It is difficult
to miss being around a coke, or coking plant. The overwhelming smell of sulfur and other components
can permeate areas even miles away from the source. These plants really stink.
I grew up not too far from one. Even visiting my mom, who still lives in that
area, one overcast day, the stench was heavy, likely due to the clouds keeping the
pollution from dissipating. Coke is made from coal. This is different from
another form of coke, known as petroleum coke, or pet coke, which is made from
heavy oil. Coke is burned in industrial ovens to make steel. I grew up in a
steel town with several steel mills up and down the Ohio River there and in
nearby towns. Air quality was always a concern. My dad worked in a town once
known as the dirtiest town in America. He was also a smoker of non-filtered cigarettes
and a frequent consumer of alcohol. Despite being a renowned athlete in his
youth, he died at age 62 after bouts of heart disease and cancer. Obviously,
his lifestyle choices led to his early death. It is also likely that air
pollution was a contributing factor. His mother, my grandmother, died of lung
cancer from tobacco smoking. His father, my grandfather who died before I was
born, died of mouth cancer due to a chewing tobacco habit. I too was a smoker
in my youth. Lucky for me I gave up cigarette smoking at age 31 back in 1996.
It was a great choice. Also lucky for me, I left that area with a higher
incidence of air pollution. No doubt since that time air pollution control
requirements and abatement have improved the local air quality considerably.
However, for people living very close to such plants or working at such plants, there are still considerable issues.
Coke: Its Manufacture, Byproducts, and Emissions
Coke is made
from coking coal, also known as metallurgical coal, or met coal, as distinguished
from coal that is burned in power plants, which is known as thermal coal. Met
coal (bituminous coal with low-ash content and low-sulfur content) is heated at
very high temperatures to drive off volatile components and arrive at a purer
form of carbon. The coke is then used for smelting iron ore for steel making. The
impurities driven off by the coking process are very toxic. Both airborne
pollution and water pollution are created. The resulting coke is a gray, hard,
porous, and somewhat glassy solid that produces far less air pollution when
burned since most of the pollution was released during the coking process. It
is made in industrial coke ovens or coke furnaces which are essentially like industrial-sized blacksmith forges. Indeed, coke is a common fuel used by blacksmiths.
Coke is basically
produced by the pyrolysis of suitable coal. Pyrolysis involves heating to extreme
temperatures under very low oxygen conditions. It acts as a distillation process
whereby different components are released according to temperature and vapor
pressure. Emissions have both aerosol (liquid droplets) and vapor phases. Emissions
include VOCs of about 20 types (including acrolein, aliphatic aldehydes, and
formaldehyde), phenol, polycyclic aromatic hydrocarbons (PAHs) of more than 40
types, inorganic compounds including ammonia, carbon monoxide, and nitrogen oxides,
and heavy metals, including cadmium, arsenic, and mercury. Gas components of
concern are benzene, toluene, xylene, and solvent naphthas.
Fortunately, for those directly downwind, many
of the emissions are collected to make byproducts, although those substances
continue to be dangerous throughout their subsequent life cycles. That was not
the case further into the past when banks of beehive coke ovens ruined the
countryside and sickened workers and locals. Usable by-products of coking
include water, coal gas, coal tar, coal tar pitch (a kind of creosote), ammonia
(NH3), hydrogen sulfide (H2S), pyridine, hydrogen cyanide, and carbon-based
material. Many of these products are toxic but some are collected to be used in
other industrial processes. One of the carbon-based materials is solid slag
left over in the furnaces. It is used in building materials. Volatile gases from
the process are typically released into the atmosphere.
Air Pollution Dangers and Health Effects from
Coking Plants
According to
Wikipedia: “Although it made a top-quality fuel, coking poisoned the
surrounding landscape. After 1900, the serious environmental damage of beehive
coking attracted national notice, although the damage had plagued the district
for decades. "The smoke and gas from some ovens destroy all vegetation
around the small mining communities", noted W. J. Lauck of the U.S.
