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Disclaimer—This paper partially fulfills a writing requirement for first year (freshman) engineering students at the University
of Pittsburgh Swanson School of Engineering. This paper is a student, not a professional, paper. This paper is based on publicly
available information and may not provide complete analyses of all relevant data. If this paper is used for any purpose other
than these authors’ partial fulfillment of a writing requirement for first year (freshman) engineering students at the University
of Pittsburgh Swanson School of Engineering, the user does so at his or her own risk.
THE CIRCLE OF LIFE
Tristan Witek ([email protected])
OUR MESS OF A WORLD
In today’s world, we have innumerable problems, ranging
from the political to the ethical to the technical. With so many
problems to solve, how has humanity not already collapsed
from lacking the intellectual infrastructure to support itself?
The answer: engineers.
To solve any problem, or complex of problems, one must
analyze the parts of the problem, and only then can it be
solved. So, this paper will fill that duty, analyzing a current
problem in the world, and analyzing problems with potential
solutions to that problem.
THE NITROGEN CYCLE
One of the most eminent problems of this century, global
warming has roots like a weed; tons of sources spreading out,
and all of them contributing to its exponential growth.
However, the nitrogen cycle could be the most dangerous
root.
The Natural Nitrogen Cycle
The nitrogen cycle is not inherently bad; it is, in fact, a
natural occurrence through which plants and animals receive
necessary nutrients, and microbes then release nitrogen back
into the air. Indeed, the Ecological Society of America (ESA)
board members note in a journal on issues in ecology that
“Nitrogen is an essential component of proteins, genetic
material, chlorophyll, and other key organic molecules. All
organisms require nitrogen in order to live” [1]. Being so
important, how does this essential cycle work? It starts with
the atmosphere; nitrogen molecules compose 78% it. But, as
Scott Fields points out, “most atoms of nitrogen… are bound
tightly in pairs as N2. Most organisms can’t break the
powerful triple bond of the N2 molecule’s two atoms” [2]. For
the organisms to get the nitrogen they need, there must be
some organic way to get nitrogen out of its unreactive state.
These more reactive states of nitrogen exist as the ammonium
(NH4) and nitrate (NO3) ions, and only lightning and certain
University of Pittsburgh, Swanson School of Engineering 1
11.1.2016
bacteria can cause this transformation. The ESA board says
that “these bacteria manufacture an enzyme that enables them
to convert gaseous nitrogen directly into plant-usable forms.
Lightning may also indirectly transform atmospheric nitrogen
into nitrates, which rain onto soil” [1]. However, lightning
does not contribute a very significant amount of reactive
nitrogen to the cycle; the majority comes from the microbes
in soil. Once ammonium and nitrate are in the soil, plants can
access these reactive nitrogen compounds, and perform
biological processes to extract the necessary nitrogen atoms.
Microbes complete the cycle when any living thing dies and
they decompose it, converting the nitrogen in the dead
organism back into gaseous, unreactive nitrogen, or the
reactive nitrogen compounds stay in the soil. Naturally, the
nitrogen cycle is perfectly fine; the problem arises when it
becomes altered.
The Altered Nitrogen Cycle
As humans discover new ways to exploit nature, nature
often pays a grave price; the exact occurrence with the
nitrogen cycle. Humans started altering the nitrogen cycle
when two scientists, Fritz Haber and Carl Bosch, developed a
chemical process that converted atmospheric nitrogen into
ammonia, which allowed humans to artificially increase the
reactive nitrogen concentration in soil, a process more
commonly known as fertilizing [2]. At the time, the
breakthrough was considered miraculous; Fields cites Smil as
saying that “for at least a third of humanity in the world’s most
populous countries, the use of nitrogen fertilizers makes the
difference between malnutrition and adequate diet” [2].
