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UVM Extension AgEngineering Blog

Vermont Farmers Food Center Heats with Biomass

Posted: May 1st, 2016 by Chris Callahan

Rob Steingress (VFFC), Bill Kretzer (12 Gauge Electric) and Greg Cox (VFFC) perform final inspections before the initial firing of the boiler.

Rob Steingress (VFFC), Bill Kretzer (12 Gauge Electric) and Greg Cox (VFFC) perform final inspections before the initial firing of the boiler.

UVM Extension and others supported the recent installation of a 341,200 BTU/hr (output) multi-fuel biomass boiler at the Vermont Farmers Food Center (VFFC) in Rutland, VT.  The boiler heats the Farmer’s Hall building with the capability to use several alternative fuels to displace propane. The boiler was fueled primarily on wood pellets but was also able to feed and burn grass biomass pucks. This demonstration project carried a cost premium when compared to a typical propane heater installation.  That premium is paid back over time due to recurring fuel cost savings. A simple payback period of 2.2 to 8.0 years is feasible against a cost premium of $51,255 for the boiler depending on the fuel used and the amount of use. For more details about the project and the economic performance please see the report.

This project was funded by The Vermont Bioenergy Initiative (VBI) of the Vermont Sustainable Jobs Fund (VSJF), the Vermont Agency of Agriculture, Food and Markets (VAAFM), and an anonymous donor in partnership with The Vermont Farmers Food Center (VFFC) with support from Smalley Mechanical, Lohsen Plumbing and Heating, 12 Gauge Electric, Renewable Energy Resources (RER) and UVM Extension.

A variety of fuels can be burned in an automated biomass boiler equipped with improved ash removal and adjustable air controls. Shown here (R to L) are wood chips, grass and ag biomass pucks and wood pellets.

A variety of fuels can be burned in an automated biomass boiler equipped with improved ash removal and adjustable air controls. Shown here (R to L) are wood chips, grass and ag biomass pucks and wood pellets.

Report Citation:

Callahan, Christopher W. (2016). Biomass Boiler Installation at The Vermont Farmers Food Center. Bennington, VT: UVM Extension with Funding from The Vermont Bioenergy Initiative. Retrieved from http://blog.uvm.edu/cwcallah/files/2016/05/Summary-Report-VFFC-Biomass-Boiler-Project-FINAL-2016-04-09.pdf

Grass and “Ag Biomass” Competitive with Wood Chips

Posted: May 1st, 2016 by Chris Callahan

Chris Davis (Meach Cove Trust) prepares the boiler and combustion testing equipment for a trial run of the new fuel.

Chris Davis (Meach Cove Trust) prepares the boiler and combustion testing equipment for a trial run of the new fuel.

Recent testing at the Meach Cove Trust has demonstrated strong economic and technical feasibility of grass-based biomass combustion fuels.  The use of solid, densified, cellulosic biomass fuels has been well demonstrated with wood pellets in residential and light commercial systems and wood chips in larger, often centralized systems.  The Grass Energy Partnership of the Vermont Bioenergy Initiative has been exploring an alternative form of fuel; grasses densified in a specially developed processor to take the form of 1.5”-2.0” round cylindrical pucks.  Grass fuels may be produced on otherwise marginal agricultural land, sometimes in perennial production and even in buffer strips offering environmental benefit.  Additionally, fuel can be made by densifying agricultural residue or biomass harvested from idle pasture or fields.  We have referred to this fuel as “Ag Biomass”. The testing summarized in this report has demonstrated the technical and economic feasibility of such fuels.

Earlier tests were done using pellets of various feedstocks (mulch hay, reed canary grass, and switch grass) and combinations of feedstocks (mixed with wood) (Sherman, 2011). This testing was done in a Solagen boiler (500,000 BTU/hr) designed for wood pellets.  The primary findings of this work confirmed reasonable heating value of the fuels, relatively high ash content of the grass fuels (4.3-6.7%), different combustion air and mixing requirements of the fuel with potential for fusion (clinkers), and relatively high levels of chlorine in the grass fuels which is suspected to accelerate corrosion of internal appliance surfaces.  This report also noted that the challenges associated with high ash content and clinker formation could be alleviated with appliance design considerations such as automated ash removal and a moving floor or cleanout cycle. Detailed emissions profiling was also conducted as part of this prior work.

