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Credit: Ohio State University  What is biomass?  A fuel derived from plant material  Types of fuels for combustion  Wood ( cord, chips, pellets )  Excluding or waste oils/grease  Grains ( corn, rye, ,…) Biomass Heating of  What is a boiler or furnace?  Cherry pits, sunflower hulls Credit: NREL  Prairie grass ( switchgrass, ) Greenhouses  Outdoor wood-fired hydronic heaters  Crop fodder ( corn stalks )  Pellet / grain fired boilers / furnaces Scott Sanford  ( wheat, , )  Stand alone Sr. Outreach Specialist  Oils  Case Study of two greenhouses Rural Energy Program

Credit: NREL Credit: University of Illinois

Material Characterization Types of Wood Fuels What is a Biomass fuel   Unit of measure – Cord, tons, pounds Energy content varies with H 20, density and ash  Cord wood  Direct use – wood, grains  Moisture  Reduces net energy content  Green mill residue  Bulky – straw, prairie grass, hay, sawdust  Water must be evaporated before burning will initiate  Hogged bark & sawdust  Densify for use – pellet / cube  Energy content – Btu / unit of measure  High moisture (>20%)  Store outside in piles  By-products –  Low Heating Value (LHV) – net energy after moisture is evaporated  Dry mill residue  Cherry pits, sunflower hulls, nut hulls, hulls  High Heating Value (HHV) – net energy if moisture is  Low moisture (< 10%) condensed after combustion.  Processed fuels – Oils or sugars  Sawdust, trimmings, wood from wood products  Size and shape companies  Ash content (pellets)  Wood Chips  Chemical contents: Chloride  Whole tree chips, round wood chips, clean chips  Typically high moisture (~50%)

Miscanthus x giganteus Credit: University of Arkansas Direct Use – Direct Use – Green Wood Chips Direct Use - Wood Cord wood  Local availability   Cord wood / logs “Low cost” ???  Low cost  Unit of measure – Cord  Labor intensive  Moisture Content  4 ft x 4 ft x 8 ft stack of wood – 128 sq ft  Handle 3 to 6 times  Green ~ 50% moisture Credit: JoAnn Sandberg  Moisture – 50% as harvested  Harvesting  Lower energy content  4500 Btu/lb  Air Dried - ~ 20% (1 – 2 years)  Cut, transport, split, pile/stack,  Energy content – varies with tree species  Bulk handling  Air dry - Minimum 1 summer / 2 better  Average – 22,300,000 Btu / cord @ 20% moisture  Augers  Plan requirements 1-2 yrs ahead  Range – 14,700,000 to 30,700,000 Btu / cord  Loaders

 Refueling labor Source: NREL  Different species vary in density (lbs / cord)  Storage  Basswood – 2100 lb / cord; Hickory 4160 lb / cord  Ash disposal  Outside pile  All wood about 7000 Btu / lb. @ 20% moisture  High emissions – new regulations  Bunker / covered

Direct Use - Grains Direct Use - Grains  Corn Calculating Heat values   Unit of measure – Bushels or pounds/tons Wheat  Bulk in bushels or 50 pound bags  Bushel – 60 lbs @ 13.5% moisture  Corn  56 lbs per bushel @ 15.5% moisture content   Moisture  Bone-dry – 8250 Btu per pound  Bushel – 32 lbs @ 14% moisture  15.5% std; also available at 12% by some retailers  If corn is 15% moisture then one pound of corn:  Energy content  Barley  0.85 pounds corn  6810 (15%) to 7130 (12%) Btu per pound  Bushel – 48 lbs @ 14.5% moisture  0.15 pounds water  Advantages  Rye  Readily available  Water require 1050 Btu / pound to evaporate  Bushel – 56 lbs @ 14% moisture  No processing  0.85 x 8250 – (1050 x 0.15) = 6855 Btu / pound  Annual crop – mechanically harvested and handled   Disadvantage  Bushel – 60 lbs @ 13% moisture  Slag / Clinkers (solid ash)  Sunflowers  There may be further losses to transfer heat to air  Drying required for storage / proper combustion  Per 100 lbs or cwt. @ 10% moisture or water in boiler or furnace.  Need wood pellets to start burning  Typical efficiencies = 80%  Flame out at lower feed rates / higher moisture levels Densification Wood Pellets Pellets / cubes Densification  Material – Sawdust, wood residue  Unit of measure – Tons or pounds  Facilitates handling  Pellets  Bulk in tons or 40-50 pound bags  Reduces transportation costs Source: Kevin Shinners, U of Wisconsin  1/4” to 5/16” diameter x 1” to 1-1/2” long  Moisture  Use of by-products / low value materials  Wood, Prairie grasses, paper  6 to 10% depending on grade  Uniform product  Use in pellet stoves/boiler  Energy content  Bulk Handling – grain handling equipment  Average – 8000 Btu / lb  Cube or Briquette  Dry storage needed  Grades (Pellet Fuels Institute)  1” x 1-1/4” cube  Automatic stoking  Utility, standard, premium, super premium  Used to replace coal  Difference is mainly ash content 6%, 2%, 1%, 0.5%  Low emissions / low smoke  Industrial boilers  Uniform product  Higher thermal efficiency – 80% to 90+%  Higher cost / energy input Ref: http://www.pelletheat.org/3/institute/standards/PFI%20Standards.pdf