However, despite the good nitrogen fertilizers do in
supporting humanity’s population, it causes some serious
detriments to the environment. Because of the exponential
growth in human population, the demand for food has risen
proportionately, requiring the over-use of these nitrogen
fertilizers. But can we have too much of a good thing? As it
turns out, this process does not solely produce “good things;”
the ESA points out that “intensive fertilization of agricultural
soils can increase the rates at which at which ammonia is
Tristan Witek
to a landfill” [5], which does ring true. Immediately, it is more
expensive to send not only recyclables, but also organic waste
to recycling and composting centers than it is to send them to
landfills. Since Tierny also asserts that “all trash generated by
Americans for the next 1000 years would fit on .1% of the
land available for grazing” [5], a fear of running out of landfill
space is also impractical.
Another potential problem lies within the net
environmental impact of the composting process. Depending
on the location of a composting center, transporting the
materials could use up so much fuel that it offsets the benefit
of using the material as compost. Howard records DatzRomero as saying “What I’m concerned about is our capacity
to handle the material locally, because that’s a big part of
making composting sustainable; otherwise you are spending
a lot of fuel transporting it, and that doesn’t make sense” [3].
What point is there in composting if it’s simply a tradeoff
from one environmental poison to another?
Again regarding negative impacts on the environment, the
process of composting can release the very potent greenhouse
gases methane and nitrous oxide [6], again contributing to
global warming. Tierny argues that landfills handle this
biogas release better than composting, because “landfill
operators have started capturing it and using it to generate
electricity” [5]. Aside from the greenhouse effect, methane
smells exactly like what one would expect from decomposing
organic matter. Nearly every source that one can find on
composting makes some mention of the rancid smell as a
byproduct of composting. By this argument, composting is an
economically, environmentally, and olfactory failure of a
solution.
volatized and lost to the air. It can also speed the microbial
breakdowns of ammonium and nitrates in the soil, enhancing
the release of nitrous oxide [(NO)]” [1]. All this fertilizer
causes a large release of ammonia and nitrous oxide into the
air, both of which carry deadly impacts for the environment.
Starting with ammonia, it can react with acidic compounds in
the atmosphere, forming particulate matter which then
becomes a basis for smog and potential lung infections if too
much is breathed in [2]. Nitrous oxide, a far deadlier beast,
has a wide array of problems it can cause, as Fields mentions
that “a single atom [of reactive nitrogen] can make mischief
repeatedly” [2]. A few of these effects include the formation
of smog in the lower atmosphere, contributions to global
warming and acid rain in the middle atmosphere, and the
destruction of protective ozone in the stratosphere. These
effects from one atom, which can stay around in the
atmosphere for over a century, makes it imperative to all
citizens of the planet to contribute some help in fixing this
massive problem. If nobody attempts to stop the destruction
of the Earth’s atmosphere, then the planet will die.
REDUCING USE OF NITROGEN
FERTILIZERS
One major source of all this extra nitrogen does come from
the artificial fertilizers we use on our farms. Logically, if there
were a way to reduce the use of those fertilizers, it should help
reduce the amount of new nitrogen added to the nitrogen
cycle. As it turns out, there is a way.
Composting already happens naturally in the nitrogen
cycle, which releases nonreactive nitrogen, but also releases
reactive nitrogen compounds back into the soil. But left on its
own, this process can take at least a year. However,
techniques exist to speed up the natural process to 1-3 months.
This sped up process involves putting organic material in a
giant grinder to grind it to a desired texture, then placing it in
a device that manages oxygen levels and heat to stimulate
microbial breakdown of the organic material. This mixture
then sits outside, receives water, and is turned occasionally to
keep the conditions ideal for microbial digestion [3]. The
resulting mixture resembles soil, but has a lot of reactive
nitrogen compounds.
Pros of Composting
On the other hand, since compost is so rich in reactive
nitrogen compounds, it makes sense that farmers can use it as
an alternative to the artificial fertilizers. In fact, Brian Howard
for the National Geographic cites Robert Weed as saying that
“such compost helps farmers rely less on chemical fertilizers”
[3]. Both compost and nitrogen fertilizers do the same job;
they add more reactive nitrogen to the soil, which helps the
plant grow. However, since compost comes from organic
material, it does not add any new nitrogen to the cycle,
whereas artificial fertilizers continue to add new nitrogen,
which causes problems in the atmosphere.
