This 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, MulchHay 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 anda 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($13.2per 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 ($5.2per million BTU)and a potential payback period of 2.4 years.
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Callahan, Christopher William, "An Update on Solid Grass Biomass Fuels in Vermont" (2016). UVM Extension Faculty Publications. 4.