HomeMy WebLinkAboutBiomass Cross Road Medical Center Draft Final Prefeasibility 2023 Review
Preliminary Feasibility Assessment
of Advanced Wood Heating
Prepared for:
Cross Road Medical Center
Glennallen, AK
March 31, 2023
Assessment for Cross Road Medical Center 2
Authors
This report was prepared in partnership by DeerStone Consulting and VEIC. DeerStone is a 9-year-old energy consulting
firm based in Alaska with work across North America and beyond. VEIC is a mission driven non-profit organization
focused on developing and implementing market solutions to expand the use of energy efficiency and renewable
energy.
Acknowledgments
The authors would also like to thank the Cross Road Medical Center personnel who provided essential information and
guidance as part of this study.
Disclaimer
The views expressed and recommendations made in this report are those of the authors, consistent with the
commissioning of this work as an independent pre-feasibility study. The analysis is intended to provide a level of detail
necessary to make informed decisions on whether to pursue a project to install advanced wood heating equipment.
This study and its findings are not based on detailed design engineering.
Assessment for Cross Road Medical Center 3
Table of Contents
Table of Contents ....................................................................................................................................................... 3
Introduction .................................................................................................................................................................. 4
Current Heating System and Load ....................................................................................................................... 6
Conceptual System Configuration .................................................................................................................... 11
Economic Analysis ................................................................................................................................................... 18
Financing Options ................................................................................................................................................... 22
Conclusions & Next Steps .................................................................................................................................... 24
APPENDICES SECTION ........................................................................................................................................... 25
Assessment for Cross Road Medical Center 4
Introduction
Alaska has a long and successful history of heating with wood. While many Alaskans heat their homes with
traditional wood stoves, fully-automated systems fueled with woodchips and wood pellets have been
reliably heating larger commercial and institutional buildings in Alaska for the last twenty years. Today,
many commercial and institutional buildings are heated with cordwood, woodchips, and wood pellets
across Alaska.
The Cross Road Medical Center, in an effort to reduce their
dependency on fossil heating fuels, stabilize energy costs, and
support the local economy is exploring the opportunity to
install an advanced wood heating system to provide hot
water for space heating and potentially for domestic hot
water. The first step toward completing a successful
advanced wood heating project is to assess the project’s
technical, logistical, and economic feasibility.
DeerStone Consulting, in partnership with VEIC, and with
funding from the Alaska Energy Authority prepared this
preliminary feasibility assessments for the potential to
install an advanced wood heating system at the Cross
Road Medical Center located MP 186.5 on the Glenn
Highway.
This report is a pre-feasibility assessment specifically tailored to the
Cross Road Medical Center outlining whether an advanced wood
heating system makes economic sense from a practical perspective. This
assessment includes site-specific fuel savings projections for the resort based on historic fuel consumption
and provides decision-makers suggestions and recommendations on next steps.
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Advantages of Wood Heating
Advanced wood heating systems can reliably provide the space heating and domestic hot water
needs for buildings while providing the following benefits:
• Lower cost heating fuel compared to oil and propane,
• Slower rate of price escalation over time (wood fuel prices have historically escalated at a
slower rate than fossil fuel prices),
• Greater price stability over time (fossil fuel prices tend to swing dramatically and make
long term energy budgeting difficult),
• Support of local fuel supply can lead to increased economic opportunity in the region and
state by keeping energy dollars in the local economy and sustaining jobs in the forestry
and forest products industries,
• Increased demand for advanced wood heating helps create vital markets for low-grade
wood which improves the economic viability of sustainable forest management,
• Support of local economies can contribute to the overall fiscal health of the community
through additional purchases and jobs,
• Reduced environmental risks. Advanced wood heating systems can help mitigate
environmental risks by reducing the need for onsite fossil fuel storage. Failing
underground tanks can pose a threat to ground and surface waters. Aboveground tanks
can pose fire hazards as well as the risk of dislodging in the event of a flood,
• Reduced carbon footprint. Fossil fuel combustion takes carbon that was locked away
underground (as crude oil and gas) for millions of years and transfers it to the atmosphere
as CO2. When wood is burned, however, it releases carbon that was recently absorbed
from the atmosphere and mimics the natural cycling of carbon between forests and the
atmosphere. Consequently, the net effect of burning wood fuel is that little or no new CO2
is added to the atmosphere, as long as the wood is harvested from forests that are
sustainably managed.
Assessment for Cross Road Medical Center 6
Current Heating System and Load
Description of Existing Buildings and Heating Systems
The Cross Road Medical Center consists of a 17,000 square foot main clinic building and a separate
2,400 square foot Administration Building. The main clinic building was historically heated with a
combination of cordwood and coal boilers but is presently heated with two oil-fired boilers
located in a stand-alone boiler building near the main clinic building. The existing Weil McClain
oil-fired boilers cover the space heating loads and are estimated to have ~1,200,000 Btu/hour of
output capacity. The boilers are estimated to be ~15 years old and are well-maintained. Domestic
hot water is provided by the oil boilers and is stored in a tank in the boiler building.
The Medical Center’s hydronic heat distribution system utilizes a multi-zone network of hydronic
piping to deliver heat throughout the building. In-room thermostats are used to regulate the heat
delivery via an air handling system and baseboard wall-mounted box radiators. The air handling
system is also heated by the oil boilers and an upgrade for the air handling controls is planned
for 2023.
The Administration building is currently heated with a 1,140,000 Btu/hour Weil McClain oil-fired
boiler, and heat is distributed through a hydronic baseboard system. There is cross-over,
underground piping to the clinic, and the goal is to heat both the administration building and the
clinic from the proposed wood heating system.
The two Weil McClain oil-fired boilers that cover the space heating load are served via two 500-
gallon oil tanks or one 1000-gallon oil tank. The oil storage is located underground so the actual
equipment is unknown. The administration building is supplied with one 500-gallon
underground tank. All storage tanks are thought to be single-wall steel construction.
