Assess and quantify the benefit of alternative and renewable energy for greenhouse operations

Final Report for FNE07-620

Project Type: Farmer
Funds awarded in 2007: $8,800.00
Projected End Date: 12/31/2010
Region: Northeast
State: Maryland
Project Leader:
John Shepley
Emory Knoll Farms, Inc.
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Project Information


We experienced extremely poor reliability of the Clean Burn boiler during the first two years of operation.
These reliability issues were not caused by any intrinsic problems with the boiler itself, as it is a proven unit
that burns all types of petroleum based waste oils with no problems. Rather, the reliability issues were caused
by the WVo fuel, and the incompatibilities of this as a fuel for the Clean Burn. We will detail the issues we
experienced, and our solutions for them, but in summary the magnitude of these issues caused us to shift our
focus from quantifying the benefits of using WVO to addressing the more practical issues of achieving reliable
operations with WVO.


Emory Knoll Farms is a wholesale grower of Sedums and other succulent ground covers for the green roof
industry. We are the only nursery in the US which is completely dedicated to providing plants to the green roof
industry and to date we have provided plants for over 85 acres of green roofs across the USA and Canada.
Emory Knoll Farms currently employs 7 full-time and 2 part-time employees, and does slightly less than $1
million in annual sales. We have grown between 40% and 100% annually for the past five years.
Although we are a relatively small operation, we are a leader in our small segment. This has enabled us to
establish national accounts, and we have partnered with other nurseries across the USA to provide plants
nationally. As a leader, we are now in a position to set standards for green roof plant products, growing
practices, and services such as delivery and consulting. We see sustainable horticulture as an important part of
this leadership and we intend to extend the positive parts of our growing practices to our partner nurseries.
We also have endeavored to be a leader in our industry and are attempting to increase the intellectual
capital of the green roof industry. We are active in industry associations (Green Roofs for Healthy Cities,
Maryland Nursery & landscape Association, American Society of landscape Architects). We support green roof
research at several major universities, and were instrumental in establishing a green roof program at the
University of Maryland. One of the owners, Ed Snodgrass, has written two successful books – "Green Roof
Plants, a Resource and Planting Guide", and "The Green Roof Manual, A Professional Guide To Design,
Installation, and Maintenance". We continue to test 100’s of plants every year and support plant testing in
other parts of the country.

Project Objectives:

Our project goal is to demonstrate and quantify the effectiveness and cost benefit of an alternative energy
heating system for greenhouses. Our specific goals, as stated in the original proposal are:
Assess the qualitative & quantitative benefits of sustainable energy solutions for agi-horticulture and to
educate and assist other regional farms in assessing and implementing renewable energy programs of their
Since a working sustainable energy system is already installed and operational at Emory Knoll Farms, we
proposed a project to perform these objectives:
• Assess and document the installation & setup costs of an alternative energy heating system as
compared to the costs for an equivalent conventional system;
• Determine the ‘true’ operational saving (or costs) of an alternative energy heating system;
• Develop an instrumentation system to measure energy consumption as a function of outside and
greenhouse temperature profiles;
• Develop a website to present the information in real time;
• Develop presentation materials based on the finding;
• Provide presentation materials to area farmers, organizations, cooperative extensions;
• Present the findings at relative regional training events j seminars.


Click linked name(s) to expand
  • David Ross


Materials and methods:

In our project, we have accomplished most of our original goals, although the data collected has been
much less detailed than was originally anticipated. Therefore our analysis is somewhat more of a qualitative,
rather than a quantitative nature. However, as will be shown in this report, the conclusions are still valid, if less
In this project we compared our heating system to 3 other comparable heating systems. Two of these are
more closely related to ours, and the third system is somewhat difficult to compare directly.
Changes to Original Project Scope
The specific objective that was not accomplished is "Develop an instrumentation system to measure
energy consumption as a function of outside and greenhouse temperature profiles; and develop a website to
present the information in real time". For several reasons, we have not been successful in collecting the real time
data that we intended. The primary reasons are:
• Numerous technical problems that affected the reliability of our heating system (described later in this
report) took a great deal of time and energy away from this project.
Our fuel supply was unreliable enough that we were not able to use Waste Vegetable Oil (WVO) for
extended periods sufficient to analyze the performance ofthe system on WVO.
• The technical challenges of installing instrumentation our nursery were greater than anticipated –
perhaps we were overly ambitious in our expectations of how much was involved with the
instrumentation. We didn’t attempt to install instrumentation in other nurseries.
• Our own growth worked against us. As a small operation, sometimes we are faced with unexpected
business challenges that absorb a significant amount of our resources.
As a result of these changes, our analysis is more of a qualitative nature than quantitative. We do,
however, feel that our results are clear, and we will make all efforts to demonstrate the reasoning behind our
We did perform more detailed modeling of the greenhouses and heat loads and flows of heat. The
Hydronic System Software from Taco makes modeling easy, and we used heat loss computations from the
internet to estimate the losses of the various greenhouses based on their construction and dimensions. These
models proved to be helpful and the results were consistent with our actual experiences.