Biomass Pellets Biomass Fuels What is a boiler versus a furnace?  Materials  Prairie grass mixes (Switchgrass, Miscanthus, hay)  Boiler heats a fluid (water, glycol/water  Straw (wheat, oat, barley, rye) Wood solution, steam)  Corn fodder (stalks & cob) Corn Pellets  Fluid can be pumped to the location where it is to  Nut hulls, sunflower hulls be used.  Wood residue  Unit of measure  Furnace heats air  Bulk in tons or 50 pound bags  Air blown through ducts to location needed  Moisture  8-11% typical  Energy content Prairie  7200 to 8000 Btu per pound Grass  Higher energy contents typically include some wood residue Small  Chloride content – Often higher than PFI standard of 300 ppm max Pellets Grains  High temperature corrosive agent – boiler corrosion over time (Rye & Vetch)

Outdoor Hydronic Heater Pellet furnace Pellet boiler & bin Credit: HarmanStoves Credit: Josh Kaurich Outdoor Wood Boiler Emissions Boilers Furnaces

 One boiler can heat multiple greenhouses  Heats air directly  One system for under-bench / floor heating  Reduces heat exchange losses and supplemental water/air heat exchanger  Located in or adjacent to greenhouse  Can be located outside the greenhouse  Takes up growing space?  Maximize growing space  No leaks to worry about  Boilers can be in central location  May need multiple furnaces per greenhouse  One fuel storage system  Multiple fuel storage bins or labor to fill  Store heat in tank of heat transfer fluid furnace hoppers

Credit: Josh Kaurich Outdoor Wood-Fired Boilers Pellet Boiler EPA Qualified Outdoor Boilers  Fuel: Wood, scrape materials, pallets  “Cheaper” Fuel? – What is the true cost?  90% lower emissions  Labor / equipment to collect / harvest fuel  Labor to re-fuel  Low emissions = higher efficiency Boiler Pellet Supply Bin  Disposal of Ash  Average efficiency of qualifying boilers - ~ 70%  High emissions rate / Smoke  Many states are restricting sales to EPA qualifying  Reduce with firebox management models  Low Efficiency  White tag / Orange tag Ash Bin  pre-2008 Efficiency range: 20 to 50% Wagon  2008 EPA Standards for outdoor boilers   Great for use with floor heating EPA information   Can use with Air Exchanger www.epa.gov/woodheaters/  Fuel with scrap materials? List of qualifying outdoor wood stoves   Increasing regulation due to smoke emissions www.epa.gov/owhh/models.htm Credit: JoAnn Sandberg Boiler Ash Auger Controls Feed Auger 500,000 Btu Pellet / corn furnace Pellet/corn furnaces Credit: Vern Grubinger, University of Vermont Credit: Vern Grubinger, University of Vermont Keep your old system for backup and COLD nights!

Pellet / corn furnace ~165,000 Btu

Credit: Vern Grubinger, University of Vermont

Pellet Boilers / Furnace Advantages How is the heat distributed?

