Miao Guo

LCA data quality: sensitivity and uncertainty analysis.

Life cycle assessment (LCA) data quality issues were investigated by using case studies on products from starch-polyvinyl alcohol based biopolymers and petrochemical alternatives. The time horizon chosen for the characterization models was shown to be an important sensitive parameter for the environmental profiles of all the polymers. In the global warming potential and the toxicity potential categories the comparison between biopolymers and petrochemical counterparts altered as the time horizon extended from 20 years to infinite time. These case studies demonstrated that the use of a single time horizon provide only one perspective on the LCA outcomes which could introduce an inadvertent bias into LCA outcomes especially in toxicity impact categories and thus dynamic LCA characterization models with varying time horizons are recommended as a measure of the robustness for LCAs especially comparative assessments. This study also presents an approach to integrate statistical methods into LCA models for analyzing uncertainty in industrial and computer-simulated datasets. We calibrated probabilities for the LCA outcomes for biopolymer products arising from uncertainty in the inventory and from data variation characteristics this has enabled assigning confidence to the LCIA outcomes in specific impact categories for the biopolymer vs. petrochemical polymer comparisons undertaken. Uncertainty combined with the sensitivity analysis carried out in this study has led to a transparent increase in confidence in the LCA findings. We conclude that LCAs lacking explicit interpretation of the degree of uncertainty and sensitivities are of limited value as robust evidence for decision making or comparative assertions.

A Review on Hydrothermal Pre-treatment Technologies and Environmental Profiles of Algal Biomass Processing

The need for efficient and clean biomass conversion technologies has propelled Hydrothermal (HT) processing as a promising treatment option for biofuel production. This manuscript discussed its application for pre-treatment of microalgae biomass to solid (biochar), liquid (biocrude and biodiesel) and gaseous (hydrogen and methane) products via Hydrothermal Carbonisation (HTC), Hydrothermal Liquefaction (HTL) and Supercritical Water Gasification (SCWG) as well as the utility of HT water as an extraction medium and HT Hydrotreatment (HDT) of algal biocrude. In addition, the Solar Energy Retained in Fuel (SERF) using HT technologies is calculated and compared with benchmark biofuel. Lastly, the Life Cycle Assessment (LCA) discusses the limitation of the current state of art as well as introduction to new potential input categories to obtain a detailed environmental profile.

The environmental profile of bioethanol produced from current and potential future poplar feedstocks in the EU

Although biofuels have the potential for mitigating climate change and enhancing energy security, controversy regarding their overall environmental sustainability is considered a significant bottleneck in their development at both global and EU levels. Life Cycle Assessment (LCA) was applied to model the current and prospective environmental profiles for poplar-derived bioethanol across various potential EU supply chains (different poplar plantation management, different pretreatment technologies for bioethanol production, five EU locations). LCA modelling indicated that E100 (100% bioethanol) and E85 (85% bioethanol, 15% petrol) fuels derived from Poplar from various locations in the EU had environmental impact scores some 10% to 90% lower than petrol in global warming potential, abiotic depletion potential, ozone depletion potential and photochemical oxidation potential depending upon the exact poplar supply chain and conversion technology modelled. Hybrid poplar clones with higher biomass yields, modified composition and improved cell wall accessibility had a clear potential to deliver a more environmentally sustainable lignocellulosic biorefining industry with environmental scores some 50% lower than with conventional poplar feedstocks. A particular aspect of the present study that warrants further research is the contribution that soil carbon accumulation can make to achieving low-GHG fuels in the future.

Multi-product biorefineries from lignocelluloses: a pathway to revitalisation of the sugar industry?

