The competitive nature of the dust suppression industry generally implies that they are a variety of products from different sources and feedstocks. Their inherent fingerprint and chemical structures are key to debunking their effect on the environment based on green ratings. Paramount to earth stewardship is addressing responsibility bestowed on the suppliers to produce dust suppressants and provide enough evidence of their product environmental rating in the Material Safety Data Sheet. Particularly it is important to provide a lifecycle analysis of their products once in the environment. The degradation chemistry into different products, breakdown kinetics determining the half-life and susceptibility to biodegradation provide an intricate account of the environmental perspective to use of dust suppressants. In this article we ask if enough is being done to assess claims of environmental ratings of dust control products whilst deducing chemistry of eco-friendly products as we seek to understand what the terminology actually entails in a technical sense.
Environmentally Friendly?
Initially, we ask ourselves what does environmentally friendly mean in the context of dust suppressants? The terminology presents a great rendezvous of various schools of thought and its use has led to many callous assumptions if and when not used appropriately and just as a selling point. Certainly, doing justice to the term would imply looking at how it has been used in a scientific narrative and for purposes of achieving true meaning as related to dust suppressant product development. Contrasts in source, manufacturing methods, bond chemistry and by-product alteration methods of bio-degradable dust suppressants result in degradation mechanisms and cycles varying from hours to years. The manufacturing process of dust suppressants should be environmentally rated focusing on availability of cheap feedstocks with a renewable backbone, potential for scale-up of manufacturing whilst making sure that formulation processes are mild and environmentally friendly.
Biodegradable
The
two-step
process of
biodegradation
occurs through
breaking down
of larger
moieties into
lower molecular
weight species
through abiotic
reactions such
as oxidation,
photodegradation
or hydrolysis
in the first
step.
Environmentally
friendly
products can be
degraded by
bacteria, fungi
or other
biological
means into
natural
elements.
Furthermore,
biotic
reactions of
microorganisms
through
bioassimilation
breakdown the
remnants by
consuming,
metabolizing
and destroying
them leading to
their
mineralization.
Other processes
such as
biovolatilization
involve
microorganisms
absorbing
residues and
releasing gases
into the air.
Emphasis is
given to
environmentally
friendly
products
because
bioaccumulation
of
non-environmentally
friendly
products leads
to accumulation
of toxins in
the microbes,
soil and water
bodies which
often leads to
harm and
detrimental
effects on the
flora, fauna
and human life.
Future-focused
environmental
good will and
intent can be
realized from
use of green
feedstocks as
opposed to
products
consisting of
metallic ions
and potentially
carcinogenic
polyaromatic
hydrocarbons.
The long-term
burden of
dealing with
these toxic
components sits
with the
environment
which gives
more reason to
think of dust
suppressant
product life
cycles starting
from the
formulation to
particular
applications.
Seldom
can we separate
the chemistry
of
environmentally
friendly dust
suppressants
from the
metabolites and
degradation
products.
Instead at a
lab scale a lot
of what happens
in the
environment can
be mimicked
prior
environmental
exposure
although the
variables in
practice tend
to present more
challenges to
application.
Material types
that are
degradable
include
polysaccharides
and fatty
polyesters and
their
copolymers with
degradation
times of 14
days and 6
months to 2
years
respectively.
Typical
examples of
polysaccharides
include
cellulose and
starch. Fatty
polyesters and
their
copolymers such
as polyglycolic
acid (PGA) and
polylactic acid
(PLA).
Cellulose
degradation
occurs through
enzymatic
oxidation of
peroxidase from
fungi and
bacteria also
participates.
Owing to the
substitution of
cellulose
derivatives
such as
cellulose
acetate,
further
decomposition
would have to
take place
under aerobic
conditions.
Starch on the
contrary has
degradation
products which
are non-toxic
and do not
require any
additional
degradation.
PGA has a low
solubility and
high rate of
degradation
which yields
acidic products
whereas PLA can
be hydrolyzed
before
microbial
decomposition
into lactic
acid, lactic
acid oligomers
and carbon
dioxide.
For Example…
Hydrophilic liquid polymer polyethylene glycol is used in dust control its metabolism and excretion provides an insight into its toxicological mechanisms. It is well known that an increase in molecular weight corresponds to prolonged residence time in the body and less of a change in excretion path. Oxalic acid is liberated in the degradation of ethylene glycol. The calcium salt of oxalic acid and acid metabolites such as glycolic acid have been found to pose the risk of chronic toxicity in humans. Scientists have implemented methoxy capping of polyethylene glycol to reduce the toxicity that leads to the absence of hydroxyl groups required to initiate toxicity. Another example is amphiphilic triblock copolymer poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) is another water-soluble polymer that is used in dust control. Its amphiphilicity enables it to harness both hydrophilic and hydrophobic properties between water and hydrophobic surfaces. On exposure to sunlight, specifically UVA which is about 8 to 12 hours a day depending on altitude it has been noted that the half-life of the polymer is about 4 to 6 months.
Environmentally Friendly vs Does it Work!
Preferably
an ideal
environmentally
friendly dust
suppressant
must execute
its mitigatory
role with
distinction
while at its
end of life it
can be entirely
broken down
into carbon
dioxide and
water by
environmental
bugs and
ultimately be
incorporated
into
nature's
carbon cycle.
Often times
compromise is
struck between
efficacy and
environmental
rating which
leads to short
term benefits
as far as the
environment is
concerned. It
is imperative
to interrogate
end of life
chemistry of
dust
suppressants
and their
effects to
earth from
production to
use. There is
need to
challenge
status quo and
the very notion
of the end
justifies the
means. This can
be done through
a holistic
approach to
safer and
greener
chemistry of
the life cycle
of
environmentally
friendly dust
suppressants.
Connecting
facts and
values of
environmentally
friendly dust
suppression
whilst
embracing
various sound
practices and
their
ecological
impact is key
to confronting
the paradigm of
earth
stewardship
from a global
environmental
perspective.
The
responsibility
extends beyond
just change and
production of
knowledge but
lies in
community
dialogue,
concrete
decision
making,
edification,
accountability
and good
governance. The
role to play in
earth
stewardship is
not only
designated to
ecologists but
belongs to
multiple
disciplines
from
anthropologists,
sociologists,
engineers,
conservation
biologists,
chemists and
other
decision-makers
and citizens
just to mention
but a few. The
ultimate goals
are in the
interest of
environmental,
economic and
social
sustainability
at an earthly
scale. The
effects of dust
suppressants on
the environment
can impact
local
communities
therefore their
participation
in Earth
stewardship
should be at
the core of
scientist’s
agenda whilst
complementing
traditional
ecological
knowledge.
REFERENCES
- Kangming, T., and Muhammad, B. 2020. Research progress of biodegradable materials reducing environmental pollution. Abatement of Environmental Pollutants.314-332.
- Lee, T., Park, J., Knoff, D,S., Kim, K., and Kim, M. 2019. Liquid amphiphilic polymer for effective airborne dust suppression. Royal Society of Chemistry Advances. 9. 1-6.
- Rozzi, R., Chaplin, F,S., Callicott, J.B., Pickett, S.T.A., Power, M.E., Armesto, J.J., and May, R.H. 2015. Introduction: Linking Ecology and Ethics for an Interregional and Intercultural Earth Stewardship. Earth Stewardship, Linking
- Webster, R., Elliott, V., Park, B.K., Walker, D., Hankin, M., and Taupin, P. 2009. PEG and PEG conjugates toxicity: towards an understanding of the toxicity of PEG and its relevance to PEGylated biologicals. PEGylated Protein Drugs: Basic Science and Clinical Applications. 127-147.