What is the binder used in charcoal?

Question

Trying to determine if it's safe for compost bins

Answer 1

Here is the information you seek:

The fine charcoal may be specially made from feedstock which can only produce powdered charcoal (22) e.g. bark or it can be residual fines from conventional wood charcoal making operations (3).

The usual binder is starch from any source, whichever is the cheapest. It doesn't have to be an edible grade. Although other binders have been used such as china clay and molasses these do not produce as satisfactory a briquette as starch. For special briquetting operation where the binder is to be carbonised later as in electrode manufacture pitch and tar can be used. Binders which produce an objectionable odour or smoke on burning are not acceptable for the domestic market. The binding agent also needs to be fairly resistant to fermentation and bacterial attack during storage to meet market fluctuations. All these considerations tend to favour starch as the best all-round binder.

The filler if used is selected on price - it has to cost less by weight than charcoal, be not abrasive to the machinery and free of objectionable odour on burning. Calcium carbonate in powder form fits the requirements. Sources are: ground limestone, chalk and ground shells.

Flame colourants and odour producing material such as hardwood sawdust have been used in order to obtain a distinctive product for high priced markets.

The manufacturing process is as follows:

First the charcoal must be pulverised and screened to reduce it to a uniform size and remove gross impurities. Hammer mills are used fed from hoppers via automatic feeding devices. The screen analysis of the ground charcoal is the coarsest which will give a satisfactory briquette with minimum binder usage.

The ground charcoal is next mixed with the binder and filler, if used, plus any other additives. If starch is the binder it must first be cooked (gelatinised) with hot water before adding to the mixer. A ribbon type mixer is normal and proper mixing is essential to reduce binder consumption to the minimum.

The mixture then passes to the briquetting press. Photo 7 shows a typical press installation. The accepted type of press is the roller type adjustable for speed and pressure. The press illustrated has moulds for making pillow shaped briquettes.



Good luck with your search for information.

Answer 2

I was told that most of the binders is from starch or gum mixed with water to form a paste used in forming charcoal briquettes. I'd assume that it would be safe to use in compost bins that you're dealing with since it contains organic residues (wood). As you probably know, charcoal has been known to be a very good soil amendment.

Good Luck!

Answer 3

Briquette Binder

Answer 4

The trouble with charcoal is that it does not break down by itself.
If you are going to use it, crush it first.
It will be a great way to aerate the soil under those conditions.