Product specific emissions from municipal solid waste landfills

For the inventory analysis of environmental impacts associated with products in Life Cycle Assessment (LCA) there is a great need for estimates of emissions from waste products disposed at municipal solid waste landfills (product specific emissions). Since product specific emissions can not be calculated or measured directly at the landfills, they must be estimated by modeling of landfill processes. This paper presents a landfill model based on a large number of assumptions and approximations concerning landfill properties, waste product properties and characteristics of various kinds of environmental protection systems (e.g. landfill gas combustion units and leachate treatment units). The model is useful for estimation of emissions from waste products disposed in landfills and it has been made operational in the computer tool LCA-LAND presented in a following paper. In the model, waste products are subdivided into five groups of components: general organic matter (e.g. paper), specific organic compounds (e.g. organic solvents), inert components (e.g. PVC), metals (e.g. cadmium), and inorganic non-metals (e.g. chlorine,) which are considered individually. The assumptions and approximations used in the model are to the extent possible scientifically based, but where scientific information has been missing, qualified estimates have been made to fulfill the aim of a complete tool for estimation of emissions. Due to several rough simplifications and missing links in our present understanding of landfills, the uncertainty associated with the model is relatively high.     

The potential of Miscanthus to sequester carbon in soils: comparing field measurements in Carlow,Ireland to model predictions

Growing bioenergy crops such as Miscanthus has the potential to mitigate atmospheric carbon dioxide emissions by the replacement of fossil fuels and by storing carbon (C) in the soil due to land use change. Here we compare direct measurements of soil organic C fractions made in Carlow (Ireland) to model predictions made by RothC and a cohort model. Our results show that when Miscanthus is grown on land previously under arable agriculture, the soil organic C will increase to a level above that of native pasture, as Miscanthus organic material is shown to have a slow decomposition rate. In addition we demonstrate that for measured organic C, fractions of different lability are similar to the C pools used in RothC. Using the model predictions from RothC and Miscanthus yields from MISCANFOR, we predict that in Ireland, changing the land use from arable to Miscanthus plantations has the potential to store between 2 and 3 Mg C ha^?1 y^?1 depending on the crop yield and the initial soil organic C level.     

Evolutionary adaptations of cochlear function in Jamaican mormoopid bats

Mormoopid bat species have their echolocation system adapted to different hunting strategies. To study the corresponding mechanical properties of their inner ear, we measured distortion-product otoacoustic emissions to assess cochlear sensitivity and tuning. Mormoops blainvillii, Pteronotus macleayii and P. quadridens use frequency-modulated echolocation signals, sometimes preceded by a short narrowband signal component. Their distortion-product otoacoustic emission-threshold curves are most sensitive between 30 and 50 kHz and show no adaptation to the narrowband echolocation components. In contrast, the constant-frequency bat P. parnellii always uses long constant-frequency call components. Its inner ear is maximally sensitive at 62 kHz, the echo-frequency of the dominant constant-frequency component, and pronounced insensitivities at 61 and 93 kHz (CF2 and CF3 call frequency) are the major evolutionary change in comparison to its relatives. Furthermore, in P. parnellii, the optimum cochlear frequency separation is minimal at 62 and 93 kHz, associated with enhanced cochlear tuning, while for the other mormoopids there is no indication of enhanced tuning. The phylogeny of mormoopids, assessed by mitochondrial DNA analysis, shows a close relationship between the Pteronotus species. This suggests that major cochlear redesign, associated with the acquisition of echolocation-call specific cochlear processing in P. parnellii, has occurred within a relatively short evolutionary time scale. Accepted: 30 April 1999     

Global relative species loss due to first‐generation biofuel production for the transport sector

The global demand for biofuels in the transport sector may lead to significant biodiversity impacts via multiple human pressures. Biodiversity assessments of biofuels, however, seldom simultaneously address several impact pathways, which can lead to biased comparisons with fossil fuels. The goal of the present study was to quantify the direct influence of habitat loss, water consumption and greenhouse gas (GHG) emissions on potential global species richness loss due to the current production of first‐generation biodiesel from soybean and rapeseed and bioethanol from sugarcane and corn. We found that the global relative species loss due to biofuel production exceeded that of fossil petrol and diesel production in more than 90% of the locations considered. Habitat loss was the dominating stressor with Chinese corn, Brazilian soybean and Brazilian sugarcane having a particularly large biodiversity impact. Spatial variation within countries was high, with 90th percentiles differing by a factor of 9 to 22 between locations. We conclude that displacing fossil fuels with first‐generation biofuels will likely negatively affect global biodiversity, no matter which feedstock is used or where it is produced. Environmental policy may therefore focus on the introduction of other renewable options in the transport sector.     

