1. Energy Return on Investment and Techno-economics of Pellet
Production from Steam Pretreated Biomass
Research Summary
Co-firing biomass pellets with coal has been considered a
method to reduce GHG emissions. However, pellets have
low calorific value and bulk density and so are not
suitable for co-firing. In this research, steam pretreatment
was considered as a suitable process to evaluate the
economic impact of the pretreatment process on the
overall supply chain.
The main objectives of the research were to develop a
process model to evaluate specific energy consumption of
steam pretreatment and compare it with regular pellet
production at various scales. The specific objectives were
to develop a process model for stream pretreatment of
ligno-cellulosic biomass for pellet production, evaluate
energy and mass balance of the steam pretreated pellet
production process, calculate the NER of the
streampretreated pellet production process, develop a
data-intensive techno-economic model to evaluate
production costs, estimate pellet production cost ($ tonne-
1 and $ GJ-1) for three feedstocks, determine the optimum
pellet production size from three feedstocks through two
processes: steam pretreated and regular pellet production.
The techno-economic model indicates that the process
production cost (calculated in $ GJ-1) is on par with the
production cost for both regular and steam pretreated
production processes. The major cost contributor for
steam pretreated production costs are capital, energy, and
delivered costs. Optimizing drying and steam
pretreatment energy costs can significantly improve the
production cost.
Major Results
The steam pretreatment process was found to be energy
intensive. The net energy ratio (NER) was calculated for
both processes. The NER of the steam pretreated pellet
process was found to be 1.29, while the NER of the
regular pellet process was found to be 5.0. The major
reason for this deviation is the high energy requirement
of the steam pretreatment and drying units.
Conclusion
The results obtained here through process modeling and
techno-economic studies would help optimize the design
and operation of a commercial pellet plant with the
addition of the steam pretreatment process.
Name Degree Year Supervisor
S M Hassan Shahrukh M.Sc. 2015 Dr. Amit Kumar
Department of
Mechanical Engineering
Schematic flowchart of the developed steam pretreatment model. The boiler is
represented as a heater unit and the steam pretreatment unit considered is a yield
reactor.
Process net energy ratio (NER) falls as temperature increases. The major contributor of
the energy input is from the steam pretreatment and drying units.
Comparison of $ GJ-1 cost between steam pretreated and regular pellets.
Acknowledgement
The authors are grateful to BiofuelNet Canada and the
University of Alberta for the financial support.
0.51
0.53
0.55
0.57
0.59
0.0
0.5
1.0
1.5
2.0
2.5
190 200 210 220
MassofPellet
NetEnergyRatio
Small Scale Large Scale Produced Pellet
0
1000
2000
3000
4000
5000
6000
7000
8000
RegularPellet 190 200 210 220
EnergyUse,kJ
Pelletization
Grinding
Drying
SteamTreatment
BiomassCollection,Processingand
Transportation