Research results and discussion:

The use of Waste Vegetable Oil (WVO) has been problematic. Some of the problems have been due to our
approach, and some are endemic to the nature of WVO as a fuel. In the end, most of the significant problems
were solved or reduced to manageable proportions and we are comfortable using WVO. Certainly the cost and
environmental benefits outweigh the few remaining difficulties.
Here are the primary fuel considerations:
Waste Vegetable oil- vTVO
The fuel itself has proved to be the cause of many operational issues that are separate from issues that are
specific to the equipment or installation.
1. Fuel Sources – Of the various cooking oil products used in the food service industry, the best to use for
heating applications are liquid, non-hydrogenated oils such as peanut, canola, or corn oil. This is often
provided as a blended product to the restaurants. Cooking causes a partial breakdown of the oil, and it
will stay liquid well below 32 degrees F. Finding a regular source of WVO has been difficult. The best
kind of oil is commonly used in Asian restaurants, but sometimes it is difficult to communicate with
owners in order to establish a relationship what will allow us to collect the oil. Even restaurants that
are willing to give us oil are often unwilling to give up their contract with the local renderer.
2. Collection Difficulties -Initially we collected our own oil from local restaurants. Most restaurants have
a dumpster or barrels that are placed by the rendering company that they are contracted with for oil
removal. Technically, the oil becomes the property of the rendering company when it is placed into
their dumpster; which means that even if the restaurant owner agrees to give oil to us, we cannot
legally remove it from the dumpster. The restaurateur must package it separately, or we must provide
our own dumpster or barrel.
3. Contamination – Often, water, food waste, and other contaminates are in the oil we collect from
restaurants. This puts a heavy burden on us to let the water settle out and filter the oil. Contaminates
such as flour and batter remnants, peanuts, and other small particles are hard on pumps and filter
elements. In a few cases, we have been successful in convincing the kitchen staff to avoid putting
excess contaminates in the oil, but this is a constant battle. Oil collected from hospital kitchens and
donated to us by Biomedical Waste Systems proved to be of such poor quality at times that it had to be
discarded. After BWS interceded with the hospital kitchen to not put wash-water in with their oil, the
quality increased significantly.
4. The Nature of Vegetable Oil- WVO has a tendency to harden over time when in contact with the air,
causing a buildup of crusty black oxidized oil on everything it touches (think of linseed oil). This creates
a challenge in keeping pumps, hoses, trucks, etc., clean
5. Combustion – WVO burns very well, but creates several unique problems. Between heating cycles
(when the burner is not running), the burner nozzle is exposed to very high heat radiating back from
the combustion chamber of the boiler. A small bit of residual oil still inside the nozzle can carbonize
and create a creosote-like buildup inside the nozzle. Even worse, a thick waxy substance precipitates
out of the oil within the nozzle which can clog the nozzle within a matter of days. Several spare nozzles have to be kept on hand, and the nozzles must be changed and cleaned on a rigorous schedule or the
spray pattern will begin to deteriorate causing incomplete combustion, soot, and oil buildup on the
burner assembly.
6. Energy Density – Vegetable oil has approximately 10% less energy per unit of volume than home
heating oil. This means the boiler produces approximately 10% less energy than its rating when
burning WVO than when burning petroleum.
Waste Motor Oil
Waste motor oil is a recycled product and is appropriate for use in our clean burn boiler. Overall, motor oil
burned very well and reliably in our boiler.
The only problem encountered with motor oil was when sludgy thick oil was not sufficiently filtered.
Home Heating / Diesel Oil
All home heating oil we tried burned reliably with no problems.
We did not have a reliable source of 100% bio-diesel. When we briefly tested it, it burned reliably with no
High-Efficiency Hydronic & Root Zone Heat
In our system, we used different methods to apply heat:
For greenhouses, we used the Delta-T system (EPDM
tubing) for both bench and under-floor heat and we also
used PEX under-floor hydronic heat. For work spaces, we
used baseboard hot water and also hot water unit heaters.
All systems draw heat from our primary boiler through a
series of primary, secondary, and tertiary loops and heat
exchangers – See diagram.
Here is a list of important design considerations and
features of our system:
1. The Clean Burn boiler is a central heat source. It is a
350,000 BTU / Hour waste oil boiler. It is located in
our barn and is about 150 feet from our heated
greenhouses. The Boiler has a primary loop that circulates water through a manifold that supplies heat
to the office and work spaces. The primary loop also feeds a 300 foot long run of 40mm PEX tubing
(greenhouse loop) that delivers approximately 140,000
Btu / Hour to our greenhouses.
Both the main Boiler and loops and the greenhouse
water use a 30% glycol solution to protect from freezing
in the even the system is off due to power failure, etc.
2. The greenhouse loop circulates water from the boiler to
a heat exchanger that transfers the heat to the
greenhouse water. The bench heat uses EPDM tubing
which is not impervious to oxygen. Because of this, the
fluid Circulating in the greenhouses can contain
corrosive oxygen and must be isolated from the boiler.
The greenhouse heat is comprised of the indirect hot water heater and an auxiliary residential grade
boiler that provides an additional 120,000 BTU / hour connected in series with a distribution loop. The
oil fired heater burn home heating oil and provides backup heat in the event that the Clean Burn boiler
fails or auxiliary heat for very cold weather. These two tanks serve to store heat, and from them the
