File S2. The method for calculating annual discharge amount of total nitrogen, total phosphorus
and chemical oxygen demand by livestock husbandry in the TGRA from 2003 to 2012.
Annual amount of major livestock and poultry in the TGRA from 2003 to 2012 (head).
Year
Swine
Cattle
Poultry
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
11461435
12055101
12723790
12308071
13108754
11711007
12536977
12499750
12522783
12660272
1120155
1137375
1129662
647972
690405
694419
721078
778419
764701
795314
133167000
142188900
156194500
154338900
135656700
169400500
185134700
204167500
216299400
230882800
Feeding cycle (days)
Animal
Feeding cycle
Swine
Cattle
Poultry
199
365
55
Data collected from Insights into the production potential and trends of China’s rural biogas.
Discharge coefficient of livestock husbandry (g/day per head)
Animal
TN
TP
COD
Swine
Cattle
Poultry
19.74
104.10
1.16
4.84
10.17
0.23
403.67
2235.21
20.50
Discharge coefficients collected from Discharge Coefficients of Livestock and Poultry Farming
Pollutants in the First National General Survey of Pollution Sources.
Calculated formulas:
𝑇𝑁 = ∑ 𝐹𝑖 𝐶𝑇𝑁 𝐹𝐶𝑖
𝑇𝑃 = ∑ 𝐹𝑖 𝐶𝑇𝑃 𝐹𝐶𝑖
𝐶𝑂𝐷 = ∑ 𝐹𝑖 𝐶𝐶𝑂𝐷 𝐹𝐶𝑖
Fi: feeding capacity of ith animal; CTN: discharge coefficients of TN; CTP: discharge coefficients of
TP; CCOD: discharge coefficients of COD; FCi: feeding cycle of ith animal.