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Heating a Small Worm Bin in the Winter

Worm Bin Heater

As all my loyal readers will know, I’m very interested in the topic of winter vermicomposting (and winter composting in general) – and it’s something I’ve been doing myself for the last few years. That being said, I’ve always advocated the use of large-scale systems during the winter, since they will generate and hold warmth a LOT more easily than a typical worm bin ever could. Of course, I’ve always been thinking in terms of natural heating – the warmth generated via microbial (aerobic) respiration during the decomposition of organic wastes.

In all honesty, it would be next to impossible to keep a normal-sized worm bin active (or the worms alive, for that matter) if kept outside in temperatures that are consistently below the freezing mark – when relying on natural heating that is!

But who says you have to heat the system naturally??!

Not Mark Glatting – someone who has recently jumped into the wonderful world of vermicomposting. You see, Mark likes to think outside the box – or the bin, I should say!
;-)

He’s come up with a really nifty way to keep his worm bin cozy during the long winter months. Mark decided he was going to keep his new worm bin out in his garage this winter – where temperatures have regularly dropped below the freezing mark – and decided to create a simple system to ensure that his bin stayed relatively warm.

MacGyver would have been proud!

Bin warmth is maintained thanks to the circulation of warm water through the system. All that’s needed is a bucket full of water, an aquarium heater, a fountain pump, a thermometer, and some tubing.

Here is Mark’s brief summary of his concept:

My goal here was maintain a sustainable habitat under the harshest conditions that I could not control…the weather. I felt that if I could do that I would be a success. The purpose of this experiment was to see if I could keep the bin from freezing. The bin is in my unheated garage. My materials consisted of a five gallon bucket,an aquarium heater, a fountain pump, 13 feet of 3/8 tubing (not PVC) and a thermometer. The tubing I coiled around the inside of the bin so the cool water would always circulate back into the bucket. I also put a brick in the bucket to displace some of the water so I do not have to cycle 5 gallons of water but four. It is easier to heat 4 gallons than 5. My project worked! The bin did not freeze nor sour after 3 weeks.

…and some additional information:

The heating system itself is very simple. As you said some insulation would help a great deal. I did not take temperature readings inside the bin. I was looking for frost and to see if it would turn sour. The aquarium heater came from Wal-Mart, it is rated at 200 watts and has a thermostat.The fountain pump came from Wal-Mart as well, but I don’t know how many watts it is. One thing I considered was to have the bucket higher than the bin using gravity as a tool to make the pump not work so hard (water flows down hill).
I have a two car garage that has no insulation at all, is not heated and it did get below freezing in the garage a number of times.I probably spent $50.00 US for the whole thing. I am not sure how much electric I used, the system itself can be used in case of an emergency. If we were expecting bitter cold I would fire it up.Remember the heater has a thermostat

Worm Bin Heater

I think Mark’s idea is fantastic, and I was really pleased when he enthusiastically granted me permission to share it with everyone here. A lot of people have asked me whether or not it was possible to keep a small bin active during cold weather, and up until now I’ve just assumed it would be more trouble than it’s worth.

In my mind, Mark’s system changes that. This is something that would be very inexpensive to set up, and – given the low wattage of the heater – almost certainly pretty cheap to maintain. I suggested that one could increase the effectiveness of the system even more if the worm bin sat in a larger box filled with straw, or some other type of insulation material (even scrunched newpaper would probably work well).

Did I mention that Mark is planning to come up with a system to keep his system cool in the summer?
8)
Stay tuned!

[UPDATE]: I received an email from Mark, letting me know that credit for the worm bin warming system should actually go to his wife Letty. My apologies, Letty!

Written by Bentley on February 13th, 2009 with 36 comments.
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Get your own gravatar by visiting gravatar.com Eve
#1. February 14th, 2009, at 5:56 AM.

What a great idea. I have been planning on building a blue barrel flow through and putting it in my unheated garage next winter. Now I know how to heat it. And I wont wait for next winter to start.

Get your own gravatar by visiting gravatar.com John H. from Orlando
#2. February 14th, 2009, at 10:07 PM.

I guess this is a good idea, but I rather see folks not use extra electricity (however minimal) to recycle their green waste. I always have thought of vermicomposting as a way to be more environmentality sensitive. Using extra energy to help decompose your food waste seems counterproductive.

