Integrated Life Cycle Framework for Evaluating the Sustainability of Emerging Drop-In Replacement Biofuels

Mounting concerns over energy independence and security, oil supply volatility and price, and anthropogenic-derived climate destabilization are driving the strategic development of low-carbon biofuels. Recently, second generation biofuels—fuels derived from non-food biofeedstocks including: perennial grasses, short rotation woody crops (SRWCs), and microalgae have gained significant interest from scientific and political actors due to their potential for reduced life cycle greenhouse gas (GHG) emissions relative to baseline petroleum fuels, and fungibility with existing transportation infrastructure and vehicles fleets. However, the environmental sustainability of these second generation biofuels and their capacity to meet U.S. regulatory biofuel mandates remains uncertain, and a point of scientific inquiry. This work investigates the sustainability of emerging second-generation drop-in replacement hydrocarbon biofuels, utilizing sustainability metrics and methodologies derived from multiple disciplines including life cycle assessment, industrial ecology, statistics, thermodynamics, and process modeling. This novel interdisciplinary life cycle framework is applied to study the environmental sustainability of several distinct emerging drop-in replacement biofuel platforms including: (1) cultivation of microalgae in open raceways ponds and hydro-processing of algal-oil to renewable diesel, (2) fast pyrolysis of perennial grasses and hydro-upgrading of bio-oil to green gasoline, and (3) multistage torrefaction of SRWCs and catalytic upgrading to hydrocarbon biofuels. Traditional process-based Life Cycle Assessment (LCA) and hybrid Ecologically-based Life Cycle Assessment (EcoLCA) models are developed to assess the degradation of ecological good and services, environmental impacts, and resource intensity of producing drop-in replacement biofuels. Rigorous process modeling and statistical analysis is performed to quantify key sustainability metrics including energy return on investment and life cycle GHG emissions for producing hydrocarbon biofuels under different combinations of biofeedstocks, fuel upgrading pathways, and coproduct scenarios, and to determine if renewable fuel(s) meet compliance with life cycle GHG emissions reductions thresholds set by U.S. federal regulatory programs. This interdisciplinary approach captures broader environmental externalities and unintended consequences of biofuel production that are outside the purview of traditional process design, and allows for holistic understanding of the potential tradeoffs, challenges, and broad-based impacts of emerging biofuels prior to their widespread commercialization—information that is pivotal for guiding the sustainable development of the nascent biofuels industry

ABSTRACT Performance of DEC Rdb Version 6.0 on AXP Systems by

The Alpha AXP family of processors provided a dramatic increase in CPU speed. Even with slower processors, many database applications were dominated by relatively slow I/O rates. To maintain a balanced system, database software must incorporate techniques that specifically address the disparity between CPU speed and I/O performance. The DEC Rdb version 6.0 database management system contains shorter code paths, fewer I/O operations, and reduced stall times. These enhancements minimize the effect of the I/O bottleneck and allow the AXP processor to run at its intended higher speeds. Empirical performance results show a marked improvement in I/O rates