Methane and Nitrous Oxide Emissions from Cattle Excreta on an East African Grassland

Greenhouse gas (GHG) emission measurements from livestock excreta in Africa are limited. We measured CH 4 and N 2 O emissions from excreta of six Boran ( Bos indicus ) and six Friesian ( Bos taurus ) steers near Nairobi, Kenya. The steers were fed one of three diets (T1 [chaffed wheat straw], T2 [T1 + Calliandra calothyrsus Meissner – 0.2% live weight per day], and T3 [T1 + calliandra – 0.4% live weight every 2 d]). The T1 diet is similar in quality to typical diets in the region. Calliandra is a leguminous fodder tree promoted as a feed supplement. Fresh feces and urine were applied to grasslands and emissions measured using static chambers. Cumulative 28‐d fecal emissions were 302 ± 52.4 and 95 ± 13.8 mg CH 4 –C kg −1 dry matter for Friesen and Boran steers, respectively, and 11.5 ± 4.26 and 24.7 ± 8.32 mg N 2 O–N kg −1 dry matter for Friesian and Boran steers, respectively. For urine from Friesian steers, the N 2 O emissions were 2.8 ± 0.64 mg N 2 O–N 100 mL urine −1 . The CH 4 emission factors (EFs) (246 ± 49.5 and 87 ± 12.7 g CH 4 –C yr −1 animal −1 for Friesan and Boran, respectively) were lower than the International Panel on Climate Change EFs (750 g CH 4 –C animal −1 yr −1 ), whereas the N 2 O EFs (0.1 and 0.2% for the Friesian and Boran feces, respectively, and 1.2% for urine) were also lower than International Panel on Climate Change estimates. The low N content of the excreta likely caused the low emissions and indicates that current models probably overestimate CH 4 and N 2 O emissions from African livestock manure. Core Ideas GHG emissions from African livestock excreta is lower than IPCC tier 1 emission factors. Low‐quality feeds with low protein content result in low N content of excreta. Supplementation of cattle diet with calliandra reduced the methane emissions from cattle feces. The species of cattle causes differences in GHG emissions from feces.