Assessment for Cross Road Medical Center 7
Figure 2 - The stand-alone boiler building and coal boiler connex
Figure 1 - Photo of existing oil-fired Weil McClain boiler #1
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Recent Heating Fuel Usage and Weather Data
Medical centers can generally have heating loads that vary widely depending on numerous
factors. Three years of heating oil fuel usage data, expenditure, and pricing were provided and
assessed – see Figure 3 below.
Figure 3 – Three years of heating oil use for Cross Road Medical Center main clinic and admin
buildings
Year Building Gallons Oil Used Annual
Expenditure
Average
$/gallon
2020 Main Clinic 3,981 $26,038 $6.54
Admin Building 380 $3,333 $8.75
2021 Main Clinic 1,161 $2,799 $2.46
Admin Building 10,937 $26,873 $2.41
2022 Main Clinic 9,175 $37,274 $4.06
Admin Building 222 716 $3.22
The heating fuel usage in this short timeframe varies widely – likely due to the past use of
cordwood and coal before these systems were discontinued and only heating oil was used to
provide full heating load coverage.
In addition to reviewing the heating fuel usage data provided, we examined daily temperature
and heating degree day (HDD) data as a supplemental way to estimate the amount of annual,
monthly, daily, and hourly thermal loads under anticipated in the future.
Heating Degree Days are simple unit of measure for heating requirements based on outside
temperature data. One heating degree day is any day where the average temperature for the day
is one degree cooler than the conceptual set point of 65 degrees Fahrenheit.1 For example, if the
average temperature outside for a particular day is 55F, then that counts as ten heating degree
days. All the heating degree days for each year are added up to get the annual heating degree
days. Generally, if one heating season has 20% more HDD, then a building will need 20% more
fuel to keep the building’s temperature at a given set-point. HDD can greatly vary from year to
year, illustrating the variability of weather—year to year- in predicting heat demands and potential
fuel savings in a fuel switching project. Considering several years of HHD data can help alleviate
this issue.
1 Another set-point may be chosen depending on building characteristics and internal heating load present.
Assessment for Cross Road Medical Center 9
Figure 4 - Distribution of Outdoor Air temperatures over the course of a heating season
The multi-year annual average HDD were 13,807 HDD in Gulkana, Alaska using 65 degrees
Fahrenheit as the set point.
Source: https://www.climate-zone.com/climate/united-states/alaska/gulkana/
Estimated Annual Heating Loads and Costs
Based on the historic heating oil use and weather data, the following table presents the estimated
annual fuel consumption and heating fuel price as a Business-as-Usual scenario that represents
the first year for what Cross Road Medical Center would pay if they chose to continue to heat
exclusively with heating oil.
Heating Season Gallons Oil Used Price per gallon Annual
Expenditure
2023/2024 Heating Season 12,100 $5.50 $66,550
For the subsequent analysis presented in this assessment, 12,100 gallons of oil at $5.50 per gallon
were used as the estimated heating load and the cost to provide that heat in absence of an
alternative heating source to cover the loads for both the main clinic and the administration
building.
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Figure 5 – Annual Spread of Thermal Demand
-
50
100
150
200
250
300
350
Monthly Heat Load (MMBtu)Monthly Thermal Energy Demand
DHW MMBtu Space Heating MMBtu
Assessment for Cross Road Medical Center 11
Conceptual System Configuration
Location
Based on site visit assessment and discussions with Cross Road Medical Center staff, the optimal
woodchip boiler plant location was determined to be where the existing Connex containing the
coal boiler system is.
Figure 6 – Cross Road Medical Center Campus Layout
Boiler Plant Layout
For this assessment, a single alternative wood heating scenario was developed – installing two
stagger-sized woodchip fueled boilers in a single new Connex container box to heat both the
Assessment for Cross Road Medical Center 12
main clinic and administration buildings. This scenario would also retain the existing Weil McClain
oil-fired boiler as space heating back-up and for use in summer months for Domestic Hot Water
(DHW). This configuration would use the wood chip boilers to carry a large majority of the annual
space heating demand and the domestic hot water in the winter months when the wood chips
boilers are already in use. In the summer and shoulder season, the oil boiler can provide the DHW
supply. If, over the time, heating demands increase due to greater occupancy or medical center
expansion, a third wood chip boiler could be added to cover the increased load.
Figure 7 – Illustrative configuration of two wood chips boilers placed in a single 40-foot Connex with outdoor wood chip fuel bins/feeding systems (image courtesy of Caluwe Inc.)
Connex Container with two Woodchips boilers
Two small woodchip fuel bins
feeding boilers inside connex
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Figure 8 - Example images from a recent woodchip boiler installed in a Connex in Mentasta, Alaska
Figure 9 - Outside view of the woodchip system in Mentasta, Alaska
Woodchip Fuel Storage Considerations
Woodchip fuel can be stored in several ways – for larger facilities below-grade bunkers are
common, but costly to construct. A simpler approach for a smaller project is to construct a small,
roof - covered bunker on-grade adjacent to the Connex with the two wood chip boilers. See figure
10 below for an illustration of this concept.
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Determining the amount of woodchip fuel storage is a balancing act between space limitations,
capital cost of the storage bins, and maximizing the onsite storage capacity to reduce the need
for frequent smaller volume deliveries. Since there will always be some fuel remaining in the bin
at the time of the next delivery, this sizing will maximize delivery efficiency. Based on the annual
heating fuel use of 129 tons of woodchips, we estimate that Cross Road Medical Center will need
34 tons of fuel storage to last 15 days under continuous “full load” heating conditions. Based on
this, we recommend installing 34 tons of fuel storage capacity. On volume basis, this equates to
111 cubic yards or 3,020 cubic feet. Assuming an average 6-foot depth for the pile of wood chip
fuel, a fuel bin measuring 40 feet in length and 12.5 feet in width would provide this amount of
fuel storage capacity.
