Earth Tub proposal 2.0 - here

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The Future of Composting at K
“Campus Compost System Design” ENVS-398 Independent Study
Samantha Jolly (K’15)
Alicia Pettys (K’13)
Advised by Dr. Binney Girdler
Abstract
This document outlines the “Campus Compost System Design” independent study course’s proposed
solution to Kalamazoo College’s need for a composting system to divert cafeteria food waste from the
landfill in order to reduce waste, methane emissions, and tipping fees. Based on research about
composting at other small liberal arts colleges, potential compost models, and a cost-benefit analysis, we
propose the purchase of two Earth Tub systems and a food pulper to reduce the volume of the food
waste. The Earth Tub is a fully enclosed composting vessel featuring power mixing, compost aeration,
and biofiltration. Also included in this proposal are recommendations for the Earth Tubs’ location on
campus, labor models, and operational work flow.
Table of Contents
Page
A Guide to Reading this Document.......................................1
Executive Summary..............................................................2
Introduction...........................................................................3
-Problem definition
-Purpose
Compost Methods Research.................................................5
-Method comparison conclusions
Earth Tub Composting System at K.......................................9
-Overview
-Location
-Composting process
-Labor
-Labor flow
Cost Benefit Analysis............................................................14
-Start-up costs
-Annual operational costs
-Cost reductions
-Return on Investment
Conclusion............................................................................18
-Acknowledgements
Bibliography………...............................................................20
A Guide to Reading this Document
Proposals like this can be difficult reading to tackle. Sometimes the important facts and sections are clear
to the authors, but less clear to their audience. To make this more useful for everyone, here’s a quick
guide to what’s in here and where to find it.
The proposal has five main sections:
Section 1: Overview of the ‘problem’
Section 2: Research on compost methods
Section 3: Implementing Earth Tubs at K
Section 4: Cost-benefit analysis
Section 5: Conclusion
So if you’re looking for:
● A description of what we think composting at K could/should look like  Section 3
● What this program would cost  Section 4
● Proof that we actually know what we’re talking about  Section 2
● Justification that composting is necessary  Section 1
1
Executive Summary
Kalamazoo College currently produces an average of 3.44 yd³ of food waste per week; extrapolated out
for the 31 weeks that school is in session, this would create an approximate annual total of 136,422 lbs or
68.2 tons. From 2010 to early 2013, the College diverted this food waste from the landfill by transporting
all pre- and post-consumer cafeteria food waste to Lake Village Homestead Farm. However, the program
was ended in March 2013 due to lack of appropriate licensing with the Michigan Department of Natural
Resources.
Since then, all College cafeteria food waste is being sent to the landfill. This costs the College $1,642 in
tipping fees per year. Moreover, while the campus generates a significant amount of yard waste each
year, there is no long term plan to manage it. A comprehensive plan could successfully manage all the
College’s food and yard waste, offset current costs and assist in the reduction of the campus’ total solid
waste, which the College committed to in its American College and Universities Presidents Climate
Commitment (ACUPCC), which President Eileen Wilson-Oyelaran signed in 2007.
This document outlines the “Campus Compost System Design” independent study course’s proposed
solution to Kalamazoo College’s organic waste issues. After developing a problem definition and
describing the scope of our research and findings, we conduct a cost benefit analysis and suggest a
solution. While we will summarize our methods and findings in this report, our full research can also be
accessed online through the Kalamazoo College sustainability webpage.
Based on this research, our recommendation is that the College purchase two Earth Tub in-vessel
composting systems and a pulper to reduce food waste volume. This system was chosen because of its
technical simplicity, minimal labor requirements, minimal site and size requirements, and climatic factors.
Additionally, our cost-benefit analysis showed that the Earth Tubs have the cheapest start up costs, most
costs potentially offset, and thus best Return on Investment (ROI). The total sticker price for two Earth
Tubs and a pulper is $33,191- 38,191, with additional annual operational costs of $162 - $398 plus $600 $5,000 depending on the labor model chosen. Using the Earth Tubs also has the potential to reduce
current annual costs by $2,837. Thus the expected Return on Investment (ROI) of the system is 16.0 20.8 years.
2
Section I: Overview of the Issue
Introduction
Waste in landfills has been identified by the US Environmental Protection Agency (EPA) as the single
largest source of man-made methane released to the atmosphere in the United States. These landfill
methane emissions have severe implications because methane is a potent greenhouse gas 21 times
more effective at trapping heat in the atmosphere than carbon dioxide (CO2) (US EPA Region 9, 2011).