Composting also reduces the amount of organic material
sent to landfills. This impacts the world positively, as Howard
writes that “she [Christine Datz-Romero] notes that when
placed in landfills, organic waste releases methane, a potent
greenhouse gas” [3]. To counter Tierny’s argument on
Cons of Composting
First off, composting does have its flaws. John Tierny in
the New York Times expresses that “Despite decades of
exhortations and mandates, it’s still typically more expensive
for municipalities to recycle household waste than to send it
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landfills handling methane better, one could simply repurpose
the same technology used at landfills to composting centers.
Thus, composting can easily perform better than simply
sending waste to landfills.
One last fantastic aspect about composting centers on
money. When cities compost organic material, they can sell
the product to farmers, companies, or regular citizens and turn
a profit. Once again, to counter Tierny, Stephanie Strom
reports in the New York Times that “The city [New York]
brought in $267,00 from the sale of 21,000 cubic yards of
Dillo Dirt [compost] in the fiscal year that ended September
30th [of 2013]” [4]. With that figure only on the rise, cities
stand to make a lot of money from compost as the years
progress. This source of revenue more than pays for the extra
cost of sending waste to composting centers, leading to a
profit.
Overall, composting is a good thing for society because it
provides our government with more money and it protects the
planet on which we live.
thrown in a dumpster. It always hurt my conscience that I was
contributing to a massive food waste problem. Thus, using
food waste, quantitatively and ethically, is a totally viable
option.
With so much food wasted, all resources that went into
making that food can be considered wasted as well. With
nitrogen fertilizers considered as a resource, logically one
could say that we used the nitrogen only to waste it. If we
must accept the amount of food American society wastes,
then we can at least try to use that food to lessen the use of
nitrogen fertilizers. With all the wasted food available, we can
add it to compost, and use it to aid in the reduction of the
usage of nitrogen fertilizers. This reduction returns to the idea
of reducing nitrogen pollution, part of the engineer’s job to
save the world. On top of saving the world, this repurposing
can help society feel a little less guilty about their enormous
waste; as Al Baker of the New York Times observes,
“Depending on the viewpoint, the sheer amount of food now
being composted is either impressive or depressing” [8]. It is
indeed depressing that we waste so much food, in light of all
the hunger that exists in the nation. However, we can take
pride as a nation that the food wasted is not totally lost.
UNTAPPED CONTRIBUTIONS TO
COMPOST
Public Compliance
Since microbes can decompose anything organic, they can
also decompose just about any food that we humans eat. If the
microbes can digest it, then humans can compost it. Cities
around the country have been collecting yard trimmings for
years, but, as Strom quotes Bob Gedert, “we have been
collecting yard trimmings from residents, but not food waste”
[4]. Since food counts as organic material, why can’t we use
it for compost?
It appears as if the green light shines bright for using food
in compost; compost effectively combats the use of nitrogen
fertilizer, food counts as a candidate for organic material in
compost, and there’s plenty of excess food lying around. Yet,
one last burden stands in the way. Since most food waste
occurs in households, governments require the participation
of the public if they have any hopes of effectively collecting
food waste for composting purposes.
In cities where the local government already collects some
food waste, officials say that education is key for encouraging
citizens to participate. Guillermo Rodriguez, an official from
San Francisco (which was the first city in the United States to
make composting food waste mandatory) commented to
Howard that “we do a lot to educate our residents about it…
there was some resistance to the mandatory program, but a lot
of that comes down to education” [3]. So for citizens to
comply with recycling food waste, it is necessary to educate
them on why they should partake in it.
If citizens can realistically be expected to contribute to the
compost of food waste, then the only remaining component to
worry about is if such a goal is fiscally possible. Elizabeth
Daigneau reports in Governing that “Portland, [Oregon]
estimates that its composting program cost about $1 million
to set up – most of which was spent on education efforts” [9].
To set up similar programs across the country would roughly
Food Waste
The answer is we can, but the real question is, should we?
