03.08.2015   Pretreatment Techniques for Biofuels and Biorefineries

The Calculation of the Process Potential in Terms of GHG Reduction

Table 13.4 shows the results of the calculation of the process potential in terms of GHG reduction per year and the amount of GHGs reduced by the BGUS. The follow­ing GWP (Global Warming Potential) ratios were used: CO2:1; CH4:25; N2O:298 [16]. The total carbon load of the shared portion of the previous biogas plant was 271 t-CO2eq ((219,260 kg-CO2eq (gas flare) + 6,042 kg-CO2eq (Buying electricity for Biogas Plant) + 45,215 kg-CO2eq (volatilization)).

Against this value, CO2 reduction in the total carbon load of common portions from the biogas plant that introduced the BGUS was counted as being produced by ~6.3 % of Town A’s households to which biogas was sent (which did not include the farm in Town A with the biogas plant installation) and by farm trucks and kitchen equipment that used refined biogas as substitute energy source in the biogas plant, besides the livestock waste treatment system that existed in the previous biogas plant.

The results of analysis show that the total carbon load of the common portions of the BGUS was 102 t-CO2eq. Compared with the carbon load of the common portion of the biogas plant before introduction of the BGUS and of the gas-utilizing equipment inside and outside the farm production system (209 t-CO2eq), a reduction of 107 t-CO2eq was achieved.

13.3 Conclusion

In this chapter, a biogas refining-compressing-filling facility that uses surplus biogas produced by a privately owned biogas plant was devised and constructed, field tests of biogas utilization systems made up of equipment using purified gas obtained from the facilities were performed, and the possibility of a regional purified biogas system in rural areas of Japan was validated. Consequently, the refining-compressing-filling facility was able to reach the biogas Wobbe Index (WI) of 49.2-53.8 and com­bustion rate of 34-47 m/s (town gas 12A specification) in production volumes of high-pressure gas that qualified for class 2 producer status under the specifications of Japan’s “High-pressure Gas Safety Act” (<100 Nm3/day).

Additionally, the budget analysis results of a biogas utilization system modeled after Town A in Northern Japan showed a distribution of the purified gas such that

0. 3 % of the purified gas produced by the biogas plant (approximately 35,000 Nm3/yr) was used for running consumption and 98.3 % was distributed to the town’s gas infrastructure, thereby satisfying the gas needs of 219 (6 %) of the 3,661 residences of Town A.

CO;(kg) CH4(kg)

N. O(kg)

Л. Previously existing Biogas plant

(before the introduction of bioeas utilization system (BGUS))

(1) Farm (Owner of the Biogas Plant)

# I Biogas plant and digested slurry

• Cias Hare (Combusted: Surplus biogas: Carbon eiifrul)

(219.260)*

—

• Buying electricity (Biogas Plant)

6,042

—

—

• Volatilization (from digested slurry in grass field.

45.215

0.27

21.62

land application, slurry spreader)

<Subtotal>

51.257

0.27

21.62

GWP

51,257

7

6,443

GWP (C02 eq) (a)

58 t — CO. eq

#2 Gas and diesel F. quipment

• Truck(Diesel) and Gas table(Propane)

70.973

GWP

70,973

0

0

GWP (CO, eq) (b)

71 t — CO, eq

(2) Town A (216 common residential units) #1 Gas Fquipment • (ias table

GWP

80.024

80.024

0

0

(ЛИ* (C O, eg) (c)______________________________________________ 80 t — CO, eg

Total GHG (A=a+h+c)__________________________________________ 209 t — CO, eg

B. Biogas Plant with hingax utili/.ation system (ii( ■ l S)

(It Farm (Owner of the Biogas Plant)

#1 Biogas plant and digested slurry

• Gas Паre(Combusted: OITGas and Surplus biogas: Carbon eatra/)

(115,177)*

—

—

• Buying electricity (Biogas Plant)

6.042

—

• Volatilization (from digested slurry in grass Held,

45,215

0.27

21.62

land applieation, slurry spreader)

<Subtotal>

51,257

0.27

21.62

GWP

51.257

7

6,443

GWP (CO, eq) (a)

58 t — CO, eq

#2 Biogas Purifiers (refining-compression-filling (RCF) facility)

• Buying electricity ( RCF facility)

43,642

—

—

GWP

43,642

0

0

GWP (C02 eq) (b)

44 t — CO, eq

#3 Refined Biogas Fquipment (Carbon enlral)

• NGV(Truck) and Cias table (Instead of Purified Biogas)

(1,407)*

—

GWP

0

0

0

GWP (CO, eq) (c)

0 t — CO, eq

(2) Town A (216 common residential units)

#1 Refined Biogas Equipment (Instead of Refined Biogas from LPG)

• (ias table (Carbon Neutra 1)

(80,024)*

—

GWP

0

0

0

GWP (CO, eq) (d)

0 t-CO, eq

Total GHG (B=a+b+c+d>

102 1-ГО, eq

C. GHG reduction (c=A — B)

107 t — CO, eq

(Effect on the introduction of BGUS)

GWP: Global W arming Potential. CO:: Carbon dioxide. CH<: Methane, N-O: Nitrous oxide CO; eq: CO; equivalents. ((a(a,(a(a(a )*:Carbon Neutral GW P were used: CO::l; CH4:25; N-0:298 (IPCC. 2007)

Fig. 13.4 Biogas utilization system (BGUS)

The results of analysis show that the total carbon load of the common portions of the BGUS was 102 t-CO2eq. Compared with the carbon load of the common portion of the biogas plant before introduction of the BGUS and of the gas-utilizing equipment inside and outside the farm production system (209 t-CO2eq), a reduction of 107 t-CO2eq was achieved.

The results show that the area’s carbon dioxide emissions can be reduced through the standardization of Town Gas 12A and that refining biogas allows for the export of biogas outside of the system to be used by common gas appliances. Purified gas is locally produced and consumed as a source of carbon-neutral energy in dairy farming areas. Packing the purified gas into tanks and supplying it to the town makes possible the reduction of the area’s carbon emissions.