Landfills create methane gas because the waste is buried underground to seal it off and minimize
leachate. 1However, this means that the waste breaks down anaerobically (no oxygen) and with minimal
moisture—the conditions that cause it to emit methane gas (USCC, 2011). Moreover, densely populated
areas of the country are increasingly beginning to see their landfills fill up, creating new waste
management challenges and causing a growing number of states to consider organic or food waste bans
from the landfill (Hasek, 2012; Willard, 2013).
Fortunately, food and other organic wastes can be diverted from landfills and decomposed in ways that
do not emit methane— and with significant impact. Food waste was the second largest category of
municipal solid waste (MSW) sent to landfills in the United States in 2007, accounting for 18% of the
waste stream at over 30 million tons of food waste (US EPA Region 9, 2011). Just like recycling for paper
and plastics, food waste can also be diverted from the landfill and put to more productive uses through
composting.
Composting is different than landfill processes because the organic waste decomposes with sufficient
moisture and aeration, creating the conditions necessary for both aerobic and anaerobic bacteria to break
down the organic waste while creating little to no methane (USCC, 2011). Moreover, the nutrients found
in the final composted product make a great fertilizer. This presents the opportunity for a closed loop
system: the nutrients found in the food waste generated by an institution can be recycled into fertilizer for
plants growing on the same campus.
Currently, all Kalamazoo College cafeteria food waste is being sent to the landfill. Moreover, while the
campus generates a significant amount of yard waste each year, there is no long term plan to manage it.
A comprehensive plan could successfully manage all the College’s food and yard waste, offset current
costs and assist in the reduction of the campus’ total solid waste, which the College committed to in its
American College and Universities Presidents Climate Commitment (ACUPCC) in 2007.
Problem definition
Food Waste
Cafeteria food waste collection data from Winter Quarter 2013 shows the average total food waste
generated per week was 4,421 lbs or 3.44 yd³. Extrapolating this average out to the whole year (31
weeks school is in session), the College creates approximately 136,422 lbs (68 tons) or 115 yd³ of
cafeteria food waste a year. 2 Without the development of an alternative plan, this food waste will continue
1 In
this context, leachate is the run-off or seepage water that contains dissolved landfill solids and thus
significantly elevated concentrations of undesirable material.
2 We could not estimate for the full year including winter and summer breaks, because the amount of food
waste produced during those times is unknown. Food waste data from Winter Quarter 2013 was used to
create a weekly average which was multiplied by the 30 trimester weeks plus 1 combined week of finals
days.
3
to be sent to the landfill, costing the school $1,642 per year and creating methane gas-- one of the most
potent greenhouse gases.
Yard Waste
Moreover, the College has a significant amount of campus yard waste to manage. The campus generates
410 yd³ of leaves, light plant waste, wood chips, and stumps per year, which in previous years has either
been delivered to Western Michigan University (WMU), transported and dumped at the Lillian Anderson
Arboretum (the Arb/LAA), or taken to a private company. However, none of these are a permanent, long
term solution. The College can no longer transport to WMU because of the construction of new facilities
on their campus; transferring yard waste to the Arb has created stewardship issues such as invasive
species because the yard waste is simply dumped, not managed through a process like windrow
composting. Nonetheless, these piecemeal solutions have an associated annual cost to the College.
Purpose
To begin addressing these issues, the “Campus Compost System Design” independent study course
sought to find the most suitable method of managing the campus’ organic waste, considering not only the
amount of food and yard waste generated but also feasible program management structures, Kalamazoo
College’s particular annual cost savings, and sustainable funding sources for necessary equipment and
staffing.
4
Section 2: Research on Compost Methods
To determine the optimal food waste diversion method for Kalamazoo College, we began by studying
composting programs at other universities. These included all schools in the Great Lakes Collegiate
Association (GLCA), of which Kalamazoo is a part, and top-ranked schools in the 2013 Recyclemania
competition 3. Based on this research, we determined the full range of potential composting methods,
including windrows, Earth Tub/Earth Flow, Rocket Composter, pulper or dehydrator, vermicompost, or a
private company.
For each of these potential methods, we investigated factors such as initial and lifetime cost, acceptable
inputs, size and location, and feasible labor models and labor flows. Some models include the additional
use of a pulper: a garbage disposal-like machine designed that reduces the volume of food waste. These
pulpers are necessary for some models (as indicated) because reduction of food waste volume makes
the smaller capacity of these models feasible. Our full research can be accessed online in the Compost
Methods document and is summarized in Table 1 below.
