[Stoves] water hyacyth and combusting plastics in briquettes

Crispin Pemberton-Pigott crispinpigott at outlook.com
Wed Jun 28 03:20:46 CDT 2017


Dear Michael

I am interested in the claimed ‘no problem’ for the glue thing. Who said what about which product?

If you know of someone who knows of someone let’s track down the source story. It is a perennial question so a proper answer would be helpful.

Thanks
Crispin


From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Michael N Trevor
Sent: 28-Jun-17 15:25
To: Discussion of biomass cooking stoves <stoves at lists.bioenergylists.org>
Subject: Re: [Stoves] water hyacyth and combusting plastics in briquettes

Dear Richard delighted to hear from you.  Thanks for you detailed coverage and I hope other find it useful and can apply it.  The waste company here was still doing just cardboard and not even that for some time.  The market sort of collapsed after someone bad mouthed them as a hazard because of the glue in cardboard.  Actually they were sent out and tested and were given a clean report safety wise.

On Wed, Jun 28, 2017 at 6:54 PM, Stanley Richard <rstanley at mind.net<mailto:rstanley at mind.net>> wrote:
Hello Michael,..
Many years ago in the Shri River at the outlet of Lake Malawi and again up in Uganda near  the outlet of Lake victoria we experimented with the use of water hyacinth as a fuel for briquettes. What we learned was that the hyacinth dries up to almost nothing in a few days once picked in the dry season. Drying it out completely will leave the fibers brittle and any disturbance such as blending with other resources before compression,  renders it into dust and crumbs which are pretty much useless unless bound by other functioning plant fiber material. However, if kept wet then chopped they can be great for binding up other more energy-dense & lower ash residues e.g.; sawdust, select leaves & grasses, charcoal dust and crumbs etc.,
We were unimpressed with the burn quality of the fiber itself though. By itself it tends to smolder. Again however using it as a binder to encapsulate more combustible materials such as mentioned above, they can be quite useful.
Michael, I have seen lots of woven articles baskets rugs etc made out of the fibers but have no direct contact with any of them.

Re., the utility of burning plastics in briquettes (presumably of the wet process type we tout), a little story
In  seeing the national flower of Mali  jokingly described  as the plastic shopping bag, I inquired about its potential and were similarly cautioned by many on this list about plastics combustion in general. We also discovered  however that both Swedish and British professional institutional waste management sources recommended its incineration—under controlled conditions— as being less harmful than dumping them into a landfill. What then emerged through our group was the advice that polyethylene, the  key source for the shopping bag-  a relatively simple short chain hydrocarbon, which can be burnt rather leanly if combusted above 400 deg c ( about  750 deg fahrenheit).

Two simple  indicators of polyethylene  are in, apparently in the way it burns:  no black smoke and the way it smells: the smell of a simple paraffin candle burning. (these and a few other means of making simple field identification of the types of plastics are found through a simple google search).


Armed with this , I made several attempts to incorporate the plastic bag into the briquette —-as it turned out, part of a month long consultancy in Bamako Mali many years ago..
What I learned was this:

1) The plastic bag has to be shredded in, most commonly, a hammer mill to assure fine wispy shards of cornflakes-sized strands.  The reason is that wet process briquettiing we tout,  requires a relatively porous structure after compression and initial dewatering, in order for the retained moisture to emigrate from the briquette.
2)  The shards themselves must be really wispy-- with lots of torn edges The resulting fibers need to function as binders, encapsulating other combustibles (paper /sawdust /leaves/ grasses /straws etc etc).
Simply cutting the plastic bags into small cornflake sizes will not suffice as such merely hinders binding and greatly retards moisture emigration.
If you have a way to shred them per above you can quite easily incorporate as much as one 7 to 9 gram shopping bag into one  4” dia x 3 “ tall briquette   weighing 125 to 140 grams dry (at ambient moisture) .

This is potentially really interesting because:
On average ten to 12  of the above sized briquettes are required per family per day in a marginalized urban or rural setting. That same family of five persons living in mid to marginalized  conditions, consumes about three of these poly bags per day, thus potentially generating a real  demand for the shopping bag where the above other resources are in short supply.
There are about of course several other cultural, social  or economic reasons why it may not work in your own area but in Bamako  the lack of acceptance had nothing to do with any of these: issue had little to do with culture or economics but rather the politics of foreign aid.  I  discovered that the good aid officials  already had selected an American contractor for setting up a conventional garbage removal  service. He was a former aid official and I was just brought in to show that the bid for the assessment was competitive for the books. The national flower of Mali like many other places remains sadly, the plastic shopping bag.

Its perhaps your turn now, Michael !
Richard
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