Net land‐atmosphere flows of biogenic carbon related to bioenergy: towards an understanding of systemic feedbacks

The notion that biomass combustion is carbon neutral vis‐a‐vis the atmosphere because carbon released during biomass combustion is absorbed during plant regrowth is inherent in the greenhouse gas accounting rules in many regulations and conventions. But this ‘carbon neutrality’ assumption of bioenergy is an oversimplification that can result in major flaws in emission accounting; it may even result in policies that increase, instead of reduce, overall greenhouse gas emissions. This commentary discusses the systemic feedbacks and ecosystem succession/land‐use history issues ignored by the carbon neutrality assumption. Based on recent literature, three cases are elaborated which show that the C balance of bioenergy may range from highly beneficial to strongly detrimental, depending on the plants grown, the land used (including its land‐use history) as well as the fossil energy replaced. The article concludes by proposing the concept of GHG cost curves of bioenergy as a means for optimizing the climate benefits of bioenergy policies.     

Quantifying GHG emissions enabled by capital and labor: Economic and gender inequalities in France

Many studies have investigated the carbon footprint of households. They rely on consumption-based responsibility and focus on how many emissions are embodied in a product. Here we open a new field by discussing the emissions that individuals enable by providing labor and capital to companies, using the framework of income-based (downstream) responsibility. This perspective focuses on the emissions enabled by providing inputs to production processes, and is relevant for discussion of sustainable work and the carbon impact of investment and financial portfolios. We compute the downstream carbon intensity of primary inputs for 35 industries in France using the multi-regional input–output database EXIOBASE. We provide a detailed picture of enabled emissions, disaggregating those by industry and primary inputs. On average, capital inputs are more carbon intensive than labor inputs. Finally, we couple downstream carbon intensities with an extensive national survey on wages to obtain a distribution of the income-based emissions of employees. Income-based emissions are much more unequally distributed than wages due to the huge variability of carbon intensity across industries: a truck driver enables far more emissions than a social-care worker. Inequalities in emissions do not strongly interact with economic inequality. Yet they are gendered because women work disproportionately in low-carbon-intensive industries such as healthcare. As a result, women contribute less to GHG emissions than their wage share would seem to indicate.     

Responses of ant communities to dry sulfur deposition from mining emissions in semi‐arid tropical Australia,with implications for the use of functional groups

Abstract The impact of dry deposition of SO₂ emissions on ant abundance, diversity and composition was investigated at Mount Isa in the semiarid tropics of northern Australia. Forty plots were sampled, stratified at two levels: sulfur deposition zones (high, medium, low, and two control zones) and habitat (Ridge and Plain). The two habitats supported distinctly different ant communities. Ants had clear responses to SO₂ emissions. Ant abundance was lowest in the high and medium sulfur zones in both habitats. Species richness in high SO² plots (up to 5 km from the source) was approximately half that of control plots in Ridge habitat, and was substantially less than controls in the Plain habitat. Ant community composition in the high sulfur zone was clearly separated from those of other zones in ordinations. Vector fitting showed soil SO₄ concentration as a primary correlative factor in this separation. Ant abundance and richness were both negatively correlated with soil SO₄ concentration, and positively correlated with plant species richness and distance away from the smelters. The abundance of 10 of the 21 most common species showed significant responses to emissions. Five species showed positive responses, and all belong to species‐groups known to be abundant at disturbed sites throughout northern Australia. Relative abundance and richness of Eyrean (arid adapted) taxa collectively responded positively to sulfur, and Torresian (tropical) and Widespread species responded negatively. Despite large changes in species composition and abundances, there was relatively little change in the abundance of functional groups that have been widely used in studies of Australian ant communities. Ants are sensitive to SO₂ emissions and appear to be good candidates as an indicator group in this context. However, an alternative functional group framework is required for the identification of recurrent responses of arid zone ant communities to disturbance.     