A review of the potential for a grass energy industry in Vermont has also been conducted earlier (Wilson Engineering, 2014). This work focused on assessing several production and marketing models (Closed Loop No Processing, Small Scale On-Farm Processing, Regional Processing, Consumer Pellet Market). The report concluded that Small Scale On-Farm Processing presents the greatest challenges and that Closed Loop No Processing would be the easiest to implement.

A variety of fuels can be burned in an automated biomass boiler equipped with improved ash removal and adjustable air controls. Shown here (R to L) are wood chips, grass and ag biomass pucks and wood pellets.

A variety of fuels can be burned in an automated biomass boiler equipped with improved ash removal and adjustable air controls. Shown here (R to L) are wood chips, grass and ag biomass pucks and wood pellets.

This new report documents recent testing involving the densification and combustion of solid, grass biomass fuels in a small commercial boiler (342,100 BTU/hr output rating). Fuel briquettes (or “pucks”) were made from Switchgrass, Miscanthus, Reed Canary, Mulch Hay and “Ag Biomass” / Field Residue as well as mixtures of these feedstocks with ground wood chips. Our findings were:

  1. On-farm, small scale densification of grass and agricultural biomass solid fuels via pucking is feasible with a conversion (densification) cost of $49-148 per ton and a finished fuel cost in the range of $85-228 per ton ($5.2 – 14.4 per million BTU).
  2. Sustained, reliable combustion of densified grass and agricultural biomass solid fuels in a light commercial boiler (EvoWorld HC100 Eco) is feasible with 73-90% combustion efficiency, and with no ash fusion or clinker development. Longer, sustained overnight runs did result in some combustion chamber clogging with ash and fuel residue which may be resolved with further boiler tuning and clean out cycle timing adjustment.
  3. The test of the Ag Biomass / Field Residue fuel demonstrated feasibility at a current delivered price of $214 per ton ($13.2 per million BTU) supporting a potential payback period of 3.6 years on the boiler. At higher production volume projects a path to $85 per ton ($5.2 per million BTU) and a potential payback period of 2.4 years.
Grass biomass pucks under test at Meach Cove Trust.

Grass biomass pucks under test at Meach Cove Trust.

This project was funded by The Vermont Bioenergy Initiative of the Vermont Sustainable Jobs Fund in partnership with UVM Extension and Meach Cove Trust.  Project partners included Chris Davis (Meach Cove Trust), Chris Callahan (UVM Extension Agricultural Engineer) and Sid Bosworth (UVM Extension Agronomist), and Adam Dantzscher and John Bootle (Renewable Energy Resources).

Report Citation:

Callahan, C. W. (2016). An Update on Solid Grass Biomass Fuels in Vermont. Bennington, VT: UVM Extension with Funding from The Vermont Bioenergy Initiative. Retrieved from http://blog.uvm.edu/cwcallah/files/2016/05/Summary-Report-Grass-Puck-Testing-at-Meach-Cove-2015-Final-2016-04-18.pdf

Other References:

Sherman, A. (2011, January). Technical Assessment of Grass Pellets as BoilerFuel in Vermont. VSJF. Retrieved from http://www.biomasscenter.org/images/stories/grasspelletrpt_0111.pdf
Wilson Engineering. (2014, May). Grass Energy in Vermont and the Northeast. Vermont Sustainable Jobs Fund. Retrieved from http://vermontbioenergy.com/wp-content/uploads/2013/03/Grass-Energy-in-Vermont-and-the-Northeast.pdf

Finish Surfaces for Produce and Food Areas

Posted: April 29th, 2016 by Chris Callahan

Smooth and cleanable surfaces are an important aspect of areas where produce is washed, packed, stored and processed.  Many farms are investing in renovations and expansions of these areas and are seeking materials to meet this “finish surface” need regardless of specific regulation.  Meanwhile, entrepreneurial food processing companies are often required to incorporate these materials due to regulation.  This is a summary of some of the finish surface materials that are available, their pro’s and con’s and pricing at this time.