Is there enough wasted food in this country to make recycling
it a viable option for addition to compost? For perspective,
Strom records that “Americans threw away more than 36
million tons of food in 2012” [4], which, as Kevin Hall and
his colleagues calculate, is about 40% of all food produced in
America [7]. To truly get a sense of how wasteful that is,
imagine going to the grocery store, buying five bags worth of
food, and then instantly throwing away two of those five bags.
That figure does not even consider unavoidable food waste,
such as egg shells, coffee grinds, and bones, which can also
become compost. I have seen this waste firsthand after
working in a kitchen for over a year. I saw countless amounts
of food go to waste from customers, entire trash bags full of
what could be repurposed into fertilizer for other crops be
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Tristan Witek
be the $1 million across about 300 cities, or $300 million; a
small figure compared to the $601 billion the US spends on
military. If we can afford to spend more than every American
collectively earns on only military, surely we can spend $300
million to try and help the environment.
As a society, it is imperative that we try to atone for our
sins; recycling food waste for compost knocks out two birds
with one stone. It repurposes all the wasted food we throw
away, and helps repair the destruction we’ve wrought upon
the atmosphere. Engineers also score a two-for-one here, as
food waste forces many critical discussions in the engineering
community, and now there’s a comprehensible solution.
“the unhappy neighbors of the composting plant successfully
campaigned to shut it down” because of complaints of
“nauseating odors” [5]. Aside from the fact that it was shut
down, the use of a composting plant in Delaware makes little
to no sense for New York City; this ties back into the potential
issue with transporting the organic materials causing too
many environmental problems of its own.
So, to be expected, the city’s efforts had a somewhat mixed
resolution; there were key successes, yet also fundamental
flaws.
IMPLEMENTATIONS OF FOOD WASTE IN
COMPOST
Finally, it appears there are three main challenges that
composting must overcome before it can truly begin to save
the nitrogen cycle.
One main point of debate is its true cost effectiveness;
sources on either side of the argument exclaim that
composting is either more or less expensive than landfills.
Since it obviously can’t be both, professionals need to
examine the costs and benefits, and determine a sound
financial result on composting before everyone is convinced
of its use.
Another challenge comes from ensuring that composting
is more environmentally friendly than alternatives. To ensure
that composting remains eco-friendly, governments must use
local plants so materials need not travel too far.
The last, and as far as I can find, the apparent toughest
challenge to overcome, is the smell. We’re shooting down this
potential solution to one of the environment’s largest
problems because delicate human noses can’t take the smell.
The real challenge here is, as Rodriguez said, to educate
people, and make composting be seen as a necessity, not an
alternative, or a way to make a quick buck. Tierny captures
David P. Steiner epitomizing this problematic way of
thinking, recording “Trying to turn garbage into gold costs a
lot more than expected. We need to ask ourselves. What are
we trying to accomplish here?” [5]. However, when we
capture biogas from sewage treatment plants, nobody
criticizes that as trying to turn fecal matter into gold, even
though sewage is just as smelly as compost. Why? Because
cleaning our sewage defines a healthy, civilized society, and
so should composting. If we can tolerate sewage, surely we
can tolerate compost as well. It’s about time that in addition
to our carbon footprint, we begin worrying about our nitrogen
noseprint as well.
FINAL THOUGHTS
A few years ago, New York City tried to follow in San
Franciso’s footsteps and impose a so-called “zero waste”
policy. This translates to the introduction of food waste
recycling, and New York City itself set an amazing example.
Successes
New York’s plan essentially accomplished all it set out to
do. The city reduced its landfill food waste by about 10%,
sending 100,000 tons of food scraps for compost in the first
year, a number which only rose and continues to rise.
Obviously due to the success the city has had, the public
obliged, and went along with the plan. In fact, many citizens
had been composting on their own before the local
government announced its plan. The city also acquired
revenue from the process, which, as mentioned before, offsets
the net cost to a net profit instead. The mayor’s plan worked
perfectly.
What’s more, public schools in the surrounding area
caught on, and added their food waste to the compost pile.
