Abstract: The benefit using biogas engineering system in a pig farm in Jiangsu Province was analyzed with vertex weighted causal loop diagram analysis approach after
and a simulation model was established to solve the problem of pollution. According to the vertex weighted causal loop diagram analysis related to annual pig feces and biogas benefit of a pig farm in Jiangsu Province in 2011， the weightings related to the diagram were calculated. Using the results of weightings， the agricultural acreage and the liquefied gas consumption， the simulation model was established. The results showed that there were three positive feedback loops including the biogas benefit， fertilized area and benefit of biogas residues， and two negative feedback loops which were biogas waste and biogas manure waste in the system in 2011. The adjustment schemes of two simulation models were established to solve the problem of pollution: one was to build gas pipeline with 168 households if the amount of livestock （1 728） was not changed， the other one was to build gas pipeline with 361 households if the amount of livestock increased to 3 721.

Key words: vertex weighted causal loop diagram analysis approach, biogas engineering system, pig, excreta, benefit