Get your own gravatar by visiting gravatar.com Dustin
#3. February 17th, 2009, at 5:30 AM.

I agree with John, but at the same time I cant imagine the heater uses a great deal of electricity. Can you deposit more food inside the bin or earlier than normal to increase bacteria activity and increase temperatures that way? I am curious what the general temperature is inside the bin. I currently have a plastic bin inside of my uninsulated garage with the lid off and night temps around freezing give or take a few degrees and my bin temp is about 75 degrees F. Does anyone have any input on my temp? What is the general range?

Get your own gravatar by visiting gravatar.com Bentley
#4. February 24th, 2009, at 3:15 PM.

John – while I agree in principle, I also feel it’s important to look at the ‘big picture’ here – if this means the difference between worm composting in the winter and throwing all your wastes in the garbage all winter long, I personally think this is a much better option to use a bit more power. It all comes down to the question of what offers the most ‘good’.
Here is an analogy which is a little ‘out there’ but hopefully it will help to illustrate what I’m getting at. Consider Al Gore, and his global warming lectures and subsequent movie. Regardless of how you feel about him as a former politician, or even whether or not you believe in Global Warming – the fact IS, he has played an important role in getting a LOT more people focused on environmental issues in general – so overall a lot of ‘GOOD’. He has however flown all over the country and around the world to promote his message. Air travel is a major cause of pollution and greenhouse gases. Some might say Gore doesn’t practice what he preaches. So, should he have just stayed at home and kept his mouth shut? (some would say ‘yes’ – haha)
Absolutely NOT – overall, I think there has been a lot more good than bad that’s come from it.
Sustainability in general is only going to come about on a large-scale by relying on modern technology. We are well past the point where we can all give everything up and go live in caves.
:lol:

Ok that was a REALLY long-winded reply. Sorry John – I don’t want you to think I’m picking on you here. I definitely agree with the essence of what you are saying. I could definitely see how this might be a bit ridiculous if this system used the same power as a major appliance etc., but in my humble opinion, this is pretty minor in the grand scheme of things.
8)

Get your own gravatar by visiting gravatar.com Bentley
#5. February 24th, 2009, at 3:21 PM.

Dustin,
Microbial heating is an awesome thing – there is no doubt about it. I am totally in awe of the fact that my outdoor worm bed is sitting at ideal worm composting temps, yet outdoor temps are very winter-like.
Volume is critical for sustained heating however. Adding more food waste to a smaller system will help add some more heat in the short term, but the law of diminishing returns will come into play eventually. Your waste will pile up and eventually you won’t have any more room in your system to add more. The bin should stay warm for a period of time, but eventually (and inevitably) it will drop in temp – especially if the location of the system drops below freezing on a regular basis

Get your own gravatar by visiting gravatar.com Mark from Kansas
#6. February 27th, 2009, at 1:08 AM.

When it came to heating my bin, I had several goals. I was trying to sustain a worm habitat under the harshest conditions. Bentley is correct when he said there would be a surplus of feed stock. Then what?
I precompost my feed stock for two reasons; first, to try to destroy weed seeds and second, to destroy as many pathogens as possible. So, there is no decomposing energy left. My opinion is, that if the habitat could not sustain, what is the point of paying $25.00 for a pond of worms, only to have them die? I also wanted high quality castings that have a lowered value of pathogens.
By the way 99% of my reasearch came from this web site.
Thank You Bentley .

Get your own gravatar by visiting gravatar.com steve
#7. March 3rd, 2009, at 6:41 AM.

ok, I wont touch on what I think of Al Gore, but he has done good, and assuming he flew commercial flights that were going where he went anyways…………………………..
Ive been tossing around the idea that a big warm compost pile, leaves grass clippings and manure as well as whatever else you compost, should be a reasonably warm temp in the middle,(run piping thru center of pile then into worm bed,)60-70 degrees even in the toughest of winter, as long as it has some mass, and maybe has a vapor barrier over it during extreme winter chills, any thoughts?

Get your own gravatar by visiting gravatar.com Mark from Kansas
#8. March 4th, 2009, at 8:56 PM.

Steve,
That’s a great idea! Go for it! May I suggest that you try your project without any worms in the bin? If your project fails or needs tweeking you won’t lose any worms.

Get your own gravatar by visiting gravatar.com Bentley
#9. March 9th, 2009, at 12:51 PM.

