Overall Summary

Primary Application

• Primary application is for treatment of separated manure solids or open-lot solids, packed beds.
• While no scale limits theoretically exist, practical economics potentially limit application to large dairies.
• No climate condition limitations exist with this technology.

Economic/Return on Investment Considerations

• Torrefaction has not yet been applied to dairy manure as feedstock, with economic considerations a strong reason for its non-application.

Industry Update

• Technology in combination with produce pelletization has begun to be commercially available due to increase in demand for biomass-derived fuels however as noted, no application to manure solids.
• Co-fired power generation industry is considering torrified biomass as coal replacement.

Technology Maturity

• Used for lignocellulosic feedstocks such as woody biomass at small scale. Not yet used for processing dairy manure.

Primary Benefits

• Reduces moisture in biomass feedstock.
• Increases heating/calorific value by increasing energy density.
• Hydrophobicity is increased in biomass, this increases storage/shelf life.
• Improves the handling characteristics of biomass (particle size, shape, and distribution).
• Increases its combustion efficiency.

Secondary Benefits

• Reduces biomass weight by more than 30%.
• Some nitrogen content of biomass can be lost.
• Phosphorus is retained with solid product (biochar).
• Odor could be reduced due to decomposition of volatile organic compounds during torrefaction.
• Pathogens do not survive at temperature of 200-300 ⁰C.

How it works?

• Torrefaction is a non-combustive thermo-chemical process in which biomass is heated in oxygen free environment with temperature range 200-300 ⁰C at low heating rates (less than 50 ⁰C/min) and less than 1 hour holding time at maximum temperature.
• Torrefaction is divided into several steps including heating, drying, and cooling.
• Removes oxygen and lowers O/C ratio of biomass by decomposing hemicellulose and not affecting cellulose and lignin content.
• Produces three products: biochar, (a charcoal like solid), torrified gas (a mixture of hydrogen, carbon dioxide, carbon monoxide, and hydrocarbons), and condensate (water, organic compounds, and lipids).
• Biochar accounts for 70% of mass and 90% energy of the original raw biomass.
• Torrified gas mixture accounts 30% mass and 10% energy.

Pretreatment and/or Post-treatment Required

• Torrefaction does not require any pretreatment of feedstock. It is itself a pre-treatment technology for lignocellulosic feedstocks for combustive technologies.
• Torrefaction requires pelletization as post-treatment to improve the energy density.
• Torrified and pelletized biomass is more convenient for transport and handling to use as feedstock for biofuel production.

Limitations

• Torrefaction has not been utilized for processing dairy manure either pilot or large scale.
• There is a lack of standardization and consistency for torrefaction protocols and qualitative assessment of their products.
• The cost of torrefied products could be higher than coal if utilized as coal replacement.

Other considerations

• Biomass feedstock’s characteristics (both physical and chemical) influence the distribution of torrified outputs including gas, liquid, and solid.
• Moisture content of biomass feedstock is critical to determinant for energy footprint of torrefaction.
• Torrefaction needs to be accompanied with pelletization to improve the economic, transport and handling viability of torrified products.
• Torrefaction is one of the thermo chemical technologies that has tremendous potential to advance the biomass-based energy industry if optimal policy and financial opportunities are created.