Figure 10 – Simple, semi-enclosed woodchip fuel bin adjacent to Connex containing boilers
Assessment for Cross Road Medical Center 15
Figure 11 - Picture depicting the fuel storage bin floor and a side-view of a fuel bin schematic.
Fuel Sourcing and Onsite Processing Considerations
Glennallen is surrounded by hundreds of miles of continuous volatile black spruce, the primary
fire prone species. Within Glennallen’s boundaries are closed stands of spruce and aspen with
thick pockets of willow adding to fuel density. A spruce beetle infestation has left 20-30% of the
spruce dead standing and 12% dying. Root rot has left 30% of the aspen dead and falling, putting
the community in a critical situation. Recent warmer summers, drought, and longer fire seasons
have increased the risk of wildfire in Alaska and the region, and this trend is expected to continue.
The summer of 2019 experienced several nearby wildfires, evacuations, smoke-filled days, and air
quality/respiratory health warnings issued. To reduce risk from catastrophic wildland fire has
identified wildfire mitigation planning as a high priority.
In 2010, the State of Alaska completed a regional inventory analysis that focused on availability
of timber to support biomass heating projects. This inventory, Forest Resources on State Forest
Lands in the Copper River Basin, confirmed that the Copper River Basin has a significant wood
biomass resource. There are 219,550 acres of timberlands, and State of Alaska forested lands that
have a net volume of 2,497,118 tons of biomass. Across all species of wood, the average acre will
produce 11.37 tons of biomass. The sustainable yield for the region was estimated at 1,878 acres
per year and 21,231 tons per year. This exceeds the wood fuel requirements for all operational
and developmental biomass heating systems in the Copper River Basin and hence represents a
viable forestry resource for meeting Cross Road Medical Center’s heating needs with biomass fuel.
The Alaska Division of Forestry (DOF) has been willing to offer small timber sales to support the
fuel needs biomass projects. The DOF Glennallen office is conducting harvest of hazardous fuels
to reduce wildfire danger, including fire breaks around Glennallen. This wood would be the most
obvious supply for a wood chip boiler.
Harvesting and transporting biomass from the forest to the boiler is the most difficult part of
supporting any wood heating facility. This is the major challenge in the Copper Valley region. A
local Tribe is currently developing a wood chipping operation, but the system will not be
Assessment for Cross Road Medical Center 16
operational until late 2023 or early 2024. As Cross Road Medical Center is developing this potential
biomass project, an important priority is working with harvesters in the region to determine the
supply, availability, and cost of the delivered wood chips. Cross Road Medical Center staff has also
expressed interest in investigating the feasibility of their own wood harvest and processing
business. With the significant spending for wildfire mitigation and the development of biomass
projects in the region, there is a regional need for wood harvest and processing services.
Wood Boiler Sizing and Back-up Systems Considerations
Proper wood fueled boiler sizing is important. Advanced wood heating systems burn cleaner and
run more efficiently when operated above 30% of full load conditions and with fewer start up and
shut down cycles. Because oil, propane, and natural gas systems can be quickly fired up and shut
off, it is common practice to routinely oversize fossil fuel boilers to 200% of the actual peak
thermal load conditions. Wood heating systems should be sized to as close to (or in many cases
considerably less than) 100% of the actual peak heating demand as possible to provide maximum
replacement of fossil fuel use, while avoiding the drawbacks of operating an oversized system for
lengthy periods of time in an idled-down mode or too many on/off cycles.
Figure 12 - a graph showing the correlation between peak load sizing and portion of the annual load covered
As illustrated in the graph above, a boiler sized to 70% of the peak load, can carry over 95% of
the annual heat load.
Another way to provide the optimal boiler output capacity is to install two or more smaller wood
boilers in parallel, rather than one large one. This allows greater flexibility to meet fluctuating heat
Assessment for Cross Road Medical Center 17
loads with either one of the boilers or several working together. This also allows for back-up
redundancy, if one of the wood boilers needs maintenance.
Based on our analysis of the heating load and also factoring the existing oil boiler’s output
capacity and the space constraints for the two options, we recommend initially installing two wood
chip boilers – one with 75 kW (250,000 Btu/hour) and the second with 200kW (680,000 Btu/hour)
of output capacity. We estimate this will cover approximately 85% of the peak space heating load
and will cover 95% of the annual demand for heat.
Assessment for Cross Road Medical Center 18
Economic Analysis
Current Heating Fuel Cost Comparison
Below is a graph illustrating the apples-to-apples comparison of current heating fuel price for
heating oil and wood chips – the cost per million Btu of delivered heat. As the graph depicts, there
are considerable fuel cost savings between oil and wood chips. Wood chips at $145 per ton,
delivered, with 30% moisture content, have wood chip users paying ∼ $15 per million Btu.
Figure 13 – Current heating fuel price bar graph
Even if oil prices drop to $2.00 per gallon, wood chips at $145 per ton are a lower cost fuel.
Future Heating Fuel Costs
Forecasting future fuel costs is difficult and generally very inaccurate. We looked at historical
trends and examined other credible forecasts. Energy Information Administration (EIA) data
reviewed suggests that propane and oil prices will remain level in the next 12 months with
increases at a gradual rate for the next ten years. In comparison to the price increases seen in oil
and propane over the past decade, the EIA forecast could be too optimistic. If the historic price
increase data are extrapolated forward, this suggests that prices will increase at a rate 1.5% over
$53.14
$15.69
$0.00
$10.00
$20.00
$30.00
$40.00
$50.00
$60.00
Heating Oil Dry Woodchips
Cost per MMBtu for Delivered Heat
Assessment for Cross Road Medical Center 19
the rate of general inflation. Our analysis uses a rate of fossil fuel price escalation of 1.5% over
general inflation.
By contrast, local wood chip prices have seen only modest price increases in Alaska over the past
decade. For our analysis, and erring on the side of being conservative, we chose to escalate wood
chip prices at the rate of general inflation.
