Oliver R. Inderwildi

Life cycle energy and greenhouse gas analysis for algae-derived biodiesel

The search for alternative fuels to alleviate our dependency on fossil-based transport fuels is driven by depleting conventional oil resources and looming climate change induced by anthropogenic greenhouse gas (GHG) emissions. Through a lifecycle approach, we evaluate whether algal biodiesel production can be a viable fuel source once the energy and carbon intensity of the process is managed accordingly. Currently, algae biodiesel production is 2.5 times as energy intensive as conventional diesel and nearly equivalent to the high fuel-cycle energy use of oil shale diesel. Biodiesel from advanced biomass can realise its inherent environmental advantages of GHG emissions reduction once every step of the production chain is fully optimized and decarbonised. This includes smart co-product utilization, decarbonisation of the electricity and heat grids as well as indirect energy requirements for fertilizer, transport and building material. Only if all these factors are taken into account is the cost of heat and electricity reduced, and GHG emissions fully mitigated.

Biofuels and synthetic fuels in the US and China: A review of Well-to-Wheel energy use and greenhouse gas emissions with the impact of land-use change

Alternative transportation fuels are projected to grow substantially due to energy security concerns especially in the US and China. Moreover, some of these fuels can potentially reduce greenhouse gas (GHG) emissions from the transportation sector and hence, can help to mitigate climate change. We present a comprehensive review on Well-to-Wheel fossil fuel use and GHG emissions of biofuels and synthetic fuels in the US and China including emissions from land-use change. Our results are carefully benchmarked to the emissions caused by crude oil-derived fuels as well as synthetic fuels from fossil feedstocks in order to estimate the potential emission reduction or increase. The review strongly suggests that biofuels and synthetic fuels can contribute to GHG mitigation in the transport sector only if appropriate feedstocks are used and emissions from land-use change are minimised.

Life cycle energy and greenhouse gas analysis for agave-derived bioethanol

The sustainability of large-scale biofuel production has recently been called into question in view of mounting concerns over the associated impact on land and water resources. As the most predominant biofuel today, ethanol produced from food crops such as corn in the US has been frequently criticised. Ethanol derived from cellulosic feedstocks is likely to overcome some of these drawbacks, but the production technology is yet to be commercialised. Sugarcane ethanol is the most efficient option in the short term, but its success in Brazil is difficult to replicate elsewhere. Agaves are attracting attention as potential ethanol feedstocks because of their many favourable characteristics such as high productivities and sugar content and their ability to grow in naturally water-limited environments. Here, we present the first life cycle energy and greenhouse gas (GHG) analysis for agave-derived ethanol. The results suggest that ethanol derived from agave is likely to be superior, or at least comparable, to that from corn, switchgrass and sugarcane in terms of energy and GHG balances, as well as in ethanol output and net GHG offset per unit land area. Our analysis highlights the promising opportunities for bioenergy production from agaves in arid or semi-arid regions with minimum pressure on food production and water resources.

Indirect emissions from electric vehicles: emissions from electricity generation

Carbon dioxide (CO2) emissions from passenger cars represent an important and growing contributor to climate change. Increasing the proportion of electric vehicles (EVs) in passenger car fleets could help to reduce these emissions, but their ability to do this depends on the fuel mix used in generating the electricity that energises EVs. This study analyzes the indirect well-to-wheels CO2 emissions from EVs when run in the US, the UK, and France and compares these to well-to-wheels emission data for a selection of internal combustion engine vehicles (ICEVs) and hybrid electric vehicles (HEVs). The study also compares the well-to-wheels emissions of the existing passenger car fleet in each country to a hypothetical EV fleet with the average electricity generation requirements of the three EVs considered in this analysis.

Dynamic Interplay between Diffusion and Reaction: Nitrogen Recombination on Rh{211} in Car Exhaust Catalysis

The adsorption and diffusion of atomic nitrogen on Rh{211} as well as formation and desorption of molecular nitrogen from this surface have been investigated by means of density functional theory (DFT) calculations. The elementary step reaction mechanism derived from this comprehensive DFT study forms the foundation of a detailed microkinetic model including diffusion, recombination, and desorption of nitrogen species. It will be shown that nitrogen formation on a stepped rhodium surface is a dynamic interplay of atomic nitrogen diffusion and reaction. Moreover, evidence will be presented that not one but several on-step recombination reactions are responsible for dinitrogen formation and desorption.

Effects of ethanol on vehicle energy efficiency and implications on ethanol life-cycle greenhouse gas analysis.

