Presented by Sonja Leitner, George Wanyama, Dónal Ring, Daniel Korir, David Pelster, John Goopy, Klaus Butterbach-Bahl and Lutz Merbold at the Tropentag 2020: Food and Nutrition Security and its Resilience to Global Crises, Virtual Conference, 9–11 September 2020

1. Greenhouse Gas Emissions and Fertiliser
Quality from Cattle Manure Heaps in Kenya
Session “Climate change - Mitigation and adaptation”, Tropentag Virtual Conference 2020
Sonja Leitner, George Wanyama, Dónal Ring,
Daniel Korir, David Pelster, John Goopy,
Klaus Butterbach-Bahl, Lutz Merbold
s.leitner@cigar.org
International Livestock Research Institute (ILRI),
Nairobi, Kenya
10 Sept 2020
Better lives through livestock

2. Background
Manure applied to soils
Enteric fermentation
Manure left on pasture
Manure management
Burning - savanna
Synthetic fertilizer
Rice cultivation
Crop residues
Cultivation org. soils
Burning – crop res.
AFOLU GHG emissions
by source (globally)
FAO, Tubiello et al. 2014
• 25% of global AFOLU GHG
emissions from livestock manure
• African countries rely on default IPCC
emission factors for GHG reporting
• Few in situ data on manure GHG
emissions from smallholder systems
• Low livestock productivity in SSA:
 Low forage quality: tropical grasses with
low protein and high fibre content
 Low fertilizer use: soil nutrient mining
 Need for sustainable intensification and
closed nutrient cycles

3. Research questions & hypotheses
Q1: What is the magnitude of CH4 and N2O emissions from manure heaps in Kenyan
smallholder farming systems?
Q2: How do animal diets affect manure CH4 and N2O emissions and manure fertilizer
quality?
H1: Manure from hungry cows has lower N concentrations and emits less N2O
compared to well-fed cows because of higher N retention under sub-maintenance
energy feeding.
H2: Poor quality tropical forage grasses result in manure with low N concentrations
and low manure N2O emissions.
H3: Forage grass with a low DM content will increase manure moisture content and
lead to higher manure CH4 emissions.

4. Animal trial 1: Sub-maintenance feeding
• Setup: Animal feeding trial with local Boran
cattle (1.5 yr young steers) fed below their
metabolic energy requirements (MER)
 100 % MER (ok)
 80 % MER (hungry)
 40 % MER (really hungry!)
• 100 kg FW manure incubated in heaps (n = 3)
 CH4 and N2O fluxes measured with manual static
chambers for 5 months (daily to 3x/week gas sampling)
 Manure chemistry (DM, C, N, ash)
© George Wanyama
& Daniel Korir
Mazingira Centre,
ILRI Campus,
Nairobi, Kenya
mazingira.ilri.org

5. Animal trial 1: Sub-maintenance feeding
*
*
*
IPCC default
0.0
1.0
2.0
3.0
4.0
5.0
120%
MER
100%
MER
60%
MER
gCH4-Ckg-1DM
Cumulative CH4 flux
b
a
a
0
20
40
60
80
100
120
140
160
120%
MER
100%
MER
60%
MER
mgN2O-Nkg-1DM
Cumulative N2O flux
0.0%
0.2%
0.4%
0.6%
0.8%
1.0%
120%
MER
100%
MER
60%
MER
%manure-CemittedasCH4-C
EF CH4
*
*
*
IPCC default
0.0%
0.2%
0.4%
0.6%
0.8%
1.0%
1.2%
120%
MER
100%
MER
60%
MER
%manure-NemittedasN2O-N
EF N2O
IPCC default
(manure solid storage)
• Manure N2O emissions of hungry cattle
lower than when fed at maintenance
levels
• No difference in manure CH4 emissions
between diets
• CH4 emissions and N2O emission
factors lower than IPCC Tier 1
default values for solid storage
100%
MER
80%
MER
40%
MER
100%
MER
80%
MER
40%
MER
100%
MER
80%
MER
40%
MER
100%
MER
80%
MER
40%
MER

6. Animal trial 1: Sub-maintenance feeding
• Manure from hungry cattle contains less N and has higher C:N
 lower fertilizer value!
30
32
34
36
38
40
42
44
120%
MER
100%
MER
60%
MER
ManureCconcentration(%)
initial
final
*
b
ab
a
c
b
a
0.0
0.5
1.0
1.5
2.0
2.5
120%
MER
100%
MER
60%
MER
ManureNconcentration%
a
ab
b
a
ab
b
0
5
10
15
20
25
30
35
40
45
120%
MER
100%
MER
60%
MER
ManureC:N
initial
final
Manure C:N ratio
100%
MER
80%
MER
40%
MER
100%
MER
80%
MER
40%
MER
100%
MER
80%
MER
40%
MER
Manure N concentrationManure C concentration
European dairy cow
Amon et al., 2001

7. Animal trial 2: Tropical forage grass diets
• Setup: Animal feeding trial with local Boran
cattle (1.5 yr young steers) fed only with
tropical forage grasses
 Napier grass (Pennisetum purpureum var Kakamega 1)
 Rhodes grass (Chloris gayana cv. Boma)
 Brachiaria grass (Brachiaria brizantha var xaeres)
• 100 kg FW manure incubated in heaps (n = 3)
 CH4 and N2O fluxes measured with manual static
chambers for 5 months (daily to 3x/week gas sampling)
 Manure chemistry (DM, C, N, ash)
© Jake Meyers &
Dónal Ring
Mazingira Centre,
ILRI Campus,
Nairobi, Kenya
mazingira.ilri.org

8. Animal trial 2: Tropical forage grass diets
IPCC default
(manure solid storage)
• No difference in manure N2O emissions
between grass diets
• Manure CH4 emissions of cattle fed on
Rhodes grass lower than fed on Napier
or Brachiaria
• CH4 emissions and N2O emission
factors lower than IPCC Tier 1
default values for solid storage

9. Animal trial 2: Tropical forage grass diets
• No difference in manure chemistry or moisture
• C:N ratio 3x higher compared to “European diet”  poor fertilizer value
European dairy cow
Amon et al., 2001

10. Conclusions
• Manure GHG emissions depend on cattle diet: feet scarcity and poor-
quality forage grasses reduce N2O emissions
• Smallholder farming systems in East Africa quite unique & diverse
 Tier 1 assumptions and default values often not valid
 over-estimation of manure GHG emissions with default values
 need for localized measurements
• Future experiments must consider breeds (local vs. improved), feed
quality & quantity, manure storage type & duration, climate

11. About 620 ILRI staff work in Africa and Asia to enhance incomes and livelihoods, improve food security, and reduce disease
and environmental degradation. Australian animal scientist and Nobel Prize laureate Peter Doherty serves as ILRI’s patron.
Organizations that fund ILRI through their contributions to CGIAR make ILRI’s work possible. Organizations that partner ILRI in
its mission make livestock research for development a reality.
www.ilri.orgThis presentation is licensed for use under the Creative Commons Attribution 4.0 International Licence.
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