Waste just another resource a case for waste wood

International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 6, Issue 3, March (2015), pp. 25-33© IAEME
25
WASTE JUST ANOTHER RESOURCE: A CASE FOR
WASTE WOOD
David Goodman
Engineering Technology Department,
Indiana University-Purdue University Indianapolis (IUPUI),
Indianapolis, U.S.A.
Arash Edalatnoor
Mechanical Engineering Department,
Indiana University-Purdue University Indianapolis (IUPUI), Indianapolis, U.S.A.
ABSTRACT
Companies around the world are looking for ways to save money. Industries implement more
efficient lighting, HVAC, and automation systems into their processes to save energy, but industries
are also looking for methods to produce energy as a byproduct in their processes. One way industries
can produce energy is by installing waste wood recovery systems to repurpose waste process
resources. This article focuses on implementing wood heating systems at multiple facility buildings
on their campus. Considering cost and energy savings calculations, this case study will determine
equipment payback time without incentives. The remainder of this article will introduce waste wood
and how it can be applied to the location. Analysis of data will be provided through calculations. The
calculations and analysis lead to the recommendation and its corresponding payback period and
provide a framework for future wood building/district heating feasibility studies.
Keywords: Waste, Energy, Wood, Biomass, Energy Efficiency, Resource, District Heating.
I. INTRODUCTION
Modern life affords us a wide variety of energy sources, but few, if any, of these sources
guarantee lifetime availability.The resources we use today, such as natural gas, coal, and
petroleum,will someday be depleted, and so scientists are searching for new ways of producing
INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND
TECHNOLOGY (IJMET)
ISSN 0976 – 6340 (Print)
ISSN 0976 – 6359 (Online)
Volume 6, Issue 3, March (2015), pp. 25-33
© IAEME: www.iaeme.com/IJMET.asp
Journal Impact Factor (2015): 8.8293 (Calculated by GISI)
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IJMET
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energy. One method that has potential is the use of waste wood, which can be used asan alternative
to natural gas in many cases. This study will examine the use of waste woodas an alternative to
natural gas in a recreational vehicle manufacturing application.This research was conducted at
afacilityin Middlebury, Indiana. In the past, the facility’s management has implemented several
successful waste reduction and recycling procedures, butthey desired outside assistance for a waste
wood system feasibility study. This investigation began with the delimitation of the existing types of
waste woods generated, and the energy content of theseparticularwaste woods was determined. The
data was collected, and the amount of energy the waste wood would need to generatewas calculated
forthe facility, followed by a discussion of implementation procedures and payback periods for the
project.
II. METHODS
During the initial site visit,the proposed project building was visited andnecessary data, such
as information about the layout, boilers, and heating systems, was collected, all of which were
augmented by data provided by plantpersonnel.The data includedinformation such as utility usage,
boiler nameplate information, plant drawings, wood types, and percentages of waste. Calculations
and analysis were done based on procedures outlined in the books listed in the reference section
[2,4,6,17].Analysiswas verified with eQuest simulation software which was used to develop
specifications for systems from various vendors [7]. The resulting equipment quotes were then
analyzed for payback period based on two types of operations: waste wood heat to
supplementnatural gas (NG) usage during normal operating hours and waste wood heat to replace
NG completely [1,8,9,11,12,13].
III. DATA AND RESULTS
District Heating – Total NG Energy Calculations
Calculations were made to determine if the waste wood energy could replace the current
natural gas demand. The current demand based on the utility bill for the past two years indicates an
annual usage of approximately 400,000 Therm. A conservative estimate of the energy content of the
on-site waste wood is 500,000 Therm, which when considering boiler efficiency, piping losses, etc.,
would not be sufficient. However, with the addition of the nearby waste hardwood which contains
750,000 Therm, it is sufficient for all heating needs and some cooling or electricity needs.
Building Heating Loads
The heating loads for the selected buildings in Table 1 were calculated based on NG usage
data provided by the facility, field data collected during the visit, and building energy simulations.
Four methods were used to calculate the heating load and to size proposed wood-fired systems; all
are based on the average amount of NG used to heat the proposed project building per actual usage
data.

