The objective of this paper is to reveal to what degree biobased jet fuels (biojet) can reduce greenhouse gas (GHG) emissions from the U.S. aviation sector. A model of the supply and demand chain of biojet involving farmers, biorefineries, airlines, and policymakers is developed by considering factors that drive the decisions of actors (i.e., decision-makers and stakeholders) in the life cycle stages. Two kinds of feedstock are considered: oil-producing feedstock (i.e., camelina and algae) and lignocellulosic biomass (i.e., corn stover, switchgrass, and short rotation woody crops). By factoring in farmer/feedstock producer and biorefinery profitability requirements and risk attitudes, land availability and suitability, as well as a time delay and technological learning factor, a more realistic estimate of the level of biojet supply and emissions reduction can be developed under different oil price assumptions. Factors that drive biojet GHG emissions and unit production costs from each feedstock are identified and quantified. Overall, this study finds that at likely adoption rates biojet alone would not be sufficient to achieve the aviation emissions reduction target. In 2050, under high oil price scenario assumption, GHG emissions can be reduced to a level ranging from 55 to 92%, with a median value of 74%, compared to the 2005 baseline level.
Problems of increasing complexity are facing decision makers within government and industry, and the key characteristic of these problems is that they are of system-of-systems type. With multiple, heterogeneous, distributed systems involved (including policies and economies as well as technologies), effective analysis for decision-support quickly becomes unmanageable within the "stovepipe" context that still characterizes many organizations in the research and development community. There is not a process/field of study in place that can enable us to systematically solve these types of problems, exemplified by the Next Generation Transportation System. While indeed numerous tools are available to help, they cannot be used effectively because the people who build and understand the tools all speak different languages. Much confusion still remains about words and phrases for system-of-systems type problems, let alone the best modeling approaches for dealing with them. While pockets of organizational restructuring may address this challenge for particular projects, there is a lack of systematic thinking at the basic level about how to address the challenges. This paper recommends that intellectual, financial, and institutional resources be invested for the purpose of initiating and nurturing a field of study that will enable us to better address this important type of problem. The future of transportation serves as a motivating example of a multidomain, system-of-systems problem of critical importance to the nation and in need of effective decision-support. The analogy of creating better maps and "navigation aids" for decision makers will be employed, emphasizing that, when navigating a minefield, knowing where not to go is the key factor in successfully traversing the terrain (i.e., making wise decisions). Copyright 2004 by The Policy Studies Organization.
In 2019, the Research Council of the Systems Engineering Research Center (SERC), a US Defense Department sponsored University Affiliated Research Center (UARC), developed a roadmap structuring and guiding artificial intelligence (AI) and autonomy research. This paper presents that roadmap and key underlying Digital Engineering transformation aspects both enabling traditional systems engineering practice automation (AI4SE), and encourage new systems engineering practices supporting a new wave of automated, adaptive, and learning systems (SE4AI).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.