The economics of producing sustainable aviation fuel: a regional case study in Queensland,Australia

The airline industry has a strong interest in developing sustainable aviation fuels, in order to reduce their exposure to increasing oil prices and cost liability for greenhouse gas emissions. The feasibility and cost of producing sustainable biomass‐based jet fuels at a sufficient scale to materially address these issues is an enormous challenge. This paper builds directly on the biophysical study by H.T. Murphy, D.A. O'Connell, R.J. Raison, A.C. Warden, T.H. Booth, A. Herr, A.L. Braid, D.F. Crawford, J.A. Hayward, T. Javonovic, J.G. McIvor, M.H. O'Connor, M.L. Poole, D. Prestwidge, N. Raisbeck‐Brown & L. Rye, In review, which examined a 25 year scale‐up strategy to produce 5% of projected jet fuel demand in Australia in 2020 (470 mL) in the Fitzroy region of Queensland, Australia. The strategy was based on the use of a mixed ligno‐cellulosic biomass feedstock and assumed, for the sake of exploring and quantifying the scenario, a simplified two‐step conversion process – conversion of biomass to crude bio‐oil within the region, and upgrade to jet fuel at a central Brisbane facility. This paper provides details on the costs of production in this scenario, focusing on two different strategies for biomass utilization, and two types of novel small–medium scale conversion technologies. The cost analyses have taken into account technology learning curves, different economies of scale and key cost sensitivities. The cost of biomass‐based jet fuels is estimated to be between 0.70 and 1.90 The airline industry has a strong interest in developing sustainable aviation fuels, in order to reduce their exposure to increasing oil prices and cost liability for greenhouse gas emissions. The feasibility and cost of producing sustainable biomass‐based jet fuels at a sufficient scale to materially address these issues is an enormous challenge. This paper builds directly on the biophysical study by H.T. Murphy, D.A. O'Connell, R.J. Raison, A.C. Warden, T.H. Booth, A. Herr, A.L. Braid, D.F. Crawford, J.A. Hayward, T. Javonovic, J.G. McIvor, M.H. O'Connor, M.L. Poole, D. Prestwidge, N. Raisbeck‐Brown & L. Rye, In review, which examined a 25 year scale‐up strategy to produce 5% of projected jet fuel demand in Australia in 2020 (470 mL) in the Fitzroy region of Queensland, Australia. The strategy was based on the use of a mixed ligno‐cellulosic biomass feedstock and assumed, for the sake of exploring and quantifying the scenario, a simplified two‐step conversion process – conversion of biomass to crude bio‐oil within the region, and upgrade to jet fuel at a central Brisbane facility. This paper provides details on the costs of production in this scenario, focusing on two different strategies for biomass utilization, and two types of novel small–medium scale conversion technologies. The cost analyses have taken into account technology learning curves, different economies of scale and key cost sensitivities. The cost of biomass‐based jet fuels is estimated to be between 0.70 and 1.90 $ L^?1 when the efficiency of conversion of biomass to biocrude and subsequently to aviation fuel is varied by ±10% of published values, with an average value of 1.10 $ L^?1. This is within the range of the projected 2035 conventional jet fuel price of 1.50 $ L^?1. Therefore, biomass‐based jet fuel has the potential to contribute to supply of Australia's jet fuel needs in the future.     

The Effects of Landmarks on Territorial Behavior in a Convict Cichlid,Amatitlania siquia

Defense of a territory is a primary factor determining the fitness of territorial individuals. Thus, territorial animals use a variety of means to lower the cost of territorial defense. Although landmarks are known to lower the defense costs of territories, little is known about how they could affect fundamental properties of territories, which could ultimately affect the demography, population regulation, individual behavior, and spatial ecology of a territorial species. This field study examined the effects of natural landmarks on territory size, shape, and defensive costs in Amatitlania siquia, a little‐studied member of the convict cichlid group native to Costa Rica and Nicaragua. We investigated the territorial behavior of 103 breeding pairs in a caldera lake in Nicaragua. During 10‐min focal observations, we recorded the locations at which residents chased intruders and then used these locations to outline the territory boundaries. Landmarks affected both size and shape of A. siquia territories. Territory size decreased as the percentage of the boundary at landmarks increased. Territories with <20% of their boundaries at landmarks were approximately circular in shape, while territories with 20–60% of their boundaries at landmarks were on average more elongated. These variations in territory size and shape significantly affected defense costs, with higher numbers of chases per square meter in small and elongated territories. These effects of landmarks on territory size and shape and defense costs are useful to understand the widely seen size and shape variations in naturally occurring territories.     