Table 1. Compost Methods Evaluation
This chart summarizes our comparison of potential composting methods.
Method
3
Advantages
Disadvantages
Approximate Startup cost
Windrows
-Would make use of an
already heavily impacted area
(the Lillian Anderson
Arboretum stump dump)
-Effective in areas with
freezing winter temperatures
-No issues of finding space
-Regular turning and mixing
speeds up process
-Creates compost usable as
fertilizer
-Manages yard waste
-A site manager would have to
be employed to manage area
-Waste would be transported
to Arb-12 miles round trip
-Front end loader or windrow
turner necessary
-Very easy to mismanage
-labor and time intensive
creation of site
≈$70,000 + paid
employee to manage
the sight year round
2 Earth Tubs +
Pulper
-Most cost effective and
comprehensive system
-Minimal transportation
- Minimal labor: small time
commitment and can be
operated by one person
-Manages yard waste
-Creates compost usable as
fertilizer
-Time efficient (product is
processed in 2-3 weeks)
-Would need at least two
vessels, creating space/
location issues
$37,000
Earth Flow
(larger model of
Earth Tub)
-Minimal transportation and
labor cost
-Simple to manage
-Manages yard waste
-Larger size which creates
issues of location
-Double the initial cost
$60,000-$65,000
http://recyclemaniacs.org/scoreboard/current-results/competition-division
5
Dehydrator
-Minimal transportation
-Minimal labor: small time
commitment and can be
operated by one person
-Final product is soil
amendment that must be
composted with other
materials
-Cannot manage yard waste
$30,000
Rocket
Composter +
Pulper
-Minimal transportation
-Minimal labor: small time
commitment and can be
operated by one person
-Manages yard waste
-Creates compost usable as
fertilizer
-Time efficient: processed in
2-3 weeks
-Requires storage under cover
and a hard standing base
$65,000
Rocket
Composter
(larger model)
-Manages yard and food
waste
-Requires storage under cover
and a hard standing base
-Size: larger than Rocket
Composter needed w/ pulper,
creating issues of space
-Double the cost of the smaller
model with pulper
$101,100
Private Company
(food waste only)
-No need for space or
student/staff labor
-No educational component for
K students (i.e. no student
collaboration/ is not visible to
students)
-Does not solve yard waste
issue
-No eventual payback on
investment
$5,000/ year
Private Company
(food and yard
waste)
-Eradicates yard waste
dumping in Arboretum
-Cost prohibitive over time
-No eventual payback on
investment
-No educational component
$12,000/year
Vermicomposting
-No turning necessary
-Various models
accommodate space needs
-Cannot be sustained through
the winter because worms may
would die of hunger
$30,000-$40,000
Method Comparison Conclusions
Upon comparison of all of the models, it became clear that the purchasing two Earth Tubs and Pulper
was the best option for Kalamazoo College. Although there were other options that had smaller initial
costs, these methods were unsuitable for the College’s particular calendar, climate, or landlocked
location.
Windrows
Windrows involve high start up costs (including paving the entire area necessary, purchasing a
tractor/front end loader and windrow turner attachment), intensive labor requirements (full time staff
member) and the level of expertise needed to manage the windrows (climatic factors, appropriate
6
material mix, troubleshooting for dynamic chemical processes). Moreover, because the Arb is located on
the way out of town on West Main Rd, the cost for daily food waste and frequent yard waste
transportation would be substantial.
Earth Flow
The Earth Flow is essentially a larger version of the Earth Tub. Due to its high price without any different
benefits than two Earth Tubs, this option was deemed unfeasible.
Dehydrator
The dehydrator is not a composter. It is, however a machine capable of reducing waste by 1/9 th into a soil
amendment that can either be thrown away or composted further. While this option looks attractive due to
its low sticker price, it would not be the most cost effective in the long run. A dehydrator would not have a
Return on Investment because cost reductions that apply to other models, such as replacing some
fertilizers with compost, do not apply to the non-composting Rocket. Also, the final product of this
machine would either have to be thrown away, still contributing to the issues associated with dumping
landfills, or composted, which would necessitate the use of another composting method.4
Rocket Composter
We examined two possible models of the Rocket Composter that could be used on campus. The biggest
difference in these two models are their size. The smaller model could handle all of the cafeteria food
waste with the use of the pulper, and the larger model could handle all of the cafeteria food waste without
the use of the pulper. Either model is significantly more expensive than the two Earth Tubs + Pulper. The
Rocket Composter is also significantly larger than other systems, and requires a structure with a roof to
be built around it. This, in combination with the high price, led us to discount either Rocket Composter
system as a viable option for Kalamazoo College.