Capital Costs Estimates
One scenario was evaluated for this pre-feasibility study – installing two pellet boilers and keeping
the oil boiler as back-up and the direct fired hot water unit for summertime domestic hot water
production. Planning level estimates of the conceptual capital costs were based on a review of
recently completed comparable pellet heating projects and discussions with equipment vendors.
Figure 14 – Capital cost estimates for Cross Road Medical Center
Cost Category Estimated Costs
Wood Boiler(s) 0.86 MMBtu/hr of capacity $217,500
Stack, Breaching & PM emission controls $0
System Controls $0
Wood Fuel Storage Shed $25,000
Heat Distribution Network Piping (0 ft) $0
Interconnect to Boiler Room $8,000
Connex container $100,000
Mechanical work $15,000
Electrical work $15,000
Thermal Storage Tanks/Buffer System $0
Shipping to AK $25,000
Total capital $405,500
Contingency 20% $81,100.00
GC markup 0% $0
Design Fees 0% $0
Grand Total $486,600
It is important to note that the capital cost estimates provided above do not account for the costs
for future replacement of the fossil fuel boilers or any upgrades to the heating system controls that
may be necessary. These costs were not included because they are costs not specific to installing a
wood heating system and would likely occur in the near future whether or not a wood chip heating
system is installed.
Lifecycle Cost Analysis
Assessment for Cross Road Medical Center 20
A propriety life-cycle cost (LCC) analysis tool was used to assess the economic performance of an
investment in an advanced wood heating system. A wood chip heating system was compared
against the status quo option of continuing to heat the facility with fuel oil with the existing boiler.
A 30-year analysis period was used and the accumulative savings over heating with fuel oil were
presented in 2023 dollars.
Below are the assumptions used in estimating the cost to purchase, install, operate, fuel, and
maintain each heating system. See Appendix E for more details on the Lifecycle Cost Analysis.
Parameter Value used in
analysis
Annual Consumption of Heating Oil (gallons) 12,100
Per Gallon Year 1 Price of Heating Oil $5.50
Heating Oil price escalation rate over general inflation 1.00%
Percent of peak demand covered by woodchip system 90%
Percent of annual heating covered by woodchip system 95%
Annual amount of wood chips required (tons) 129
Year 1 price of wood chips (per ton) $175
Wood chip fuel price escalation rate At general inflation
Percent of capital cost covered by grant 80%
Percent of project cost financed 20%
Term of financing (years) 20
Interest rate 6.00%
Life Cycle Cost Analysis Results
Below are the economic performance results.
Economic performance indicator Result
First year fuel savings $42,136
Simple payback (years) 2
Annual debt service $8,367
30-year NPV Heating Oil heating $1,996,500
30-year NPV Bulk Woodchips heating $958,146
30-year NPV of Savings $1,038,354
In the first year, the woodchip heating system is expected to save Cross Road Medical Center over
$42,000 in annual expenses and take 2 years to pay off the net investment (capital cost less the
grants received). Over a thirty-year period, the project will save Cross Road Medical Center over
$1,000,000 in today’s dollar value.
Assessment for Cross Road Medical Center 21
The graph below illustrates the comparative cash flow of a “business as usual” scenario of continued fuel oil heating versus the combined costs (fuel, debt service, and O&M) for the wood
pellet heating scenario.
Even with O&M costs and the debt service on a loan added to the woodchip fuel cost, the
woodchip heating option is cash flow positive in the first year compared to the oil heating option
and the annual savings are expected to increase over time – especially in year 20 when the debt
service is completed.
$0
$20,000
$40,000
$60,000
$80,000
$100,000
$120,000
$140,000
$160,000
$180,000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
Year
Annual Cost Comparison
Heating Oil Dry Woodchips
Assessment for Cross Road Medical Center 22
Financing Options
Purchase and installation of a wood chip heating system represents a significant capital cost.
There are financial assistance programs that can offset some of those capital costs. Each of the
programs listed below have eligibility requirements and may or may not be available to the Cross
Road Medical Center depending on the program requirements. The LCCA analysis assumed that
80% of the capital cost would be covered by grants, but if additional incentives can be secured,
this would improve the economics of the project.
State incentives
Alaska
The State of Alaska Renewable Energy Fund (REF) provides benefits to Alaskans by reducing and
stabilizing the cost of energy through the development of renewable energy projects. This grant
program is designed to produce cost-effective renewable energy for heat and power to benefit
Alaskans statewide. The REF was established by the Alaska State Legislature in 2008, and in 2012
was extended 10 years to 2023.
The REF is managed by the Alaska Energy Authority in coordination with a nine-member REF
Advisory Committee. The program provides grant funding for the development of qualifying and
competitively selected renewable energy projects. Since its inception 271 REF grants have been
awarded and funded via legislative appropriations totaling $300 million. Over 100 operating
projects have been built with REF contributions, collectively saving more than 30 million gallons
of diesel each year.
More information is available at the Alaska Energy Website: https://www.akenergyauthority.org/What-We-Do/Grants-Loans/Renewable-Energy-Fund
Federal
U.S. Department of Interior – U.S. Forest Service
THE WOOD INNOVATIONS AND COMMUNITY ENERGY GRANT funding through the United
States Forest Service supports traditional wood utilization projects, expands wood energy
markets, and promotes using wood as a construction material in commercial buildings. These
grants and cooperative agreements support the nationwide challenge of disposing of hazardous
fuels and other wood residues from the National Forest System and other forest lands in a
manner that supports wood products and wood energy markets.
The Forest Service supports proposals that significantly stimulate or expand wood products and
wood energy markets that support the long-term management of National Forest System and
Assessment for Cross Road Medical Center 23
other forest lands. https://www.fs.usda.gov/science-technology/energy-forest-
products/wood-innovations-grants
U.S. Department of Agriculture REAP
The U.S. Department of Agriculture administers a small number of programs that provide
incentives for renewable energy. One USDA program that could be applied is REAP. The program
is very competitive for grants but does provide attractive fixed interest rates for financing.
