A common farm weed could make a 'greener' jet fuel with fewer production-related environmental impacts than other biofuels, a new study indicates.
From: Ohio State University
August
2, 2021 -- Growing the weed, pennycress -- often called stinkweed -- as a crop
requires less fertilizer and fewer pesticides than other plants that can be
used to make renewable jet fuel, according to the study. Pennycress also
requires fewer farm operations, such as soil tilling, than other potential
biofuel crops, reducing the associated environmental costs. Those costs include
carbon dioxide emissions that cause the climate to change, as well as other
emissions that pollute the air.
Environmental
impacts could be further mitigated through farm management techniques that keep
fertilizer on fields, rather than allowing it to run off into nearby
watersheds, the study suggests. Such techniques can add to the
financial cost of growing crops, but reduce their environmental footprints.
"Reducing greenhouse gas emissions
from air travel will mean not just incremental changes, but a fundamental
change in how we have been producing fuel and where that fuel comes from,"
said Ajay Shah, senior author of the study and associate professor of food,
agricultural and biological engineering at The Ohio State University in
Wooster. "And what we found is that pennycress might make a very good
alternative fuel, especially when you consider the environmental costs of
producing it."
The study was published recently online
in the journal Applied Energy.
For this study, the researchers
estimated the environmental impacts of growing pennycress, transporting it to a
biorefinery and converting it to a usable jet fuel. They also accounted for the
environmental costs of burning leftover byproducts of refining the pennycress
seed into fuel.
Those environmental costs include
fertilizer and pesticide use, water consumption and the energy required to
harvest and transport pennycress seeds from a farm to a biorefinery and process
them into usable fuel.
The researchers built computer models to
determine how much total energy it would take to produce jet fuel from
pennycress seeds and compared those estimates with the energy needed for
producing biofuels from other crops. The data for the models came from existing
studies about biofuel production.
Their models showed that it took about
half as much energy to produce jet fuel from pennycress as it did to produce
jet fuel from canola or sunflowers, two other potential bio-jet fuel crops.
Pennycress oil production used about a third as much energy as soybean oil production,
the researchers found, and the energy needed for turning pennycress into jet
fuel was about the same as that used to produce fuel from the flowering plant
camelina, another biofuel crop.
Renewable jetfuels are not yet
financially competitive with fossil fuel-based fuels, Shah said. But
calculating the environmental impacts of alternative bio-based fuels should
help both farmers and policymakers as they try to limit carbon dioxide in the
Earth's atmosphere and, hopefully, to slow or stop climate change.
"Pennycress also makes an appealing
alternative jet fuel because of its growing season," Shah said. "It
is a winter cover crop that can be grown between corn season and soybean
season, giving the same body of farmland an extra production cycle each year.
"Pennycress can be planted when
corn is still standing in the field, before the corn harvest," he said.
"And it can be harvested before the soybean crops are planted. The bottom
line is it can be used as a cover crop, it doesn't divert any agricultural production
land, and it has suitable properties for renewable jet fuel production."
Greenhouse gas emissions from air travel
contribute to climate change, accounting for about 2% of all human-induced
carbon-dioxide emissions, according to various groups that study the effects of
transportation on climate change.
"Reducing those emissions will
almost certainly mean finding cleaner alternatives to jet fuels made from
fossil fuels," Shah said. "Studies like this one can help determine
the best alternative.
"When it comes to pennycress,
production and logistics are the big contributors to both the environmental
impacts and the costs, and those are the challenge areas - they have to be
streamlined and solved to make it more efficient," he said. "If we
could improve those areas, we could make production more energy-efficient and
substantially lower the costs and environmental impacts."
This work was supported by funding from
the U.S. Department of Energy.
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