Private Company
Sending food waste to a private company has the advantage of ease. The only necessary labor would be
transport to the dumping site. However, the number of trips that would be needed to deal with the amount
of waste currently produced by K College would create high annual fees in labor and gas prices. These
fees, in addition to the dumping fees, make this option cost prohibitive in the long run. Not only are the
annual fees considerably high due to transport of waste, but they would also never be offset by cost
reductions created by other methods, such as such as supplementing fertilizer with compost and
eradicating food waste tipping fees. Using a private company also eliminates the presence of composting
on campus and the educational possibilities created by on campus composting systems.
Vermicomposting
Vermicomposting is a composting process that utilizes worms to create compost. Although this can be a
relatively inexpensive method for composting, it would not suit the needs of our school. The worms used
in composting require constant feeding or will die. The amount of food needed to feed the number of
worms that would be used to compost waste while schools is session would require much more food
than is created while school is not in session. Therefore, it would be impossible for Kalamazoo College to
successfully implement vermicomposting.
Based on this research, we propose that the Earth Tub in-vessel composting system is the best option for
Kalamazoo College. We believe this system is best suited for Kalamazoo College because of its technical
4
Although composting currently happens on a small scale in the Grove, this operation would not be large
enough to handle the soil amendment produced by a dehydrator.
7
simplicity, minimal labor requirements, minimal site and size requirements, and climatic factors. Also, as
will be discussed later in this proposal, our cost-benefit analysis showed that the Earth Tubs have the
best Return on Investment (ROI).
8
Section 3: Earth Tub Composting System at K
Earth Tub Overview
The Earth Tub system is a fully enclosed composting vessel designed specifically for on-site composting
of food waste featuring power mixing, compost aeration, biofiltration of air, and leachate cycling back into
the compost. Inside the tub is a rotating auger, controlled by handles outside the vessel that can be
pushed to facilitate rotation. The vessel is also equipped with an aeration system to minimize odor,
maximize production, and stabilize the final result. The insulated container holds in heat generated by the
composting process to provide for all-season composting.5 The life span of the Earth Tubs is 15 to 20
years.
The Earth Tub composting vessel is 5.5 feet tall by 7.5 feet in diameter. It can take up to 100 lbs of food
waste per day, up to a three cubic yard capacity. 6 Kalamazoo College produces an average of 3.44 yd³
per week; however, food waste volume can be reduced by up to 85% by being run through a food pulper.
Post-pulping, this means the college would produce approximately 0.5 yd³ of food waste per week. This
food waste will require an equal amount of yard waste, creating 1 yd³ of organic material to be loaded into
the Earth Tubs each week. When factoring in the amount of yard waste needed to be mixed in with the
food waste, two Earth Tubs and a pulper will be sufficient to manage the College’s organic waste.
Figure 1. The Earth Tub
Figure 2. Pulper
Location
Paul Manstrom, Director of Facilities Management has offered two possible sites for the Earth Tubs,
shown below in Figure 3 and 4. Both locations are in the Facilities Management (Fac Man) parking lot on
the north side of the Fac Man offices. Figure 3 is the north side of Anderson Athletic Facility near the
boiler rooms. Figure 4 is directly to the north of the main entrance to the Facilities Management office
building, in the corner between the Fac Man office and garage. In both figures, the Earth Tubs are
expected to take up approximately the space of two parking spots.
5 http://compostingtechnology.com/wp-content/uploads/2012/10/ET_Quick_Operating_Guide.pdf
6 http://compostingtechnology.com/products/compost-systems/earth-tub/
9
Fig. 3- Parking on north side of Fac Man office
Fig. 4- Parking between Fac Man office and garage
Additionally, Paul Manstrom pointed out a strip of land behind a College rental property off West Main St
as the probable location for curing compost (compost must be cured for 20-40 days for further
stabilization).
Composting process7
To begin, the Earth Tub should be filled halfway with woody bulking material such as shavings or wood
chips. Organic materials such as food scraps, manure or yard waste are loaded through the large
hatchway in the cover. These wet organic materials are then covered with dry materials such as wood
chips, shavings, leaves or small weeds to prevent odors and insure that porosity and moisture levels are
ideal for composting. It is suggested that the ratio of food to yard waste is 1:1; yard waste should be half
wood chips and half leaves. Wood chips are an important input because their volume make a beneficial
bulking agent.
