Muhammad Afzal 1 , Alemayehu Bedane 1 , Shahab Sokhansanj 2

1. Storage of comminuted and uncommunited woody biomass , its effect on fuel quality and modeling for natural wind drying Muhammad Afzal1, Alemayehu Bedane1, Shahab Sokhansanj2 1Faculty of Forestry and Environmental Management,UNB 2Department of Chemical and Biological Engineering, UBC CSBE Annual Conference, Brudenell River Resort Prince Edward Island, July 12-15, 2009

2. 1.1 Background • Wood biomass is a source of energy • Biomass storage plays an important role in forest industry • Better storage can result in low moisture and high energy content in the fuel • Forest biomass residue can be stored either in the form of chipped or compacted into bundles • Identifying the best storage method would be helpful to improve forest harvesting operation

3. 1.2 Objectives • Identify the best method for wood biomass storage • Examine the changes in woody biomass properties during the storage period • Provide a drying model for predicting moisture and temperature profiles inside the storage piles

4. 2.1 Material and Methods • Material • Brown forest biomass of White Birch (Betula papyrifera) • One of the most commonly available species in Atlantic Canada • Stored for one year (Aug. 2007-Aug. 2008)

5. Methods : Experimental Piles • Wood chips • Covered pile • Covered with tarp- prevents rainwater from penetrating into it • Underneath covered pile • Prevents moisture penetration into the piles from the ground • Uncovered pile • Have adequate air flow from all directions • Each pile has an average of 3m height

6. Bundles • Old slash of birch was compacted into twelve bundles • Each bundles, average 3m in length, 0.5m in diameter and about 50 kg in weight • Loose Slash • the wood biomass was collected and stored loosely to have adequate airflow for natural air drying

7. At regular interval samples were taken to determine moisture content heating value ash content CNS composition Data collected during the storage period by using data loggers to measure the daily temperature in the piles ambient temperature relative humidity 2.2 Sampling techniques

8. 2.3 Heat and mass transfer model • Fick’s diffusion law • Heat balance equation • Initial conditions • Boundary conditions

9. Assumptions for the model • The wood sample is homogenous and the thermophysical properties are constant • The initial moisture and temperature distribution in wood was uniform • Perfectly compacted wood bundles so that heat and moisture do not get directly inside the piles • No heat generation inside the wood piles

10. 3.0 Results and Discussion • Changes in Moisture Content (MC) • Bundles • IMC ~29.50 %(db) • MC showed an increasing trend during the first 6 months Max. avg. ~80% (db) • MC ~40% db between Feb. – May 2008 • FMC ~50% db at the end of the drying period

11. Wood chips • Covered wood chip piles • IMC ~59.5% (db) • MC has been decreasing during the storage period • uniform drying in all part of the piles • FMC ~15% d.b at the end of the drying period

12. Underneath covered and Uncovered wood chip piles both had IMC ~59.5% An increasing trend during the whole storage period higher MC at the top part of the pile at center and bottom part of the piles showed approximately the same value of MC FMC is ~149% and 166% for Underneath covered and Uncovered piles, respectively

13. Loose slash wood biomass storage IMC~ 45.42 % (db) non-uniform MC trend in the piles during the storage period higher MC is at the top part the FMC ~67% at the end of the storage period • Moisture content versus time in loose slash pile

14. Changes in Calorific Values • Slightly higher loss of HV was observed in wood chip piles • Very low change in HV in bundles

15. Changes in ash content • Higher ash content change observed in wood chip piles • Low ash content change occurred in bundles and loose slash piles

16. Change in CNS composition • Higher sulphur content change observed in wood chip piles after storage 16

17. Temperature changes in the pile the same pattern with the ambient temperature during the whole storage period slight difference in different form of wood chip piles and bundles • Underneath covered woody chips pile • Covered woody chips pile

18. Temperature profile for uncovered wood chips pile The bottom part of the piles had higher temperature during low ambient temperature Temperature inside in all part of the bundles had slightly the same magnitude comparing to wood chips pile • In general woody chips pile has a high internal temperature than bundles due to low thermal conductivity of wood chip • Self heating was not observed in the piles during the storage period • Bundles temperature profile

19. Drying Model simulations • The model equations were solved using Finite Element Method (FEM) and depending on the moisture contents, average values: • It was simulated with the ambient temperature and relative humidity recorded during the experiment • Due to influence of rain during the storage, only moisture profile model for covered wood chips piles was done

20. Modeling of moisture profile • Covered wood chips pile

21. Temperature in covered wood chips pile • Temperture in uncovered wood chips pile

22. Modelling of temperature profile in Bundles

23. 4.0 Conclusions • Moisture content had a significant change through out the storage period • Rate of moisture increase was low in bundle storage but in undeneath and uncovered wood chips was higher • Covered wood chip piles • MC continuously decreasing during the storage period • uniform moisture content profile • Higher loss of calorific and dry matter was observed in wood chip piles than in bundles

24. Cont… • In general the storage of biomass in bundles can reduce the moisture contents and loss of calorific value. However, in case of wood chip piles proper covering can reduce moisture content. • The proposed drying model closely predicted the moisture and temperature profiles.

25. Acknowledgment • Financial assistance from NSERC and help from the research assistants and staff in the logistics of the experiment is greatly appreciated.

26. Thank you !!