Composting alkaline batteries

Here's a win-win way of recycling trash from our modern culture and at the same time adding micronutrients to the soil. The products of modern civilization are churned out according to what the consumer will buy, with their eventual disposal only a dim afterthought. Lead-acid car batteries, NiCad batteries, these have some nasty elements in them and are best left to the professional recycling operations, where the lead and cadmium will be recovered for another use and kept out of the biosphere. On the other hand, alkaline batteries are mostly zinc and manganese, and have only tiny, trace quantities of any elements that would cause environmental concern. Don't just take my word for it, here is a paper that goes into detail about the chemical characterization of spent alkaline batteries.

So take your spent battery and use a sharp knife to peel off the plastic wrapper, so you can get down to the zinc can. If you have salvaged the battery from a parking lot or off the pavement, the action of numerous cars and trucks running over it may have saved you this step. Next, put the battery in a small plastic container (yogurt cups work great) and cover it with pool acid diluted with about 3 parts of water. This is known as "extract solid material with an excess of 3M HCl" for those of you with training in the chem lab. This will dissolve the zinc can and neutralize the potassium hydroxide (KOH) that is in the electrolyte matrix. It won't do much to the manganese dioxide electrolyte, which will remain as a black sludge at the bottom of the container. Let the container sit covered for a couple of days, just to make sure that all acid soluble materials have dissolved.

Now you have a solution of zinc and potassium ions, maybe some iron ions if there was steel used in the manufacture of the can, a little bit of manganese ion in solution, but most of the manganese is still insoluble sludge at the bottom of the plastic container. What we are going to do now is to chelate these ions to increase their bio-availability. Remove the carbon rod from the plastic container (that should be the only piece that survives the acid digestion) and toss it in the compost heap. It's not biochar because it's an industrial product, but it's still char (carbon) and better to put it into the ground than to burn it and add to the CO2 in the air. Stir up the sludge in your reaction cup and dump the whole thing (~200ml) into a 2-liter plastic bottle of urine. Uh-oh, did I just gross you out with that last reagent? If you are going to make chelated fertilizer, you need to use some gross ingredients; it's either urine or rotted fish guts. Chelation is the chemical process of binding up a positive metal ion with a negative electron pair and the nitrogen in urine, ammonia, or decaying protein works very well to do this. And the added benefit is that when the chelate decomposes in the soil, the plant ends up using both the metal and the nitrogen.

You will notice that as soon as you add the metal ion solution to the urine, the whole mass will turn cloudy. The chelate forms a precipitate and will settle out if you let the bottle sit overnight. But this isn't necessary, you can re-suspend the material by shaking it up and it is now ready to: (1) add to some compost tea or (2) pour on the compost pile or (3) add it to a newly made batch of biochar or (4) add to some wood chip mulch that you intent to spread right away. Or you can keep it in the bottle and label it Mn/Zn nutrient fertilizer. There isn't that much potassium in the batteries to consider it as a significant source, especially considering the amount of potassium in biomass. It may also have some copper and iron in it, but not much. If you think that your soil is iron deficient, you can do this same process with little bits of iron and steel you accumulate if you want to make a chelated iron fertilizer.

If you have had a soil test done and it came back noting a deficiency in either zinc or manganese, I hope you will consider this as a cheap and easy way to amend your soil.

I will never do this in all likelyhood, but this is very cool!

This is amazing!

One question though. When I googled pool acid I came up with "Dry Acid (Sodium bisulfate)" Is this what you used? I have never had a swimming pool so I am unfamiliar with the chemicals that are commonly used.

Adam Moore wrote:One question though. When I googled pool acid I came up with "Dry Acid (Sodium bisulfate)" Is this what you used? I have never had a swimming pool so I am unfamiliar with the chemicals that are commonly used.

Concentrated hydrochloric acid (12M HCl) is commonly known as "pool acid". It is usually sold in home stores in a twin pack of 1 gallon plastic jugs. Besides adjusting pH in swimming pools, it is also used for clean up in stone and brickwork, as it dissolves away excess mortar and cement and leaves the stone and brick.

Thanks John!

SCIENCE!

I (finally!) refound this thread.

Hi have a bunch of batteries sitting around looking for a home. John - is it possibly to over do this? We have HCL, plenty of urine and some plastic pots to do it all in. We have a big old compost heap too.

Is it best applied to compost to further break down, or diluted further and watered directly onto beds?

Strong hydrochloric acid (you may know of it as "battery acid) is a tricky product to handle safely. Mistakes, splashed droplets, unexpected trickles, leaky containers, unventilated fumes -- these can damage work sufaces, clothing, skin, eyes, and lungs. It's not ALL that hard to do safely, but the required level of care may be more than you want to volunteer for in your routine gardening activities.

That said, I don't see anything in this idea that would disqualify it from working with a weaker acid that's safer to handle. Say, white vinegar (acetic acid, usually 5%).