Renewable energy grants range from a minimum of $2,500 and a maximum of $500,000.
Requirements:
• Applicants must provide at least 75 percent of the project cost if applying for a grant only.
• Applicants must provide at least 25 percent of the project cost if applying for loan.
• All projects must have technical merit and utilize commercially available technology.
• Energy efficiency projects require an energy audit or assessment.
Contact information for USDA RD REAP Program in Alaska:
Robert Chambers Director, Community Facilities & Water and Environmental Programs & Business
Programs
Office: (907) 761-7770 Cell: (907) 982-8641
robert.chambers@usda.gov
Assessment for Cross Road Medical Center 24
Conclusions & Next Steps
Assessment Findings
Results of the financial analysis show that the woodchip heating scenario would lower annual fuel
costs substantially and have a positive life-cycle savings over continued use of oil. Annual fuel cost
savings would be over $42,000 in the first year alone.
Our preliminary assessment suggests two wood chip boilers could be situated in a single 40-foot
Connex located where the existing coal system is. For this scenario, the medical center would have
a simple payback of 2 years and a positive cash flow in the first year of operation even taking debt
service into consideration.
Anticipated incentive from the State of Alaska or USFS was factored in the analysis, but Cross Road
Medical Center should pursue additional grant sources to further lower their portion of the project
costs.
In conclusion, the Cross Road Medical Center appears to be an excellent candidate for a wood chip boiler system.
Recommended Next Steps
If the Cross Road Medical Center is interested in pursuing a woodchip boiler system, we
recommend the following steps to further investigate the feasibility of a woodchip boiler heating
system:
1. Engage the Alaska Wood Energy Development Task Group to participate in a tour of
operating wood heating systems in Alaska and learn about other Alaska Specific
educational opportunities at biomass@seconference.org.
2. Contact a Woodchip Boiler Vendor to help refine the project concept and to obtain firm
local estimates on project costs and how best to serve the space heating and domestic
hot water loads with the woodchip boilers and oil systems. Another consideration is
whether thermal storage would be advantageous for the Cross Road Medical Center. Our
analysis did not include thermal storage, but it is important to note that modern woodchip
heating systems can operate more efficiently and effectively (improving cost savings) if
thermal storage is designed into the overall system. With thermal storage, a modern wood
heat boiler can quickly ramp up to high fire and will shut down when the thermal storage
has reached its optimum temperature, this type of system can supply a greater portion of
the annual heating load and will therefore provide greater savings. We recommend that
any woodchip boiler system that is specified for this project consider thermal storage as a
component of the overall design.
3. The facility manager should contact multiple woodchip fuel providers to get delivery quotes and identify the lowest cost fuel supplier.
Assessment for Cross Road Medical Center 25
APPENDICES SECTION
Assessment for Cross Road Medical Center 26
Appendix A - Operation and Maintenance Considerations
A woodchip boiler will take more time to maintain and operate than a traditional gas, oil, or electric
heating system. At the institutional or commercial scale, however, many of the maintenance
activities can be cost-effectively automated by installing off-the-shelf equipment such as soot
blowers or automatic ash removal systems. Some of the typical maintenance activities required
for woodchip systems are:
Weekly
• Emptying ash collection containers
• Monitoring control devices to check combustion temperature, stack temperature, fuel consumption, and boiler operation
• Checking boiler settings and alarms, such as those that alert to a problem with soot
buildup
Yearly
• Greasing augers, gear boxes, and other moving parts as recommended by the
manufacturer
• Checking for wear on conveyors, augers, motors, or gear boxes.
When considered on a weekly basis, the total time required for maintaining a fully automated
woodchip boiler system equates to roughly 1 – 1 1/2 hours per week over the entire heating
season but maintenance is not required every day during the heating season.
Assessment for Cross Road Medical Center 27
Appendix B - Air Emissions
The emissions from wood-fired boilers are different from emissions from natural gas, propane, or
oil boilers. A number of these components are air pollutants and are discussed below. Boiler
emissions are typically measured in pounds of pollutant per million British thermal units (mmBtu).
One million British thermal units is the amount of heat energy roughly equivalent to that produced
by burning 8 gallons of oil.
All heating fuels— including wood—produce particulate matter (PM), carbon monoxide (CO),
nitrogen oxides (NOx), and sulfur dioxide (SO2) in varying amounts. Burning wood in a modern
and well-maintained wood fuel boiler, for example, produces slightly more particulate matter than
burning oil, but less SO2 than oil. Modern wood systems typically emit more particulates, SO2 and
NOx than propane. All fuel combustion processes produce carbon monoxide (CO). The level
produced by wood combustion depends very much on how well the system is tuned. However,
wood combustion typically does produce more CO than propane. This, in addition to PM, is a
good reason to make sure the facility is fitted with the best available controls and that the stack
is tall enough to disperse any remaining emissions away from ground level. However, CO
emissions from burning wood are of relatively minor concern to air quality regulators, except in
areas like cities that have high levels of CO in the air from automobile exhaust.
Volatile organic compounds (VOCs) are one component of total organic compounds (TOC),
another pollutant of concern. VOCs are a large family of air pollutants, some of which are
produced by fuel combustion. Some are toxic and others are carcinogenic. In addition, VOCs
elevate ozone and smog levels in the lower atmosphere, causing respiratory problems. Both wood
and propane combustion produce VOCs – wood is higher in some compounds and propane is
higher in others. VOC emissions can be minimized with good combustion practices.
In terms of health impacts from wood combustion, particulate matter (PM) is the air pollutant of
greatest concern. Particulates are pieces of solid matter or very fine droplets, ranging in size from
visible to invisible. Relatively small PM, 10 micrometers or less in diameter, is called PM10. Small
PM is of greater concern for human health than larger PM, since small particles remain air-borne
for longer distances and can be inhaled deep within the lungs. Particulate matter exacerbates
asthma, lung diseases and increases mortality among sensitive populations.