27
Table 1. Energy Usage
Bldg# kWh / Month
Therm /
Month
Therm /
Year Btu / Hr (op)
Btu / Hr
(wd)
4 5,255 144 1,728 115,200 34,286
5 31,167 856 10,272 684,800 203,810
7 62,481 1,716 20,592 1,372,800 408,571
8 48,636 1,336 16,032 1,068,800 318,095
10 10,829 297 3,564 237,600 70,714
12 11,739 322 3,864 257,600 76,667
13 16,292 447 5,364 357,600 106,429
15 92,175 2,532 30,384 2,025,600 602,857
16 55,692 1,530 18,360 1,224,000 364,286
1 38,583 1,059 12,708 847,200 252,143
The first method is based on the amount of boiler capacity needed to heat the proposed
project building only during operating hours, shown in the ‘Btu/hr (op)’ column of Table 1. The
second is based on the amount of boiler capacity needed to heat the proposed project building during
the whole day on average, shown in the ‘Btu/hr (wd)’ column of Table 1. Not shown in Table 1 are
two calculations based on peak demand per month, the eQuest simulation, and the actual utility bill
peak, shown in Figure 1, which revealed a necessary capacity of 459,000 Btu/hr and 587,000 Btu/hr,
respectively. However, due to factors listed later in this paper, the wood boilers were quoted at 1
MMBtu/hr.
IV. WOOD ENERGY ANALYSIS
The amount of energy that can be extracted from wood varies primarily with wood density,
moisture content, and wood dimension. The types of waste wood shown in Table 2 contain various
wood species, such as poplar, pine, and oak, which have different wood densities, as well as
adhesives with unknown heating values. The energy content range in Table 2 was developed based
on the typical woods used in the waste wood products [14,15].
Moisture content will vary with humidity levels, but typical lumber products have a moisture
content of around 20% +/- 10% [10,14,15]. Energy content is reduced as the moisture content
increases, but extremely dry wood will have higher ash and particulate counts. Homogenizing the
on-site and kiln dried wood will tend to increase overall energy content and reduce emissions.

28
Table 2. Waste Wood Characteristics
Chipped/Shredded
Wood
Wood Type
Mass by
%
Mass by
Ton
Energy Content
Range
Volume
(m³)
Volume
(ft³)
countertop 5/8" 10% 500
9-17 MMBtu/ton
based on 20%
moisture and wood
density [10,14,15]
772 27,250
fiberboard 20% 1000 1,544 54,501
plywood 10% 500 772 27,250
paneling 20% 1000 1,544 54,501
wrapped stiles 20% 1000 1,544 54,501
dimensional wood 10% 500 772 27,250
skids/ large dim.
Lumber 10% 500 772 27,250
Total: 100% 5000 10 MMBtu/ton 7,718 272,505
Wood Type
Mass by
%
Mass by
Ton
Energy Content
Range
Volume
(m³)
Volume
(ft³)
Kiln dried Harwood 100% 5000 15 MMBtu/ton 7717.5 272504.925
The third factor, wood dimension, affects energy content due to surface area, which is
directly proportional to the ease of combustion. Most industrial wood systems require wood to be at
or below a ½-inch cube and prefer a chip or pellet. Based on the wood density, moisture content, and
wood dimension, a conservative 10 MMBtu/ton rating was used for the on-site wood, and 15
MMBtu/ton was used for the kiln wood in various calculations to determine wood system size.
Figure 1 shows the NG usage over the past two years and reveals an approximate seven
month cycle for the heating season. For a district heating system this would help to determine the
amount of wood that would need to be stored during the summer for later use. (Also see volume
calculations in Table 2.) However, the amount of wood required for the pilot building is less than 2
tons/day during peak demand, which is well under the average daily waste wood generation rate.
Figure 1. NG Usage

29
Wood Furnace/Boiler Equipment
Two types of waste wood systems exist: a wood furnace burns wood and heats air (a forced
air system), while a wood boiler burns wood to heat water (a hydronic system). Two air systems are
shown on the left of Figure 2 and two hydronic systems are on the right. Cost estimates for both
systems were provided, but the hydronic system is preferred in industrial settings because it can
carry more energy with a smaller unit and would not require a duct system to be installed in the
proposed project building. The system shown in the upper left side of Figure 2 was proposed by
Onix, the BCS system is on the lower left, the New Horizon system on the upper right, and the Ran
system on the lower right.
Figure 2. Wood Systems
A typical wood system will consist of the following components: wood chipper, wood
storage tank, feeder system, heater (furnace/boiler), and stack. The wood chipper is required, by all
except the BCS system, to reduce the size of the wood to approximately a ½-inch cube to enable
temperature-controlled, automatic feeding [1]. Smaller chips are generally better; they have more
surface area for better burning, and they reduce clogging in the feeder mechanism. With the wood
storage tank there are three size levels to consider: a small system will store approximately four
hours of wood at peak load, while a medium system will store one or two weeks’ worth of wood for
extended plant shutdown periods and a large system will store all off-season waste wood. Ideally,
each building would have a small storage system with the boiler indoors, a medium storage system
outdoors feeding into the small system, and a centralized large storage system near the
chipper/shredder.
The feeder system transfers wood from storage through a hopper grate and auger on route to
the furnace/boiler. The feeder is controlled by a variable frequency drive connected to a PLC control
system to provide the proper amount of wood based on desired temperature. The furnace/boiler then
combusts the wood and, via an internal heat exchanger, transfers the heat to air/liquid for distribution
by blower/pump. Combustion occurs at relatively high temperatures—above 1,000 °F—to improve
combustion efficiency and reduce or eliminate undesirable exhaust components. The exhaust gas is
routed up the stack. The stack height is important in determining how the exhaust mixes with the