Food waste inputs
The system is designed to process kitchen prep waste and plate scrapings. Meats, cheese, and other
fatty foods should be kept below 25% of total waste input. Avoid adding large pieces of meat, fats or oils
to the system.
Time
Heat generated in the Earth Tub rapidly breaks down the food scraps. The volume reduction is typically
50% or higher. After 2-3 weeks of active composting, the discharge door can be opened and the compost
product removed. This time frame will function perfectly for the amount of food waste Kalamazoo College
generates, allowing us to create a 3 week rotation cycle between the tubs. By inserting 1 yd³ of material
(0.5 yd³ food waste + 0.5 yd³ yard waste) into the Tub each week, we will fill the 3 yd³ capacity after three
weeks. The second Earth Tub will then begin to be filled while the first Tub composts. The first Tub’s
material will be finished within 3 weeks, by the time the second Tub is full of material. We will then empty
the first tub, begin refilling it, let the second Earth Tub compost, and so forth. After removal, the compost
should be cured for 20-40 days for further stabilization at the curing location described above.
Labor
The Earth Tub requires 1-2 hours of maintenance labor per week, in addition to the labor needed for daily
transport and loading of food and yard waste into the Earth Tubs. Two revolutions of the rotating cover
7 http://compostingtechnology.com/wp-content/uploads/2012/10/ET_Quick_Operating_Guide.pdf
10
are required to mix the outside and center of the Earth Tub. To operate the Earth Tubs, the auger motor
is turned on before rotating the cover in order to shred and mix the new organic material into the active
compost. The auger will shred and mix a ton or more of compost in 10-15 minutes.
We have determined three potential staffing and organization models for the labor necessary to manage
the Earth Tub food and yard waste composting system.
●
Model 1: Compost Intern & Student Volunteers: This innovative model would allow student
volunteers from across the K College sustainability community to work on a “Compost Crew.”
This idea is based off volunteer student models from other colleges, including Oberlin College 8. In
this model, student organizations that are engaged with issues of sustainability such as Env Org,
Farms to K, DIRT, the Sustainability LLHU, and the Kalamazoo Outing Club will supply one
compost crew volunteer per quarter. We have met with some current and future leaders of these
organizations, who have agreed to build the position of compost volunteer into their organization.
Each volunteer will be required to attend a workshop at the beginning of each quarter where they
will learn how to fill and operate the Earth Tubs. This workshop will be led by the Compost Intern
(an already existing position), employed by Recycling, who will manage the scheduling and
overseeing of the volunteer crew. The greatest advantages of this model are 1) the education of
students on issues of waste management and sustainability, 2) a bringing together sustainability
minded groups on campus, and 3) cheaper labor costs. The downside is relying on volunteers,
though our goal in designing the model as we have was to build in greater accountability.
●
Model 2: Facilities Management: 15 - 20 hours per week, as one part-time position or spread
between a few staffers. The advantage of this option is utilizing reliable workers with regular
schedules who are already integrated into the Facilities Management department. The downside
is the higher cost of labor for these staff versus minimum wage student workers.
●
Model 3: Recycling Department student workers: 15 - 20 hours per week, divided up between a
few student workers in the Recycling Department. The benefit of this option is the cheaper labor
cost (minimum wage). The disadvantage is the unpredictability of students’ schedules which
could limit their reliability. However, the Recycling Department has successfully depended on
student workers for years, mitigating these potential downsides through clear communication and
accountability mechanisms.
All three models will involve coordination with Dining Services and Facilities Management, but these tasks
are not additional to their current responsibilities (ie moving food waste to dumpsters, chipping wood,
leaving yard waste for use in Earth Tub) and thus will not create additional labor costs.
Labor Flow
As was evident from our research on School’s Composting Best Practices, a successful compost program
will require coordination between multiple departments at Kalamazoo College. For Kalamazoo, we expect
this to involve Dining Services (Creative Dining), Facilities Management, the designated compost
workers, and students.
8
http://new.oberlin.edu/office/facilities-operations/recycle/compost-pilot-program.dot
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As seen in Figure 4, the composting process will begin with A) students sorting their post-consumer food
waste and B) Dining Services staff sorting pre-consumer food waste. We have seen successful examples
at other institutions of student volunteers providing intensive training for their fellow students about how to
correctly sort their compostable and non-compostable food waste during the first few weeks of the year.
We are confident that education of this nature would prepare students to sort their food waste
correctly.This sorting would take place in the same location as with the previous composting program-directly outside the dish return into large rolling bins (64-gallon toters).