 Fuel homogenous  Variety of fuel pellet sources  Furnace – Ducts and fans  Wood  Poly bags – may not be suitable depending on Credit: Focus on Energy  Paper outlet temperature.  Biomass  Boiler  Accurately adjust burn rate  Water to air heat exchanger  Feed auger speed  Bench-top or under-bench or floor heating  Low emissions  Develop a micro climate  High efficiency  Warm roots increases growth  May still need water to air heat  80% typ., up to 90+% exchangers for cold spells.  Low labor – automatic stoking and ash removal Water to air heat exchanger Source: www.thermpex.com Credit: Vern Grubinger, University of Vermont Bench heating system Credit: Vern Grubinger, University of Vermont Wood Chip Boiler Supply and Return piping  Higher capital investment  Higher maintenance

 Many moving parts Source:www.danvillek12vt.org  Suited for industrial applications  Uses low cost product  Labor to re-fill charge hoppers required daily  Wood chips – 25 to 50% moisture Small heating tubes run in loops on growing bench  Need storage for tractor trailer load Plus of chips 3,000 gallon tank stores heat in water,  Availability of supply?? which allows furnace to run hot

Credit: Vern Grubinger, University of Vermont

Credit: Vern Grubinger, University of Vermont Fuel Comparison Stand Alone Stoves Energy Content Boiler Thermal Cost per Fuel type Unit Cost 1 Btu per unit Efficiency 4 1,000,000 Btu

 Advantage Corn 380,000 / bu 70-85% (80%) $5.00 / Bu $16.45  Low cost Wood Pellets 15,400,000 / ton 70-85% (80%) $220/ton $17.82  Easy to install Outdoor Wood 19,200,000 / full 40% $200/ full $24.04  Fast payback Boiler - typical cord 2 cord 5  Supplemental heating Outdoor Wood 19,200,000 / full 69% $200/ full $13.94 Boiler – EPA P2 cord cord 5  Disadvantage Electricity 3413 / kWh 100% $0.11/kWh $32.23  Hopper may be too small to last all night Propane 91,500 / gallon 70-85% (78%) $1.70/gallon $23.82  May not be thermostatically controlled – overheating Natural Gas 100,000 70-85% (78%) $1.15 / Therm $14.74  Heat distribution not optimal /Therm 3 Heating Oil 138,000 / gallon 70-85% (75%) $2.50/gallon $24.15  Low Btu output - ~ 30,000 to 70,000 Btu/hr

1) Costs available in Madison, WI – October 2008. 2) Full Cord has a volume of 4 feet x 4 feet x 8 feet or 128 cubic feet 3) 1 Therm (100,000 Btu) equals approximately 1 CCF – hundred cubic feet equals 4) (XX%) Efficiency value used to calculate “Cost per 1,000,000 Btu” 5) Based on purchasing cut and split wood from a vendor Sizing a heating system Case Study #1 Options for Biomass Heating

 What percent of the heating do you want to Option A  30’ x 96’ freestanding gothic greenhouse replace?  Residential/shop pellet  Double poly glazing  Full Replacement  Rated output - 70,000 Btu/hr  Some proportion of total heating  Used Feb to June – veg. & bedding plants  Supplement heating  System capacity can be smaller  Currently has two 200,000 Btu power-vented  operated mainly at night  No Thermostat Source:www.bixbyenergy.com/sto  Runs continuously to be most efficient unit heaters – ves/index.php  Propane fuel - $2.00 /gallon  Installed cost $4350  Stove efficiency = 80%  Set point temperature: 70°F day, 60°F night  Wood pellet cost - $4.20 / 40 lb bag ($210 / ton)  Location: Madison, WI

Options for Biomass Heating Options for Biomass Heating Options for Biomass Heating