30
ambient air, as well as local air quality. The higher the stack, the longer the mix time will be and the
less likely it is that local air quality will be affected. However, if the stack is too high there may be
back pressure issues and more particle build-up in the stack. IDEM does not regulate stack height or
wood combustion exhaust components. However, three of the four quotes recommend a stack height
of 20 to 25 feet. Given the pilot project location next to a raised highway, the higher stack height
value is recommended to reduce negative visibility issues on the roadway.
V. EQUATIONS AND ASSUMPTIONS
The amount of energy that soft wood can produce can be calculated by the amount of
available wood, measured in tons/yr, multiplied by the unit of energy in Btu/ton that the soft wood
can provide, as shown in Formula 1.The same equation would be used for hard wood.
ܳ = ܹ‫݀݋݋‬ௌ௢௙௧ & ு௔௥ௗ × ‫ݕ݃ݎ݁݊ܧ‬ (1)
For the saving calculations,we can use Formula 2, where the transportation savings are added to the
NG savings.
ܵܽ‫ݏ݃݊݅ݒ‬ = ܶ‫ݏ݃݊݅ݒܽܵ ݊݋݅ݐܽݐݎ݋݌ݏ݊ܽݎ‬ + ܰ‫ݏ݃݊݅ݒܽܵ ܩ‬
ܵܽ‫ݏ݃݊݅ݒ‬ =
$175,000
500,000 ܶℎ݁‫ݏ݉ݎ‬
× 18,360 ܶℎ݁‫ݏ݉ݎ‬ +
$0.9
ܶℎ݁‫ݏ݉ݎ‬
× 18,360 ܶℎ݁‫ݏ݉ݎ‬
ܵܽ‫ݏ݃݊݅ݒ‬ = $22,950 (2)
Savings on wood can be calculated by total cost of wood divided by the total Therms. At the
end it will be multiplied by amount of Therms that have been used. The summation of savings on
transportation and natural gas will be multiplied by UF or utilization factor. Utilization factor is the
ratio of time that system has been used over the total time that it could be in use. In this study
utilization factor has been assumed to be at 60% (This percentage is based on how long they use
their system and the data was collected on site) In order to estimate the peak demand for natural gas
usage first, the amount of energy should be determined in Btu for each year. Then the most amount
of energy that has been used in a month divided by the total amount of energy will give us the peak
percentage of usage in each year.
ܷ‫݁݃ܽݐ݊݁ܿݎ݁ܲ ݁݃ܽݏ‬ =
ா௡௘௥௚௬ಾ೚೙೟೓
ா௡௘௥௚௬ೊ೐ೌೝ
(3)
ܲ݁ܽ݇ ‫݀݊ܽ݉݁ܦ‬ =
ா௡௘௥௚௬×௎௦௔௚௘ ௉௘௥௖௘௡௧௔௚௘
஽௔௬௦×ு௢௨௥௦
(4)
Payback Analysis
After determining energy costs and annual energy, the next step would be to calculate the
equipment’s payback. The payback can be determined using Formula 5.
ܲܽ‫ܾ݇ܿܽݕ‬ =
்௢௧௔௟ ா௤௨௜௣௠௘௡௧ ஼௢௦௧
஺௡௡௨௔௟ ா௡௘௥௚௬ ௌ௔௩௜௡௚௦
(5)
The total cost of equipment has been provided in Table 3, and theannual energy savings have been
calculated for transportations and natural gas usage.

