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Morales M.,Pontifical Catholic University of Valparaiso | Morales M.,Bioenercel Sa Barrio Universitario S N | Aroca G.,Pontifical Catholic University of Valparaiso | Aroca G.,Bioenercel Sa Barrio Universitario S N | And 7 more authors.
Journal of Cleaner Production | Year: 2015

Short rotation woody crops appear to be a promising option of biomass for bioethanol production. The traditional short rotation periods for Eucalyptus globulus vary between 8 and 12 years, however intensive forest management practices and genetic improvement have increased the productivity of plantations and reduced the rotation periods up to 5 years. This study aims to assess the potential environmental impacts associated with Chilean short rotation E. globulus plantations for bioenergy production from a Life Cycle Assessment perspective. Thus, for the first time it is presented a detailed life cycle inventory and environmental assessment of a forest system in Latin America. Forest operations carried out over a lifespan of 12 years, with rotation periods of 4 years, were divided into four phases: crop establishment, harvesting, hauling and logistics infrastructure. The managed life cycle inventory included forest site data from a representative plantation dedicated to Eucalyptus chips production for energy purposes, and the inventory of the fuels production in Chile was also determined to fulfil the information requirement. The environmental profile was analysed in terms of several impact categories: climate change, ozone depletion, terrestrial acidification, freshwater y marine eutrophication, photochemical oxidant formation, human toxicity, terrestrial ecotoxicity, freshwater ecotoxicity, marine ecotoxicity, water depletion and fossil fuel depletion. The harvesting phase was the main contributor to almost all the impact categories with contributing ratios higher than 56%. Within the harvesting phase, fertilisation and forwarding were the main processes responsible for derived environmental impacts. The results in terms of climate change and terrestrial acidification were compared with those reported for Eucalyptus biomass production in European countries. The comparison was performed considering the same system boundaries and functional unit. Differences identified were related to different forest management activities carried out as well as different biomass yields. The LCA study remarked those stages where the researchers need to improve the environmental performance. The results suggested that both fertiliser dosage and fuel consumption in forest activities should be optimised in order to decrease most effectively the global environmental impacts. © 2015 Elsevier Ltd. Source


Scott F.,Pontifical Catholic University of Valparaiso | Scott F.,Bioenercel Sa Barrio Universitario S N | Li M.,Michigan State University | Williams D.L.,Michigan State University | And 6 more authors.
Bioresource Technology | Year: 2015

Uncertainty associated to the estimated values of the parameters in a model is a key piece of information for decision makers and model users. However, this information is typically not reported or the confidence intervals are too large to be useful. A semi-mechanistic model for the enzymatic saccharification of dilute acid pretreated corn stover is proposed in this work, the model is a modification of an existing one providing a statistically significant improved fit towards a set of experimental data that includes varying initial solid loadings (10-25% w/w) and the use of the pretreatment liquor and washed solids with or without supplementation of key inhibitors. A subset of 8 out of 17 parameters was identified, showing sufficiently tight confidence intervals to be used in uncertainty propagation and model analysis, without requiring interval truncation via expert judgment. © 2014 Elsevier Ltd. Source


Scott F.,Pontifical Catholic University of Valparaiso | Scott F.,Bioenercel Sa Barrio Universitario S N | Conejeros R.,Pontifical Catholic University of Valparaiso | Conejeros R.,Bioenercel Sa Barrio Universitario S N | And 2 more authors.
Biotechnology for Biofuels | Year: 2013

Background: Despite its semi-commercial status, ethanol production from lignocellulosics presents many complexities not yet fully solved. Since the pretreatment stage has been recognized as a complex and yield-determining step, it has been extensively studied. However, economic success of the production process also requires optimization of the biochemical conversion stage. This work addresses the search of bioreactor configurations with improved residence times for continuous enzymatic saccharification and fermentation operations. Instead of analyzing each possible configuration through simulation, we apply graphical methods to optimize the residence time of reactor networks composed of steady-state reactors. Although this can be easily made for processes described by a single kinetic expression, reactions under analysis do not exhibit this feature. Hence, the attainable region method, able to handle multiple species and its reactions, was applied for continuous reactors. Additionally, the effects of the sugars contained in the pretreatment liquor over the enzymatic hydrolysis and simultaneous saccharification and fermentation (SSF) were assessed. Results: We obtained candidate attainable regions for separate enzymatic hydrolysis and fermentation (SHF) and SSF operations, both fed with pretreated corn stover. Results show that, despite the complexity of the reaction networks and underlying kinetics, the reactor networks that minimize the residence time can be constructed by using plug flow reactors and continuous stirred tank reactors. Regarding the effect of soluble solids in the feed stream to the reactor network, for SHF higher glucose concentration and yield are achieved for enzymatic hydrolysis with washed solids. Similarly, for SSF, higher yields and bioethanol titers are obtained using this substrate. Conclusions: In this work, we demonstrated the capabilities of the attainable region analysis as a tool to assess the optimal reactor network with minimum residence time applied to the SHF and SSF operations for lignocellulosic ethanol production. The methodology can be readily modified to evaluate other kinetic models of different substrates, enzymes and microorganisms when available. From the obtained results, the most suitable reactor configuration considering residence time and rheological aspects is a continuous stirred tank reactor followed by a plug flow reactor (both in SSF mode) using washed solids as substrate. © 2013 Scott et al.; licensee BioMed Central Ltd. Source


Scott F.,Pontifical Catholic University of Valparaiso | Scott F.,Bioenercel Sa Barrio Universitario S N | Venturini F.,Pontifical Catholic University of Valparaiso | Aroca G.,Pontifical Catholic University of Valparaiso | And 3 more authors.
Bioresource Technology | Year: 2013

This work proposes a decision-making framework for the selection of processes and unit operations for lignocellulosic bioethanol production. Process alternatives are described by its capital and operating expenditures, its contribution to process yield and technological availability information. A case study in second generation ethanol production using Eucalyptus globulus as raw material is presented to test the developed process synthesis tool. Results indicate that production cost does not necessarily decrease when yield increases. Hence, optimal processes can be found at the inflexion point of total costs and yield. The developed process synthesis tool provides results with an affordable computational cost, existing optimization tools and an easy-to-upgrade description of the process alternatives. These features made this tool suitable for process screening when incomplete information regarding process alternatives is available. © 2013 Elsevier Ltd. Source

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