An Exploration of the Relationship between Socioeconomic and Well‐Being Variables and Household Greenhouse Gas Emissions

This research reports on a multivariate analysis that examined the relationship between direct greenhouse gas (GHG) emissions and socioeconomic and well‐being variables for 1,920 respondents living in Halifax Regional Municipality, Nova Scotia, Canada, using results from the Halifax Space‐Time Activity Research Project. The unique data set allows us to estimate direct GHG emissions with an unprecedented level of specificity based on household energy use survey data and geographic positioning system–verified personal travel data. Of the variables analyzed, household size, income, community zone, age, and marital status are all statistically significant predictors of direct GHG emissions. Birthplace, ethnicity, educational attainment, perceptions of health, life satisfaction, job satisfaction, happiness, volunteering, or community belonging did not seem to matter. In addition, we examined whether those reporting energy‐efficient behaviors had lower GHG emissions. No significant differences were discovered among the groups analyzed, supporting a growing body of research indicating a disconnect between environmental attitudes and behaviors and environmental impact. Among the predictor variables, those reporting to be married, young, low income, and living in households with more people have correspondingly lower direct GHG emissions than other categories in respective groupings. Our finding that respondents with lifestyles that generate higher GHG emissions did not report to be healthier, happier, or more connected to their communities suggest that individuals can experience similar degrees of well‐being regardless of the amount of GHG emissions associated with his or her respective lifestyle.     

Under what circumstances can the forest sector contribute to 2050 climate change mitigation targets? A study from forest ecosystems to landfill methane emissions for the province of Quebec,Canada

Meeting climate change mitigation targets by 2050, as outlined in international pledges, involves determining optimal strategies for forest management, wood supply, the substitution of greenhouse gas-intensive materials and energy sources, and wood product disposal. Our study quantified the cumulative mitigation potential by 2050 of the forest sector in the province of Quebec, Canada, using several alternative strategies and assessed under what circumstances the sector could contribute to the targets. We used the Carbon Budget Model of the Canadian Forest Sector to project ecosystems emissions and sequestration of seven alternative and one baseline (business-as-usual [BaU]) forest management scenarios over the 2018–2050 period. Three baskets of wood products were used in a Harvested Wood Products model to predict wood product emissions. The mitigation potential was determined by comparing the cumulative CO₂e budget of each alternative scenario to the BaU. The proportion of methane emissions from landfills (RCH₄%) and the required displacement factor (RDF) to achieve mitigation benefits were assessed both independently and jointly. The fastest and most efficient way to improve mitigation outcomes of the forest sector of Quebec is to reduce end-of-life methane emissions from wood products. By reducing methane emissions, the RDF for achieving mitigation benefits through intensification strategies can be reduced from 1.2–2.3 to 0–0.9 tC/tC, thus reaching the current provincial mean DF threshold (0.9). Both a reduction and an increase in the harvested volume have the potential to provide mitigation benefits with adequate RCH₄% and RDF. Increased carbon sequestration in ecosystems, innovations in long-lived wood products, and optimal substitution in markets offer potential avenues for the forest sector to contribute to mitigation benefits but are subject to significant uncertainties. Methane emission reduction at the end of wood product service life is emerging as a valuable approach to enhance mitigation benefits of the forest sector.     

Improvements in Life Cycle Energy Efficiency and Greenhouse Gas Emissions of Corn-Ethanol

Corn-ethanol production is expanding rapidly with the adoption of improved technologies to increase energy efficiency and profitability in crop production, ethanol conversion, and coproduct use. Life cycle assessment can evaluate the impact of these changes on environmental performance metrics. To this end, we analyzed the life cycles of corn-ethanol systems accounting for the majority of U.S. capacity to estimate greenhouse gas (GHG) emissions and energy efficiencies on the basis of updated values for crop management and yields, biorefinery operation, and coproduct utilization. Direct-effect GHG emissions were estimated to be equivalent to a 48% to 59% reduction compared to gasoline, a twofold to threefold greater reduction than reported in previous studies. Ethanol-to-petroleum output/input ratios ranged from 10:1 to 13:1 but could be increased to 19:1 if farmers adopted high-yield progressive crop and soil management practices. An advanced closed-loop biorefinery with anaerobic digestion reduced GHG emissions by 67% and increased the net energy ratio to 2.2, from 1.5 to 1.8 for the most common systems. Such improved technologies have the potential to move corn-ethanol closer to the hypothetical performance of cellulosic biofuels. Likewise, the larger GHG reductions estimated in this study allow a greater buffer for inclusion of indirect-effect land-use change emissions while still meeting regulatory GHG reduction targets. These results suggest that corn-ethanol systems have substantially greater potential to mitigate GHG emissions and reduce dependence on imported petroleum for transportation fuels than reported previously.