Fuel Characteristics of (1) Glycerol and (2) Yam peel Briquettes

As a by-product of biodiesel production, glycerol seems like a good candidate for fuel application.
However, according to this review paper, it is NOT!
The reasons are:

1. Low calorific value (~18.0 MJ/kg) compared to kerosene and gasoline (~40 MJ/kg), making it incapable to sustain a stable flame in a conventional burner
2. High self-ignition temperature (370°C) compared to gasoline (280°C) and kerosene (210°C)
3. Its viscosity is high, making it hard to be atomized.
4. High salt content (ash content of ~3.5%), can cause corrosion in the burner injectors and in post-combustion systems.
5. One of the products of glycerol combustion is acrolein, an hazardous irritant and a possible carcinogen.

In a separate paper, the fuel quality of yam peel briquettes was investigated. If you click the link, it will direct you to download the PDF of the paper.

I was interested with this paper because yam is one of my favorite food. The fuel quality is decent, but not as good as commercial wood pellets that Pinnacle Renewable Energy Group made. Below lists the comparison between these two fuels.

1. Gross calorific value as received (the analysis basis is not stated in the paper)
   Yam peel briquette: 17.5 MJ/kg ; PREG Wood pellet: 19.0 MJ/kg
2. Moisture and ash content as received (basis not stated)
   Yam peel briquette: 11.0%, 3.9% ; Wood pellet: 6.0%, 1.0%
3. Sulphur and nitrogen content (dry basis)
   Yam peel briquette:  1.4%, 1.4% ; Wood pellet: <0.02%, <0.05%
4. Bulk density
   Yam peel briquette: 500 kg/m3 ; Wood pellet: 700 kg/m3

As you see from the above comparison, you can see that the briquette fuel quality is inferior compared to wood pellet. However, quoting the paper, it is a good fuel for "household cooking and small scale industrial cottage application".