Material Description Pro’s Con’s Pricing ($/ft2)
Fiber Reinforced Plastic (FRP) – Textured – Class C Fiberglass-based wall sheathing material. Dimpled or textured surface. Very common and familiar to trades and suppliers.

Can be installed with rivets or with adhesive.

Wide array of trim pieces to aid in clean installation.

Requires a backer board of some sort to install.

Drilled and riveted installations can allow moisture and water leakage into wall.

1.39
Fiber Reinforced Plastic (FRP) – Smooth – Class C  Fiberglass-based wall sheathing material. Smooth,  flat surface.  ”

Smooth surface is appealing to some for cleanability.

1.92
Galvalum Roofing – Ridged Painted, aluminum coated, galvanized steel sheets intended for roofing material but often used for wall sheathing as well. Does not require a backing board, can be installed on firring.

 

0.92
Galvalum Roofing – Flat Flat version of the ridged product above sheet galvalum sheathing. (see p.25 of linked manual) Does not require a backing board, can be installed on firring.

Flat surface may be easier to clean for some.

0.76
Trusscore Paneling PVC twin-wall plastic panels Does not require a backing board, can be installed on firring. 1.52
WallTuf Paneling Recycled PVC-based wall sheathing. Considered more environmentally benign than FRP panels. Requires a backer board of some sort to install.

Drilled and riveted installations can allow moisture and water leakage into wall.

1.25
Extrutech Twinwall PVC twin-wall plastic panels Does not require a backing board, can be installed on firring. 2.20
Utilite Paneling Polypropylene twin-wall plastic panels. Does not require a backing board, can be installed on firring. 1.85

Notes:

  1. These are not necessarily compliant for food contact surfaces; they are meant to be finish materials for areas where food is being washed, packed or stored.  I.e., the guidance is “smooth and cleanable.”
  2. The prices above are material cost only, the products differ in terms of installation labor as well.  For example, “sheathing” will require some sort of rigid wall material to mount to where as rigid panels can be installed into firring strips.  No installation costs have been captured above.
  3. I have generally included links to manufacturer info.  Most manufacturers sell via distribution channels.  Check with your local building supply company about availability.
  4. The pricing on these materials is quite variable depending on the source, when you obtain a quote, the quantity being ordered and how it is delivered. The list above is the best information available at the time of writing.  Shop around and obtain quotes from several distributors.

We will plan on updates in the future.  If you know of a material that should be included, please email us.

New Crop Storage Planning Tool

Posted: January 21st, 2016 by Chris Callahan

DSCN1606I have been toying with an Excel-based crop storage planning tool for several years.  I finally have it at point where I want to make it available to others and start collecting feedback for improvement.  You can download the tool here, and instructions are available in the tool and at this page.  Enjoy and please be in touch with feedback.

 

Update on Heating Greenhouses with Biomass

Posted: September 14th, 2015 by Chris Callahan

Get the report.

Get the report.

In the Northeast, early and late season production of food crops using greenhouses requires the addition of heat to maintain temperature and also to control humidity. The heating fuel used is generally propane or other fossil fuels.

Jericho Inside - Manifold

This hot water distribution manifold allows heating of late and early season crops directly in the ground.

The use of greenhouses, and greenhouse heating, are on the increase in Vermont as growers respond to increased demand for local food throughout the year. Greenhouse production is also on the rise because it allows growers to protect against extreme weather events such as heavy rain or drought, and it affords better control of the growing environment, leading to improved yield and quality. However, using fossil fuels to control the growing environment is costly and these fuels also contribute to greenhouse gas emissions. Vermont greenhouse growers produce $24.5 million in crops using 2.6 million square feet of growing area at an estimated annual heating cost of $1.8 million. Many of these growers are interested in alternatives to fossil fuels for heating in order to improve their profitability and/or reduce their environmental impact.

Testing emissions from biomass boiler at Jericho Settlers Farm in Jericho, VT.

Testing emissions from biomass boiler at Jericho Settlers Farm in Jericho, VT.