Immigration Commission in 1911. Passing through the region on train, University
of Wisconsin president Charles Van Hise saw "long rows of beehive ovens
from which flame is bursting and dense clouds of smoke issuing, making the sky
dark. By night the scene is rendered indescribably vivid by these numerous
burning pits. The beehive ovens make the entire region of coke manufacture one
of dulled sky: cheerless and unhealthful."
There are strict limits
to working around coke ovens for occupational safety. According to The National
Institute for Occupational Safety and Health (NIOSH), a division of the CDC: “People
can be exposed to coke oven emissions in the workplace by inhalation, skin
contact, or eye contact. The Occupational Safety and Health Administration
(OSHA) has set the legal limit for coke oven emissions exposure in the
workplace as 0.150 mg/m3 benzene-soluble fraction over an eight-hour workday.
The National Institute for Occupational Safety and Health (NIOSH) has set a
recommended exposure limit (REL) of 0.2 mg/m3 benzene-soluble fraction over an
eight-hour workday.”
Daniel Valero in
his textbook, Fundamentals of Air Pollution, writes:
“The chronic human health effects of coke oven emissions
include disorders of the skin, respiratory, liver, and digestive systems. Human
and animal data indicate that exposure to coke oven emissions leads to cancer
of the lung, trachea, bronchus, kidney, prostate, and other sites.”
According to
the National Cancer Institute: “The emissions are complex mixtures of dust,
vapors, and gases that typically include carcinogens such as cadmium and
arsenic. Chemicals recovered from coke oven emissions are used as raw materials
for producing items such as plastics, solvents, dyes, paints, and insulation.”
Workers and nearby populations are exposed to this pollution by inhaling the fumes
and by absorption through the skin. Increased lung cancer and possibly kidney cancer
is possible near these plants. Occupational exposure can occur in the aluminum,
steel, graphite, electrical, and construction industries.
Environmental
Health News reported in early 2018 that: “Children at an elementary school
15 miles south of Pittsburgh have roughly double the asthma rates of
Pennsylvania children …” The school, in Clairton, Pennsylvania just 15
miles south of Pittsburgh, is also the location of U.S. Steel's Clairton Coke
Works, the largest coke plant in the U.S. After testing 213 it was found that
18.4% had asthma, or basically double the average rate of 9 to 10%. About 15% of
the students that tested positive for asthma were unaware that they had it.
Most of those with asthma were poor and black kids. The kids, on average, lived
within a mile from the plant, with a quarter of them living downwind from the
plant. Kids are good research subjects for respiratory issues since there are
fewer lifestyle factors like smoking to filter out. Two of the primary pollutants
from the plant, PM2.5 and black carbon, are known asthma triggers.
Another study
involves the closing of a big coke plant in 2016, also near Pittsburgh. This one,
the Shenango, Inc. coke plant. After the closure, the researchers documented a
90% decrease in nearby SO2 concentrations and “significant reductions in
coal-related fine particulate matter constituents (sulfate and arsenic).” Nearby
cardiovascular ER visits dropped immediately by 42 percent and continued to
shrink weekly for years. Although an environmental epidemiologist characterized
this research as a co-benefit of the energy transition, coke is still the preferred
fuel for smelting and making steel. While there are new techniques being tested
and deployed for so-called “green steel,” they are at an early stage. This
study was a landmark study with an ideal way to test the relationship between
improving air quality and health outcomes and no doubt other similar studies should
and will be done. The researchers noted in their conclusion:
“Overall, our research provides compelling scientific
evidence that this intervention eliminating fossil-fuel related coal-coking air
pollution emissions significantly improved both the air quality and
cardiovascular health of the nearby community. In addition, this work provides
rigorous validation of past policy applications of statistical associations
found between acute air pollution exposures and adverse health to estimate
clean air health benefits.”
