RESUMEN
In 2018 and 2019 the City of Boston (Massachusetts, USA) conducted zero waste and carbon neutral planning efforts. Here we present the results of an accompanying analysis of the impacts of zero waste strategies on greenhouse gases (GHG) emissions associated with waste treatment. Emissions analysis in the waste sector is complicated by the contribution of significant indirect impacts that can exhibit temporal and spatial heterogeneity. For example, lifecycle GHG analysis of waste-to-energy combustion grants credits for the emissions avoided due to electricity generated from organic waste (biogenic carbon) that displaces electricity generation that could be carbon-emitting. As electricity grids decarbonize, this credit approaches zero. Long-term emissions planning needs to account for such dynamics to realistically assess the GHG mitigation potential associated with alternative waste management strategies. Here, we seek to capture these dynamics in a forward-looking analysis of waste sector emissions under a zero-waste strategy for the City of Boston. Using publicly available data sets such as EPA's Waste Reduction Model (WARM), we show that the implementation of zero waste strategies reduces the combustion of plastics and biomass in waste-to-energy (WtE) combustion facilities and associated GHG emissions. While WtE has been considered less-carbon intensive than other forms of waste treatment and fossil-based electricity generation, our analysis shows that more renewables will eventually eliminate the perceived GHG benefits associated with waste-to-energy combustion. While our approach provides policymakers with an understanding of the impacts of decisions in a dynamic context, we also identify common knowledge gaps in conducting forward-looking waste-GHG assessments.
Asunto(s)
Efecto Invernadero , Administración de Residuos , Boston , Gases/análisis , MassachusettsRESUMEN
During the past 12000 years agricultural systems have transitioned from natural habitats to conventional agricultural regions and recently to large areas of genetically engineered (GE) croplands. This GE revolution occurred for cotton in a span of slightly more than a decade during which a switch occurred in major cotton production areas from growing 100% conventional cotton to an environment in which 95% transgenics are grown. Ecological interactions between GE targeted insects and other insectivorous insects have been investigated. However, the relationships between ecological functions (such as herbivory and ecosystem transport) and agronomic benefits of avian or mammalian insectivores in the transgenic environment generally remain unclear, although the importance of some agricultural pest management services provided by insectivorous species such as the Brazilian free-tailed bat, Tadarida brasiliensis, have been recognized. We developed a dynamic model to predict regional-scale ecological functions in agricultural food webs by using the indicators of insect pest herbivory measured by cotton boll damage and insect emigration from cotton. In the south-central Texas Winter Garden agricultural region we find that the process of insectivory by bats has a considerable impact on both the ecology and valuation of harvest in Bacillus thuringiensis (Bt) transgenic and nontransgenic cotton crops. Predation on agricultural pests by insectivorous bats may enhance the economic value of agricultural systems by reducing the frequency of required spraying and delaying the ultimate need for new pesticides. In the Winter Garden region, the presence of large numbers of insectivorous bats yields a regional summer dispersion of adult pest insects from Bt cotton that is considerably reduced from the moth emigration when bats are absent in either transgenic or non-transgenic crops. This regional decrease of pest numbers impacts insect herbivory on a transcontinental scale. With a few exceptions, we find that the agronomics of both Bt and conventional cotton production is more profitable when large numbers of insectivorous bats are present.
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Quirópteros , Cadena Alimentaria , Gossypium/parasitología , Mariposas Nocturnas/fisiología , Plantas Modificadas Genéticamente/parasitología , Agricultura/economía , Animales , Toxinas de Bacillus thuringiensis , Proteínas Bacterianas/genética , Endotoxinas/genética , Gossypium/genética , Proteínas Hemolisinas/genética , Interacciones Huésped-Parásitos , Larva/fisiología , Modelos BiológicosAsunto(s)
Biomasa , Fuentes Generadoras de Energía , Etanol , Zea mays , Celulosa , Combustibles FósilesRESUMEN
Most of the progress in human culture has required the exploitation of energy resources. About 100 years ago, the major source of energy shifted from recent solar to fossil hydrocarbons, including liquid and gaseous petroleum. Technology has generally led to a greater use of hydrocarbon fuels for most human activities, making civilization vulnerable to decreases in supply. At this time our knowledge is not sufficient for us to choose between the different estimates of, for example, resources of conventional oil.