water is distributed through mixing valves to provide 140 degree water to each of 3 greenhouses.
a. The first greenhouse (Koko) uses bench heat – a Delta-T heat system which is an industry
standard bench heat system. Two 4′ benches run the length of the greenhouse are heated
with tubing on 2" spacing. This provides about 90 BTU’s / Hour per square foot for a total
maximum of approximately 25,000 BTU / Hour. This greenhouse has a single layer of
polycarbonate covering
b. The second greenhouse (Gatemouth) also uses the Delta-T system. It is a combination of one
bench – 5 x 80 feet, and a heated floor area approximately 10 x 60 feet. In the floor system the
Delta-T system is embedded in about 2" of crushed stone and insulated by a double bubble
insulation layer beneath it. This greenhouse uses an inflated double layer of PE greenhouse
c. The third greenhouse uses PEX tubing embedded in the floor. The system has 4" of expanded
polystyrene insulation below the floor, about 3 inches of crushed stone with the PEX loops on
9" centers tubing embedded in it, and pavers for thermal mass. There is a 4 inch wide thermal
barrier around the periphery of the house that extends 18" into the ground. This house is
intended to be our warmest house, where we keep tender plants. It is covered with twin wall
The figure below shows a worst case analysis of the greenhouse heat loads. (NOTE: The analysis includes
additional hot water unit heaters. These were not included as the bench and floor heat provides sufficient heat
in the coldest weather.)Baseboard and Hot Water Unit Heater Heat
We also used baseboard heaters in our existing offices and small forced air
unit heaters in our lunch room. All of these provide adequate heat for the
space. The table below shows the computed heat loads for each space. Under
floor hydronic heat would be preferable because it is typically more efficient
than baseboard heat, but was not an option in our already-built office spaces.
Back-Up and Auxilliary Heat
Based on the model, above, we knew that the worst case amount of heat
required by the greenhouses (252AOO btu / hr.) would be greater than the
amount of heat that can be delivered through the underground path (about
200,000 btu / hr.) We also desired to have a secondary source of heat in case
of failure of the Clean Burn boiler or any associated systems. Therefore we
implemented a backup boiler. This system consists of:
• A Used Sears 120,000 btu / hr. residential boiler
• A 275 gallon oil tank
• Circulator and controls
• Heat Exchanger
This system is housed in a small building built to hold it along with
all the greenhouse heat circulator pumps and controls.
This is designed to come on at a lower temperature than the
{normal’ hot water temperature. The secondary boiler comes on at
about 1400 F and runs until the water reaches 1600 F. This runs
autonomously, and will come on whenever the water temperature
drops, whether the drop is due to extreme cold temperatures or due
to the Clean Burn boiler tripping off.
Photo 7 – Building for Backup and
Greenhouse Manifolds While the secondary boiler does not have sufficient capacity to keep
the greenhouses at optimum temperatures by itself it will keep the
houses and the rest of the heating system above freezing on even the coldest nights.
Comparative System – Heartwood Nursery
During the time this project was underway, nearby Heartwood Nursery built a new propagation house.
The greenhouse itself is innovative: It was constructed as a traditional wood post and beam shed building and
the Nursery Owner had it covered with twin wall polycarbonate rather than sheet metal. The result was a very
tight and well insulated greenhouse as well as saving considerable money as compared to a traditional gothic
greenhouse structure. The prop house is 40 feet x 70 feet, and the owner specified two heated benches at 10
feet x 40 feet each.
For this system, reliability was critical. Heat modeling suggested the greenhouse would require less than
l00,000 BTU / Hour, and we also wanted to heat a workshop building that would house the boiler. In order to
have some reserve capacity and allow for future growth, we chose a Burnham 200,000 BTU / Hour residential
oil-fired boiler. Similar to Emory Knoll Farms, the workshop the houses the boiler is about 300 feet from the
greenhouse. A loop of 1" PEX tubing buried in an insulated pipe runs from the workshop to the greenhouse
and feeds a flat plate heat exchanger at the greenhouse.
The Heartwood greenhouse heat is also a Delta-T bench heat system. The nursery owner wanted to reuse
as many components from their old site as possible. We were able to use a thermostatic control system, and
zone valves and incorporate them into the new system allowing for four separate zones on the benches. Later,
to improve reliability and simplicity, the zones were eliminated and both benches are heated from a single
Provisions for hot water unit heaters were included in the design for both the workshop and the
greenhouse. In the final implementation, we learned that unit heaters were not required in the greenhouse
and a single 50,000 BTU / Hour unit heater was sufficient for the workshop. The diagram below shows the
system and calculated worst case heat loads. Comparative System – Green Meadow Farm
Green Meadow Farm has been heating greenhouses with WVO for many years. They grow organic produce
in the summer, and organic greens & specialty root vegetables in heated houses in the winter for restaurants in
the Philadelphia area. Owner Glenn Brendle has been an inspiration to our adoption of WVO heating and a
source of technical and practical expertise.
Green Meadow Farms originally used a typical outdoor wood-fired furnace that had been modified to burn
WYO. About the time our project began, they switched to a new heating plant comprised of two Clean Burn
CBT-350 boilers, the same model we are using. They also have the advantage of being close to the
manufacturer, Clean Burn, Inc. They collaborated with the engineers at Clean Burn to modify the boilers for
use with WYO. Their early success at using WVO in a Clean Burn boiler gave us confidence that our choices
would work, even as we experienced difficulties in implementing our project.