The bar graph below illustrates the comparative emissions of particulate matter from different
heating fuels and systems.
Assessment for Cross Road Medical Center 28
Figure 15 - PM emissions graph
Fine particulates, 2.5 micrometers or less in diameter (PM2.5), are increasingly a concern as they
are known to increase health-related problems more than the larger particulates. All modern
pellet boilers that are eligible for State of Alaska rebates have been independently reviewed and
determined their combustion efficiency and PM emission ratings and have been determined to
fully meet all state and federal emission limits.
Stack Location and Height
Typical modern wood heating systems emit virtually no visible smoke (sometimes there is a white
plume of condensed water vapor visible on cold days). Nevertheless, even the very best wood
heating systems tend to emit slightly higher PM than do corresponding oil or propane systems.
For this reason, it is necessary to use a stack with a sufficient height that will effectively disperse
0.0083 0.013 0.032 0.49
1.4
4.6
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
propane boilers new oil boilers modern pellet boilers modern pellet stove modern certified wood stove
old non-certified wood stove or OWBLBS OF PM PER MMBTUComparative PM Emissions
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any emissions and reduce ground-level concentrations of PM (and other pollutants). In addition,
close attention should be paid to the location of the stack and the distance from key HVAC
equipment like roof-top air intake units.
Carbon Emission Reductions
For decades wood energy has been deemed by energy policy makers, regulators, and experts
around the world as “net neutral” in terms of carbon emissions – meaning the amount of gross
CO2 emissions from burning renewable biomass materials like wood are directly offset by the
sequestration of atmospheric carbon as forests regrow new wood over time. While the “net
neutral” characterization is over-simplified, the basic concept is solid and remains the energy
policy position of many European countries where sustainable forest management laws have been
in place for hundreds of years.
Burning wood emits slightly higher (gross) amounts of CO2 per unit of energy than burning oil.
However, burning wood for heat emits biogenic carbon that has been constantly cycling between
forests and the atmosphere over time as part of the natural carbon cycle. By contrast, burning oil
emits geologic sources of carbon – taking this fossil carbon stored beneath the surface of the
earth for millions of years and creating a one-way path to the atmosphere. Put simply, burning
wood emits CO2 that was previously in the atmosphere 20-100 years ago, whereas burning oil
emits carbon that was in the atmosphere 20-100 million years ago. Even though a molecule of
CO2 from burning wood has the same warming effect in the atmosphere as a molecule of CO2
from burning oil, there is still an important and fundamental distinction that needs to be made.
After three years of research and debate, the US EPA has stated they will treat biogenic carbon
emissions from wood energy distinctly more favorably than geologic carbon from burning fossil
fuels.2 There is a long-standing scientific and energy policy recognition that using wood fuel to
substitute other fossil fuel energy sources (also using wood products to replace concrete, steel
and plastics as building materials) has significant, long-term net carbon emission mitigation
benefits. Over the past few decades in Northeastern US, we have practiced sustainable forest
management and we harvest less wood than is grown each year. So, assuming we continue to
manage our forests sustainably and continue to cut less wood than we grow in the years ahead,
using wood fuel to replace heating oil and using wood products to replace carbon intensive
materials like plastic, steel, and concrete is an excellent carbon emission mitigation strategy for
our region.
The analysis performed for this pre-feasibility study shows an annual carbon reduction of
over 229,500 pounds, adding up to 3,443 tons of carbon reduction over 30 years.
2 http://www.epa.gov/climatechange/Downloads/ghgemissions/Biogenic-CO2-Accounting-Framework-Report-Sept-2011.pdf
Assessment for Cross Road Medical Center 30
Appendix C - Wood Fuels
Woodchip Fuel
Woodchip heating systems will function and perform better with
a high-quality fuel. Using consistent, uniform sized woodchips
results in fewer mechanical jams of the fuel feeding
equipment. Feeding lower moisture content woodchips to
the system typically requires less fuel to produce the same
amount of heat. Cleaner woodchips (free of excess bark,
needle, dirt, and debris) produce less ash and can burn longer
without maintenance and removal of ash. Not all woodchip
heating systems will require the same quality of fuel, so
matching the right fuel source and quality to the right system and
application is extremely important. If possible, larger woodchip
systems should be designed for a range of fuel quality. Larger woodchip systems can be equipped
with fuel feeding systems designed to remove oversized materials.
Quality woodchips are consistent in shape and size. Typical high-quality chips vary in size from 1”
x 1” x 1/8” thick to 2 ¼” x 2 ¼” x ¼” thick. Conveying and feeding chips that are relatively square
and flat into the system is easier and goes more smoothly. While the majority of woodchip heating
systems can handle some oversized material, long “stringers” (i.e. small branches and long fibers)
can present a risk for jamming feed augers and shutting the system down. Long stringy wood can
also often “bridge” in hoppers and bins, meaning it can form hollow cavities as the material below
is removed. Material bridging can cause some systems to shut down due to the perception that
the bin is out of fuel when it is not. Similarly, while most woodchip heating systems are designed
to handle some amount of wood “fines” (i.e. sawdust), a high fines content can present issues
when moisture content is either too low or too high. The table below (Table 3)3 presents the typical
quality characteristic of several different grades of woodchips commonly used as heating fuel.
Table 1: Characteristics of Different Woodchip Grades Sawmill Screened Bole Standard Bole Whole-tree
Target chip dimensions 1.5” x 1.5” x 0.25” 2”x 2” x 0.25” 2”x 2” x 0.25” 2” x 2” x 0.25”
Target percent over sized 1% 3% 5% 8%
Target percent fines 2% 4% 5% 8%
Target moisture content 35-42% 38-45% 38-45% 38-45%
Target ash content 0.5% 1.0% 1.5% 2.0%
Target “as is” energy value (Btu/lb) 5,160 4,988 4,902 4,816
3 Woodchip Heating Fuel specification in the Northeastern United States, BERC, 2011,
http://www.biomasscenter.org/images/stories/Woodchip_Heating_Fuel_Specs_electronic.pdf
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Cordwood Fuel
Cordwood is produced from the trunk or top wood of a tree that has been cut and split, and then dried. Cordwood boilers are designed to handle wood that has been dried to less than 20%
moisture content. Cordwood can be stored on site and does not require the construction of a
dedicated storage structure, but to maintain its low moisture content, it needs to be stored
protected from the elements.
