Adaptation and mitigation synergies to improve sanitation: a case study in Morelos, Mexico

The management of wastewater is the fifth largest single source of CH 4 emissions and the sixth of N 2 O. Options to improve sanitation within the Morelos State in Mexico were compared applying a modification of the IPCC guidelines to estimate greenhouse gas (GHG) emissions. A 2030 business-as-usual scenario which considers current sanitation practices and 2010 baseline-scenario, showed that septic tanks, the main state option for sanitation, were the principal source of emissions, even higher than from non-controlled wastewater discharges. These scenarios also revealed that the two metropolitan areas were key in terms of mitigation as they contributed 88% of the total GHG emissions. For the 2030A scenario (sanitation + adaptation), it was seen that if the policy of septic tank usage continues, and the existing wastewater treatment plants are rehabilitated, the GHG emissions would be reduced by 2% compared to the BAU scenario. In contrast, if a policy were adopted considering in addition mitigation measures, 26% GHG emissions reduction might be achieved. Additional co-benefits will be obtained in several sectors, including health (diarrheal and dengue diseases control), agriculture, and the environment, performing a more efficient and integrated management of water and achieving savings on the operating costs of WWTP through co-generation.