4.3.2 Biomethane production

For the calculation of biomethane production, the following basic data were used:

used and of the substituted fuels (electricity, natural gas, diesel fuel). We used the

• Diesel 69.95 kg CO2eq/GJ [52] • CNG 49.75 kg CO2eq/GJ [52] • Electricity 391 kg CO2eq/kWh [53]

• CHP 11 kg CO2eq/GJ [37] • Upgrading and feed-in station 41 kg CO2eq/GJ [37] • Upgrading and fuelling 22 kg CO2eq/GJ [37]

Value Measure Source

The use of the systemic approach in city operation and regional development requires that the interest and demand of the environment, the local communities and the economy would be satisfied on a mutually beneficial level [54]. We also

If the sewage plant itself was evaluated environmentally, the decision would be very simple: because of lack of CBM-fuelled vehicle, the CHP technology would be considered as the most favourable option. At the level of municipality (considering the waste management, local transport and central heating system), we need to

In the case of the conventional CHP technology, direct emission from the oper-

pipeline

Heat Electricity Natural gas Diesel GJ/yr MWh/yr GJ/yr GJ/yr

Upgrading + transport

Table 6 shows that CBM production for feed-in has the highest energy demand and the lowest emission saving potential. The other two options could be regarded near equal, since though CBM for fuelling has slightly better emission saving

consumed heat and electricity. In this case the saved emission of local transport and of central heating remains the same. Regarding the other two technologies, the emission savings will be derived from the saved natural gas or diesel fuel of buses,

Savings in fuel (in given unit above) 4357 1815 15,316 15,316 Savings in CO2eq (t/yr) 217 710 762 1072

Emission from technology (t/yr) 165 615 330 CO2eq emission (t/yr) 762 147 742

ation should be considered as basis, and it should be reduced with the self-

Technology CHP Upgrading + gas

following emission factors in our calculations (Table 5).

The Possible Role of Large-Scale Sewage Plants in Local Transport

DOI: http://dx.doi.org/10.5772/intechopen.86699

used this approach.

Table 5.

Substitution of fuel

Operation of sewage plants

Substitution and operation factors.

respectively (Table 6).

Source: Own calculations.

Table 6.

149

make a three-sided comparative analysis.

Biogas input (GJ/yr) 15,004

CO2 emission balance of the evaluated technologies.

potential, it needs more energy for the operation.


The amount of biomethane produced is 1860 Nm<sup>3</sup> /day \* 65% biogas methane content \* 98% efficiency/96% biomethane methane content = 1234 Nm3 /day biomethane.

In the case of supply to the natural gas network, the expected revenue is 1234 Nm<sup>3</sup> /day biomethane \* 34 MJ/Nm<sup>3</sup> \* 0.0078 EUR/MJ = 327 EUR/day = 119,000 EUR.

When using the output as a fuel (CNG/CBM), since the prices are expressed in kg, it is therefore appropriate to convert the resulting quantity into this unit of measure: 1234 Nm<sup>3</sup> /day biomethane = 963 kg/day biomethane.

Value of this: 963 kg/day biomethane \* 1.18 EUR/kg = 1136 EUR/day = 415 EUR/ year. This may further contribute to the potential recovery of CO2 obtained during the cleaning process.

The value of the required cleaning equipment (120–130 Nm<sup>3</sup> /h capacity), based on our own calculations: 860,000 EUR (this does not include investment costs related to sales).

However, it is important to take into account that if we convert biogas to biomethane, we need to purchase the sewage plant's self-consumption needs. Their values in the present case are:


The remaining sales revenue from biomethane sales:


## 4.3.3 Effects on CO2 emission

When calculating the effects of CBM on the CO2 emission, we should start the calculation with the emission values of the given technological process (CHP, upgrading). Then we need to make a comparison between the CO2 emissions of the used and of the substituted fuels (electricity, natural gas, diesel fuel). We used the following emission factors in our calculations (Table 5).


#### Table 5.

4.3.2 Biomethane production

calculation)

biomethane.

119,000 EUR.

measure: 1234 Nm<sup>3</sup>

the cleaning process.

values in the present case are:

4.3.3 Effects on CO2 emission

148

related to sales).

1234 Nm<sup>3</sup>

• The amount of biogas produced: 1860 Nm3

• The methane content of biogas: 65%

Transportation Systems Analysis and Assessment

• CNG/CBM density: 0.78 kg/Nm<sup>3</sup>

• CNG average price: 1.18 EUR/kg

For the calculation of biomethane production, the following basic data were used:

• Cleaning technology: 2% methane loss and 96% methane gas recovery

• Natural gas purchase price: 0.0078 EUR/MJ (EU wholesale average price)

• The calorific value of the biomethane obtained: 34 MJ/Nm<sup>3</sup>

content \* 98% efficiency/96% biomethane methane content = 1234 Nm3

The value of the required cleaning equipment (120–130 Nm<sup>3</sup>

In the case of supply to the natural gas network, the expected revenue is

/day biomethane \* 34 MJ/Nm<sup>3</sup> \* 0.0078 EUR/MJ = 327 EUR/day =

When using the output as a fuel (CNG/CBM), since the prices are expressed in kg, it is therefore appropriate to convert the resulting quantity into this unit of

/day biomethane = 963 kg/day biomethane. Value of this: 963 kg/day biomethane \* 1.18 EUR/kg = 1136 EUR/day = 415 EUR/ year. This may further contribute to the potential recovery of CO2 obtained during

on our own calculations: 860,000 EUR (this does not include investment costs

However, it is important to take into account that if we convert biogas to biomethane, we need to purchase the sewage plant's self-consumption needs. Their

When calculating the effects of CBM on the CO2 emission, we should start the calculation with the emission values of the given technological process (CHP, upgrading). Then we need to make a comparison between the CO2 emissions of the

• Electricity: 7709 kWh/day \* 0.112 EUR/kWh = 863 EUR/day

• Heat: 18,500 MJ/day \* 0.0078 EUR/MJ = 144 EUR/day

• Total: 1007 EUR/day = 368,000 EUR/year

The remaining sales revenue from biomethane sales:

• Sales of propellants: 415–368 = 47,000 EUR/year

• Natural gas sales: 119–368 = () 249,000 EUR/year

The amount of biomethane produced is 1860 Nm<sup>3</sup>

/day (from the previous

/day \* 65% biogas methane

/day

/h capacity), based

Substitution and operation factors.

The use of the systemic approach in city operation and regional development requires that the interest and demand of the environment, the local communities and the economy would be satisfied on a mutually beneficial level [54]. We also used this approach.

If the sewage plant itself was evaluated environmentally, the decision would be very simple: because of lack of CBM-fuelled vehicle, the CHP technology would be considered as the most favourable option. At the level of municipality (considering the waste management, local transport and central heating system), we need to make a three-sided comparative analysis.

In the case of the conventional CHP technology, direct emission from the operation should be considered as basis, and it should be reduced with the selfconsumed heat and electricity. In this case the saved emission of local transport and of central heating remains the same. Regarding the other two technologies, the emission savings will be derived from the saved natural gas or diesel fuel of buses, respectively (Table 6).


#### Table 6.

CO2 emission balance of the evaluated technologies.

Table 6 shows that CBM production for feed-in has the highest energy demand and the lowest emission saving potential. The other two options could be regarded near equal, since though CBM for fuelling has slightly better emission saving potential, it needs more energy for the operation.
