5 research outputs found
Montana Kaimin, March 5, 1981
Student newspaper of the University of Montana, Missoula.https://scholarworks.umt.edu/studentnewspaper/8304/thumbnail.jp
Spatially-Explicit Life Cycle Assessment of Sun-to-Wheels Transportation Pathways in the U.S.
Growth in biofuel production, which is meant to reduce
greenhouse
gas (GHG) emissions and fossil energy demand, is increasingly seen
as a threat to food supply and natural habitats. Using photovoltaics
(PV) to directly convert solar radiation into electricity for battery
electric vehicles (BEVs) is an alternative to photosynthesis, which
suffers from a very low energy conversion efficiency. Assessments
need to be spatially explicit, since solar insolation and crop yields
vary widely between locations. This paper therefore compares direct
land use, life cycle GHG emissions and fossil fuel requirements of
five different sun-to-wheels conversion pathways for every county
in the contiguous U.S.: Ethanol from corn or switchgrass for internal
combustion vehicles (ICVs), electricity from corn or switchgrass for
BEVs, and PV electricity for BEVs. Even the most land-use efficient
biomass-based pathway (i.e., switchgrass bioelectricity in U.S. counties
with hypothetical crop yields of over 24 tonnes/ha) requires 29 times
more land than the PV-based alternative in the same locations. PV
BEV systems also have the lowest life cycle GHG emissions throughout
the U.S. and the lowest fossil fuel inputs, except for locations with
hypothetical switchgrass yields of 16 or more tonnes/ha. Including
indirect land use effects further strengthens the case for PV
Investigating the Energy-Water Usage Efficiency of the Reuse of Treated Municipal Wastewater for Artificial Groundwater Recharge
This
project investigates the energy-water usage efficiency of
large scale civil infrastructure projects involving the artificial
recharge of subsurface groundwater aquifers via the reuse of treated
municipal wastewater. A modeling framework is introduced which explores
the various ways in which spatially heterogeneous variables such as
topography, landuse, and subsurface infiltration capacity combine
to determine the physical layout of proposed reuse system components
and their associated process energy-water demands. This framework
is applied to the planning and evaluation of the energy-water usage
efficiency of hypothetical reuse systems in five case study regions
within the State of California. Findings from these case study analyses
suggest that, in certain geographic contexts, the water requirements
attributable to the process energy consumption of a reuse system can
exceed the volume of water that it is able to recover by as much as
an order of magnitude
Life Cycle Assessment of Solar Photovoltaic Microgrid Systems in Off-Grid Communities
Access to a reliable source of electricity
creates significant
benefits for developing communities. Smaller versions of electricity
grids, known as microgrids, have been developed as a solution to energy
access problems. Using attributional life cycle assessment, this project
evaluates the environmental and energy impacts of three photovoltiac
(PV) microgrids compared to other energy options for a model village
in Kenya. When normalized per kilowatt hour of electricity consumed,
PV microgrids, particularly PV–battery systems, have lower
impacts than other energy access solutions in climate change, particulate
matter, photochemical oxidants, and terrestrial acidification. When
compared to small-scale diesel generators, PV–battery systems
save 94–99% in the above categories. When compared to the marginal
electricity grid in Kenya, PV–battery systems save 80–88%.
Contribution analysis suggests that electricity and primary metal
use during component, particularly battery, manufacturing are the
largest contributors to overall PV–battery microgrid impacts.
Accordingly, additional savings could be seen from changing battery
manufacturing location and ensuring end of life recycling. Overall,
this project highlights the potential for PV microgrids to be feasible,
adaptable, long-term energy access solutions, with health and environmental
advantages compared to traditional electrification options
Chemical Recycling of Polyethylene by Tandem Catalytic Conversion to Propylene
Although polyethylene (PE) and polypropylene (PP) are
by far the
world’s largest volume plastics, only a tiny fraction of these
energy-rich polyolefins are currently recycled. Depolymerization of
PE to its constituent monomer, ethylene, is highly endothermic and
conventionally accessible only through unselective, high-temperature
pyrolysis. Here, we provide experimental demonstrations of our recently
proposed tandem catalysis strategy, which uses ethylene to convert
PE to propylene, the commodity monomer used to make PP. The approach
combines rapid olefin metathesis with rate-limiting isomerization.
Monounsaturated PE is progressively disassembled at modest temperatures
via many consecutive ethenolysis events, resulting selectively in
propylene. Fully saturated PE can be converted to unsaturated PE starting
with a single transfer dehydrogenation to ethylene, which produces
a small amount of ethane (1 equiv per dehydrogenation event). These
principles are demonstrated using both homogeneous and heterogeneous
catalysts. While selectivity under batch conditions is limited at
high conversion by the formation of an equilibrium mixture of olefins,
high selectivity to propylene (≥94%) is achieved in a semicontinuous
process due to the continuous removal of propylene from the reaction
mixture