BackgroundDriven by a range of sustainability challenges, e.g. climate change, resource depletion and expanding populations, a circular bioeconomy is emerging and expected to evolve progressively in the coming decades. South Africa along with other BRICS countries (Brazil, Russia, India and China) represents the emerging bioeconomy and contributes significantly to global sugar market. In our research, South Africa is used as a case study to demonstrate the sustainable design for the future biorefineries annexed to existing sugar industry. Detailed techno-economic evaluation and Life Cycle Assessment (LCA) were applied to model alternative routes for converting sugarcane residues (bagasse and trash) to selected biofuel and/or biochemicals (ethanol, ethanol and lactic acid, ethanol and furfural, butanol, methanol and Fischer–Tropsch synthesis, with co-production of surplus electricity) in an energy self-sufficient biorefinery system.ResultsEconomic assessment indicated that methanol synthesis with an internal rate of return (IRR) of 16.7% and ethanol–lactic acid co-production (20.5%) met the minimum investment criteria of 15%, while the latter had the lowest sensitivity to market price amongst all the scenarios. LCA results demonstrated that sugarcane cultivation was the most significant contributor to environmental impacts in all of the scenarios, other than the furfural production scenario in which a key step, a biphasic process with tetrahydrofuran solvent, had the most significant contribution.ConclusionOverall, the thermochemical routes presented environmental advantages over biochemical pathways on most of the impact categories, except for acidification and eutrophication. Of the investigated scenarios, furfural production delivered the inferior environmental performance, while methanol production performed best due to its low reagent consumption. The combined techno-economic and environmental assessments identified the performance-limiting steps in the 2G biorefinery design for sugarcane industry and highlighted the technology development opportunities under circular bioeconomy context.

Is it possible to develop biopolymer production systems independent of fossil fuels? Case study in energy profiling of polyhydroxybutyrate-valerate (PHBV)

A life cycle assessment (LCA) approach was used to explore fossil energy profiles of current and future scenarios for the production of the biopolymer polyhydroxybutyrate-valerate (PHBV). The study was based on primary data collected from industry sources and laboratory research, focused on evaluating the long-term quantitative and qualitative depletion of fossil fuel resources associated with the production of PHBV. The results show that corn farming and corn-glucose production were the dominant contributors to fossil fuel depletion (expressed in MJ surplus energy) over the life cycle of PHBV produced under the current production scale. However, PHBV is presently undergoing substantial development in comparison with the well-developed petrochemical alternatives. The results of forward-looking scenarios under an expanded production scale indicate that the use of renewable resources for process energy requirements for PHBV and glucose production coupled with improved C-utilization efficiency have the potential to reduce fossil fuel depletion by over 50% compared with its current production scale. The use of appropriate lignocellulosic feedstocks and processing technology for glucose production offers potential for further improvement. These results with PHBV support the view that it will be possible with future developments to move to biopolymer production systems that are largely independent of fossil fuels.

Bioethanol from poplar: a commercially viable alternative to fossil fuel in the European Union.

BackgroundThe European Union has made it a strategic objective to develop its biofuels market in order to minimize greenhouse gas (GHG) emissions, to help mitigate climate change and to address energy insecurity within the transport sector. Despite targets set at national and supranational levels, lignocellulosic bioethanol production has yet to be widely commercialized in the European Union. Here, we use techno-economic modeling to compare the price of bioethanol produced from short rotation coppice (SRC) poplar feedstocks under two leading processing technologies in five European countries.ResultsOur evaluation shows that the type of processing technology and varying national costs between countries results in a wide range of bioethanol production prices (€0.275 to 0.727/l). The lowest production prices for bioethanol were found in countries that had cheap feedstock costs and high prices for renewable electricity. Taxes and other costs had a significant influence on fuel prices at the petrol station, and therefore the presence and amount of government support for bioethanol was a major factor determining the competitiveness of bioethanol with conventional fuel. In a forward-looking scenario, genetically engineering poplar with a reduced lignin content showed potential to enhance the competitiveness of bioethanol with conventional fuel by reducing overall costs by approximately 41% in four out of the five countries modeled. However, the possible wider phenotypic traits of advanced poplars needs to be fully investigated to ensure that these do not unintentionally negate the cost savings indicated.ConclusionsThrough these evaluations, we highlight the key bottlenecks within the bioethanol supply chain from the standpoint of various stakeholders. For producers, technologies that are best suited to the specific feedstock composition and national policies should be optimized. For policymakers, support schemes that benefit emerging bioethanol producers and allow renewable fuel to be economically competitive with petrol should be established. Finally, for researchers, better control over plant genetic engineering and advanced breeding and its consequential economic impact would bring valuable contributions towards developing an economically sustainable bioethanol market within the European Union.

Influence of agro-ecosystem modeling approach on the greenhouse gas profiles of wheat-derived biopolymer products.

