scholarly journals Environmental, Ecological, and Economic Benefits of Biofuel Production Using a Constructed Wetland: A Case Study in China

2019 ◽  
Vol 16 (5) ◽  
pp. 827
Author(s):  
Dong Liu ◽  
Changxin Zou ◽  
Mengjia Xu
Keyword(s):  
Wastewater Treatment ◽  
Life Cycle ◽  
Greenhouse Gas ◽  
Constructed Wetland ◽  
Biomass Yield ◽  
Greenhouse Gas Emission ◽  
Treatment Plant ◽  
Economic Benefits ◽  
Biofuel Production ◽  
Net Energy

Here we show a constructed wetland (CW), a viable alternative wastewater treatment system, be used to produce biofuels from biomass by using nitrogen contained in domestic wastewater. We summarize the potential biomass yield evaluated as cellulosic ethanol bioenergy production, and combine the life cycle analysis with a mass balance approach to estimate the energetic, environmental, and economic performance of a CW biofuel system. The results showed that the annual aboveground biomass yield of a CW in Zhoushan, Zhejiang Province, China, averaged 37,813 kg ha−1 year−1 as the by-product of treating waste N, which is about one order of magnitude larger than traditional biofuel production systems. The biomass yield in the Zhoushan CW system had life cycle environment benefits of 8.8 Mg (1 Mg = 106 g) CO2 equivalent ha−1 year−1 of greenhouse gas emission reduction. The CW in Zhoushan had a net energy gain of 249.9 GJ (1 GJ = 109 J) ha−1 year−1 while the wastewater treatment plant (WTP) consumes 7442.5 GJ ha−1 year−1. Moreover, the CW reduced greenhouse gas emissions to 2714 times less than that of the WTP. The CW also provided various ecosystem services, such as regional climate regulation and habitat conservation. We suggest that the potential use of a CW as biofuel production and carbon sequestration via nitrogen-negative input can be explored more widely in the future.

Perspectives on greenhouse gas emission estimates based on Australian wastewater treatment plant operating data

2013 ◽  
Vol 69 (3) ◽  
pp. 451-463 ◽  
Author(s):  
D. W. de Haas ◽  
C. Pepperell ◽  
J. Foley
Keyword(s):  
Wastewater Treatment ◽  
Steady State ◽  
Greenhouse Gas ◽  
Greenhouse Gas Emission ◽  
Electrical Power ◽  
Research Work ◽  
Treatment Plant ◽  
Emission Factors ◽  
N2o Emissions ◽  
Operating Data

Primary operating data were collected from forty-six wastewater treatment plants (WWTPs) located across three states within Australia. The size range of plants was indicatively from 500 to 900,000 person equivalents. Direct and indirect greenhouse gas emissions were calculated using a mass balance approach and default emission factors, based on Australia's National Greenhouse Energy Reporting (NGER) scheme and IPCC guidelines. A Monte Carlo-type combined uncertainty analysis was applied to the some of the key emission factors in order to study sensitivity. The results suggest that Scope 2 (indirect emissions due to electrical power purchased from the grid) dominate the emissions profile for most of the plants (indicatively half to three quarters of the average estimated total emissions). This is only offset for the relatively small number of plants (in this study) that have significant on-site power generation from biogas, or where the water utility purchases grid electricity generated from renewable sources. For plants with anaerobic digestion, inventory data issues around theoretical biogas generation, capture and measurement were sometimes encountered that can skew reportable emissions using the NGER methodology. Typically, nitrous oxide (N2O) emissions dominated the Scope 1 (direct) emissions. However, N2O still only accounted for approximately 10 to 37% of total emissions. This conservative estimate is based on the ‘default’ NGER steady-state emission factor, which amounts to 1% of nitrogen removed through biological nitrification-denitrification processing in the plant (or indicatively 0.7 to 0.8% of plant influent total nitrogen). Current research suggests that true N2O emissions may be much lower and certainly not steady-state. The results of this study help to place in context research work that is focused on direct emissions from WWTPs (including N2O, methane and carbon dioxide of non-biogenic origin). For example, whereas non-biogenic CO2 contributions are relatively minor, it appears that opportunities to reduce indirect emissions as a result of modest savings in power consumption are at least in the same order as those from reducing N2O emissions. To avoid potentially high reportable emissions under NGER guidelines, particularly for methane, the onus is placed on WWTP managers to ensure that accurate plant monitoring operating records are kept.

scholarly journals Production of Methane From Microalgae Biofilms Growing in Wastewater Treatment Plants in the Canary Islands

2017 ◽  
pp. 904-917
Author(s):  
Giovana O. Fistarol ◽  
Mario Rosato ◽  
Nerieida M. R. Rodríguez ◽  
Mauela A. Bastidas ◽  
Paulo Sérgio Salomon ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Canary Islands ◽  
Nutrient Removal ◽  
Biomass Yield ◽  
Wastewater Treatment Plants ◽  
Low Cost ◽  
Treatment Plant ◽  
Methanogenic Bacteria ◽  
Biofuel Production ◽  
Gran Canaria

Two recurrent topics among the scientific community are the use of microalgae in wastewater treatment plants as a biological agent for nutrient removal, and, more recently, the use of microalgae for biofuel production. In this study we have analysed the possibility of coupling these two processes, using microalgae that naturally form biofilms on wastewater treatment tanks to produce methane. The proposal is to develop a low cost, environmental friendly methodology, with the economical and environmental advantages of enhancing the removal of nutrients from wastewater, and producing sustainable biofuel. A methane assay using microalgae biofilms from the primary and secondary treatment tanks from a wastewater treatment plant (WWTP) on the Canary Islands (EDAR-del Sureste, Gran Canaria, Spain) showed that, when this substrate is added to a suitable methanogenic bacteria, in this case marine sludge from a fish farm, it gives a methane yield of 0.104 Nm3 kg-1 VS. We also checked the in situ biomass yield of the biofilm (3.16 g AFDW m-2 d-1 and 7.71 g AFDW m-2 d-1, for the primary tank and secondary tank respectively), and the growth of this biofilms in photobioreactors (PBR). When grown in PBR, the algae composition of biofilm from the primary tank becomes dominate by a unicellular chlorophyta and produces 0.24 kg AFDW m- 3 d-1 of biomass; while biofilm from the secondary tank becomes dominated by the filamentous chlorophyta Stigeoclonium, and has a biomass yield of 0.48 kg AFDW m-3 d-1. The biofilms growing the WWTP of the EDAR del Sureste, in Gran Canaria, are a free naturally available source of biomass, and we have shown in this study that this biofilm, besides being used as a natural agent for nutrient removal in a WWTP, it has also the potentialof being used as a low cost, green source of biomass for methane production.

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