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Earth Fridge – made for under $30!

earthfridge

So, you are starting your adventure in living off the grid. Some practical things you will need very early on in the project are; toilet, steady water supply, basic shelter and somewhere to store food. It can get quite expensive to buy groceries day by day because of limited cold storage in your off-grid set up.

We have a 1kw solar system that supplies all our power needs. Lights, stereo, computers, slow juicer, phone chargers and our 110 litre solar fridge. We do not like to run the fridge all the time as it eats into the bulk of our power usage. We keep the fridge mainly for things like meat and dairy when we like to indulge in such culinary delights.

Vegetables do not need to be kept as cold as meat and dairy for as long a period of time. We decided to utilise certain elements in nature to keep the vegetables at a fairly consistent temperature. Ground temperatures can vary depending on what bioregion you are building in. So, do your research to find out what the average ground temperature is for in between 50cm – 1 metre deep. This will determine how deep you should go for the best end results.

We used a steel 44 gallon drum. The reason we chose to use steel is because it is much easier for steel to transfer the cool ground temperature than plastic. The drum we used was a food grade drum which is very important if you are using the drum to store food.

The fridge was built out of 100% recycled, reused and natural materials. The only thing I paid for was the drum which I bought second hand off a lovely fellow who recycles old drums and does wonderful things with chickens. Check him out here.

The rest of the materials were stuff I either dug up, came into, found or collected from building sites. Below I will give you a list of the materials that I used but feel free to adapt it to whatever replacement you find for free. Its about looking at trash as its potential rather than its waste properties. The world looks like a much different place once you observe it for its potential instead of its burden. Start to look at things for its shape, structural properties, workability and aesthetic value. The line between trash and treasure will really start to blur. If you feel like checking out an interesting article about reuse, home/land design as well as a host of others variables necessary to living off grid, check out this page. Finish reading about the fridge first though!

What materials I used:

  • 1 x 44 gallon steel drum (food grade) = $20
  • 1 x bucket of chunky biochar (home made) = $2 in timber
  • 1 x milk crete (found inside a skip bin on a building site) = $0
  • 1 x round steel frame thingy, perfectly fitted to drum (collected from a Uteman job i did) = $0
  • 1 x piece of rope (someone left it here a year ago) = $0
  • 1 x hessian bag (no idea) = $0
  • 1 x cement board (gifted to me by a close friend) = $0
  • 1 x besser block (found inside skip at building site) = $0
  • 1 x large rock (found it over there) = $0

Tools that we used:

 

  • pointed nose shovel
  • electric drill
  • 7mm drill bit (for steel work)
  • concrete shovel
  • builders level

Below is a step by step guide to how I made the fridge using the materials and tools I had to work with. Please feel free to adapt and change anything if you feel it would serve your situation better.

So tally ho! Pip pip! Let’s get on with the bloody thing!

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Step 1 – dig a hole

This is where your pointy nose shovel comes in handy. I like using the pointy nose shovel because once you get to the sub-soil, it makes it much easier to use.

Firstly, before you get shovelling, find (preferably) a high an dry, well drained spot close to your cooking area and preferably in the shade.

Then use your drum as a size guide for how big the hole needs to be. Using your pointy nose shovel, start digging roughly 10cm outside the perimeter of the drum. This will allow for some wiggle room when you eventually drop the drum in.

When digging, make sure that you dig straight down and that the diameter doesn’t get smaller, the deeper you dig. If the diameter does decrease, your drum wont fit inside the hole.

You want to dig down to that at least 1/2 – 2/3 of the drum is buried in the ground. allow for an extra 10 – 20cm below drum level for a bell nosed finish. So this is where you start to decrease the diameter of the drum. This will allow the drum to sit snuggly on the rim of the bell nose.

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Step 2 – drilling holes

Now its time to grab your drill and your desired drill bit and start drilling holes! This allows any moisture that builds up from decomposing vegetables to escape out the bottom of the drum. You wont have to clean the drum as often by doing this very simple step.

Don’t make the holes too big and try not to make them too small. just big enough for the moisture to escape. Allow some space on the outside that is free of holes. You will sit a very heavy rock in the centre of the base which will sink slightly and direct the moisture to the holes in the centre.

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Step 3 – add the biochar

This step is for drainage and pathogen regulation. You can also add some river stones on the base before adding the biochar for extra drainage if you feel so inclined.

Biochar holds a lot of moisture, filters pathogens plus a host of so many other benefits that we wont get into. If you havent heard of it, check it out! You can learn from the charmaster himself. He will show you the way.

I find it best to make the charcoal yourself from local timbers, bamboos, etc. Here is a link to how I went about making my own biochar.

Fill your 20cm bull nose base full of biochar. Make sure the char is fairly chunky to allow for better drainage. Doing this step will minimise the risk of a flooded fridge as well.

