Steven A. NyanziDepartment of Chemistry

Makerere University

29th November 2013

Seminar Room, Department of Chemistry,College of Natural Sciences, Makerere University

STRATEGIES FOR REDUCING GREENHOUSE GAS EMISSIONS FROM

LIVESTOCK WASTES

OVERVIEW• 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

O

C

NH

CH

O

NH

O

O

NH2H2N

-

Allantoate

H2N NH2

O

O

C

CH

HN

C

NH2

O

UreidoglycolateOH O

-

Urea

Állantoate Aminohydrolase

CH

C

HN

C

NH

O

O

NH

C

NH2

OO

C

NH

CH

O

NH

O

O

NH2H2N

-

Allantoin Allantoate

Allantoinase

Mechanism for Conversion of Allantoin to Urea

HN

HN

O

NHCNH2

Allantoin

O

C C

O

H OH

O

Glyoxalic acid

+ 2 O

H2N

H2N

Urea

O

Conversion of Allantoin to Urea

HN

NH

NH

HN

O

O

O

Uric acid

CH

C

HN

C

NH

O

O

NH

C

NH2

O

Allantoin

2) Oxidation

1) Hydration

3) Decarboxylation

O

C

CH

HN

C

NH2

O

UreidoglycolateOH O

-

H2N NH2

O

Urea

Ureidoglycolate Urea-Lyase

O

HC

O

O -

Gloxylate

Mechanism Contd.

NH3 N2O

Nitrification/Denitrification

2 NH3 N2O+ O2Oxidation

+ 3 H2O

O

C

CH

HN

C

NH2

O

UreidoglycolateOH O

-

Ureidoglycolate AminohydrolaseCO2 + 2 NH3

O

HC

O

O -

Gloxylate

Processes Contd.

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

• 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

0

0.2

0.4

0.6

0.8

1

1.2

1 3 5 7 9 11 13

Time (days)

Ure

a co

nce

ntr

atio

n (

g/d

L)

pH 3

pH 4

pH 5

pH 6

pH 7

pH 8

pH 9

pH 10

pH 11

pH 12

Pre-concentration

• 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

7

8

9

10

11

12

13

14

0 2 4 6 8 10 12

Urine pH against Time in Days

Time (Days)

pH

A

B

C

D

A and B without substrate X; C and D with substrate X

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 2 4 6 8 10 12 14

A

B

C

D

Urea content in Urine against Time in Days

Abs

Time (Days) A and B without substrate X; C and D with substrate X

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 Molar proportion of urea in Complex

Heptane (n-C7H16) 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

• 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