Research conclusions:

We will present the adoption by discrete components as we have addressed these components in other
areas of the report.
Alternative / Renewable Fuel
Alternative Fuel: Ultimately, the Waste Vegetable Oil fuel has proven to be viable for our application. The
net results are:
• We are now nearly 100% carbon neutral for heat energy
• Our cost for fuel is approximately}S the cost of heating oil
• Our production has increased as a result of a ready source of heat for our propagation houses
eHydronic Heating
While our basic boiler / Hydronic heating system has a few minor problems, primarily due to our own
expertise in the design & installation stages; the fundamental principal is sound. We will continue to use
hydronic heat systems and recommend them.
The primary result of this project is that we’ve proven that bench root-zone heat and under-floor hydronic
heat are efficient, effective, and reliable. We are able to keep greenhouse air temperatures down, yet keep
newly-propagated plants in a growth mode throughout the winter. This type of heat makes maximum use of
the available heat with very little loss.
The Modeling system we used (Obtained free from Taco company – Taco’s Hydronic Heating Solution
software) provided valuable analysis and design validation. By plugging the rated heat transfer for our Delta-T
heating system into the modeling tool, we were able to model the actual heat consumption for each

Participation Summary

Education & Outreach Activities and Participation Summary

Participation Summary

Education/outreach description:

We have provided outreach in many areas and often it is combined with information about our core
market / product, Green Roofs. Because green roofs are energy & environmentally positive building elements,
we often have the opportunity to speak about our alternative / renewable energy systems when we are also
talking about green roofs.
Presentations Given
John has made presentations on the various alternative / renewable energy systems in use at Emory Knoll
Farms at several regional events, including the annual Energy Field Day sponsored by the MD Cooperative
Extension and MD Greenhouse Growers Association.
• November 8, 2007 – Getting Green: Sustainable Energy Use for the Green Industry, Timonium
Fairgrounds, Timonium, MD
• November 11, 2008 – Energy Program for the Green Industry – Moving Toward Sustainability,
Montgomery College, Rockville, MD
• November 30, 2010 – 3rd annual Chesapeake Green Energy Conference, Howard County
Fairgrounds, West Friendship MD
• Visits to our nursery by various schools and environmental organizations. These schools visit
our farm annually, and an overview of our alternative / renewable energy systems are always a
part of the tour:
o Franklin and Marshall College
o Harford Friends School
o Roland Park Country School
We have been featured in several articles and also on the Sundance Channel:
Real-World Energy Efficiency, Practical ways garden centers are saving the planet – and protecting their
bottom lines, by Lisa Duchene
( EcoGardenCenter.pdf)
Emory Knoll Farms, A Profile of a Green, Green Nursery, Green Roof Infrastructure Monitor, 2007 Spring2007.pdf
Eco-Green Series: Emory Knoll Farms, Sundance Channel, 2007. Presented an overview of our renewable
energy heating system.
This project has provided visibility and exposure to other agricultural organizations and allowed us to share
lessons learned in relation to particular projects that others are planning. We consulted with the Beltsville
Agricultural Research Center, part of the US Department of Agriculture for one of their greenhouses located in
Beltsville, MD.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.