Hey Steve,
That’s exactly what I did this year – check out my posts in the “winter composting” category on the blog. I have straw bale walls, and a layer of straw over the top – along with a thick tarp. It has worked very very well, maintaining temps in the 70′s during some extremely cold winter weather.
8)

EDIT: Just realized what you meant, Steve! That’s a great idea too.
:-)

Get your own gravatar by visiting gravatar.com David
#10. April 18th, 2009, at 3:58 AM.

I’ve read about a particular farmer stacking up an enormous compost heap in early winter, he has a system of copper tubing going through it to heat water for his home. I think it might also heat his house…

Get your own gravatar by visiting gravatar.com Order Your Domain
#11. July 11th, 2009, at 12:56 PM.

Actually as Mark mentions about the siphon idea, the pump should be lowered as to have water siphon push water into the pump. This will put less stress on the pump as long as not set too much lower. Set the pump level to where the siphon begins to work. This will prolong the life of the pump.

Bruce

Get your own gravatar by visiting gravatar.com Rom.Calgary
#12. July 29th, 2009, at 9:24 PM.

You could use this setup to cool the bin as well. I used to keep a marine aquarium and had to get a chiller for the few months of summer that we get. It is controlled the same way an aquarium heater works and if you combine the two (depending on the power of the heating and cooling systems, the amount of water being cooled, max and min temperatures, etc.) in your setup you may be able to maintain a very small temperature range.

Get your own gravatar by visiting gravatar.com Bentley
#13. July 30th, 2009, at 2:09 PM.

ROM – thanks for sharing that – sounds interesting. I’d be curious to know how much these ‘chillers’ might cost. I certainly wouldn’t need to use one in my location, but those living in extremely hot regions might want to use something like that.

Get your own gravatar by visiting gravatar.com rom
#14. July 30th, 2009, at 3:04 PM.

I hear you, where I live my basement does a pretty good job of keeping my worm bin from overheating.

It’s cost prohibitive to buy one for a worm bin (in the $500 and up range, mine was borrowed for a couple years), unless you can find a used one at a good price. Cheaper than buying new fish and coral every fall though. Probably more cost effective to get a cheap air conditioner unit and jerry-rig it to cool the area around your worm bin which still would be more than I would want to spend for a worm bin. I just saw the aquarium heater setup and thought to myself, “hey, that works the other way too”. I like tinkering but not if I have to spend a lot of money.

Here’s a thought. Same setup minus the heater and use a larger container of water (long rubbermaid bin?). Have the water returning to the bin fall onto a pile of stuff, (rocks,small rubber balls) whatever you can pile up above the water line to give lots of surface area to get as much of the water to evaporate as possible. The evaporation should cool the water. Not like a chiller or air conditioner but cooler than the water returning from the worm bin.

The creel I use for fly fishing works in the same way. You just dunk it in the water every now and then and the evaporating water keeps the fish from smelling without the use of a cooler full of ice.

Not really necessary where I live but i like tinkering with stuff.

Get your own gravatar by visiting gravatar.com Greg
#15. July 19th, 2010, at 11:42 PM.

John,

You could always use a solar panel and battery to produce the electricity for the system. That would add cost to the system, but would be green.

Get your own gravatar by visiting gravatar.com Ryan Green
#16. December 26th, 2010, at 3:42 PM.

Hey i have had my worms in freezing tempatures and they can stay alive but im not sure if they feed or eat quiet as readily. It would be a great experiment for someone to try whether or not the cold weather will slow the eating cycle down of a worm or not? If someone trys it let me know what your results are.

Thanks,

Ryan

Get your own gravatar by visiting gravatar.com Dale Seavey
#17. November 1st, 2011, at 8:25 PM.

Have you heard of anyone using an electric blanket to keep worms in the above freezing zone in the winter for a bin?

Get your own gravatar by visiting gravatar.com Louise
#18. November 4th, 2011, at 5:53 PM.

Hej Dale
I plan to use heating cables as the ones I use to keep the waterpipes from freezing in the barn, they come in different lengths and are controlled by a termostat – and they are suited for outdoor use.

Get your own gravatar by visiting gravatar.com Dale Seavey
#19. November 8th, 2011, at 2:59 AM.

