Biofuels | Wind | Solar | Hydro
Glycerin Disposal/ Bioremediation/Compost 101
Hey all,
I poked around and asked questions of more people and found out more glycerin disposal stuff (The thing below is a reply from Keith Addison to something I posted a while back, it looks really confusing in this format, so look carefully if you're interested, it's two of us talking in one message.). Also, note that there are tons of useful things to do with your glycerin rather than composting it. 'Glop', on the other hand, is another matter (you can sometimes make soap out of it too, though).
I kept seeing Todd Swearingen's posts talk about disposal problems and warning about people creating 'hot spots' in their back yard trying to compost glycerin from homebrew biodiesel. Here's some suggestions I found out asking a local bioremediation guy:
Composting, as gardeners know, requires a few simple factors. Oxygen ranks as one of the most important. If you've ever seen a sealed and forgotten bucket of compost get slimy and disgusting (I've been around hippies, by God!) it's partly due to the lack of oxygen, and the resulting anaerobic digestion process caused by anaerobic-loving bacteria. They're different critters than the oxygen-loving bacteria you encourage with proper hot-pile composting. Getting oxygen to the bacteria and discouraging anaerobic bacteria growth is one of the reasons you 'turn' a compost pile . It's also a reason why people don't usually use sawdust as a carbon source (it compacts and prevents air from getting through a pile), we use wood chips or leaves or straw- more ways to retain gaps in the decaying mass for o2 to reach the aerobic bacteria. This is Compost 101, but lots of people don't know this stuff.
Composting glycerin (or failed batches) involves sticking a gooey mass of gel into a compost pile, which effectively seals oxygen out of the whatever it's dripped all over. So it is extra important to mix the glycerin with other matter- wood chips, straw, dry leaves etc- and to make sure you get it plenty of air and to turn it frequently. The wood chips et al are also the carbon source that is essential for getting quality compost. Other compost 101 factors that apply equally to this as to the composting of your table scraps are: getting the pile big enough to start with so it gets hot enough for the bacteria you're trying to encourage, keeping the neighborhood dogs out of it (DOGS REALLY LIKE USED OIL AND BIODIESEL MESSES!), and keeping it from getting too dry or too wet. These gel messes, depending on what you mix them up with, also have a tendency to run out of your compost pile, past your dog-proof barrier, and into your neighbor's yard, scaring them into calling the EPA or whatever on you. So controlling liquid leaks is another factor to take into consideration.
The scary stuff for us comes in when you talk about what else is in your glycerin or in your 'failed batch of glop'. The catalyst, lye in my case, ends up in the glycerin. So do small amounts of methanol. Both of these are poisons and the pH of lye does damage to the biology of compost piles, I believe. The good thing about methanol is that it evaporates with time if exposed to air. Most biodieselers who use glycerin (as soap, not as compost) try and 'vent' the methanol out of it first. the sources, ( I can't remember if it's From the Fryer to the Fuel Tank or Journey to Forever,) say to let it sit open to the air for a week. This depends on what quantity you're 'venting' , I think. I stir it a lot during the process. Also, you need to keep rain and other things, including the hippie neighbor's dogs, out of it (yup, there's a pattern here) . I have a tub with a screen cover to keep dogs and insects and falling leaves, and try to also protect it from rain. You can 'vent' your failed batches of 'glop' emulsion this way as well, but there's probably more than a minute amount of methanol floating in the 'failed batch'. WEAR YOUR RESPIRATOR, SAFETY GEAR, AND GOGGLES working with under reacted 'failed batches'. They are not biodiesel. The other alternative to 'venting' or evaporating the methanol is to heat the stuff to drive off the methanol (above 140 F) but that's energy intensive. Of course if you're using some fancy piece of equipment with a vacuum pump for methanol recovery you already know that it takes a lower temperature to evaporate methanol in a vacuum. the lye is a bit trickier to deal with. Test the pH of your glycerin. It is alkaline. You don't want to dump that on your compost pile. I believe the answer to not creating the 'hot spots' Todd's talking about is partially to add some kind of acid to the alkali you're composting to neutralize it. The bioremediation guy I was talking to about this last week suggested that the cheapest acid to use for this is muriatic acid. This is nasty stuff. We use it for concrete etching prior to concrete painting, and for getting zinc galvanizing off of metals prior to welding them. Both processes are supposed to involve the wearing of an organic vapor cartridge respirator. Which you should have anyway if you're getting anywhere near sodium methoxide! but anyway. The bioremediation guy suggested diluting the muriatic acid with water and adding it slowly to the glycerin (or 'glop') and checking the pH until it becomes neutral (7). be careful, you don't want an acidic mess to dispose of any more than you want an alkaline one.
Personally, I'd rather use vinegar, but I haven't tried these experiments myself and so don't know how much vinegar it would take- probably a lot. People using acid for bubble washing (usually vinegar, sometimes citric acid) might have something else already available. Just be careful and use your pH strips. I think having a dedicated compost pile for this kind of thing is a good idea if you've got a lot of mess to dispose of. I also feel like your composting device needs to have an impermeable bottom because you dont want this stuff to leak into groundwater, or leak out and tempt the neighborhood wildlife, or whatever. there are ways of dealing with all these issues, however. It sounds like you'd need to keep oxygen, methanol venting, and lye neutralizing in mind.
As far as the mushroom bioremediation stuff goes, it sounds like that was a way to deal with speeding up the process or something, but I still didn't have much luck tracking down the science behind this rumor. Keith is right, though- there's all kinds of gadgets you can buy or build that speed up composting of kitchen scraps and lawn clippings at least, to two weeks. It usually involves some kind of drum that lets you turn the pile easily every day.
the other thing the bioremediation guy said about 'bad batches' is to try taking them to the county (or whatever) motor oil recycling places. I think that means government facilities, not to your neighborhood auto parts store! He said those facilities have the capability to separate the portion of the 'glop' emulsion that has turned into biodiesel from the water soluble soap portion of the emulsion. (by the way what I mean by emulsion is the gel of failed 'too much-catalyst' batches, not the mono and diglycerides 'emulsion' that Todd Swearingen has talked about recently that comes out in a wash) Again, I haven't tried it, but I have a few gallons of collectively produced glop, and will try and find it a home like that just to test this theory out. Also I would be slightly worried about someone hauling 55 gallons of it to some suspicious authorities and getting investigated for playing with dangerous chemicals without permission, but... I don't know.
Anyway, everyone starting out with biodiesel always wants to know what to do with failed batches and with glycerin... I'd like to hear people's thoughts on this post and about what it is that you do for disposal. Also, anyone who doesn't already know, there is a big section on dealing with glycerin, making soap, etc, on the Journey to Forever website...
regards,
girl Mark