This project demonstrated the use of biomass heating for greenhouse vegetable production at sites across Vermont. From 2008 through 2015, 25 growers received cost-share funds for greenhouse biomass heating systems. The total installed cost of these systems was $312,766; the average cost per system was $12,511 and the average cost-share (i.e. sponsor funding) on these projects was 44% of the total cost. The growers installed a variety of system types depending on desired fuel, heating load and method of heat distribution (hot air or hot water). The project started in 2008 and the systems have operated for the equivalent of 96 growing seasons in total with an average of 3.8 growing seasons per system, an average net fuel savings of $2,696 per system per year, and an average payback of 4.8 years (at full cost). From 2008 through 2015 a total of 15.3 trillion BTU of biomass energy was provided to these greenhouses, equivalent to 167,000 gallons of propane. The cumulative equivalent carbon dioxide emissions avoided by this substitution of fuel is estimated to be 2.14 million pounds. This is roughly equivalent to the annual emissions from 204 cars, or 2.3 million miles of car travel.

You can download the final report here.

Dave Marchant (Riverberry Farm, Fairfax, VT) explains some of the features of his biomass heating system during a twilight meeting.

Dave Marchant (Riverberry Farm, Fairfax, VT) explains some of the features of his biomass heating system during a twilight meeting.

Final Report – Increasing Supply and Quality of Local Storage Vegetables

Posted: September 14th, 2015 by Chris Callahan

We recently completed a project aimed at improving the ability of Vermont vegetable farms to store crops such as beets, carrots, parsnips, potatoes, onions, squash and sweet potatoes, all of which have unmet demand in late winter when local supplies run out.

Beets can be stored in bulk bins for months at the right conditions.

Beets can be stored in bulk bins for months at the right conditions.

The physiology of these crops allows them to be stored for many months after harvest if specific storage conditions are met. However, several distinct sets of conditions are optimal for different groups of crops, and achieving each condition requires careful control and monitoring of temperature and relative humidity in storage. Currently, Vermont’s commercial vegetable farms rarely achieve the optimal conditions due to lack of sufficiently separated storage compartments, and lack of modern environmental monitoring and control equipment.

Installing a remote monitoring system to keep track of temperature and humidity of a storage facility.

Installing a remote monitoring system to keep track of temperature and humidity of a storage facility.

This project installed environmental monitoring equipment to improve storage conditions and ultimately the quality of 1,736 tons of winter storage crops at 9 farms throughout Vermont .  The cumulative market value of these storage crops produced during the 2012-2014 growing seasons was $3.5 million.   Improved storage monitoring led to better control of storage conditions, in part through automated notification to farmers when abnormal conditions were occurring. This allowed for prompt correction of problems such as open doors and failing or inoperative cooling equipment. Losses of storage crops (cull rates) were reduced from ~15% to ~5% of stored volume. Sixty-six  energy efficiency measures were also implemented at 5 of these farms, saving a total of 40,269 kWh of electricity and $5,800 annually.  The systems deployed have increased the confidence of growers to expand their winter storage of Vermont-grown vegetables, leading to an increased supply of local produce outside of the traditional growing and marketing season.

You can download the complete report here.

Doser for Small Scale Vegetable Washing with Sanitizer

Posted: June 16th, 2015 by Chris Callahan

I recently put together a simple doser for manually measuring accurate doses of sanitizer into wash water solutions.  It is really just a homemade burette. The process of mixing a treatment dose of santizer requires metering a specific dose of concentrate into a larger volume of water.  I have also created a calculator to help with that. The UVM Extension Produce Safety Program maintains a great set of resources for general guidance on use of sanitizers including this guide sheet.  It is important to always have a copy of the official product “label” (not necessarily the same thing as the label on the container).  For easy reference, labels for typical sanitizers are linked below. Please check with your supplier to be sure you have the most recent version for the product you are using and the intended application.

There are a number of options available to avoid actually pouring these chemicals when dosing a mix tank.  You can download a summary of these options here.  When pouring them, splashing and spills can occur which are best avoided due to the corrosive and hazardous nature of the chemicals at stored concentrations. Even when using enclosed dispensing options, wear proper personal protective equipment including goggles and resistant gloves in case there are unexpected leaks or spills.