I have been using a heating pad along side of the bin, which is covered in towels to keep light out and heat in, and have placed it on a timer so it will go on for a couple of hours a night and be enough to keep those wriggling worms happy. They seem to be thriving!
Thanks for the feed back and the ideas!

Get your own gravatar by visiting gravatar.com Gramps
#20. January 24th, 2012, at 9:37 PM.

I use some heating cables for reptile tanks. I have a 50 watt and a 25 watt both controlled by a HydroFarm Thermostat. So that I can use the heater on different bins of desired I mounted the cable on some expandabe screens from Walmart. Without the thermostat the 25 watt works better as it only get to about 85 degrees in my 65 degree basement. The 50 watt will go to around 108 degrees. When sung the thermostat the 50 watt seems to work better. Without the heat cab;es the temp is about 65 degrees and with it’s 78 degrees.

Get your own gravatar by visiting gravatar.com Nancy Lichty
#21. April 1st, 2012, at 10:17 AM.

Your system in intriguing. We also keep our worms in bins in our garage during the winter. If we don’t leave our doors open when plowing snow, it doesn’t freeze. However, when it is cold, they don’t do much composting. So we wrapped the bins in an old Velux (velveteen foam) blanket and left a light on them. They seemed happier this winter. I do check to see if the bins are TOO moist and leave the top uncovered and the drain open for a litter air circulation.

Get your own gravatar by visiting gravatar.com Jeanne Sandstrom
#22. July 18th, 2012, at 12:54 PM.

What do your outdoor bins look like? Is there any danger the redworms would escape and cause a problem?

Get your own gravatar by visiting gravatar.com Nate
#23. July 28th, 2012, at 12:05 AM.

What about using a solar hot water heater panel to heat water and store under the worm bin?

Get your own gravatar by visiting gravatar.com Bentley
#24. August 2nd, 2012, at 8:13 AM.

Wow – I’m way behind in commenting on this one. Sorry folks.
Lots of great ideas being shared – thanks!

JEANNE – my outdoor “bins” are actually windrow beds. Composting worms stay in environments that are favorable to them so it’s not so much that they would “escape” as it would be moving to a more favorable environment. Red Worms (Eisenia fetida/andrei) have not been found to cause any “problems” whatsoever (assuming you are talking the concerns relating to forest ecosystem disruption) – largely since they don’t thrive when not living in very rich organic matter (such as that found in compost heaps and manure piles).
—————
NATE – sounds like a great idea! Makes me wish I was more of a DIY-tech kinda guy!
8)

Get your own gravatar by visiting gravatar.com jen
#25. August 6th, 2012, at 2:22 AM.

I just started vermicomposting this year and feel it has been a great success. I’m going to bring them in for the winter but one whiff of rotting anything and they’ll be banished to the garage. I’m gathering that as long as the bin is in good shape they’ll just hibernate til spring?

Get your own gravatar by visiting gravatar.com Gusty
#26. October 15th, 2012, at 10:37 AM.

And how about if in the middle of compost bin you put a coil to heat water. Rather than conveys in a tank it circulates near the wall of the bin.
Are at the beginning and I don’t mean much.
What do you think?

Get your own gravatar by visiting gravatar.com ron
#27. October 25th, 2012, at 1:47 PM.

I have a worm inn that i keep outside during the spring and summer months, but going to try the garage this yr during the winter instead of the basement. My plan was if the temp got to low, i was going to dig a hole in the middle of the bedding and place a plastic container in the hole. Maybe something as simple as a milk gallon, fill it with water, and put a small aquarium heater in it rated for a 1-5 gal tank. The ratio of width vs height may be a factor, but I would figure that even on the lowest setting of the heater, the heat will radiate and allow the worms to either migrate up/down as needed for food.

Get your own gravatar by visiting gravatar.com ralph
#28. October 27th, 2012, at 12:32 PM.

it seems like the simplest heating system would be a heat mat for seedlings(40 watts, about 9 by 18 inches) attached to a timer. It would be placed under the bin and the timer used to regulate the temperature. I suppose insulation could surround the bin for colder climates. What is the lowest recommended temp for worm activity?

Get your own gravatar by visiting gravatar.com Dale Seavey
#29. October 29th, 2012, at 2:08 PM.

I have to say, the heating pad wrapped on the side of the bin with towels over the bin worked like a charm in an unheated shed in Oregon.

Get your own gravatar by visiting gravatar.com Dale Seavey
#30. October 29th, 2012, at 2:09 PM.