Bioethanol is the worlds largest-produced alternative to petroleum-derived transportation fuels due to its compatibility within existing spark-ignition engines and its relatively mature production technology. Despite its success, questions remain over the greenhouse gas (GHG) implications of fuel ethanol use with many studies showing significant impacts of differences in land use, feedstock, and refinery operation. While most efforts to quantify life-cycle GHG impacts have focused on the production stage, a few recent studies have acknowledged the effect of ethanol on engine performance and incorporated these effects into the fuel life cycle. These studies have broadly asserted that vehicle efficiency increases with ethanol use to justify reducing the GHG impact of ethanol. These results seem to conflict with the general notion that ethanol decreases the fuel efficiency (or increases the fuel consumption) of vehicles due to the lower volumetric energy content of ethanol when compared to gasoline. Here we argue that due to the increased emphasis on alternative fuels with drastically differing energy densities, vehicle efficiency should be evaluated based on energy rather than volume. When done so, we show that efficiency of existing vehicles can be affected by ethanol content, but these impacts can serve to have both positive and negative effects and are highly uncertain (ranging from -15% to +24%). As a result, uncertainties in the net GHG effect of ethanol, particularly when used in a low-level blend with gasoline, are considerably larger than previously estimated (standard deviations increase by >10% and >200% when used in high and low blends, respectively). Technical options exist to improve vehicle efficiency through smarter use of ethanol though changes to the vehicle fleets and fuel infrastructure would be required. Future biofuel policies should promote synergies between the vehicle and fuel industries in order to maximize the society-wise benefits or minimize the risks of adverse impacts of ethanol.

Global and local impacts of UK renewable energy policy

Energy policies within one country or region can have significant global impacts, with unforeseen consequences. As an example, the EU requirements for 20% of final energy to be derived from renewable sources by 2020 feeds in to a UK target for renewable energy to make up 15% of UK final energy demand by 2020; the implications of this are investigated and found to have global repercussions. In order to achieve the UK target it is essential that the existing strategies for delivering wind power and coupling it to the grid are successful but there is an additional, greater, challenge. A large part of the UK renewables target will need to be met by the use of biomass and we show here that the amounts of biomass needed far exceed the supply capacity of the UK; imports will dominate the supply. The imports required are far greater than present day UK imports of coal with substantial potential implications; globally for biomass markets with potential impact on food supply and deforestation, and locally for UK infrastructure in shipping, ports, rail, road freight, electricity transmission networks and the coal industry. The way that a single countrys response to a regional energy strategy can have global implications are investigated using one reference scenario for future UK fuel needs as an example. A strong outcome is that to implement this level of rapid change in the energy supply chain whilst avoiding negative impacts in a rapidly expanding global market there is a need for synchronisation of policies across economies as a whole, including anticipated effects beyond national borders, rather than policy measures in separate, isolated areas such as energy.

The Catalyst Selectivity Index (CSI): A Framework and Metric to Assess the Impact of Catalyst Efficiency Enhancements upon Energy and CO2 Footprints