What About the Potential Toxicity of Pyrolysis in
Wood Chemistry and Biochar Production?
Knowing that
pyrolysis of wood is used to make charcoal and a soil amendment known as
biochar that can increase CO2 uptake of soils when used as an amendment, I
decided to look into the potential toxicity of biochar pyrolysis as well.
So-called “green chemistry” or “wood chemistry” has been advocated as an
alternative to petrochemistry by environmentalists. However, it is generally
not feasible or economical as a replacement. Wood pyrolysis is a part of that
process. I did find one scientific paper in the Chemical Engineering Journal
that addressed this topic and confirmed my suspicions. The paper’s abstract
notes:
“Biochars produced by pyrolysis at high temperatures
under oxygen limited conditions can contain both well-known contaminants
(polycyclic aromatic hydrocarbons (PAHs), potentially toxic elements (PTEs),
dioxins, volatile organic compounds (VOCs)) and emerging contaminants (e.g.,
persistent free radicals, metal cyanide). Their potential to induce
phytotoxicity, cytotoxicity, and neurotoxicity highlight the need to establish
effective strategies to control and eliminate contaminants for sustainable
biochar use.”
There are also post-application chemical reactions that
can affect soils and ecosystems in high-volume applications. Many of these can likely
be mitigated and improved, still making biochar a good general choice for
improving the CO2 uptake of soils. It is, however, not without its potential
downsides, which would be amplified if it becomes more widespread as a decarbonization
solution.
References:
When a
Coke Plant Closed in Pittsburgh, Cardiovascular ER Visits Plunged. Gina
Jimenez. Inside Climate News. August 13, 2023. When
a Coke Plant Closed in Pittsburgh, Cardiovascular ER Visits Plunged - Inside
Climate News
Coke
Ovens: Pushing, Quenching and Battery Stacks: National Emission Standards for
Hazardous Air Pollutants. U.S. EPA. Coke
Ovens: Pushing, Quenching and Battery Stacks: National Emission Standards for
Hazardous Air Pollutants | US EPA
Coke
plant pollution linked to “asthma epidemic” in Pittsburgh-area elementary
school. Brian Bienkowski. Environmental Health News. February 27, 2018. Coke
plant pollution linked to “asthma epidemic” in Pittsburgh-area elementary
school - EHN
Coking
Coal of the United States—Modern and Historical Coking Coal Mining Locations
and Chemical, Rheological, Petrographic, and Other Data from Modern Samples. Open-File
Report 2020-1113. Michael H. Trippi, Leslie F. Ruppert, Cortland F. Eble, and
James C. Hower. U.S. Geological Survey. pubs.usgs.gov/of/2020/1113/ofr20201113.pdf
Coke
oven emissions. The National Institute for Occupational Safety and Health
(NIOSH). CDC - NIOSH
Pocket Guide to Chemical Hazards - Coke oven emissions
Coke
(fuel) – Wikipedia. Coke
(fuel) - Wikipedia
Coke
Oven Emissions. National Cancer Institute. Updated December 5, 2022. Coke
Oven Emissions - Cancer-Causing Substances - NCI
Fundamentals
of Air Pollution (Fifth Edition). Daniel Valero. 2014. Academic Press/Elsevier.
An
interrupted time series analysis of the cardiovascular health benefits of a
coal coking operation closure.Wuyue Yu and George D Thurston. July 31, 2023. Environmental
Research: Health, Volume 1, Number 4. An
interrupted time series analysis of the cardiovascular health benefits of a
coal coking operation closure - IOPscience
Contaminants
in biochar and suggested mitigation measures – a review. Huawen Han, Wolfram
Buss, Yuanzhang Zheng, Peizhi Song, Muhammad Khalid Rafiq, Pu Liu, Ondřej Mašek,
Xiangkai Li. Chemical Engineering Journal. Volume 429, 1 February 2022, 132287.
Contaminants
in biochar and suggested mitigation measures – a review - ScienceDirect
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