[1] Chengdu Univ Technol, State Key Lab Geohazard Prevent & Geoenvironm Prot, Chengdu 610059, Peoples R China
[2] Minist Agr & Rural Affairs, Biogas Inst Minist Agr & Rural Affairs, Biomass Energy Technol Res Ctr, Key Lab Dev & Applicat Rural Renewable Energy, Chengdu 610041, Peoples R China
[3] Univ Nebraska Lincoln, Dept Civil & Environm Engn, Lincoln, NE 68588 USA