Haybox how to and description
Haybox cooking (also called retained-heat cooking) is an age-old method that can be used to conserve energy not only during times of crisis, but anytime. Depending on the food item and amount cooked, the use of a haybox or insulated cooker saves between 20% and 80% of the energy normally needed to cook a food. The longer an item usually takes on a stovetop, the more fuel is saved. For example, with a haybox, five pots of long-cooking dry beans will use the same amount of fuel to cook to completion as just one pot cooked without a haybox.
The principle of retained-heat cooking is simple. In conventional cooking, any heat applied to the pot after it reaches boiling temperature is merely replacing heat lost to the air by the pot. In haybox cooking, food is brought to a boil, simmered for a few minutes depending on the particle size (5 minutes for rice or other grains, 15 minutes for large dry beans or whole potatoes), then put into the haybox to continue cooking. Since the insulated cooker prevents most of the heat in the food from escaping into the environment, no additional energy is needed to complete the cooking process. The hayboxed food normally cooks within one to two times the normal stovetop cooking time. It can be left in the haybox until ready to serve, and stays hot for hours. "Timing" is much less important than in stovetop cooking: stick a pot of rice, beans, or stew in at lunch time, and it will be ready when you are, and steaming hot, at dinner time.
The haybox itself is any kind of insulated container that can withstand cooking temperatures and fits relatively snugly around the pot. Hayboxes have been made using hay, straw, wool, feathers, cotton, rice hulls, cardboard, aluminum foil, newspaper, fiberglass, fur, rigid foam, and/or other suitable materials as insulation. The insulation is placed between the rigid walls of a box, within a double bag of material, or lining a hole in the ground. "Instant hayboxes" have been created by wrapping a sleeping bag, blankets, and/or pillows around a pot. The most effective insulating materials create many separate pockets of air, which slow down the movement of heat. 2 to 4 inches of thickness (depending on the material) are necessary for good insulation. Some materials, such as aluminum foil or mylar, actually reflect heat back toward the pot. Important characteristics of any insulating material incorporated into a haybox include:
- It must withstand cooking temperatures (up to 212 degrees F or 100 degrees C) without melting.
- It does not release toxic fumes (any kind of foam insulation needs to be covered with aluminum foil or mylar) or dangerous fibers (fiberglass also needs to be covered).
- It can be fashioned to be as snug-fitting as possible around the pot. A little pot in a big box will not cook as effectively; it's better to wrap pillows, towels, or blankets around it to fill up the space.
- It can be made to form a relatively tight seal, so that heat does not escape from the cooking cavity. Since hot air rises, a container designed to open at the base rather than the top will retain more heat.
- It is dry, and can be kept dry, since wet materials don't insulate as well. An inner layer of aluminum foil or mylar helps keep cooking moisture from entering the walls of the box. Mylar, which can be salvaged from used food storage containers, balloons, etc., tends to be a more durable inner layer than aluminum foil.
Cooking containers, too, should have tight-fitting lids, to prevent the escape of heat and moisture.
Since water is not lost in haybox cooking the way it is during extended stovetop simmering, the amount of water used to cook grains and beans is normally reduced by one-quarter. Instead of adding 2 cups of water per cup of dry rice, try adding 1 1/2. Also, the larger the amount cooked, the more effective haybox cooking is, since a full pot has more mass and therefore more heat storage capacity than a half-full pot. Haybox cooking is ideally suited for a family or large group, or anytime there's a reason to cook in quantity. If you're cooking alone, try cooking full pots of food using a haybox, then reheating small portions for individual meals--this too can conserve fuel.
Retained-heat cooking has many other advantages in addition to energy and water conservation. As mentioned, it makes "timing" less critical, since it keeps meals hot until serving time. Once the initial boil-and-short-simmer stage is past, it also eliminates the danger of burning the food on the bottom of the pot (the sad fate of too many pots of grains, beans, or other foods left simmering too long without stirring on the stove). Hayboxed food can actually be better for you, and tastier, than food prepared exclusively on a stovetop, because most of the cooking takes place in the 180 degrees F to 212 degrees F range, rather than at a constant 212 degrees F (lower temperatures preserve more flavor and nutrients, as they also do in crockpot cooking and solar cooking).
If you want to prepare multiple items for a meal but have only a limited number of flame sources, hayboxes can also greatly facilitate the logistics of food preparation. For example, you can bring your beans to a boil, simmer them 15 minutes, put them in a haybox; then bring your rice to a boil, simmer it 5 minutes, put it in another haybox; then prepare your vegetable stir-fry or soup, etc. At the end, you'll have a uniformly hot, unburnt, multi-dish meal, all off a single flame, probably consuming less total fuel than you would have used simply to cook the longest-cooking item alone without a haybox. You'll also have used one-quarter less of your drinkable water supply in preparing the food.