31
ܲܽ‫ܾ݇ܿܽݕ‬ =
$30,000
$22,950
ܲܽ‫ܾ݇ܿܽݕ‬ = 1.3 ‫ݏݎܽ݁ݕ‬
Table 3. Equipment Provided, Price, and Payback Comparison
Air Systems Water Systems Auxiliary
Onix Corp BCS
New
Horizon
Ranheat
Eng. RamGroup
Equipment
xChipper/Shredder
Storage Tank x *** x *
Fuel Feeder x x x
Auto Feed
System x x x
Heater x x
Boiler x x
Stack x 18'6" ** 26'
req. new air
duct req. new air duct
Quote Price $164,191 $83,600 $49,500 $140,000 $30,000
Quote Details
ON-04,
4MMBtu/hr
4 - 800kBtu/hr
heaters
Goliath -
300 Ran - 300
Extended Price $52,500 $140,000 $30,000
Payback Period
(yrs)
out of
contention out of contention 2.3 6.1 1.3
* one week storage
** - recommend, but do not provide a 49' stack (at
$60/ft = $3k)
*** - AFS comes with 4 hour storage hopper
The simple payback based only on equipment costs is shown in Table 3 along with the quotes
for thefour systems shown in figure 2 [18]. The systems for which each company provided quotes
were not identical, nor were the installation requirements, but some of these differences were
adjusted for in the extended price row.
Both air systems would require a major duct system installation (actual price not quoted),
which drove these alternatives out of contention.The most cost-effective system was the Goliath-300
from New Horizon Corporation. The base system with four hour storage, fuel auger, automatic PLC
control, and a boiler was $49,500. However, it did not come with a stack, which is estimated at
$3,000 and required a chipper/shredder for an additional $30,000. The total payback period for the
Goliath was 3.6 years for the equipment. Additional costs for installation were expected to be under
$10,000 since the system can be placed in the existing mechanical room in the proposed project
building. An outdoor, medium-sized storage silo with feeder into the indoor storage silo would be a
nice option for an estimated $25,000 but cost savings from reduced labor were not determined and
payback was not calculated for this option.

32
VI. CONSIDERATIONS
Due to the variability of wood energy content, concerns about moisture infiltration into
storage wood, and uncertainty about absolute peak day versus average peak day during peak month
of NG usage, the quoted wood systems were sized for 1 MMBtu/hr (hydronic) and 4 MMBtu/hr (air)
for the proposed project building, despite the calculations and building simulation data which would
have allowed them to be smaller. Thus, the systems quoted at the calculated values may be slightly
cheaper and have slightly better payback periods, but to mitigate the risk of ‘worst day’ low heating
capacity, we recommend the quoted systems. Additionally, there was concern about system size,
despite calculations based on actual NG usage and eQuest simulation, due to plant data that showed
an existing capacity of 1.9 MMBtu/hr of NG boilers. We suspect that not all of the listed NG boilers
were in fact hydronic systems. We noted several NG heaters (air systems) during the site visit which
required three or four times as many Btu’s to heat a space as a hydronic system would; thus, mixing
the ratings would produce a number higher than needed for a straight hydronic system. The type and
rating of the existing system should be verified before the proposed system is ordered.
The maintenance tasks for wood systems are not insignificant and include ash removal,
loading wood, chipping wood, auger jams, oil system, and chimney/boiler cleaning. Ash removal is
required weekly and can take from one to one and a half hours. Loading wood during peak season
requires approximately five minutes per hour, although with the proposed storage system it will
likely take fifteen minutes every three hours for a total of two hours per day. Chipping and
transporting wood for the proposed project building may require another two hours per day
depending on the location of the waste wood and the chipper/shredder.Improper chipping/shredding
randomly creates pieces too large for the storage hopper or auger, which will occasionally starve the
boiler and requires that the system be periodically monitored. Finally, the manufacturers recommend
periodic oiling and chimney cleaning; adding a few hours per year to the total effort, may require
additional equipment or professional assistance. It is very likely that most of the maintenance tasks
mentioned above will be absorbed into the existing processes, with chimney cleaning and on-site
wood hauling likely incurring more labor and/or new equipment or service costs.
A large chipper/shredder, that is capable of handling all on-site waste wood, was quoted for
$75,000. Calculations were not completed, but there are possible costs savings due to reduced waste
transportation costs for the volume of chipped versus un-chipped wood that may offset increased
labor. This option is the only portion of the system that could be reused if a district
heating/cooling/electricity system is developed in the future.
Exhaust Gas Analysis
Many potential air contaminants are common between natural gas boilers and wood-fired
boilers. These include such regulated contaminants as NOx, SOx, PM, CO, and the various VOCs
[5,8]. The main difference exists in the amount of particulate matter produced from combusting
wood products versus burning clean fuels such as natural gas. Another issue is the type of waste
woods being burned and any other materials (e.g., glues) that would be included with the burn.
Burning wood alone may only produce low levels of dioxins in the air, but additives could increase
these amounts substantially. Treated woods have the added concern of containing regulated toxic
metals such as arsenic and cadmium. Control techniques can be used to keep emission levels of
particulate within regulatory guidelines, including the electrostatic precipitator (ESP). Some of the
various regulated air contaminants that are common to both natural gas and wood-fired boilers
include formaldehyde, BTEX compounds, acrolein, and PAHs [5,8].
The levels of emissions of any contaminant of concern are dependent upon the system chosen
and the input material quality. Thus, as with any new implementation like this, the best course of
action is to have an analysis of the emissions conducted immediately after installation. Furthermore,

