Technology Type - Torrefaction



Technology Strengths,Weaknesses and Critical Indicators

Torrefaction:

  • May produce a soil amendment in the form of biochar or ash
  • Biochar does not yet have an established, stable commercial market
  • There is significant variation in energy use and recovery depending on feedstock
  • There is significant variation of operational intensity by site and by technology, many technologies require pairing with other technologies to offer a comprehensive manure management solution
  • There is significant variation of cost depending on site and by technology
  • Proven technology for phosphorous recovery, storage reduction, GHG reduction, odor control and pathogen reduction
  • This technology loses nitrogen to the atmosphere

image/svg+xml Nitrogen Recovery Phosphorus Recovery Storage Reduction GHG Reduction Odor Control Pathogen Reduction Negative Positive NEAT MATRIX - Peer Reviewed P - Documented D - Expert Opinion E P D E P D E

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.


References
Acharya, B., Dutta, A., & Minaret, J. (2015). Review on comparative study of dry and wet torrefaction. Sustainable Energy Technologies and Assessments, 12, 26-37.

 

Bakri, S. N. S. B., Iwabuchi, K., Ito, K., & Taniguro, K. (2017). Investigation of torrefaction reaction on high moisture content biomass using dairy manure. In 2017 ASABE Annual International Meeting (p. 1). American Society of Agricultural and Biological Engineers.

 

Dai, L., Yang, B., Li, H., Tan, F., Zhu, N., Zhu, Q., ... & Hu, G. (2017). A synergistic combination of nutrient reclamation from manure and resultant hydrochar upgradation by acid-supported hydrothermal carbonization. Bioresource technology, 243, 860-866.

 

De Mena Pardo, B; Doyle, L; Renz, M and Salimbeni, A (Editors) (2016): Industrial Scale Hydrothermal Carbonization: new applications for wet biomass waste.

 

Heilmann, S. M., Molde, J. S., Timler, J. G., Wood, B. M., Mikula, A. L., Vozhdayev, G. V., ... & Valentas, K. J. (2014). Phosphorus reclamation through hydrothermal carbonization of animal manures. Environmental science & technology, 48(17), 10323-10329.

 

Toufiq Reza, M., Freitas, A., Yang, X., Hiibel, S., Lin, H., & Coronella, C. J. (2016). Hydrothermal carbonization (HTC) of cow manure: carbon and nitrogen distributions in HTC products. Environmental Progress & Sustainable Energy, 35(4), 1002-1011.

 

Wu, K., Gao, Y., Zhu, G., Zhu, J., Yuan, Q., Chen, Y., ... & Feng, L. (2017). Characterization of dairy manure hydrochar and aqueous phase products generated by hydrothermal carbonization at different temperatures. Journal of Analytical and Applied Pyrolysis, 127, 335-342.

 

Wu, K., Zhang, X., & Yuan, Q. (2018). Effects of process parameters on the distribution characteristics of inorganic nutrients from hydrothermal carbonization of cattle manure. Journal of environmental management, 209, 328-335.

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