Heterogeneous catalysts are not only a venerable part of our chemical and industrial heritage, but they also occupy a pivotal, central role in the advancement of modern chemistry, chemical processes and chemical technologies. The broad field of catalysis has also emerged as a critical, enabling science and technology in the modern development of “Green Chemistry”, with the avowed aim of achieving green and sustainable processes. Thus a widely utilized metric, the environmental E factor—characterizing the waste-to-product ratio for a chemical industrial process—permits one to assess the potential deleterious environmental impact of an entire chemical process in terms of excessive solvent usage. As the many (and entirely reasonable) societal pressures grow, requiring chemists and chemical engineers not only to develop manufacturing processes using new sources of energy, but also to decrease the energy/carbon footprint of existing chemical processes, these issues become ever more pressing. On that road to a green and more sustainable future for chemistry and energy, we note that, as far as we are aware, little effort has been directed towards a direct evaluation of the quantitative impacts that advances or improvements in a catalyst’s performance or efficiency would have on the overall energy or carbon (CO2) footprint balance and corresponding greenhouse gas (GHG) emissions of chemical processes and manufacturing technologies. Therefore, this present research was motivated by the premise that the sustainability impact of advances in catalysis science and technology, especially heterogeneous catalysis—the core of large-scale manufacturing processes—must move from a qualitative to a more quantitative form of assessment. This, then, is the exciting challenge of developing a new paradigm for catalysis science which embodies—in a truly quantitative form—its impact on sustainability in chemical, industrial processes. Towards that goal, we present here the concept, definition, design and development of what we term the Catalyst Sensitivity Index (CSI) to provide a measurable index as to how efficiency or performance enhancements of a heterogeneous catalyst will directly impact upon the fossil energy consumption and GHG emissions balance across several prototypical fuel production and conversion technologies, e.g. hydrocarbon fuels synthesized using algae-to-biodiesel, algae-to-jet biofuel, coal-to-liquid and gas-to-liquid processes, together with fuel upgrading processes using fluidized catalytic cracking of heavy oil, hydrocracking of heavy oil and also the production of hydrogen from steam methane reforming. Traditionally, the performance of a catalyst is defined by a combination of its activity or efficiency (its turnover frequency), its selectivity and stability (its turnover number), all of which are direct manifestations of the intrinsic physicochemical properties of the heterogeneous catalyst itself under specific working conditions. We will, of course, retain these definitions of the catalytic process, but now attempt to place discussions about a catalyst’s performance onto a new foundation by investigating the effect of improvements in the catalyst’s efficiency or performance on the resulting total energy and total CO2 footprint for these prototypical fuel production and fuel conversion processes. The CSI should help the academic and industrial chemical communities, not only to highlight the current ‘best practice catalysts’, but also draw specific conclusions as to what energy and CO2 emissions saving one could anticipate with higher efficiency/higher performance from heterogeneous catalysts in a particular fuel synthesis or conversion process or technology. Our aim is to place discussions about advances in the science and technology of catalysis onto a firm foundation in the context of GHG emissions. We believe that thinking about (and attempting to quantify) total energy and CO2 emissions reductions associated with advances in catalysis science from a complete energy life cycle analysis perspective is extremely important. The CSI will help identify processes where the most critical advances in catalyst efficiency are needed in terms of their potential impact in the transition to a more sustainable future for fuel production and conversion technologies.

The feedstock curve: novel fuel resources, environmental conservation, the force of economics and the renewed east–west power struggle

Rapid technological advancements can make previously uneconomic resources and/or feedstock available within significantly reduced timeframes. This can and will further transform the global energy landscape and moreover, will impact the mix of feedstock we use for energy provision and material production—the so-called Feedstock Curve. Herein, three current examples are assessed to illustrate that this restructuring has by far wider reaching implications: Firstly, we examine how unconventional resources—mainly produced using fractured cracking techniques—have restructured the US energy landscape, are now fueling the US economic recovery and will impact the geopolitical balance. Secondly, we assess how unconventional resources could impact European energy security, the Crimean crisis and redirect global cash flows. Thirdly, we analyse the potential impact of so-called methane hydrates deposited off the shores of Japan on the energy transition of the Island nation and how they might impact its trade deficit and long-term economic outlook. Last but not least, we will present arguments that unconventional resources, when regulated properly, may be a blessing for the environment. With these examples, this think piece and concept note will illustrate the interconnectedness of economics, politics, environmental conservation and technology.

Response to Comment on "effects of ethanol on vehicle energy efficiency and implications on ethanol life-cycle greenhouse gas analysis"

Bioethanol is the world’s largest-produced alternative to petroleum-derived transportation fuels due to its compatibility within existing spark-ignition engines and its relatively mature production technology. Despite its success, questions remain over the greenhouse gas (GHG) implications of fuel ethanol use with many studies showing significant impacts of differences in land use, feedstock, and refinery operation. While most efforts to quantify life-cycle GHG impacts have focused on the production stage, a few recent studies have acknowledged the effect of ethanol on engine performance and incorporated these effects into the fuel life cycle. These studies have broadly asserted that vehicle efficiency increases with ethanol use to justify reducing the GHG impact of ethanol. These results seem to conflict with the general notion that ethanol decreases the fuel efficiency (or increases the fuel consumption) of vehicles due to the lower volumetric energy content of ethanol when compared to gasoline. Here we argue that due to the increased emphasis on alternative fuels with drastically differing energy densities, vehicle efficiency should be evaluated based on energy rather than volume. When done so, we show that efficiency of existing vehicles can be affected by ethanol content, but these impacts can serve to have both positive and negative effects and are highly uncertain (ranging from −15% to +24%). As a result, uncertainties in the net GHG effect of ethanol, particularly when used in a low-level blend with gasoline, are considerably larger than previously estimated (standard deviations increase by >10% and >200% when used in high and low blends, respectively). Technical options exist to improve vehicle efficiency through smarter use of ethanol though changes to the vehicle fleets and fuel infrastructure would be required. Future biofuel policies should promote synergies between the vehicle and fuel industries in order to maximize the society-wise benefits or minimize the risks of adverse impacts of ethanol.