

12. Oxygen concentration
0.0
5.0
10.0
15.0
20.0
25.0
5 10 15 20 25 30
Data 1
Aerated manure
Non-aerated manure
Aerated biosoids/wood
Non-aerated biosolids/wood
OxygenConcentration(%)
Time (days)

13. Moisture content
40%
50%
60%
70%
80%
90%
0 4 8 12 16 20 24 28
Aerated manure
Non-aerated manure
Aerated biosolids/wood
Non-aerated biosolids/wood
Moisturecontent
Time (days)

14. Sample Time (days) pH
Manure 0
8.2
Aerated manure 28
8.5
Non-aerated manure 28
8.6
Biosolids/wood-product 0
7.8
Aerated biosolids/wood 28
6.2
Non-aerated biosolids/wood 28
6.4
Results: pH

15. Sample Time
(days)
C:N
Manure 0
36.7 ± 0.76
Aerated manure 28
23.3 ± 2.36
Non-aerated manure 28
21.8 ± 0.08
Biosolids/wood-product 0
10.3 ± 0.47
Aerated biosolids/wood 28
14.4 ± 1.50
Non-aerated biosolids/wood 28
13.1 ± 0.95
Carbon and nitrogen

16. Composting
 Temperatures reached 65-75°C
 Manure remained 75% water
 Biosolids dropped from 65% to 50%
water
 pH values were 8.6 for manure and 6.2
for biosolids compost
 Finished compost had C:N ratios of 23
for dairy manure and 14 for biosolids
compost
16

17. Antibiotic concentration over time
17
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 4 8 12 16 20 24 28
Aerated manure
Non-aerated manure
Aerabted biosolids
Non-aerated biosolids
[Florfenicol]/[Florfenicol]
0
Time (days)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 4 8 12 16 20 24 28
[Sulfadimethoxine]/[Sulfadimethoxine]
0
Time (days)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 4 8 12 16 20 24 28
[Sulfamethazine]/[Sulfamethazine]
0
Time (days)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 4 8 12 16 20 24 28
[Tylosin]/[Tylosin]
0
Time (days)

18. Antibiotic Concentration During and prior
to Composting
0 d 7 d 14 d 21 d
Antibiotic Concentration Concentration Percent
reduction
Concentration Percent
reduction
Concentration Percent
reduction
Florfenicol
Manure 230 ± 80 3.6 ± 3.9 98% < 2.6 ± 1.6 99% <2.6 ± 1.9 99%
Biosolids 240 ± 10 36 ± 13 85% 18 ± 10 93% 12 ± 10 95%
Sulfadimethoxine
Manure 410 ± 30 62 ± 64 85% 18 ±21 96% 9.8 ± 9.5 98%
Biosolids 510 ± 90 42 ±29 92% 22 ±17 96% 12 ± 7.7 98%
Sulfamethazine
Manure 2,200 ± 300 320 ± 260 85% 99 ± 81 96% 65 ± 66 97%
Biosolids 4,200 ± 100 220 ± 108 95% 110 ± 58 97% 52 ± 16 99%
Tylosin
Manure 2,800 ± 200 403 ± 400 86% 71 ± 62 97% 61 ± 95 98%
Biosolids 2,300 ± 300 140 ± 35 94% 150 ± 24 93% 99 ± 39 96%± one standard deviation

19. Conclusion
 The dairy manure solids and biosolids/wood
feedstock facilitated rapid antibiotic
degradation during pilot-scale static pile
composting.
 90-95% of the antibiotics were removed after
4 weeks.
 Final compost material obtained under these
conditions may present minimal human and
ecological health risk when applied to the
environment.

20. Thank You!