You'll need more of it, and it will need more time to work. Warmth will help. Perhaps put the batteries in a pop bottle of vinegar, store in sunny place, shake from time to time?

Likewise your chelating agent. If conditions of your life make collecting and saving urine inconvenient, I should thing a bit of cleaning ammonia (the cheap stuff, no added soaps or perfumes, just dilute ammonia) would work.

Disclaimer: I haven't done this. I am musing about possibilities. Be careful out there. Don't make any accidental soda-pop-bottle bombs.

I'm a chemist/chemical engineer - should be able to cope with HCL safely, but thanks for the heads up.

But that's sort of my point. Not everybody has those skills. Me, I just had one college-prep chemistry course in high school about 30 years ago. And lots of folks have even less prep than that for handling strong chemicals.

I also thought there might be some merit in mentioning an alternative input (vinegar) that some permies are already producing themselves.

Dan - I wasn't really disagreeing with you, but the nature of these forums is that almost everything we discuss demands an element of caution and common sense. Ever seen a digger topple due to poor driving? Rocket stoves can, if poorly assembled, leak fumes back into the home. I wield chainsaws on a regular basis and use fairly chunky bits of mechanical hardware that could rip off fingers and do serious damage.

Any of these things could kill me I guess, but I still think I'm more likely to die on the roads while driving.

Likewise with chemicals - sensible precautions are the order of the day, but they should be respected not necessarily feared.

Oh, I quite agree, there's no reason for somebody comfortable with dangerous instrumentalities not to use them. But familiarity matters, nonetheless. I'm comfortable with guns and very sharp hand tools, but I mistrust chainsaws and I wouldn't try anything tricky with a tractor or an excavator on a bet. Somebody else will lift his wife in an excavator bucket to chainsaw the top out of a tree, but they have never worked with large animals and wouldn't dream of keeping a horse or a milk cow. Some cowboy may think that his horse is a perfectly good substitute for a winch and a come-along, and he's a dab hand at dynamiting fence post holes, but he wouldn't drive a hay baler to escape from hell. Happy people pick the risks that they take so they can stay inside their comfort zones.

Thus it just sort of seems useful to me when describing projects to keep in mind the skillsets needed and say "and by the way, if you aren't comfortable doing it this way, there's another way that might work better for you." In the spirit of that Sepp Holzer attributed quote "if you do not have a pig, then you must do the work of the pig." If you choose not to use a strong acid, you could use more of a weaker acid and add in mechanical and heat inputs to get to the same place.

I didn't for a minute mean to suggest that people comfortable handling strong hydrochloric acids shouldn't do so! I was just doing my bit to expand the usefulness of the notion by making it more accessible to folks who stopped reading when they got to "pool acid".

Here's a second option for people who want to stay clear of industrial strength corrosives -- cleaning products available at the dollar store. Thinks like "Lime-away", "Tile Works" and "Acme Super Scrubbo" are weak acids that will do the job of dissolving the metals you want to add to your vat of urine. As will plain ordinary vinegar. Read the label, and if it contains sulfamic, oxalic, or phosphoric acid, then the product will probably dissolve enough metal so you can get it to chelate with urine. However, it may take more time than my preferred HCl. When I drop a battery into HCl, it's ready to go the next day; with other acids, you may have to let it sit for a week to dissolve.

And what if your soil test indicates that you need to add copper? Metallic copper is available either as old plumbing fittings, or pre-1982 pennies. But copper doesn't dissolve in HCl. It's pretty much non-reactive with sulfamic, oxalic, and phosphoric acid as well. The one way to get copper into solution is to use acetic acid (vinegar), but there is a catch -- it also needs oxidizing conditions, meaning you have to add some hydrogen peroxide to it. If you put pennies in a solution of equal parts white vinegar and hydrogen peroxide and let it sit (like for a week), you will notice that the solution takes on a blue color -- and that would be copper acetate, which will chelate with urine.

Michael: I usually add my chelated metals to compost tea just to dilute it up so it will spread farther. One of the problems of adding trace mineral is that it is easy to overdo. That's why it's better to make lots of small applications rather than the BigAg one-pass-over-the-field method.

And a final thought for those of you who are hesitant to try your hand at chemistry -- it's just cooking. You follow the recipe, mix the ingredients in the right order, cook it at the right temperature for the right time and it pretty much comes out the same each time.

Hi - I'm new to group. Found you because I was googling "battery found in leaf compost pile". So...I freaked when I saw a rusty torn apart AA battery with part of it's innards still intact. I suppose this battery could have been tossed around over and over again during compost process but I'm focusing on the possibility that it leached into my portion of the pile which is going into my chemical free garden.

I doubt there was any urine near by when battery cracked open. : }

I have plenty of other worries so maybe I should let these thoughts go and move on to my garden plans.

Thanks!

Welcome to Permies, Daisy! As you can see, an alkaline battery is nothing to freak about, and if it spilled its guts in your compost pile, soil microbes will go to work recycling those micronutrients. My acid and urine processing steps merely speed up that recycling a little bit.