When dry, clean cordwood is burned in a well-tuned, modern cordwood
boiler, it can be a very good option for heating with a source of
locally available wood that undergoes minimal processing.
The energy content of cordwood (by volume) will depend on the tree species that the wood came from, any decomposition of the wood fiber that already occurred as a result of improper storage and moisture content of the wood at the time of combustion.
While tree species affects the amount of energy content of wood in a set volume of cordwood (because tree density varies by species), in reality, when purchasing cordwood, the buyer typically purchases a mix of species that is representative of the mix of low-grade trees that was cut on a particular forest stand.
Cordwood heat content greatly depends on the amount of moisture present in the wood. Drier cordwood contains more energy by volume than cordwood with a higher moisture content (“green”). Green cordwood may contain 50% or more of water by weight. Cordwood can be air-dried (“seasoned”) or dried in kilns to bring the moisture content down.
Cordwood is typically sold by volume, a standard cord or full cord measures 4 feet tall by 8 feet
long, by 4 feet deep. Local dealers are located throughout Alaska and delivery distances from the
woodlot or processing yard to the facility can often be kept short, as long as a local supply is
available.
Cordwood can be purchased green and dried on-site, or it can be purchased air or kiln-dried.
Boilers can burn most efficiently when the wood supply is uniform in moisture content. Kiln-dried
firewood is typically more uniform in moisture content than wood dried in a woodshed, where
drying will be affected by where a piece of wood is located in the stack. Kiln-dried wood has a
relatively uniform moisture content, usually around 20-25%. Kiln-dried firewood usually costs
more by volume than seasoned or green wood, and delivery distances may be greater depending
on the location of the supplier.
Cordwood should be used locally and not transported over long distances to avoid transporting
pest species to areas where they are not present yet. Many states, including Alaska, have
quarantines in place that limit the movement of wood into the state from out of state sources.
Heat treating cordwood to a standard set in state or Federal rules can destroy insect pests. Heat
treating cordwood certified by state or Federal agencies limits the spread of insect pest and is
Assessment for Cross Road Medical Center 32
specified in quarantine areas. It is important to note that heat treated wood may not be kiln dried and kiln-dried wood may not be heat treated.
Dry firewood typically costs more by volume than green firewood, but it can be burned right away
without requiring lengthy on-site storage for drying. If only green cordwood is purchased, the
storage and drying area will have to be sized large enough to store at least one full heating season
worth of cordwood.
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Appendix D – Advanced Wood Heating Systems
Woodchip Systems
Typically, equipment provided and installed by a woodchip boiler vendor includes:
• Storage area with access to unload the woodchips from a delivery truck,
• Fuel handling equipment that carries woodchip fuel from the storage bin to the boiler
(conveyors and augers, and metering bins),
• Combustion chamber and boiler,
• Combustion air supply fans,
• Boiler connection to the stack,
• System electronic controls,
• Safety devices (back-burn fire suppression), and
• Emissions control equipment (usually). Various manufacturers of biomass boilers offer different fuel feeding, fuel combustion
configuration, thermal storage, and ash removal features.
A more detailed discussion of woodchip boiler components can be found in Woodchip Heating
Systems, A Guide for Institutional and Commercial Biomass Installations:
www.biomasscenter.org/pdfs/Wood-Chip-Heating-Guide.pdf. Fuel Receiving and Storage Area and Fuel Handling Equipment
Typically, woodchip fuel storage is co-located with the central boiler house. The amount of fuel
required to be stored will determine the size of the storage area. The exact location of the
woodchip receiving and storage area should be chosen to help facilitate easy truck access.
As with pellet boilers, woodchip systems can be
designed to be either fully automated with
conveyors, augers and/or moving floors moving the
woodchips from storage to the burner, or semi-
automated, with an operator using a small bucket
loader to move chips from a long-term storage area
to a day bin that feeds it to the burner.
Fully-automated systems generally require limited
operator attention – typically about a half hour daily
during the heating season. They are a good match
for buildings where the maintenance staff has a large
workload and does not have much time to devote to the heating plant. These systems are well
suited to buildings with significant heat loads and high fossil fuel costs. This high level of operator
convenience usually requires costly equipment and a costly building. Fully-automated systems
Figure 16: Auger collecting woodchips from storage and moving them to a conveyance system
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(Figure 8) typically employ a below-grade chip storage bin or, if the situation requires, vertical
storage silos equipped with a heating loop to keep woodchips from freezing can be used.
Semi-automated wood systems use less expensive slab-on-grade fuel storage: the woodchips sit
in a big pile on the slab. Where conditions dictate, a separate woodchip receiving and roofed
storage area can also be used. Woodchip deliveries are then received in the main yard and chips
could then be pushed up into a simple pole barn woodchip storage shed to keep chips dry. Once
or twice a day the operator uses a small tractor or skid steer to move the chips to a small day bin
that in turn feeds the boiler automatically. Operator time to fill the day bin is as much as one hour
daily. The day bin could be placed inside the building if that is the preference of the owner and/or
design team. The day bin is generally sized to store 24 hours of woodchips, if the system were
operating continuously at peak load conditions. From the chip day bin, the fuel is fed automatically
to the boiler. No operator assistance is required for fuel handling from the day bin to the boiler.
Semi-automated systems are less costly initially but require more labor and moving equipment
such as bucket-loaders. Semi-automated systems are simpler and have fewer advanced features
than fully automated systems.
