Leonor Patricia Güereca

Methane emissions from stabilization ponds for municipal wastewater treatment in Mexico

Abstract Wastewater treatment (WWT) is applied for environmental protection and water reclamation. However, this activity has been identified as a source of methane (CH4), contributing to climate change. WWT (municipal and industrial) is estimated to produce 8 to 11% to overall CH4 emissions. In order to apply effective mitigation strategies in the water sector, a more precise inventory of CH4 emission should be accomplished. The application of the Tier 1 methodology in the Guidelines for National Greenhouse Gas Inventories of the Intergovernmental Panel on Climate Change (IPCC) results in rough estimations, as default emission factors are used. An effort should be done for determining actual emission factors for the more representative treatment processes in a given region or country. In this work, a detailed inventory of CH4 emissions form municipal wastewater management in Mexico was obtained, based on the Tier 1 IPCC methodology. In addition, on-site CH4 emission measurements in five stabilization ponds (SP) were realized. The total CH4 emissions generated by municipal WWT in Mexico were 600.4 Gigagrams (Gg) for year 2010. Also, the IPCC (theoretical) estimations showed that CH4 emissions were overestimated if compared with the results obtained in the five sampled facilities. The on-site emission factors obtained showed wide variation as they are specific to each sampled system and to their particular environmental and operating conditions. In Mexico, the value of 0.431 kg CH4/kg BOD removed (0.110 kg CH4/m3 treated water) may be used for SP with good operational practices.

Methane correction factors for estimating emissions from aerobic wastewater treatment facilities based on field data in Mexico and on literature review

Wastewater treatment (WWT) may be an important source of methane (CH4), a greenhouse gas with significant global warming potential. Sources of CH4 emissions from WWT facilities can be found in the water and in the sludge process lines. Among the methodologies for estimating CH4 emissions inventories from WWT, the more adopted are the guidelines of the Intergovernmental Panel on Climate Change (IPCC), which recommends default emission factors (Tier 1) depending on WWT systems. Recent published results show that well managed treatment facilities may emit CH4, due to dissolved CH4 in the influent wastewater; in addition, biological nutrient removal also will produce this gas in the anaerobic (or anoxic) steps. However, none of these elements is considered in the current IPCC guidelines. The aim of this work is to propose modified (and new) methane correction factors (MCF) regarding the current Tier 1 IPCC guidelines for CH4 emissions from aerobic treatment systems, with and without anaerobic sludge digesters, focusing on intertropical countries. The modifications are supported on in situ assessment of fugitive CH4 emissions in two facilities in Mexico and on relevant literature data. In the case of well-managed centralized aerobic treatment plant, a MCF of 0.06 (instead of the current 0.0) is proposed, considering that the assumption of a CH4-neutral treatment facility, as established in the IPCC methodology, is not supported. Similarly, a MCF of 0.08 is proposed for biological nutrient removal processes, being a new entry in the guidelines. Finally, a one-step straightforward calculation is proposed for centralized aerobic treatment plants with anaerobic digesters that avoids confusion when selecting the appropriate default MCF based on the Tier 1 IPCC guidelines.

Life cycle assessment of Mexican polymer and high-durability cotton paper banknotes

This study compares the environmental performance of Mexican banknotes printed on high-durability cotton paper (HD paper) and thermoplastic polymer (polymer) through a life cycle assessment to appraise the environmental impacts from the extraction of raw materials to the final disposal of the banknotes. The functional unit was defined considering the next parameters: 1) lifespan of the banknotes, stablished in 31.5 and 54months for HD paper and polymer, respectively; 2) denomination, selecting

Typology of Municipal Wastewater Treatment Technologies in Latin America

200 pesos banknotes; 3) a 5year time frame and 4) a defined amount of money, in this case stablished as the monthly cash supply of an average Mexican household, equaling

Carbon Footprint as a basis for a cleaner research institute in Mexico

12,708 pesos. Accordingly, 121 pieces for the HD paper and 71 pieces for the polymer banknotes were analyzed. The results favor the banknotes printed on polymer substrate primarily because of the longer lifespan of this type of material; however, there is a considerable environmental impact in the stages of distribution, followed by the extraction of the raw materials (crude oil) during manufacturing. Regarding the HD cotton paper, the major impact corresponds to extraction of the raw materials, followed by the distribution of the banknotes. The inclusion of the automatic teller machines (ATMs) in the life cycle assessment of banknotes shows that the electricity required by these devices became the largest contributor to the environmental impacts. Additionally, the sensitivity analysis that the average lifetime of the banknotes is a determining factor for the environmental impacts associated with the whole life cycle of this product. The life cycle stages that refer to the extraction of the raw materials, combined with the average lifetime of the banknotes and the electricity required during the usage stage, are determining factors in the total environmental impact associated with Mexican banknotes.