Tell us more about your garden plans; we like to share strategies and tips.

Thanks, John! Sorry for delay...I was having trouble with website.

I'm not a homesteader but dreaming of having a very tiny urban farm some day. Presently gardening in a community plot and a small area of a friend's property. Interested in permaculture and being self sufficient but presently everything is very temporary and I have no money to work with. Hopefully that's temporary too. : ) I will post more later.

Hydrochloric acid is also known as muriatic acid and is indeed sold in places like Home Depot usually in the pool supplies section.

It is different from "battery acid" which is sulfuric acid, also known historically as vitriol.

Don't confuse them! 30% hydrochloric acid, while not something to give your toddler to play with, is nowhere near as dangerous as 30% sulfuric acid. In any event, the normal precautions about eye protection goggles, gloves, and first aid should be taken. A possibility for eye washing should always be available-- a garden house ought to work. Likewise baking soda with some water can help to neutralize any acid you might get on your skin. (Also, vinegar is a good thing to have around if you are working with lime, to neutralize it if on the skin.)

Do not store hydrochloric acid near any steel/iron articles you care about. Even with the cap securely on the bottle, vapors will escape and promote rust. My mother left a gallon jug of muriatic acid sitting on the way tubes of my Shopsmith (woodworking tool) for a year (I moved to Slovakia, so didn't find it until visiting home for Christmas). The area of the way tubes immediately around the bottle got horrible rust that after sanding and cleaning off still left pits in the metal.

Btw, if you need to get galvanization off of steel, hydrochloric acid works for that, just need to throughly was the steel afterwards to prevent salts of the acid from causing rust (and likewise paint the steel with something, since it would be bare and clean). This I did when building my rocket stove as the barrel I had was galvanized.

Andrew, even that pitting that you mention has its good side. If you are looking to rough up a surface so that it has more area to contact with a coating, then this pit corrosion by the HCl will help you. If you wanted to line your rocket stove barrel with a clay or ceramic, taking off the galvanization with HCl and letting it do a little pit corrosion would prepare the surface very nicely so that the clay/ceramic would have lots of bonding sites when it was applied.

This is awesome! It's incredible what you can process down through composting, yeah? I've seen some pretty awful anaerobic piles of nast transform into some of the most beautiful inoculant I've seen. The implications are astounding... Thanks for sharing!

Welcome to Permies, Scott!

I wish that there were more products of our society that could be recycled so easily. Unfortunately, some man-made products persist for a long time, so that subducting them under a continental plate is the only method that will get rid of them. When they come back up in a few more million years with the lava, the toxins are no longer there.

Fascinating. Bump.

OK. Got my batteries


Since there are too many to peel, I'm thinking of building a hugel bed with them and pouring the hydrochloric acid over the top.

OK, I'm joking. Sorry I couldn't resist

Since the thread is rather old - are you still using the method? Does vinegar really work?

Hi! I'm interested in this topic, because I have a biology's project and I chose to do a fertilizer with alkalines batteries, so I found your information really good and helpful.Is this fertilizer useful for plants like sunflower, rose or corn? And How much manganese and zinc is necessary to prepare the solution?
I hope to have an answer soon, I need to do it and check that it works.If you can help me with more infromation I will be more thankful.

And how much pool acid I need?

Sorry to dig up an old post, BUT, looking for info on the topic and this is the only thread I come up with, and I have a question on the start post.

It sounds as if John was describing carbon-zinc batteries, not alkaline, right?

This would work the same for either, right?

Randall

Dan Boone wrote:Strong hydrochloric acid (you may know of it as "battery acid) is a tricky product to handle safely.  Mistakes, splashed droplets, unexpected trickles, leaky containers, unventilated fumes -- these can damage work sufaces, clothing, skin, eyes, and lungs.  It's not ALL that hard to do safely, but the required level of care may be more than you want to volunteer for in your routine gardening activities.

That said, I don't see anything in this idea that would disqualify it from working with a weaker acid that's safer to handle.  Say, white vinegar (acetic acid, usually 5%).

You'll need more of it, and it will need more time to work.  Warmth will help.  Perhaps put the batteries in a pop bottle of vinegar, store in sunny place, shake from time to time?

Likewise your chelating agent.  If conditions of your life make collecting and saving urine inconvenient, I should thing a bit of cleaning ammonia (the cheap stuff, no added soaps or perfumes, just dilute ammonia) would work.

Disclaimer:  I haven't done this.  I am musing about possibilities.  Be careful out there.  Don't make any accidental soda-pop-bottle bombs.

Thanks for this! I never would have gone out to buy pool acid but I do have vinegar already and so may try it!

Randall McLaughlin wrote:Sorry to dig up an old post, BUT, looking for info on the topic and this is the only thread I come up with, and I have a question on the start post.

It sounds as if John was describing carbon-zinc batteries, not alkaline, right?

This would work the same for either, right?

Randall

Did you get answer to this??