Pyrolysis - Biomass Gasification, Pyrolysis and Torrefaction - page 175

5.8.1 Potential Benefits of Biochar
Biochar has a number of benefits as listed below ( www.biochar.ca , www.
biocharfarms.org ):

1. Sequesters carbon and thereby minimize climate change
2. Carbon negative emission
3. Displaces carbon positive fossil fuels
4. Reduces nutrient losses in soils
5. Reduces fertilizer use
6. Enhances marginal soil productivity
7. Increases sustainable food production
8. Improves water retention, aeration, and tilth
9. Higher cation exchange capacity (CEC)
10. Improves water quality by reducing contaminated runoff and nutrient
loss
11. Soil remediation
12. Reversal of desertification on massive scales and can work in tandem
with reforestation
13. A better alternative to slash-and-burn of agricultural residues
14. Decreases nitrous oxide and methane emissions from solids
15. Net primary production
16. Generates carbon offsets and increased on-farm profitability for the
company.

As mentioned earlier, biochar is produced through pyrolysis as the
solid by-product. The quality of biochar is defined by its following

characteristics:

The BET or internal surface area
pH of the char
CEC of biochar
Carbon recovery in char.

Above characteristics of biochar depend on how biochar is produced. It is
thus influenced by the following three processes and feed parameters:

1. Temperature
2. Type of biomass
3. Residence time.

Pyrolysis temperature is the most important parameter influencing the
properties of biochar. Figure 5.10 shows that there is a sharp increase in sur-
face area between temperature 450 C and 550 C. The CEC also increases
during the period. The pH increases steadily within the temperature range of
200 800 C. The carbon yield or carbon recovery decreases with temperature