Presoaking and draining beans always makes them easier to cook, as well as to digest. A few particularly long-cooking foods, such as garbanzo beans, may need reboiling part-way through the cooking process. For health reasons, meat dishes should always be reboiled before serving.
Hayboxes are second only to solar cookers (which, however, are dependent on sunshine) in their potential to conserve resources. They're easy to build, easy to use, and have many other advantages. Y2K or no Y2K, they deserve a place in every home.
Solar Box Cooking
Solar box cooking is a method closely related to haybox cooking, but needs no external fuel source other than sunlight. Solar box cookers come in various designs, and are themselves only one category (probably the most versatile) of solar cooker. They are basically "hayboxes" with windows and, usually, reflectors--insulated boxes with a glazed area on top or at an angle in front, facing the sun, and commonly using either one or multiple reflectors. The greater the reflector area--the more sunlight gathered in relation to the insulated cooking space--the more powerful the cooker.
Important elements in solar cooker design include making sure the cooker is "tight," with no air leaks or thermal leaks (caused by metal bridging the space from inside to outside). Dark surfaces within the cooker (dark baking trays, and, if possible, dark cooking pots with tight-fitting lids--shiny pots will work too, albeit less efficiently) convert sunlight to heat, which is trapped within the cooker by the insulated sides and bottom and by the single- or double-glazed window. Cooking trays and pots should be kept thermally separate from the floor--lifted off by cookie racks, strips of cardboard, etc. The insides of the cooker are generally reflective, though some designs use black walls as well as a black bottom. Aluminum foil is among the most effective reflective materials, both inside the cooker and on rigid external reflectors--better than mirrors, and just slightly inferior to mylar.
Cooking times in a solar box are generally 1 1/2 to 2 times conventional cooking times, and almost any kind of food can be cooked using this method. Solar box cookers are ideal for cooking grains, beans, or soups, or baking breads, muffins, vegetables, casseroles, etc.
Most materials suitable for insulating hayboxes are also suitable for solar ovens, with the exception of materials that cannot withstand temperatures above boiling point. Temperatures in a solar box cooker can reach 350 degrees F to 400 degrees F, so any material (such as foam) that may either melt or release fumes at these temperatures need to be either well-sealed and thermally separated from the inside cooking chamber, or not used.
Using a solar cooker is easy, and with a little experimentation anyone can become a solar cook. The cooker is positioned to face the sun throughout the day (the amount of refocusing needed, if any, depends on the particular design and the food being cooked). Solar cooking has the same advantages of flavor- and nutrient-retention, and burnt-food-prevention, as retained heat cooking.
For detailed plans on building and cooking with solar cookers, contact:
Solar Cookers International
1919 21st St., Suite 101
Sacramento, CA 95814
phone (916) 455-4499, fax (916) 455-4498
http://www.solarcookers.org/
and check out the Solar Cooking Archives website (with plans, publications, links, etc.) http://solarcooking.org/
Also see Aprovecho Research Center, next page.
Rocket Stoves
These are low-mass stoves designed to burn small pieces of wood very efficiently. Cooking is done on top of a short insulated chimney. The stoves are typically constructed out of trash: tin cans, old stovepipes, etc. A skirt around the pot will help hold heat in, increasing the efficiency.
Rocket stoves use branches, twigs, small wood scraps, or just about any small combustible material. The pieces of wood or other material burn at their tips, increasing combustion efficiency, creating a very hot fire, and eliminating smoke. The low-mass stove body and insulated chimney assure that the heat goes into the cooking pot, not into the stove. Rocket stoves used in conjunction with hayboxes can save enormous amounts of fuel, cooking complete meals while using very few resources.
A related design, the rocket bread oven, is constructed using two 55 gallon drums, one inside the other. The outer drum is split open to create an insulated chimney space between the two drums and to allow for a doorway. Baking is done inside the inner drum--in a sealed compartment within the chimney, above the firebox.
For a booklet with detailed plans for both of these designs as well as others contact:
Aprovecho Research Center
80574 Hazelton Rd.
Cottage Grove, OR 97424
phone (541) 942-8198, apro@efn.org .
Illustrations in this article based on original illustrations in Capturing Heat drawn by Loki Quinnangeles, Cathy White, Shon Lenzo, Lynn Forbes, and A. Ettinger.
This article is excerpted and adapted from the Spring/Summer 1999 issue of Talking Leaves: A Journal of Our Evolving Ecological Culture. Chris Roth is managing editor of Talking Leaves and a staff member at Lost Valley Educational Center intentional community/conference center.