Reconciling the optimal and empirical approaches to modelling stomatal conductance

Models of vegetation function are widely used to predict the effects of climate change on carbon, water and nutrient cycles of terrestrial ecosystems, and their feedbacks to climate. Stomatal conductance, the process that governs plant water use and carbon uptake, is fundamental to such models. In this paper, we reconcile two long‐standing theories of stomatal conductance. The empirical approach, which is most commonly used in vegetation models, is phenomenological, based on experimental observations of stomatal behaviour in response to environmental conditions. The optimal approach is based on the theoretical argument that stomata should act to minimize the amount of water used per unit carbon gained. We reconcile these two approaches by showing that the theory of optimal stomatal conductance can be used to derive a model of stomatal conductance that is closely analogous to the empirical models. Consequently, we obtain a unified stomatal model which has a similar form to existing empirical models, but which now provides a theoretical interpretation for model parameter values. The key model parameter, g₁, is predicted to increase with growth temperature and with the marginal water cost of carbon gain. The new model is fitted to a range of datasets ranging from tropical to boreal trees. The parameter g₁ is shown to vary with growth temperature, as predicted, and also with plant functional type. The model is shown to correctly capture responses of stomatal conductance to changing atmospheric CO₂, and thus can be used to test for stomatal acclimation to elevated CO₂. The reconciliation of the optimal and empirical approaches to modelling stomatal conductance is important for global change biology because it provides a simple theoretical framework for analyzing, and simulating, the coupling between carbon and water cycles under environmental change.     

Toward a Carbon Dioxide Neutral Industrial Park

The industrial park of Herdersbrug (Brugge, Flanders, Belgium) comprises 92 small and medium‐sized enterprises, a waste‐to‐energy incinerator, and a power plant (not included in the study) on its site. To study the carbon dioxide (CO₂) neutrality of the park, we made a park‐wide inventory for 2007 of the CO₂ emissions due to energy consumption (electricity and fossil fuel) and waste incineration, as well as an inventory of the existing renewable electricity and heat generation. The definition of CO₂ neutrality in Flanders only considers CO₂ released as a consequence of consumption or generation of electricity, not the CO₂ emitted when fossil fuel is consumed for heat generation. To further decrease or avoid CO₂ emissions, we project and evaluate measures to increase renewable energy generation. The 21 kilotons (kt) of CO₂ emitted due to electricity consumption are more than compensated by the 25 kt of CO₂ avoided by generation of renewable electricity. Herdersbrug Industrial Park is thus CO₂ neutral, according to the definition of the Flemish government. Only a small fraction (6.6%) of the CO₂ emitted as a consequence of fossil fuel consumption (heat generation) and waste incineration is compensated by existing and projected measures for renewable heat generation. Of the total CO₂ emission (149 kt) due to energy consumption (electricity + heat generation) and waste incineration on the Herdersbrug Industrial Park in 2007, 70.5% is compensated by existing and projected renewable energy generated in the park. Forty‐seven percent of the yearly avoided CO₂ corresponds to renewable energy generated from waste incineration and biomass fermentation.     

The cost of phage resistance in a plant pathogenic bacterium is context‐dependent

Parasites are ubiquitous features of living systems and many parasites severely reduce the fecundity or longevity of their hosts. This parasite‐imposed selection on host populations should strongly favor the evolution of host resistance, but hosts typically face a trade‐off between investment in reproductive fitness and investment in defense against parasites. The magnitude of such a trade‐off is likely to be context‐dependent, and accordingly costs that are key in shaping evolution in nature may not be easily observable in an artificial environment. We set out to assess the costs of phage resistance for a plant pathogenic bacterium in its natural plant host versus in a nutrient‐rich, artificial medium. We demonstrate that mutants of Pseudomonas syringae that have evolved resistance via a single mutational step pay a substantial cost for this resistance when grown on their tomato plant hosts, but do not realize any measurable growth rate costs in nutrient‐rich media. This work demonstrates that resistance to phage can significantly alter bacterial growth within plant hosts, and therefore that phage‐mediated selection in nature is likely to be an important component of bacterial pathogenicity.     

Effect of neighbour visibility on nest attendance patterns of Barn Swallows Hirundo rustica in loose colonies

To assess the benefits of nesting at a site hidden from neighbours in a loosely colonial species, the Barn Swallow Hirundo rustica, we carried out two field experiments, obstruction removal and mirror placement, both replicating a situation in which a nest is made visible from another nest. Under manipulated conditions in both experiments, females increased the length of time they stayed at their nests during the egg‐laying and late incubation stages, while males extended their duration of stay during the egg‐laying and early nestling stages in mirror placement experiments only. The results suggest that Barn Swallows conceal their nests to reduce fitness costs imposed by neighbours nesting in view and that hiding the nest can reduce the amount of time spent guarding the nest during certain stages of the breeding period.