Figure 17: Examples of Configurations of Fully Automated Woodchip Boiler and Storage Area
Below-grade storage bin equipped with a moving floor and augers to move the woodchips to the boiler. Woodchips are unloaded from the truck through a trap door. 4
On-grade V-bottom storage bin equipped with an auger connected to the boiler. Requires a blower truck for fuel delivery. 5
Below-grade bins accessed via garage bays for fuel deliveries. Bins use traveling auger to feed conveyor
to boiler. 6
4 Figure courtesy Schmid Energy Solutions
5 Figure courtesy Schmid Energy Solutions
6 Figure courtesy Messersmith Manufacturing, Inc.
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Boiler
Combustion Chamber
The combustion chamber is the part of the
combustion appliance where burning of the
solid fuel actually takes place. Fuel is
automatically injected into the combustion
chamber, combustion air is added, and the fuel
burns to produce heat. The hot exhaust gases
then flow out of the furnace area and into the
heat exchanger. As they pass through the heat
exchanger, heat is transferred to the
surrounding water. The cooled exhaust gases
then pass up the chimney for discharge into the
outdoor air.
Chimney and Emission Control
The chimney or stack’s job is to remove the
products of combustion from the combustion system and the building, and to disperse the flue
gases to the atmosphere. Adequate dispersal of stack gases is extremely important when the
wood heating plant is located in a heavily populated area or near at-risk populations. Institutional
and commercial wood systems burners typically burn with very low levels of undesirable stack
emissions and are required to meet state emissions standards. Like all boilers, wood heating
systems have stacks to exhaust the resulting emissions and breaching to connect the boiler to the
stack. Larger woodchip boilers frequently employ emission control devices between the boiler
and the stack to further control the amount of fine particulates emitted.
Smaller wood pellet and cordwood boilers do not typically require
additional emission control technologies to meet air quality
standards.
System Controls
The conditions for efficient wood fuel combustion are set
by controlling the rates at which fuel and combustion air
are fed to the fire. The simplest systems have on/off fuel
feed. When the boiler water temperature drops below a set
value, this type of system turns on and supplies fuel (and
combustion air) to the fire until the water temperature is
brought back up to its set value. Then the system shuts off the
fuel feed system and combustion air. Most woodchip systems
have controls that allow the system to go into an idle mode so they
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can hold a flame during periods when there is little or no load without requiring automated or
manual re-ignition. More sophisticated systems use a control strategy with multiple, separate
firing modes. Controlling how the system switches back and forth between the different firing
modes (such as low, medium, and high) can achieve a much greater degree of control and a very
good turn-down performance. It also avoids the potential for smoking when an on/off system
switches frequently out of its “off” mode. The most precise combustion control can be achieved
when the rates at which fuel and air are fed to the fire can be automatically varied or modulated.
In addition to combustion controls, system controls integrate other components, such as backup
boilers and thermal storage with the woodchip boiler, which can improve overall system efficiency
and emissions.
Ash Collection
Ash — unburnable minerals in the fuel, mixed with any unburned carbon — accumulates in the
combustion chamber and the heat exchange routing and needs to be removed regularly. For every
ton of green woodchips burned, there is typically only 25 pounds of ash produced. Most of the
ash accumulates in the combustion chamber – this is called bottom ash. If there are sloped or
moving grates, the ash moves to the bottom of the grates. It is important that this ash be removed
on a continuous or daily basis. One method is removal by automatic ashing augers (also called
screws), which collect ash at low points and move it outside the combustion chamber. Automatic
ashing is sometimes preferred, since it reduces maintenance time for staff. However, it can add
capital cost to the system. Many plants, including some relatively large ones, use manual ashing:
the ash is raked and shoveled out of the boiler by hand, a task that typically takes about 10-20
minutes a day. In most systems, manual ashing can be done easily without shutting down the
boiler.
Fly ash or fine ash that is often carried with hot combustion gases from the primary combustion
chamber can be filtered from the gas stream and with larger boilers the fly ash is typically collected
in separate containers for storage and eventual reuse. Smaller boiler systems tend to collect the
fly ash and co-mingle it with the bottom ash.
Thermal Storage
Thermal storage can provide many benefits when properly designed, installed and controlled in conjunction with wood-fired hydronic heating systems. The idea behind thermal storage is to prolong the operation of the boiler, providing greater efficiency and responsiveness to load.
Cordwood Systems
Modern cordwood systems use wood-fired combustion and gasification (“two-stage”) technology
to achieve high efficiencies and burn temperatures between 1,800-2,000°F. They differ from older
cordwood boilers in their use of modern controls and automation features. For cordwood boilers
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thermal storage (in the form of a large-volume hot water tank) is essential – allowing batches of
fuel to be burned quicker, at higher temperatures, higher efficiency, and with fewer emissions.
The fire is stoked periodically (once or twice a day in cold weather) to charge the water storage
with heat. This keeps the fire continually hot, fast, and clean, unlike old wood stoves or cordwood
boilers that burn less efficiently when less heat is called for. Once charged, a circulating pump
removes heat from the tank as needed to serve the space heat or domestic hot water
requirements. This allows for shorter, more efficient burn cycles and full heat recovery otherwise
wasted as fuel in the firebox slowly dies out.
Each system includes a cordwood boiler, an induced draft fan, controls, and stack connection.
They can differ among companies in configuration of the water storage: either as an integral water
storage with the combustion chamber surrounded by the water jacket tank, or as an external
thermal storage tank. An advantage of cordwood systems is that cordwood is widely available and
can be stored without a costly bin or expensive building construction. Stacking of cordwood will
potentially require a large area, and the stacks will need to be sheltered from the elements, under
a pole-barn structure or woodshed for example. They are only attractive in cases where the
operator wants to hand fire the system. Although they can be used for relatively large loads (up
to 1 million Btu per hour), the amount of wood that must be manually handled can become a
constraint for the operator.
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Appendix E – Life Cycle Cost Analysis