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Step 4 – put the drum in the hole

Put the drum in the hole…

Make sure there is a tiny gap between your biochar and your drum for better drainage. As we said before, make sure the drum is at least 1/2 – 2/3 buried into the ground.

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Step 5 – level the drum

Levelling the drum will ensure that your food doesnt all fall to one side and squish all the delicate stuff. Also your friends and family will take you seriously because you are using a builders level.

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Step 6 – make a suspended floor

For my suspended floor, I used a milk crete and this funny looking round steel thing I found. This is where you will need to get creative, using what you have available to you for the same effect.

What we are doing in this step is allowing a void space for moisture to drop down. This keeps the vegetables from sitting in a swamp of its own soup. It also makes it easier to reach the vegetables if you dont have exceptionally long arms.

I firstly sat the really heavy rock on the base in the centre to create a slight dip to direct the fluids. The crete sat perfectly on top of the rock. I fixed the steel wheel thingy to the crete using the bit of rope i found and then lowered it into the drum.

From there you would either tie some mouse or snake wire to the steel wheel thingy to make the suspended floor. I didnt have any of that handy so I simply sat a hessian bag on top which made a great floor.

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Step 7 – bury the bastard!

This is the fun part. Using the dirt you used to dig the hole out to begin with is now going to be used to back fill the drum for extra ground cover. You will need extra dirt from somewhere on your site for this step.

Firstly, start filling the gap between the ground and the drum. All around the edges. Then begin back filling the drum. You want to fill nearly all the way to the top only exposing about a couple of inches of the drum. Dont be shy when it comes to filling. The more dirt you back fill with, the cooler the fridge will become.

If you are a wild shoveller, make sure you put the lid on the drum first before you start shovelling.

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Step 8 – shelter the fridge

Once you are satisfied with your burial, it is time to provide some shelter for the fridge. Find a brick or a small besser block to make a little air tunnel above the lid. Place a large, flat, hard, weatherproof-ish board ontop of the brick and then either a heavy stone or block to weigh it down.

This helps restrict the effect that the sun will have on your fridge. The air pocket between the board and the fridge provides somewhat of a thermal void.

refreshments

Step 9 – enjoy the food!

Thanks for reading. Please feel free to comment below on how you went with making your own earth fridge and if you came across any easier and more efficient methods of building them.

Many thanks,

Duuvy

9 Comments

    1. duuvy

      agreed. the idea was to use only what i had laying around so i compromised and made an air gap between the lid and the board on top to provide a thermal void area. not as effective as insulation but its still something

      1. gran

        hi,

        With outdoor temperatures in the district ranging from -1 C winter and up to 34+ C in summer (SW Tassie)…for over 20 years we happily used what we called the “cold cupboard” which was incorporated into an unused window cavity on the south facing wall of the house. Insulated wooden door (simply galv sheet covering vegie box polystyrene) providing ready access from inside.

        The house was on a concrete slab.. stone walls.. The exterior timber on the bottom 2.5 feet of cupboard was celery top pine, then a piece of scrap steel sheeting (similar to what I’ve seen used on walkways eg regular holes) made up the rest of the ‘cage’. The bottom 2.5 foot was lined with polystyrene & galv sheeting… and the ‘cage’ was lined with a mesh to keep out rodents etc.

        When we had more income we eventually purchased a fridge for his cold beers & my icecream 😀

        house still standing — original owners have moved on to a boat.

        cheers,

        1. gran

          hi,

          looks great!

          reminded of our old house –

          with outdoor temperatures in the district ranging from -1 C winter and up to 34+ C in summer (SW Tassie)…for over 20 years we happily used what we called the “cold cupboard” which was incorporated into an unused window cavity on the south facing wall of the house. Insulated wooden door (simply galv sheet covering vegie box polystyrene) providing ready access from inside.

          The house was on a concrete slab.. stone walls.. The exterior timber on the bottom 2.5 feet of cupboard was celery top pine, then a piece of scrap steel sheeting (similar to what I’ve seen used on walkways eg regular holes) made up the rest of the ‘cage’. The bottom 2.5 foot was lined with polystyrene & galv sheeting… and the ‘cage’ was lined with a mesh to keep out rodents etc.

          When we had more income we eventually purchased a fridge for his cold beers & my icecream 😀

          house still standing — original owners have moved on.

          cheers,

          1. duuvy

            awesome! thanks for sharing. have wanted to make it down to tasmania for so long but fate hasnt let it happen yet! sounds like a beautiful place 🙂

  1. Carmi

    Hi Duuvy,
    What temperature does your earth fridge generally maintain during the seasons especially spring and summer. We are in the subtropics Byron region and wondering if it would work well here.
    Thanks for your well explained information on how to make the earth fridge.🙂

    1. duuvy

      Hi there! not sure about the exact temperature but i kept greens inside of it and they stayed fresh for over a week or so. i would be hesitant to keep meat or dairy as it doesnt get cold enough for that. it may be possible if you use more insulation qualities etc 🙂

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