An approach is presented to include a wider range of factors involved in the nitrogen and carbon cycles in agro-ecosystems than is typical of many Life Cycle Assessments (LCAs) of agriculture-based products. This use results from the process-oriented Denitrification-Decomposition (DNDC, modified version) model. Here we evaluate the effects of using site-specific N(2)O emissions derived from the DNDC model rather than the values derived from the commonly used Intergovernmental Panel on Climate Change (IPCC) Tier 1 empirical model on the results of whole life cycle greenhouse gas (GHG) profiles for wheat-based biopolymer products. Statistical methods were also used to analyze the quality of the DNDC and IPCC outputs and to characterize the uncertainty in the GHG results. The results confirm that the GHG profiles of the wheat-derived biopolymer products are sensitive to how the agricultural system is modeled and uncertainty analyses indicate that DNDC is preferred over the IPCC Tier 1 approach for site-specific LCAs. The former allows inclusion of a wider range of important site-specific agricultural parameters in the LCA, provides for improved quality in the LCA data, and permits better calibration of uncertainty in the LCA inventory.

Hydrothermal upgrading of algae paste: inorganics and recycling potential in the aqueous phase

Hydrothermal Liquefaction (HTL) for algal biomass conversion is a promising technology capable of producing high yields of biocrude as well as partitioning even higher quantity of nutrients in the aqueous phase. To assess the feasibility of utilizing the aqueous phase, HTL of Nannochloropsis sp. was carried out in the temperature range of 275 to 350°C and Residence Times (RT) ranging between 5 and 60min The effect of reaction conditions on the NO3(-),PO4(3-),SO4(2-),Cl(-),Na(+),andK(+) ions as well as Chemical Oxygen Demand (COD) and pH was investigated with view of recycling the aqueous phase for either cultivation or energy generation via Anaerobic Digestion (AD), quantified via Lifecycle Assessment (LCA). It addition to substantial nutrient partitioning at short RT, an increase in alkalinity to almost pH10 and decrease in COD at longer RT was observed. The LCA investigation found reaction conditions of 275°C/30min and 350°C/10min to be most suitable for nutrient and energy recovery but both processing routes offer environmental benefit at all reaction conditions, however recycling for cultivation has marginally better environmental credentials compared to AD.

Economic and environmental evaluation of nitrogen removal and recovery methods from wastewater.

The driver for waste-based economic growth is long-term strategic design, and a paradigm-shift from waste treatment to resource recovery. This study aims to use an integrated modelling approach to evaluate the holistic economic and environmental profiles of three alternative nitrogen removal and recovery methods integrated into wastewater treatment systems, including conventional nitrification-denitrification, Anammox, and the anaerobic ion exchange route, to provide insights into N recovery system designs which are key elements in building a sustainable circular economy. Our results suggest that ion exchange is a promising technology showing high N removal-recovery efficiency from municipal wastewater and delivering competitive sustainability scores. In comparison with the well-developed conventional route, ion exchange and Anammox are undergoing significant research and development; as highlighted in sensitivity analyses, there is considerable room for process design and optimisation of ion exchange systems to achieve economically and environmentally optimal performance.

Anaerobic digestion of starch-polyvinyl alcohol biopolymer packaging: biodegradability and environmental impact assessment

The digestibility of a starch-polyvinyl alcohol (PVOH) biopolymer insulated cardboard coolbox was investigated under a defined anaerobic digestion (AD) system with key parameters characterized. Laboratory results were combined with industrial operational data to develop a site-specific life cycle assessment (LCA) model. Inoculated with active bacterial trophic groups, the anaerobic biodegradability of three starch-PVOH biopolymers achieved 58-62%. The LCA modeling showed that the environmental burdens of the starch-PVOH biopolymer packaging under AD conditions on acidification, eutrophication, global warming and photochemical oxidation potential were dominated by atmospheric emissions released from substrate degradation and fuel combustion, whereas energy consumption and infrastructure requirements were the causes of abiotic depletion, ozone depletion and toxic impacts. Nevertheless, for this bio-packaging, AD of the starch-PVOH biopolymer combined with recycling of the cardboard emerged as the environmentally superior option and optimization of the energy utilization system could bring further environmental benefits to the AD process.