In Ecuador, the net energy contribution of biofuels is unknown or unnoticed. To address this issue, we determined the Energy Return on Investment (EROI) for bioethanol and biodiesel.The selection of raw materials relied on their productive capacity, export and import records, and historical yields. Consequently, the scope included three raw materials for ethanol (sugar cane, corn, and forest residues) and four for biodiesel (African palm, pinion, bovine fat, and swine fat).Using a method based on the Life Cycle Analysis (LCA) of each biofuel, we assessed the entire production chain through statistical processing of primary and secondary information. Then we calculated the calorific values in the laboratory, compared energy inputs/outputs, and finally obtained the energetic returns.EROIs for bioethanol were: 1.797 for sugarcane, 1.040 for corn, and 0.739 for wood. The results for biodiesel were: 3.052 for African palm, 2.743 for pinion, 2.187 for bovine fat, and 2.891 for swine fat. These values suggest feasibility only for sugarcane in the case of ethanol. In contrast, biodiesel has better prospects because all the feedstocks analyzed had EROIs higher than two. Nevertheless, biodiesel is not available for trading in Ecuador because energy policy has overlooked systems based on higher energy return. Future studies should consider more comprehensive variables such as climate change, land use, and water management.
Rivers substantially contribute to global greenhouse gas emissions, yet emissions from headwater streams are poorly constrained. Here, we report dissolved concentrations of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) in Andean headwater and piedmont streams in the Napo River basin in Ecuador, part of the Amazon River catchment. Concentrations increased exponentially with elevation decrease between 3990 and 175 m above sea level. Concentration changes scaled with catchment slope, and were attributed to variations in gas transfer velocity, forest cover, inundation extent, and water temperature. We estimate river emissions across the whole Amazon basin using existing data for the lowland Central Amazon. We find that Andean mountainous headwater and piedmont streams are hotspots of CO2 and CH4 emission, with respective areal fluxes being 1.7 and 4.5 higher in headwater streams, and 1.2 and 6.6 higher in piedmont streams than in lowland streams. Together, Andean mountainous headwater and piedmont streams and rivers represented 35% CO2 and 72% CH4 of basin scale integrated fluvial diffusive emissions. Conversely, N2O emissions from headwater and piedmont streams were low compared to lowland streams.
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