18 Study on the Quantitative Evaluation of Greenhouse Gas (GHG) …
285
18.5 Summary
In this study, nine scenarios of different sewage-sludge treatment processes were
analyzed to estimate the GHG emissions. According to national statistics, the limiting
design values of mainstream WWTPs were defined as the limit values in the scenario
study. The sewage flow rate was assumed to be 40,000 m
3 /d, and the 1-A standard
was assumed as effluent limit. Results shown that three sources, direct emissions
of CO 2 and N 2 O, and indirect emissions of electricity consumption are significant
contributors to the GHG emissions of sewage-sludge systems. The total GHG emission ranged from 58-127 ktCO 2 e per year, with the lowest GHG emissions obtained
from the SBR-Combustion scenario and the largest GHG emissions obtained from
the AAO-Composting scenario.
N 2 O emissions and electricity consumption are the primary sources of GHG
emissions, and the sum of the contributions of these two sources exceeds 70% in all
scenarios. CO 2 emissions have not been considered in GHG emissions estimation of
IPCC, as it is of the biogenic origin. This study highlights that not considering CO 2
emissions in the results of GHG emissions estimation may cause deviations in the
results.
According to China’s statistics, total GHG emissions from the wastewater treatment industry in 2005 was 114 million tons of CO 2 equivalent (National Development
and Reform Commission for responding to climate change 2013), and the ratio of
three processes (AAO, OD, and SBR) treatment capacity and the total processing
capacity were 37%, 24%, and 13%, respectively (MEPPRC 2015). The result of this
study revealed that the contribution of direct CO 2 emissions to GHG emissions in
three processes were 1.65%, 10.52%, and 15.97%, respectively. Therefore, it can be
inferred that in the scenario of calculating direct CO 2 emissions from the sewage
treatment when calculating GHG emissions, total GHG emissions from the wastewater treatment industry in 2005 should be 150 million tons of CO 2 equivalent, an
increase of approximately 32% compared to the statistics in 2005.
Acknowledgements This work were supported by Science Foundation of Shandong Jianzhu
University (Grant No. XNBS1824)and Shandong Key Research and Development Program (No.
2019GSF109064).
References
Carr M (2007) Reducing greenhouse gas emissions industrial biotechnology and biorefining. In:
2007 Taiwan international chemical industry forum, Taiwan Chemical Industry Association,
Taipei
Chen ZX (2009) Low-carbon economic zone: a test site for China’s economic transformation. China
Econ Wkly 41:34–35
Climate Change Division (2014) Average CO2 emission factors of regional electric grids in China
during 2011 and 2012. National Development and Reform Commission of People’s Republic of
China, Beijing
285
18.5 Summary
In this study, nine scenarios of different sewage-sludge treatment processes were
analyzed to estimate the GHG emissions. According to national statistics, the limiting
design values of mainstream WWTPs were defined as the limit values in the scenario
study. The sewage flow rate was assumed to be 40,000 m
3 /d, and the 1-A standard
was assumed as effluent limit. Results shown that three sources, direct emissions
of CO 2 and N 2 O, and indirect emissions of electricity consumption are significant
contributors to the GHG emissions of sewage-sludge systems. The total GHG emission ranged from 58-127 ktCO 2 e per year, with the lowest GHG emissions obtained
from the SBR-Combustion scenario and the largest GHG emissions obtained from
the AAO-Composting scenario.
N 2 O emissions and electricity consumption are the primary sources of GHG
emissions, and the sum of the contributions of these two sources exceeds 70% in all
scenarios. CO 2 emissions have not been considered in GHG emissions estimation of
IPCC, as it is of the biogenic origin. This study highlights that not considering CO 2
emissions in the results of GHG emissions estimation may cause deviations in the
results.
According to China’s statistics, total GHG emissions from the wastewater treatment industry in 2005 was 114 million tons of CO 2 equivalent (National Development
and Reform Commission for responding to climate change 2013), and the ratio of
three processes (AAO, OD, and SBR) treatment capacity and the total processing
capacity were 37%, 24%, and 13%, respectively (MEPPRC 2015). The result of this
study revealed that the contribution of direct CO 2 emissions to GHG emissions in
three processes were 1.65%, 10.52%, and 15.97%, respectively. Therefore, it can be
inferred that in the scenario of calculating direct CO 2 emissions from the sewage
treatment when calculating GHG emissions, total GHG emissions from the wastewater treatment industry in 2005 should be 150 million tons of CO 2 equivalent, an
increase of approximately 32% compared to the statistics in 2005.
Acknowledgements This work were supported by Science Foundation of Shandong Jianzhu
University (Grant No. XNBS1824)and Shandong Key Research and Development Program (No.
2019GSF109064).
References
Carr M (2007) Reducing greenhouse gas emissions industrial biotechnology and biorefining. In:
2007 Taiwan international chemical industry forum, Taiwan Chemical Industry Association,
Taipei
Chen ZX (2009) Low-carbon economic zone: a test site for China’s economic transformation. China
Econ Wkly 41:34–35
Climate Change Division (2014) Average CO2 emission factors of regional electric grids in China
during 2011 and 2012. National Development and Reform Commission of People’s Republic of
China, Beijing