I did use a timer on the heating pad.

Get your own gravatar by visiting gravatar.com nate
#31. November 19th, 2012, at 5:08 PM.

i made a similar system integrated into by blue barrel system using 3/4 metal pipe i could use 1/2 in. tubing running threw the pipe in the bottom of the flow threw bin and one in the middle of the barrel heating the pipe and in turn the barrel. in the summer i put frozen 2 liter bottles in the water and it cools it quite nicely

Get your own gravatar by visiting gravatar.com Corey
#32. November 16th, 2013, at 4:46 PM.

I had supplemented heat to my “1-2-3″ ft. worm bin with a 25 watt aquarium heater submerged in water in a 1 gal. pickle jar. It’s only November and we had a cold week. Today I built an exterior box for the worm bin and lined it with 2 inch insulation panels with a fitted, insulated top. The worm bin fits perfectly snug. Unfortunately after poking around in the bin (after I built the insulating box of course) I see the frost last week killed all my worms. The aquarium heater couldn’t hack it. Logic tells me that instead of US desperately trying to provide heat to the WORMS, a system large enough should provide an overabundance of heat, enough that could not only keep the worms’ habitat comfortable, but also add supplemental heat to OUR homes/green houses without the odor! If this can’t be accomplished on an individual/single household level, then maybe all organic wastes from residential neighborhoods could be allocated to an enormous centralized worm bin with piping somehow delivering the heat to the homes. My garbage plus your garbage definitely won’t produce much heat. But if the entire neighborhood’s food-waste/yard-clippings etc. went to one gigantic worm bin, the heat being generated would be enormous. In large cities especially this concept could be revolutionary, where the restaurants alone output considerable amounts of food waste. Combine this with schools/cafeterias/apartments/hospitals and homes… we’re talking some serious heat! As long as the worms can safely keep their distance from the core of all that heat. Just some thoughts. If anybody has anything for me to read or look into on this matter I’d be very ambitious to read it. As for me, I’d be grateful to just not have to pay an extra utility bill to keep my worms from dying in the winter, even if this meant building a deeper bin and building an additional, well insulated box around my bin, that I could easily disassemble for the summer months. I rent and can’t create an enormous compost heap to pipe the heat to my bin as some people suggested. Thanks a lot everyone, Corey.

Get your own gravatar by visiting gravatar.com Gary wildeveld
#33. January 28th, 2014, at 5:17 PM.

My bin is outside on a stand using cinder blocks for the walls. I attached a heating pad under the floor keeping the compost temp over 50 deg.

Get your own gravatar by visiting gravatar.com angusmacduff
#34. May 24th, 2014, at 8:45 PM.

I built my VB24 this past winter. I didn’t have to buy anything to build it – everything was down cellar or in the sheds. I used a piece of 1/4 inch plexiglass for the front and it is covered by a sheet of Naugahyde to keep it dark. I had planned on keeping the bin in the cellar but decided to move it to the garage so that I can use horse manure. I’ve added another sheet of lighter plexiglass to the front with some washer spacers. Now I can slide the seed starter heating pad down between the two sheets of plexiglass. I have some two inch solid foam insulation that I will add next fall – along with a couple of furniture pads to go over the top. I think that I or “we” will be fine.

Get your own gravatar by visiting gravatar.com Bobb241
#35. July 2nd, 2014, at 11:12 PM.

I have been keeping outside compost bins for a fair amount of years, and up until completing Bentley course last, had never really thought of intentionally working with worms. That has all changed now, and I think the heated bin is outstanding. When you live in North Dakota, you need to temper the need to use some amount of energy to help keep the worms alive, and solar doesn’t help much when the sun is gone for days at a time. I plan to keep my “gonna-be-built-soon” bin in our unheated garage, which last winter spent many consecutive day well below -1F. I understand that folks in Florida can get away with no heat, but just like keeping engines idling and the car plugged into electricity (and not to keep charged) some ideas come from the environment we live in, and some should be mindful of that point.

Get your own gravatar by visiting gravatar.com Ralph
#36. July 7th, 2014, at 4:31 PM.

I got lazy and didn’t heat my worm bin in the unheated garage last winter and they survived quite a bit of cold, down to upper teens outside. They were on the floor and I didn’t check to see if they were starting to freeze or not.

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