Dining Services would then responsible for putting students’ sorted food and their pre-consumer waste
into the pulper. Post-pulping, Dining Services would move the compost-ready food waste in the 64-gallon
toters from within Hicks to outside on the loading dock. This is the first two arrows of the process seen in
Figure 5.
Figure 5. This figure is an illustration of the labor flow involved with filling the Earth Tubs.
From the loading dock area, the compost workers will transport the food waste to the Earth Tubs, load the
Tubs with the appropriate food-to-woodchips ration, and rotate the lid with auger for aerating. Facilities
Management staff will bring the yard waste (wood chips post-chipping) to the Earth Tub location when
appropriate for storage. These steps are shown in the final two arrows of Figure 5.
Once the decomposition process is complete after about three weeks, compost workers will remove the
finished product from the Earth Tubs and transport it to the curing location for stabilization over the next
20 - 40 days, as seen in Figure 6. During the curing process, compost workers will turn the compost pile
for continued aeration. Finally, the finished compost can be added as fertilizer to new plantings! When the
program is operational, we suggest that the finished compost be sent off for nutrient testing through a
program such as Michigan State University’s Soil and Plant Nutrient Laboratory in order to confirm the
nutrients and nutrient levels present in finished compost before application as fertilizer.
12
Figure 6. This figure is an illustration of the labor flow involved with the removal and transport of finished
compost to an external curing site and its eventual use as fertilizer.
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Section 4: Cost-Benefit Analysis
Conducting the cost-benefit analysis confirmed our developing hypothesis that the 2 Earth Tubs + pulper
is the most appropriate system for Kalamazoo College. To calculate the Return on Investment (ROI), we
determined start up costs, annual costs, and annual cost reductions for each model as seen in Table 2, 3,
and 4 and the Fees document.
While the calculations below focus on the 2 Earth Tubs + pulper, it is important to note that our costbenefit analysis was not solely Earth Tub focused. From the outset, it was clear that at $33,191-38,191
sticker price and minimal annual labor costs, the 2 Earth Tubs and pulper was the least expensive option.
However, we still examined whether other methods could be cost competitive by achieving more annual
cost reductions than the Earth Tubs + pulper. After generating a comprehensive list of potential cost
reductions and knowing the specifications of each method, we were able to clearly see that, of all the
models, the Earth Tub system achieves the greatest annual cost reduction. This is because the Earth Tub
system: A) manages all the College’s food waste (offsetting all tipping fees) B) utilizes yard waste and C)
creates usable compost (offsetting a portion of current fertilizer costs).
Start Up Costs
The start up costs are any costs associated with one time purchases. These include two Earth Tubs, a
pulper, installation, 2 Positive Aeration Systems and 2 Earth Tub on-Floor Heating Systems. The pulper,
as mentioned earlier, is needed to reduce the volume of cafeteria food waste in order to fit the volume
constraints of the two Earth Tubs. T
he 2 Positive Aeration Systems and 2 Earth Tub on-Floor Heating Systems are optional add-ons that are
not included in the two Earth Tub package. However, due to the density of pulped food waste, Green
Mountain Technologies has very strongly suggested the use of the Positive Aeration Systems. They have
also suggested the on-Floor Heating Systems to prevent the potential of compost freezing during the
winter months. Since Green Mountain Technologies has strongly suggested these two add-ons for
effective composting , the associated prices have been included in the total cost.
Installation has a cost of $0, because the sites we have chosen for the Earth Tub require no preparation,
and there is no additional charge from Green Mountain Technologies for installation. The cost range of
the start-up price is due to the range of the price of the pulper. All start-up costs are listed below in Table
2.
Table 2. Start-Up Costs
One time purchases and costs associated with the Earth Tub.
Expense
Cost
Two Earth Tub Package
$17,895
InSinkErator WX-300-6-WX-101 Waste Xpress
(Pulper)
$14,000-$19,000
Installation
$0
14
2 Positive Aeration Systems
$698
2 Earth Tub on-Floor Heating Systems
$598
Total Start-up Cost
$33, 191 - $38,191
Annual Operational Costs
Annual operational costs include any electricity, water, maintenance and labor expenses associated with
the continued use of the earth tubs. All costs are calculated using current pricing and are therefore
subject to change over time. The way in which we arrived at each cost is detailed below. A final list of
costs can be found in Table 3.
Electricity- Approximate electricity usage of the two Earth Tubs is presented in annual fees as a range.
