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Para ilmuwan mengubah tanah berminyak menjadi lahan subur
Date:
August 20, 2015
Source:
Rice University
Summary:
Para ilmuwan membersihkan tanah yang terkontaminasi oleh tumpahan minyak dengan cara yang menghemat energi dan mengambil kembali kesuburan tanah , menggunakan proses yang dikenal sebagai pirolisis , yang melibatkan pemanasan tanah terkontaminasi dalam ketiadaan oksigen .
................... Mereka menggunakan proses yang dikenal sebagai pirolisis , yang melibatkan pemanasan tanah terkontaminasi dalam ketiadaan oksigen . Pendekatan ini jauh lebih baik untuk lingkungan daripada teknik pembakaran standar untuk perbaikan cepat, kata insinyur Rice environmental Pedro Alvarez ........more
Scientists turn oily soil into fertile ground
Discovery uses less energy while
reclaiming soil at oil spills
Date:
August 20, 2015
Source:
Rice University
Summary:
Scientists are cleaning soil
contaminated by oil spills in a way that saves energy and reclaims the soil's
fertility, using a process known as pyrolysis, which involves heating
contaminated soils in the absence of oxygen.
......................
Rice University scientists are cleaning
soil contaminated by oil spills in a way that saves energy and reclaims the
soil's fertility.
They use a process known as pyrolysis,
which involves heating contaminated soils in the absence of oxygen. This
approach is much better for the environment than standard incineration
techniques for fast remediation, said Rice environmental engineer Pedro
Alvarez.
"Our original goal was to speed the
response to oil spills, but our aspiration was to turn contaminated soil into
fertile soil," said Alvarez, the George R. Brown Professor and chair of
Rice's Civil and Environmental Engineering Department.
The new paper by Alvarez and his Rice
colleagues in the American Chemical Society journal Environmental
Science and Technology demonstrates how they've done just that.
Off-shore oil spills tend to get the
most attention, Alvarez said, but 98 percent of spills -- more than 25,000 per
year -- occur on land. Industry and governments worldwide spend more than $10
billion annually to clean up oil spills.
The Rice team found that pyrolyzing
contaminated soil for three hours not only reduced the amount of petroleum
hydrocarbons left to well below regulatory standards (typically less than 0.1
percent by weight), but also enhanced the soil's fertility by turning the
remaining carbon into beneficial char.
"We initially thought we could turn
the hydrocarbons into biochar," Alvarez said. "We turned out to be
partly wrong: We didn't get biochar, but [we got] a carbonaceous material that
we call char and resembles coke.
"But we were correct in thinking
that by removing toxic pollutants and the hydrophobicity that repels water that
plants need, and by retaining some of the carbon and perhaps some of the
nutrients, we would enhance plant growth," he said.
The researchers proved that by
successfully growing lettuce in reclaimed soil in the lab. "There's no one
plant officially accepted as the standard for testing petroleum toxicity, but
lettuce has been accepted by the community as very sensitive to toxins,
especially petroleum," said Rice graduate student Julia Vidonish, the
paper's lead author. "Reclaimed soil may not necessarily be used to grow
food, but it certainly could be used for re-greening: planting grass to
minimize erosion and to restore vegetation," Alvarez said.
"Our process is part thermal
desorption, but it takes advantage of petroleum chemistry," said Rice
chemical engineer and co-author Kyriacos Zygourakis. "By heating the
contaminated soils to about 420 degrees Celsius in the absence of oxygen, we
first drive out the lighter hydrocarbons. That's the desorption part. But when
the temperature gets above 350 degrees, the high-molecular-weight hydrocarbons,
the resins and asphaltenes, undergo a series of cracking and condensation
reactions to form solid char, similar to the petroleum coke produced in
refineries.
"We leave some of the hydrocarbons
in the treated soil but in a solid, more benign form," he said. "The
Environmental Protection Agency does not classify petroleum coke as hazardous
waste. If, on the other hand, you want to remove everything, you have to raise
the temperature even higher and introduce oxygen to incinerate the char. But
you destroy the soil and use 40 to 60 percent more energy."
The char produced by pyrolyzing
oil-soaked soil is different from biochar, Rice biogeochemist and co-author
Caroline Masiello said. Where biochar is a particle unto itself, the coke-like
char appears to coat existing soil particles.
"Biochar is a particle that is
separate from the soil's mineral grains," she said. "It has an
internal physical structure that allows it to hold water and nutrients and
provides a home for microbes, but here, we're not making any of those things.
We're making an organic film that coats the minerals."
Vidonish said the process is scalable
and should work with existing remediation equipment. "Incineration and
thermal desorption are established technologies, and while this is different,
there are similarities," she said. "We expect companies can take a
mobile, field-scale thermal desorption unit and make a couple of modifications
to do pyrolysis."
"We proved we can remove all the
bad actors and all the contaminants and at the same time have a final product
with agricultural value," Zygourakis said. "We don't just turn it
into desert sand."
Much work remains to optimize the
process, Vidonish said. "Moving forward, we want to understand how the
pyrolysis time and the temperature affect the quality of the char in the
soil," she said.
Story Source:
The above post is reprinted from materials provided by Rice University. Note: Materials may be edited for content
and length.
Journal Reference:
1.
Julia E. Vidonish, Kyriacos Zygourakis,
Caroline A. Masiello, Xiaodong Gao, Jacques Mathieu, Pedro J. J. Alvarez.Pyrolytic
Treatment and Fertility Enhancement of Soils Contaminated with Heavy
Hydrocarbons. Environmental Science & Technology, 2015;
150818162617008 DOI:10.1021/acs.est.5b02620