33
in order to add a new source, the air regulations set forth by IDEM would likely require this to be
done before the new system can be brought to full operation [8].
VII. CONCLUSIONS AND RECOMMENDATIONS
In conclusion, this report has quantified the potential for waste wood to completely offset NG
usage at the proposed project building and, with a district system, all of the facility buildings. If the
proposed system is installed, it is estimated that financial returns will payback the equipment costs in
3.6 years, without considering price escalations in waste shipping and natural gas.This company
should contact the local air quality manager todiscuss the project further and to ask about proposed
regulations, existing guidelines for wood boiler heating systems, and local stack height preferences.It
is also recommended that the company should verify the type (hydronic/air) and size of existing NG
boilers as a third check on the proposed wood hydronic heating system capacity.If the payback
period is considered reasonable, install the Goliath-300 system from New Horizon Corporation in the
mechanical room of the proposed project building as a pilot and learning opportunity on operating a
wood boiler system.We recommend contacting Ran Heat or Covanta about designing and quoting a
district heating-cooling-electricity system that would utilize all on-site wood, the nearby kiln dried
hardwood, and other sources, which should be brought into the project during the planning stage.
Bringing in the local government may also provide access to low interest bonds to fund the project.
REFERENCES
[1] Biomass Combustion Systems (BCS), Charlie Cary. Wood Forced Air Quote.
crcary@biomasscombustion.com
[2] Capehart B., et. al. 2012. Guide toEnergy Management, 7th
Edition. The Fairmont Press Inc.
[3] Carrier Corp. Absorption chillers and CHP systems. Ashley Hildebrandt. 317-821-3031.
[4] Cengul Y. and Boles, M. 1998. Thermodynamics: An Engineering Approach, 3rd Edition.
McGraw-Hill Inc.
[5] Environmental Protection Agency. Outdoor Wood Boilers. http://www.epa.gov/owhh/
[6] Granet, I.and Bluestein, M. 2000. Thermodynamics and Heat Power, 6th
Edition. Prentice
Hall Inc.
[7] Hirsch, James J. 2008. eQUEST Energy Simulation Software. http://www.doe2.com/equest/.
[8] Indian Department of Environmental Management (IDEM). Wood Boilers.
www.nirpc.org/oldnirpc/pdf/Woodburner.pdf
[9] New Horizon Corporation, Zenon Pawlinski. Wood Hydronic Quote.
newhorizoncorp@gmail.com
[10] Oak Ridge National Laboratories (ORNL). http://bioenergy.ornl.gov/
[11] Onix Corporation, Cliff Lupton. Wood Forced Air Quote. Clupton@theonixcorp.com
[12] Ram Group, Rob Martin. Wood Chipper/Shreadder Quote. ramgroup@gmail.com
[13] Ran Heat Engineering, Chris Franklin. Wood Hydronic Quote. chris@ranheat.com
[14] University of Alaska (UA).http://www.alaskawoodheating.com/
[15] University of Wisconsin (UW).http://www.uwsp.edu/wcee/keep/Mod1
[16] UTC Power Systems. Combined Heat Power systems. www.utcpower.com
[17] Turner, W. and Doty, S. 2006. Energy Management Handbook. The Fairmont Press Inc.
[18] Ahmed Khouya and Abdeslam Draoui, “Experimental and Theoretical Analysis of Heat And
Moisture Transfer During Convective Drying of Wood” International Journal of Advanced
Research in Engineering & Technology (IJARET), Volume 5, Issue 5, 2012, pp. 17 - 29,
ISSN Print: 0976-6480, ISSN Online: 0976-6499.

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