I've been interested in hay box cookers ever since I learned about them a couple of years ago. Also known as straw box or fireless cookers, they are a simple, but ingenious design, to cook food while saving enormous amounts of fuel or electricity (up to 80%!).
Basically, it's a well insulated box big enough to hold a pot of food. Hay or straw was often used in the oldy days (hence the name), but other insulating materials will work too. You begin cooking your food on the stove as usual and then you move the pot into the cooker, close it up and leave it to use the retained heat to complete the cooking process. It works for anything that is boiled, stewed or steamed. Think of it as a slow cooker unplugged.
Historically they were used by pioneers, cowboys working out on the range all day, and people during the depression and WWII. Today they are used by the Canadian military to keep food warm when delivered in the field and in developing countries, where wood fuel is a scarce resource.
I love the idea of turning off my stove and using retained heat to finish the cooking process. What a great way to conserve energy! So the hay box cooker has been on my list of DIY projects for some time, along with a rocket stove and solar dehydrator.
I haven't gotten around to making any of those projects yet, so I was excited when a fellow permaculture friend contacted me, asking if I would be interested in teaming up with her in organising a workshop on hay box cookers and how to make them. Great! I thought. This will be the perfect opportunity to finally get around to making one for myself.
Then, while researching the cookers a bit more, getting a sense of how they are constructed and viewing different models online, I suddenly had a smack-myself-in-the-forward moment. Duh! I already own a hay box cooker. Yes, it's true. I've had a hay box cooker right under my nose the whole time, I just didn't realise it. A hay box cooker is just an insulated box that holds a pot, right? Folks, I have an insulated box that holds a pot. It's my sun oven! Why didn't I think of it before?
So I immediately gave it a trial run with a pot of beets. The chamber of the sun oven is already insulated, but I also wanted the entire pot to be surrounded by insulating material. While the beets were coming to a boil on the stove, I gathered up a few towels and a couple of flannel sheets. I laid one towel on the bottom of the oven.Then a I draped a flannel sheet over that.
Once the beets had been boiling for about 10 minutes, I carefully placed the pot into the oven.
Two more towels went over the pot, and I folded the first sheet over top of them. Then one more flannel sheet was placed on top it all, completely filling the chamber of the oven.
I closed the glass door, lowered the reflective panels and walked away.
Two hours later I opened the whole thing up, pulled out the still piping hot pot and stuck a fork in the beets. Then I immediately did a happy dance. Success!
I already practice some retained heat cooking in minor ways. I often turn my cast iron pan off 5 or 10 minutes early, knowing that the retained heat of the pan will continue cooking the food 'till done. And when I cook pasta, I bring the water to a boil for a few minutes, turn the heat off, put a lid on the pot and I have perfect pasta every time, without needing to keep the stove element on for the entire process. But now, well now I can't tell you how thrilled I am to have this option of really conserving resources, even if it did take a little while for my brain to connect all the dots! And the best part about it is that I now have another function for my sun oven, all year long, whether the sun is shining or not.
If you don't have a sun oven to give it this double duty, making your own haw box cooker is really easy. There are many resources online. Gone, but not forgotten blogger Chilli posted about the one she made. And I like this one, using a repurposed cooler.
There are a couple things to keep in mind when cooking this way. Firstly, everything will take longer, so will require advanced planning. Cooking times will vary depending on a number of different factors, including the type of box you have and how long you initially have the food on the stove for.
Also, cooking this way does increase the risk of bacterial growth, especially if the slowly reducing heat enters the danger zone. You can mitigate this by using a thermometer to keep track of your temperature or by briefly reheating the food on the stove.
I'd love to hear if anyone else uses retained heat cooking or plans to. Please share your experiences, tips and techniques!