2015-06-14 005

Some of the dispensing options available include:

  • Dosatron – $940-$1000 – Allows for injection of sanitizing chemical directly into the flow stream of water being used in the process.  Measurement is done by adjusting flow ratio similar to a fertigation system.
  • Goat Throat – $299 – GoatThroat 300 Pump with Viton seals. Allows a manual, enclosed pumping with integral valve.   No closed measurement.
  • EnviroSelect Dispensing Pump (BioSafe Safety Value Pack) – $75 – Allows a manual pumping of liquid directly from container without pouring.  No integral valve, and no closed measurement.

When I reviewed these options, I felt there was still a need for something at the lower end of use volume.  Something that would work for 30 to 300 gallon washing batches.  So that is why I put together the assembly that is posted on FarmHack with a parts cost of less than $50 and assembly time of less than 1 hour.  I think it may be helpful. Let me know what you think, and feel free to join in the design discussion on FarmHack.

Farm Building Plans

Posted: June 15th, 2015 by Chris Callahan

I sometimes receive requests for help designing barns, sheds and other structures. It is a bit out of my scope of practice, but there are loads of designs available from the Midwest Plan Service (at Iowa State University) including their free building plans section.  There are also other plans available from the Canadian Plan Service and North Dakota State University.

 

Calculating Greenhouse and High Tunnel Heat Loss

Posted: April 1st, 2015 by Chris Callahan

I am often asked by growers to help estimate what size heater is needed for a greenhouse or what minimum temperature their high tunnel will reach at a certain outside temperature.  Below are some tools to help you do this yourself.  I have presented them in a range of complexity depending on how much you really want to get into the math.  Enjoy.

1. SIMPLEST – Online greenhouse heat load calculator. http://www.greenhousemegastore.com/greenhouse_btu_calculator This online calculator allows you to enter the dimensions, construction material and temperatures you are interested in and it estimates the heat (and cooling) load.

2. LITTLE MORE COMPLEX – VirtualGrower – http://ars.usda.gov/services/software/download.htm?softwareid=309. This is a free software tool from USDA ARS that is a bit more complicated than the simple form above. But there is benefit to the complication. As with any analysis, the more you put into it, the more you get out of it. VirtualGrower allows easier management of multiple “what-if” scenarios, includes regional weather and light data automatically, and accounts for heating and ventilation systems. You may find it interesting and useful.

3. HEAVY LIFTING, but FULFILLING – Do the calculations yourself! The formulae behind all of the tools above are well described in “Greenhouse Engineering, NRAES-33” by R. A. Aldrich and J. W. Bartok. Available here as a PDF: http://host31.spidergraphics.com/nra/doc/Fair%20Use%20Web%20PDFs/NRAES-33_Web.pdf. See p. 65-71 specifically.

LED Lights – Status, Cost/Benefit and Pro’s and Cons

Posted: February 25th, 2015 by Chris Callahan

I have been receiving several inquiries recently on supplemental lighting for greenhouse production. The most common question is “Should I install LED lights to support growing?”
I have found one report to be the most complete and current on this topic and wanted to share it here.

Economic Analysis of Greenhouse Lighting: Light Emitting Diodes vs. High Intensity Discharge Fixtures by Jacob A. Nelson and Bruce Bugbee. Published: June 6, 2014. DOI: 10.1371/journal.pone.0099010. http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0099010. Erik Runkle at Michigan State University also summarizes some of this work in Greenhouse Product News here.

There are some industry responses to this including this one from Inda-Grow. And a recent USDA report is somewhat contradictory in its findings here.

There is a also a nice summary by Robert Morrow in Hort Science (HortScience December 2008 vol. 43 no. 7 1947-1950) available here.

Nelson and Bugbee conclude;

The most efficient HPS and LED fixtures have equal efficiencies, but the initial capital cost per photon delivered from LED fixtures is five to ten times higher than HPS fixtures. The high capital cost means that the five-year cost of LED fixtures is more than double that of HPS fixtures. If widely spaced benches are a necessary part of a production system, LED fixtures can provide precision delivery of photons and our data indicate that they can be a more cost effective option for supplemental greenhouse lighting.

Manufacturers are working to improve all types of lighting technologies and the cost per photon will likely continue to decrease as new technologies, reduced prices, and improved reliability become available.

My take-away from all of this; LED’s have a higher initial cost, can have lower recurring costs, can be more effective for specific physiological benefit, and can support certain production layouts.  But the cost/benefit does not seem to pencil out quite yet.
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