Research Article
Emergy Analysis of Biogas Systems Based on Different Raw Materials
Table 1
Energy accounting for BPC system.
| No. | Itema | Units | Raw date | Transformity | References | Solar emergy | Em | (sej/unit) | (sej/yr) | ($) |
| Local renewable resources | 1 | Underground water | J | | | Odum, 1996 [16] | | 0 | 2 | Corn straw | J | | | Odum, 1996 [16] | | 3180 |
| Total (RR) | | | | | | 3180 |
| Renewable purchased inputs | 3 | Human labor | J | | | Xi and Qin, 2006 [17] | | 5804 |
| Total (RP) | | | | | | 5804 |
| Nonrenewable purchased inputs | 4 | Steel plateb | US $ | | | Brown and Ulgiati, 2004 [18] | | 846 | 5 | Equipments, PE pipesb | US $ | | | Brown and Ulgiati, 2004 [18] | | 5441 | 6 | Civil work costb | US $ | | | Xi and Qin, 2006 [17] | | 605 | 7 | Maintenance cost | US $ | | | Xi and Qin, 2006 [17] | | 605 | 8 | Coal | J | | | Odum, 1996 [16] | | 2177 | 9 | Electricity | J | | | Xi and Qin, 2006 [17] | | 1886 | 10 | Protein powder | US $ | | | Xi and Qin, 2006 [17] | | 931 |
| Total (NP) | | | | | | 12491 |
| Total input | | | | | | 21475 |
| System feedback | 11 | Biogas (heated) | J | | | Bastianoni and Marchettini, 2000 [15] | | 7666 |
| Total (F) | | | | | | 7666 |
| Yield | 12 | Biogas (output) | J | | | Bastianoni and Marchettini, 2000 [15] | | 28996 | 13 | Nitrogen fertilizer | g | | | Zhang et al., 2005 [19] | | 145 | 14 | Phosphate fertilizer | g | | | Zhang et al., 2005 [19] | | 218 | 15 | Potash fertilizer | g | | | Zhang et al., 2005 [19] | | 193 |
| Total yield (Y) | | | | | | 29553 |
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aLocal nonrenewable resources can be neglected.
bItems have been divided by a lifetime of 20 years.
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