STRATEGIES FOR REDUCING
GREENHOUSE GAS EMISSIONS
FROM LIVESTOCK WASTES
Steven A. Nyanzi
Department of Chemistry
Makerere University
29th November 2013
Seminar Room, Department of Chemistry,
College of Natural Sciences, Makerere University
OVERVIEW
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Background
Livestock and GHG Emissions
Approaches for reduction of NH3 Emissions
Emission reduction via urea recovery?
Harvesting & stabilizing urea in urine
Effect of Temp and pH on urea in urine
Pre-concentration with an urease inhibitor
Extraction of urea as clathrate
Characterization
Conclusion
Background on Climate Change
• Over 180 Countries are signatory to United Nations
Framework Convention on Climate Change
(UNFCC) by early 1990s
• UNFCC aims at stabilizing the conc’n of GHG in
the atmosphere and reduce –ve impacts of climate
change
• Green House Gases (GHG) include:
CO2, CH4, N2O,
• Global Warming Potential (GWP): I kg CH4= 23
times CO2; I kg N2O = 310 times CO2
IPCC on NITROUS OXIDE
• IPCC Guidelines for estimating N2O
emissions from agricultural systems
1) Direct emissions of N2O from agric fields
2) Direct emissions of N2O in animal production
systems
3) Indirect emissions of N2O derived N used in
agriculture
• IPCC Guidelines for National Greenhouse Gas
Inventories (IPCC, 1997) excludes 2 and 3 !
Estimates of nitrous oxide emissions from agricultural systems worldwide,
directly from agricultural fields (direct) from animal waste management systems
(AWMS) and from indirect sources (indirect).
Livestock and GHG Emissions
• Uganda has one of the fastest growing population
growth rate (3.3% per annum)
• Livestock = cattle, goats, sheep, pigs, chicken
• Cattle pop. in Uganda is about 11.4 million
• Cattle belching and fatting produce about 100 – 200
L of CH4 per cow per day
• 90% of urea + other urea derivatives ((i.e.,
allantoin, uric acid) are excreted in animal urine
• Urea, Allantoin and Uric acid break down to
produce CH4, CO2 and N2O
Mechanism for Conversion of Allantoin to Urea
-O
H
N
O
O
O
C
CH
Allantoinase
C
NH
C
-O
CH
H2N
N
H
NH2
N
H
NH2
Allantoate
Allantoin
O
O
O
O
C
H2N
O
O
C
N
H
O
N
H
H2N
Állantoate Aminohydrolase
CH
N
H
NH2
Urea
NH2
O
Allantoate
H
N
C
-O
CH
OH
Ureidoglycolate
NH2
C
O
Conversion of Allantoin to Urea
O
H
N
H
N
HN
1) Hydration
O
O
N
H
N
H
H
N
O
CH
C
N
H
NH
NH2
3) Decarboxylation
Allantoin
Uric acid
O
C
C
2) Oxidation
O
O
O
NHCNH2
H
O
O
C
C
H2N
OH
+
O
2
HN
Glyoxalic acid
O
Allantoin
H2N
Urea
Mechanism Contd.
O
C
-O
O
H
N
CH
NH2
C
Ureidoglycolate Urea-Lyase
OH
H2N
NH2
O
Urea
Ureidoglycolate
O
O
HC
O -
Gloxylate
Processes Contd.
O
H
N
C
-O
CH
NH2
C
Ureidoglycolate Aminohydrolase
OH
O
+
CO2
O
Ureidoglycolate
2 NH3
O
HC
O -
Gloxylate
N2O
NH3
Nitrification/Denitrification
2 NH3
+
O2
Oxidation
N2O
+
3 H2O
APPROACHES FOR REDUCTION OF
NH3 EMISSIONS
• A) Land application of animal manure
• B) Dietary manipulation of crude protein
• C) Use of animal feed diets containing tannins and
polyphenols
• D) Use of additives to livestock wastes –
 a variety of additives including urease inhibitors
Emissions Reduction via Urea
Recovery ?
• Urea 16th most highly produced substance
• World production ~ 2.0 x108 tonnes/ year
• Applications :
 Fertilizer (> 90%), Liu et al (2003)
 Resins (melanine-formaldehyde, etc)
 Supplementary protein source
 Pharmaceutical, fermenting & brewing,
petroleum industry, soap production
 Hydrogen carrier (Renewable Energy) ! !
Harvesting & Stabilizing Urea in Urine
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Challenges in urine collection
Enzymatic degradation of urea
Production and control of stench
Local materials as urease inhibitors
Indigenous practices
Environmental benefits –Less NH3 emissions
NH3 emissions responsible FPM (d<2.5 μm)
Improved Agricultural productivity - Fertilizers
Determination of Urea in Urine
• Colorimetric methods most widely used
• Indirect Methods:
Determine products of urea e.g., NH3
Berthelot reaction (λmax 640 nm)
Macro-method but NH3 interferes
• Direct Methods :
Determine urea directly i.e.,
Fearon’s method (λ max 525 nm)
Modified Fearon’s method (Nyanzi et al, 2010)
Effect of pH on urea concentration
pH 3
Urea concentration (g/dL)
1.2
pH 4
1
pH 5
0.8
pH 6
0.6
pH 7
0.4
pH 8
pH 9
0.2
pH 10
0
1
3
5
7
Time (days)
9
11
13
pH 11
pH 12
Pre-concentration
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Filter to remove solids
Stabilization of urine extract at pH 9
Pass through bleaching material
Heating extract at 96 OC for max 20 min
Heating at < 96 OC for longer
Conversion of allantoin to urea
Use of a solar drier to reduce moisture
Urine pH against Time in Days
14
D
13
C
12
11
pH
10
9
A
8
B
7
0
2
4
6
8
10
Time (Days)
A and B without substrate X; C and D with substrate X
12
Urea content in Urine against Time in Days
0.7
C
0.6
D
0.5
Abs
0.4
0.3
0.2
B
A
0.1
0
2
4
6
8
10
12
Time (Days)
A and B without substrate X; C and D with substrate X
14
Urea-Hydrocarbon Clathrates
• Previous Applications:
– Purify fatty acids from fats and vegetables
– Separate straight chain from branched chain
or cyclic compounds
– Separate different petroleum fuel fractions
• Current Application
– Use urea to extract FAs from plant oils ?
– Use these FAs to extract urea from urine
Extraction of Urea as Clathrate
Moles of Hydrocarbon
Heptane (n-C7H16)
Molar proportion of urea
in Complex
6
Decane (n-C10H22)
8.3
Hexadecane (n-C16H34)
12
Octacosane (n-C28H58)
21
n-Alkane-Urea complex: (a) cross section;
(b) Hydrogen bonding (Courtesy of A. E. Smith)
Infrared spectra of: (a) extracted urea (b) pure urea
Urea from indigenous and Friesian cattle urine
Conclusion
• Reduction of GHG Emissions from livestock
wastes is possible
• Urea stabilization, enrichment and extraction
have lots of potential in odour control and urea
production from livestock wastes! 3.08x103
tonnes urea could be recovered everyday!
• Production of urea from livestock wastes can
create wealth, protect the environment & reduce
ammonia emissions
• Sustainability through the process (Fertilizer Animal feeds- Animal wastes-Urea)
A cow excreting liquid gold
Acknowledgement
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Organizers of this Interface
Mr. G. Wamala
Mr. Lubwama
Mr. Magada
Dr. J. Hawumba
Dr. Emmanuel Tebandeke
Mr. Hassan Kigozi Wasswa
Mr. Christopher Biteinensha (FTIR spectra)
I THANK YOU