Option B Option C Option D  Thermostatically controlled pellet furnace  EPA Phase 2 outdoor wood boiler  Same as Option C except non EPA qualifying  Heating capacity range: 10,000 to 160,000 Btu/hr  Average capacity (8 hour period) – 160,000 Btu/hr boiler  Furnace efficiency = 80%  Two water to air heat exchangers (HE) in center  Installed cost $11,634  Air ducted directly into the greenhouse above of greenhouse to distribute heat plants  Thermostatically controlled  Estimated Efficiency = 40%  Located at one end of greenhouse  Pump to HE turns on when greenhouse requires heat  Installation cost = $6030  Installed cost - $13,050 (boiler, all piping, heat exchanger)  Includes 14 bushel fuel bin  Average boiler efficiency = 75%  Bagged pellets assume to avoid cost of bulk  Full Cord of Wood - $150/cord (assuming self storage - $4.20 / 50 lb bag harvested) Average Night Heating How much heat can Biomass provide? Summary of Biomass Heating Options Requirements by Month Baseline: 1592 gallon propane @ $2.00/gal = $3184 / year Heating Biomass Simple Month Heating requirements Approx. average hourly  Option A – 100% of heating down to ~40F System Biomass Propane Propane Total System Energy Payback Cost Quantity (gallons) Cost Savings Btu/day heating - Btu/hr  Estimated 50% reduction in propane use Cost (years) A) Residential February 1,643,818 136,985  Options B, C & D – 100% of heating down to ~ 282 pellet stove $ 4350 $ 1184 639 $ 1278 $ 722 6.0 March 1,119,650 93,304 10F 40# bags B) Pellet 355 April 732,940 61,078  Average monthly minimum Feb temperature $ 6030 $ 1491 318 $ 636 $ 1057 5.7 furnace 40# bags May 343,839 28,653  14.3°F C) Outdoor wood  Based on Average Options B, C & D can supply 100% $ 13050 6 cords $ 900 318 $ 636 $ 1648 7.9 of needs boiler-EPA • Day-time heating, on-average, are fully met by solar Certified radiation except for February  Reality – estimated 20% will be supplied by propane D) Outdoor wood $ 11634 10 cords $ 1500 318 $ 636 $ 1048 11.1 • Average February day-time heating – 12,800 Btu/hr boiler

Average Night Heating Case Study #2 Outdoor Wood Boiler Option Requirement by Month

Heating  Gutter-connected T-shaped greenhouse  75% efficient Boiler Approx. average hourly heating Month Requirements Btu/hr  33,000 square feet  Require 389 cords of wood Btu/day September 8,424,853 702,071  Double Poly film glazing – roof and walls  Would increase labor requirements October 15,018,403 1,251,534  Year-round production  Handling and refueling November 22,012,158 1,834,346  Heating system – In-floor heating with unit  No “Free” wood source December 29,167,064 2,430,589 heaters for peaking on cold nights January 31,150,243 2,595,854  Fuel: Propane @ $2.00 / gallon February 28,137,714 2,344,809  Not included in analysis  Baseline energy use – 85,581 gallons LP gas March 21,901,552 1,825,129 April 15,388,874 1,282,406  $ 171,162 annual heating cost May 5,862,478 488,540 Heating Demands Options for Biomass Heating Options for Biomass Heating

 Based on Madison, WI the recommend Option A  Option B design temperature for a heating system is -  Meet 100% of heating requirements  Boilers sized to meet average heating 20°F  Two pellet boilers – 3.5 MBtu/hr & 1.5 MBtu/hr requirement  Recommend design temperatures available from  Average efficiency = 78%  Two pellet boilers – 2.5 MBtu/hr & 1.0 MBtu/hr National Greenhouse Manufacturers Association  Use smaller boiler during spring and fall months  Use smaller boiler during spring and fall months  www.ngma.com  Large boilers hard to throttle for low demand  Large boilers hard to throttle for low demand  Under “downloads” - Heating systems standard  Estimated 5% of season would use propane heaters  Estimated propane use – 20%  Heating requirement - 4,200,000 Btu/hr  Bins for bulk delivery of pellets  Bins for bulk delivery of pellets  Installed Cost: $291,000  Installed Cost: $211,000

Credit: Josh Kaurich The Flower Farm Resources Pellet Boiler Eau Claire, WI Summary of Options  U of Wisconsin Extension Bulletins  Biomass Energy for Heating Greenhouses, A3907-04 Tons of Wood Simple  Biomass Heating in Greenhouses: Case Studies, A3907-05 Capital Propane Energy Option Wood Pellet Payback Cost Cost Savings  http://learningstore.uwex.edu/Energy-Conservation-C29.aspx Pellets Cost years  Pellet Fuels Institute – www.pelletheat.org  Educational material, pellet manufacturers list A $291,000 465 $82,770 $8,558 $79,834 3.6  Biomass for combustion calculator  www.ruralenergy.wisc.edu/esa B $211,000 392 $69,776 $34,232 $67,154 3.1  Focus on Energy – www.focusonenergy.com  Installer list, factsheets, grant information  Burning Shelled Corn—A Renewable Fuel  http://energy.cas.psu.edu/shellcorn.html Questions

This presentation was develop by: Scott Sanford Sr. Outreach Specialist Rural Energy Program University of Wisconsin-Madison

Comments and suggestion should be directed to [email protected] The contents of this presentation can be used in whole or in part for greenhouse grower education.