Vermont Experience With Anaerobic Digesters Dan Scruton

Vermont Agency of Agriculture, Food and Markets Vermont Methane Pilot Project Started in 1999 with DOE funds thanks to Senator Jeffords Started in 1999 with DOE funds thanks to Senator Jeffords Initially wanted to set up pilot sites Initially wanted to set up pilot sites Decision to step back and determine why the systems from the 1970s and 80s did not catch on Decision to step back and determine why the systems from the 1970s and 80s did not catch on

Vermont Agency of Agriculture, Food and Markets Program Mission Identify, and help overcome, the strategic hurdles to widespread adoption of agricultural methane recovery and use technologies Identify, and help overcome, the strategic hurdles to widespread adoption of agricultural methane recovery and use technologies

Vermont Agency of Agriculture, Food and Markets What Did We Do ? Vermont Methane Pilot Project Initial Literature Search Vermont Methane Pilot Project Initial Literature Search  Most of the systems from the 1980’s no longer in use Resource Assessment Resource Assessment  Cows = 28 megawatts Attached Growth Research Attached Growth Research  Dramatically shorter retention times are possible

Vermont Agency of Agriculture, Food and Markets Feasibility farms Positive cash flow in the 500 cow and up Positive cash flow in the 500 cow and up  7 year pay-back or better 300 to 500 cows positive if put a value on odor 300 to 500 cows positive if put a value on odor Small farms may be viable for hot water only systems if manure liquid or niche (making cheese so have supply of whey) Small farms may be viable for hot water only systems if manure liquid or niche (making cheese so have supply of whey) Farmer generally gets better return on capital with other uses of the money Farmer generally gets better return on capital with other uses of the money

Vermont Agency of Agriculture, Food and Markets Hurdles MARGINAL ECONOMICS MARGINAL ECONOMICS Traditional designs only suitable for largest farms Traditional designs only suitable for largest farms Perception of Complicated Operation Perception of Complicated Operation Problematic designs causing high maintenance Problematic designs causing high maintenance

Vermont Agency of Agriculture, Food and Markets Hurdles Gas quality Gas quality  low BTU  H 2 S is corrosive Sale to grid was complicated Sale to grid was complicated Low wholesale price Low wholesale price Little to no existing service industry Little to no existing service industry Ancillary benefits not quantified Ancillary benefits not quantified

Vermont Agency of Agriculture, Food and Markets Hurdles Time. Time. Farmers already working long days and do not want more headaches. Farmers already working long days and do not want more headaches.

Vermont Agency of Agriculture, Food and Markets Hurdles Significant problems with recent systems Significant problems with recent systems Technology need to improve before widespread adoption is recommended Technology need to improve before widespread adoption is recommended Hasn’t slowed the flow of salespeople Hasn’t slowed the flow of salespeople

Vermont Agency of Agriculture, Food and Markets Solutions Legislative Legislative Technical Technical On-farm On-farm Just keep nibbling away.

Vermont Agency of Agriculture, Food and Markets Net Metering Credit power from generation meter to other farm meters Credit power from generation meter to other farm meters  Barns, houses, employees, etc. 150 kW max 150 kW max No demand or time of day charges No demand or time of day charges Simplified regulations while still safeguarding safety and power quality Simplified regulations while still safeguarding safety and power quality Can “BANK” power for one year Can “BANK” power for one year

Vermont Agency of Agriculture, Food and Markets Existing Demonstration Site Foster Brothers Farm in Middlebury, VT Foster Brothers Farm in Middlebury, VT  Active digester since 1982 Side-by-side system Side-by-side system Investigate simpler designs Investigate simpler designs Reduce maintenance Reduce maintenance Shorter retention times Shorter retention times Can try things without major expenses Can try things without major expenses

Vermont Agency of Agriculture, Food and Markets Research at Fosters Steam for heating Steam for heating  Reduced start-up from months to weeks  Gas output starts much faster  Excellent at dealing with frozen manure Economics reasonable on whole manure systems Economics reasonable on whole manure systems

Vermont Agency of Agriculture, Food and Markets New On-Farm Systems? Three systems are under construction Three systems are under construction Plug Flow Plug Flow Vertical Plug Flow Tank Vertical Plug Flow Tank Mixed Tank Attached Growth Mixed Tank Attached Growth

Vermont Agency of Agriculture, Food and Markets Whole Manure Horizontal Flow “U” shaped cross agitated plug-flow digester “U” shaped cross agitated plug-flow digester 20 day retention time 100°F 20 day retention time 100°F Generator selling all of its power to the utility Generator selling all of its power to the utility Working with CVPS on Cow Power Working with CVPS on Cow Power

Vermont Agency of Agriculture, Food and Markets Digested Solids for Bedding Separating manure after the digester Separating manure after the digester Digested solids Digested solids  ½ Dried down partial for use as bedding  ½ Available for land use or sale off farm

Vermont Agency of Agriculture, Food and Markets Whole Manure Vertical System

Vermont Agency of Agriculture, Food and Markets Swamp-On-A-Rope Totally different approach to manure handling Totally different approach to manure handling Separate manure first Separate manure first Liquid to a digester designed to: Liquid to a digester designed to:  Be delivered fully assembled  Digest in 2 days (normally 20) Liquid then goes through a system that outputs: Liquid then goes through a system that outputs:  Nutrients in a sludge  Clear water that meets EPA discharge standard

Vermont Agency of Agriculture, Food and Markets Major Ramifications No hauling water around on the roads No hauling water around on the roads No liquid manure storage to stir No liquid manure storage to stir No odors from spreading liquid manure No odors from spreading liquid manure Potentially the nutrients will be segregated between P and N Potentially the nutrients will be segregated between P and N  Farmers could easily match application rates to soil needs

Vermont Agency of Agriculture, Food and Markets Thank you Dan Scruton