Baker notes that “children are still as picky and wasteful as
ever, but at least now there’s a happier ending – that bananafilled bin is a composting container, part of growing effort to
shrink the amount of perfectly good food being hauled to
landfills every year” [8]. With so many schools adding to the
compost heap, which has already been shown to be a good,
effective solution, New York has been basking in the glory of
many jobs well done.
Failures
However, after a few years of the program, New York ran
into one major obstacle. One of the main composting plants
the city used was based in Delaware, and, according to Tierny,
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Tristan Witek
http://www.governing.com/topics/energy-env/gov-curbsidecomposting-added-to-major-city.html
SOURCES
ADDITIONAL SOURCES
[1] S. Carpenter et al. “Human Alterations of the Global
Nitrogen Cycle: Causes and Consequences.” Issues in
Ecology.
11.1.1997.
Accessed
10.28.2016.
http://www.esa.org/esa/documents/2013/03/issues-inecology-issue-1.pdf
[2] S. Fields. “Global Nitrogen: Cycling Out of Control.”
Environmental Health Perspectives. 7.2004. Accessed
10.28.2016.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1247398/
[3] B. Howard. “How Cities Compost Mountains of Food
Waste.” National Geographic. 7.18.2013. Accessed
10.28.2016.
http://news.nationalgeographic.com/news/2013/06/130618food-waste-composting-nyc-san-francisco/
[4] S. Strom. “Recycling the Leftovers.” New York Times.
5.16.2014.
Accessed
10.28.2016.
http://www.nytimes.com/2014/05/17/business/cities-andcompanies-tackle-the-food-waste-problem.html?_r=0
[5] J. Tierny. “The Reign of Recycling.” New York Times.
10.3.2015.
Accessed
10.28.2016.
http://www.nytimes.com/2015/10/04/opinion/sunday/thereign-ofrecycling.html?rref=collection%2Ftimestopic%2FCompost
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am&module=stream_unit&version=latest&contentPlacemen
t=2&pgtype=collection&_r=0
[6] National Academy of Engineering. “Manage the Nitrogen
Cycle.” Grand Challenges for Engineers. Accessed
10.28.2016.
http://www.engineeringchallenges.org/9132.aspx
[7] K. Hall et al. “The Progressive Increase of Food Waste in
America and its Environmental Impact.” PLoS One.
11.25.2009.
Accessed
10.28.2016.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2775916/
[8] A. Baker. “At School, Turning Perfectly Good Food into
Perfectly Good Compost.” New York Times. 6.22.2014.
Accessed
10.28.2016.
http://www.nytimes.com/2014/06/23/nyregion/at-new-yorkcity-schools-turning-good-food-into-perfectly-goodcompost.html?rref=collection%2Ftimestopic%2FCompost&
action=click&contentCollection=timestopics&region=strea
m&module=stream_unit&version=latest&contentPlacement
=10&pgtype=collection
[9] E. Daigneau. “Curbside Composting Added to a Major
City: Is it Yours?” Governing. 2.2012. Accessed 10.28.2016.
“Compost.”
Accessed
10.28.2016.
http://www.madehow.com/Volume-5/Compost.html
“List of United States cities by population.” Wikipedia.
Accessed
10.28.2016
https://simple.wikipedia.org/wiki/List_of_United_States_citi
es_by_population
B. Thomas. “The Nitrogen Cycle.” 2.25.2000. Accessed
10.28.2016.
https://www.cas.miamioh.edu/mbiws/biogeochemicalcycles/nitrogen/nitrogen.htm
ACKNOWLEDGEMENTS
I would like to thank Trevor Lingle for imparting his
formatting knowledge once again, and for his supplemental
information on the subject matter. I would also like to thank
Shohini Banerjee for assisting me in cultivating the idea for
this paper before the research even started. As always, I must
thank Claude Debussy for the music which keeps me busy at
work. Finally, I would like to thank Tim Miller, the man who
hired me in his kitchen and sparked my interest in food waste
in the first place, sending my brain on a scavenger hunt to look
for solutions.
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