The price will be dependent on whether or not the college chooses to purchase the positive aeration
systems and/or the on floor heating systems. The low end of the range represents the estimated energy
usage of the Earth tubs without these two add-ons, and the high end represents energy costs with both
add-ons. This annual range as provided by Green Mountain technologies is 1080 kWh - 2920 kWh per
year. This was then multiplied by the current costs of electricity, $0.128/kWh. The final estimate ranges
from $138-$374 per year.
Water- Costs are estimated to be $0. Although the pulper installed in the kitchen will use water, it will use
less water than the garbage disposals currently used in the kitchens. Pulpers are designed to recycle
water and will therefore cost less than using the garbage disposals, which use but do not recycle water.
Maintenance- The Earth Tubs are an extremely low maintenance composting system. Green Mountain
Technologies estimates that with proper care, the only maintenance that may be needed is the
replacement of burned out motor. Because this is not a normal occurrence, annual maintenance costs
have been calculated as the price of a motor ($365) divided out across each year of the the average
estimated lifespan of the Earth Tub (15 years).
Labor- Costs for each organizational model were calculated to estimate the annual cost of labor for each
individual model.
The cost of labor in Model 1 is the least expensive. Most all labor will be done by a set group of
volunteers, thus eliminating operating costs. This model does include the management of a compost
intern. However, due to the composting in the Grove, this position already exists and a new job would not
have to be created. The compost intern would assume some administrative duties associated with the
operation of the earth tubs, but this extra labor would most likely not exceed 2-3 hours a week. At a rate
of $7.75 an hour, this extra labor will total roughly $600 per year.
Labor in Model 2 would either split the 15-20 hours per week between a few Facilities Management
workers, or include those hours as a regular responsibility for one Facilities Management worker. Since
the hours per week would not change depending on the number of workers, the time has been multiplied
15
by the average Facilities Management wage of $13/hour 9 to provide a weekly cost of $195-$300. This
was then multiplied by the number of weeks in a school year to get an annual cost range of $6,045$9,300.
Labor Model 3 would involve a few recycling student workers splitting the 15-20 hours per week. This
range was multiplied by the recycling hourly wage, $7.75 to get a weekly cost of $116-$155. This was
then multiplied by the number of weeks per school year to get an annual cost range of $3,596-$4805.
Table 3. Annual Operational Costs
The costs listed in this table are the costs associated with running and maintaining of the Earth Tub
compost program. These costs, unlike start-up costs, will be present every year, and are subject to
change due to continually changing costs of electricity and worker wages..
Expense
Annual Cost
Electricity
$138-$374
Water
$0
Maintenance
$24
Subtotal
$162- $398
Labor
Model 1
$600
Model 2
$6,045-$9,300
Model 3
$3,596-$4805
Total Annual Cost
$762-$998
$6,207-$9,698
$3,758-$5,203
Annual Cost Reductions
In order to collect data on annual cost reductions, we first researched other composting cost benefit
analyses to formulate a list of potential reductions. These reductions include tipping fees and fertilizer
costs. All costs are calculated using current pricing and are therefore subject to change over time. The
rationale for these reductions are detailed below and then listed in Table 4.
Tipping fees- Tipping fees are solid waste disposal fees charged for the hauling and management of
waste. In order to determine the current price of Michigan tippings fees, invoices for the 2012-2013 school
year were provided by Facilities management and showed an average tipping fee of $14.28/yd 3. This was
then multiplied by the yearly quantity of food waste 10 to obtain the yearly cost of sending cafeteria food
waste to a landfill-$1,642 per year.
9
This wage average was provided by Victor Garcia, Grounds Manager.
Quantitative food waste data was estimated using records of an 8 week food inventory done by Rob
Townsend in Winter 2012.
10
16
Yard waste dumping was found to be a common cost reduction listed in other cost benefit analyses
studied. However, the amount of reduction in our campus’ yard waste was found to be negligible due to
the small amount that will be used in the Earth Tubs. While the majority of Kalamazoo College’s yard
waste is leaves, the Earth Tubs primarily use wood chips. Tthere is a possibility of composting leaves
during the summer (when less food waste is produced and the Tubs will have more free space for leaves)
but the cost savings can not be projected at this time.
Fertilizer- The college buys roughly $4,500 worth of organic fertilizer per year- $1,195 of which could be
provided by the Earth Tubs instead of purchased. 11
In total, the estimated cost reductions created by the implementation of the Earth Tubs sum $2,766 per
year. This is illustrated below in Table 4.
Table 4. Annual Cost Reductions
The costs listed in this table are money that would potentially be saved each year after the
implementation of the Earth Tub compost program.
Expense
Annual Cost Reduction
Food waste tipping fees
$1,642
Fertilizer
$1195
Total Annual Cost reduction
$2,837/yr
Return on Investment (ROI):
To calculate the Return on Investment, we subtracted the annual costs from the annual cost reductions to
find the net annual cost reduction. Based on the ranges of potential Earth Tub price (based on variation in
pulper prices) and net annual cost reduction, the expected ROI is 16.0 to 20.8 years as seen in Table 5.
Table 5. Return on Investment (ROI)
This table lists the costs used to calculate the final ROI. The ROI was found by dividing the Earth Tub
Start-up price by the Net Annual Cost Reduction.
Earth Tub Start-up Price:
$33,191 - $38,191
Annual Cost Reduction:
$2,837
Annual Costs:
Annual Labor:
Total:
$163 - $398
$600 (Model 1)
= $763 - $998/yr
Net Annual Cost Reduction:
$1,839 - $2,074
ROI:
16.0 - 20.8 years
11
This information was provieded by Victor Garcia, Grounds Manager
17
Section 5: Conclusion
Based on these considerations, our recommendation is that the College purchase two Earth Tub invessel composting systems and a pulper to reduce food waste volume. The total sticker price for this
system is $38,191, with additional annual operational costs of $162 - $398 plus $600 - $5,000 depending
on labor model. Using the Earth Tubs also has the potential to reduce current annual costs by $2,837.
Thus the expected Return on Investment (ROI) of the Earth Tubs and pulper is 16.0 - 20.8 years.
While this ROI is barely within the life of the system, pursuing the Earth Tub composting method is still the
right decision for the College. Earth Tubs are the most feasible solution to the College’s food and yard
waste issues because they require minimal space, labor, and maintenance. The reasons for the poor ROI
are largely due to the low cost of tipping fees in Michigan, which are considerably higher nationwide.
The tipping fee charged by the state of Michigan in 2011 was $0.21 cents for a ton of trash-- one of the
lowest in the country. The surrounding Great Lakes states all charge more expensive tipping fees than
Michigan: $0.50 in Indiana, $2.22 in Illinois, $4.75 in Ohio, $7.25 in Pennsylvania and $13 in Wisconsin.
These tipping fees are set by state governments and then factored into the tipping fee charged by private
waste management companies and landfills. Thus states with low state-set tipping fees generally pay less
in tipping fees and have less of an incentive to divert waste from the landfill.
This low rate has created issues for Michigan in the past; in 2008, more than 30% of the solid waste
dumped in Michigan landfills was from out of state. The largest source of imported waste was from
Canada with 62 percent of the total imported waste (Shin 2009). As a result, the state of Michigan has
already increased their tipping fees; Governor Snyder’s 2012 budget increased the state’s tipping fees to
$0.36 (WMEAC; Kurlyandchik 2013). Wisconsin made a similar move in 2006, increasing its tipping fees
from $3 per ton to the current $13 to address the same “flood” of imported waste and increase funding for
recycling programs (Lemoine and Lugas, 2006). If Michigan’s tipping fees were to be increased so that
they are more expensive and appropriately priced, this would completely change the Return on
Investment calculations for any composting system at Kalamazoo College, significantly reducing the
number of years in which the project would pay for itself. Thus we maintain that Earth Tubs are still a
prudent investment for the school and one that should be made.
One example of recent legislation that attempts to address tipping fees in a more proactive way was
recently passed in Massachusetts. The state of Massachusetts’ Department of Environmental Protection
(DEP) recently decided to ban commercial businesses from discarding food waste beginning in 2014
(Willard, 2013). Cities like Austin, Texas, are also beginning to organize compost pilot programs with
restaurants in order to achieve the same goal of diverting food waste from rapidly filling landfills (Price,
2013). While no legislation of this sort is yet on the horizon in Michigan, the trend could continue to grow
and make composting a necessity. Starting composting in the near future would allow Kalamazoo College
to continue becoming a leader in sustainability— developing an innovative, student staffed compost
program that can be both the result of and fuel for student experiential learning.
18
Acknowledgements
The research presented in this proposal would not have been possible without the consultation and
support of the following staff and faculty: Victor Garcia-Grounds Manager, Dr. Binney Girdler-Associate
Professor of Biology, Ross Greedy-Assistant Director of the Lillian Anderson Arboretum, Paul ManstromDirector of Facilities Management, Susan Matheson-General Manager for Sodexo, Jim Prince-Vice
President of Finance, Rob Townsend-Director of Recycling, and Paul Sotherland- Associate Provost for
Teaching, Learning and Assessment,
19
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