Composting 102

This post is meant to follow Composting 101 . Originally published in the Golden Rule Garden blog, it's been updated for Circle of the Sun.

Alright, now for some application of the principles. First, where does one acquire such copious amounts of mature and immature material? There are three options: don't worry about it and build piles with what you've got, scavenge from your neighborhood or surrounding land, or plan to grow enough of what you need. Each option has its upside and downside.

Using what you have available is easiest, but does not always end in a balanced pile. Usually you will be heavier on the immature material, unless you buy a bale of straw, which leads to the second option.

Scavenging from the woods, fields, lawns and farm supply stores can also lead to an unbalanced pile, but that is less likely. The only three objections I can think of are that it might cost money, the material may have qualities you don't want to introduce to your system (like pesticides, weed seeds, etc.), and you would technically be stealing fertility from another source. Granted, the local coffee shop may only have one other outlet for all those grounds (the trash) but you are still importing it to your system. Obviously this last objection is more philosophy than practicality. The farmer we learned from in our first internship made a deal with the township that, when they went around in the fall collecting leaves from curbs, they would dump them on his farm. He would then mix these massive piles with some nitrogenous material (horse manure) and let it compost. Often, when spreading this compost, we would find little plastic toys that got raked up with the leaves. It kept us amused... and sometimes made us wonder what else the leaves carried with them. But this farmer had found an incredible amount of mature material, delivered right to his farm, for free. And you can't really argue about the practicality of that. He was farming on a market scale, though, where most of the farm's nutrients are being exported as food. You have to balance things somehow.
Ok, so addressing the first point of the second paragraph: a pile that is unbalanced, favoring the immature. For the record, "unbalanced" is completely relative here, because things will compost no matter what. But when we are trying to get the best possible result, we should keep an eye on what goes in. Allow me to dig briefly into the biology of the compost pile: Once you have built it, the microorganisms in the environment go to work, assuming there is enough moisture. They consume, among other items, nitrogen, carbon, and oxygen. Unless the pile is too wet, in which case the pile turns anaerobic, meaning the microorganisms doing the work operate without oxygen. This will smell bad, your neighbors will resent you, and the finished product will not be so pleasant. I speak from experience.
But assuming it is aerobic, meaning oxygen is involved, your compost will smell nice or not at all. As the microorganisms go to work their metabolisms rise and with it their temperature, so much so that the temperature of the whole pile rises. Eventually it will get too hot for the active population of microbes, at which point other populations will become active. This continues until the material available to the microbes is consumed by them.
How hot does it get? That depends on the food you are presenting to the microbes. Two things will affect temperature most: the amount of immature material and the amount of oxygen. If you build a pile only out of grass clippings your pile may get quite hot, upwards of 180° F. If you forget to apply water to a pile of grass clippings and chicken manure (which is HIGH in available nitrogen) it can conceivably get hot enough to combust. Don't try this at home, kids. When a pile gets turned, oxygen is brought into the system in new quantities, which will cause the microbes to become active again, heating up the pile.
Heat is beneficial, to a degree (ha!). It means things are working, and at a faster pace than if the temperature were lower. But at a certain level heat becomes unproductive, causing some of the nutrients to which you'd like to hold on turn into gases and exit the pile. Additionally, high heat will kill populations of microbes. Which is actually the point in some composting schools of thought. If you can get your compost pile to reach 160° F or more it will kill most of the disease-causing microbes and many of the seeds that made it into the pile. The downside is that, along with most of the pathogens, all of the beneficial microbes will be killed off. And what holds your garden's diseases in check? Beneficial microbes. So all you have left in your pile is the most tenacious population. In Grow Biointensive we aim not to eradicate negative populations, but keep them balanced by the beneficial populations.
What, then, is the ideal temperature? We aim for no higher than 140° F. Oops! How did that picture get there? We have compost thermometers with 18" probes to get to the middle - a very handy educational tool. This pile got a little too warm by our standards. The photo at right showcases a more reasonable temperature.
These are both examples of classic late-spring piles. Our mature materials from the year before are almost used up, but we still have immature cover crops to pull out. These immature crops are becoming more and more mature in quality, but still have that slightly higher nitrogen content. So the piles, like the days, tend to be warmer. In the fall we have lots and lots of mature material but not much immature. They tend to be cooler. The air temperature plays a role, too. If it is freezing outside you probably won't have a 140° F pile.
As to the turning, it is a trade-off. Some nutrients will be lost in the turning, it's true, but if you don't turn it at least once the materials on the edges of the pile will not break down. We generally compromise by turning each pile once. (For the uninitiated, turning involves taking the pile, fork-full by fork-full, and rebuilding it in a neighboring location. Not flipping it over all at once.) There are contraptions called "Compost Tumblers", which are drums that pivot on a horizontal axis. They allow you to put your materials in and turn them as often as you like. Once again, more oxygen, higher heat, and cured compost faster. With greater nutrient loss.
What is turning into a series will probably wrap up with the third post, which will cover manure, undesirable material, compost quantities, and miscellaneous other. Enjoy!

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Adventures in Solar Cookery

This summer with Peris and Mary we explored a subject that has great potential in Kenya, as it does here: solar cooking. In Kenya a significant amount of time and/or money goes into fuel for cooking. Either you pay for coal, gas, or wood, or you wander far and wide (and risk assault) looking for a source of wood, which is scarce in the largely deforested country. The capacity of sunlight to heat a surface offers an endless supply of energy which, when used passively, doesn't even require much in the way of raw materials to harness it.

Much credit for spreading the word about solar cooking must go to the organization aptly named Solar Cookers International. Former Ecology Action Garden Manager Carol Cox was fascinated by their work, and taught many years' worth of EA interns how to make simple and cheap cardboard box cookers. Which is how we, in turn, learned how to share the low-tech, high efficiency tool with others.
Our first foray into the world of solar cooking actually came in the form of a wedding present from our friends Sarah and Jim. This Sun Oven is a portable, high-powered solar cooker that involves a collapsible reflector, adjustable prop, and and a few other features that even make it possible to bake bread (at left) on a clear day.
The one Carol taught us to make, while not as powerful, is still capable of cooking grains, potatoes, meat, etc., pasteurizing water, and canning fruit and tomatoes. It involves two cardboard boxes, some glue, aluminum foil, silicon caulk, and a piece of glass. Plans can be found on the SCI website in book form for a mere $7. The book includes recipes and principles of using the box cooker.
Last but not least, the product of another gift... The Jeavons' gave me a book called The Solar Food Dryer which, among other things, gives plans for building an entirely passive-solar food dehydrator (no electricity involved). Aficionados of the Golden Rule Garden blog will undoubtedly have read my post on constructing it back in 2009, but for a much clearer explanation of the process check out the Gardenerd blog post on the topic. After building a third iteration, pictured at right, I only have a couple points of advice to add to the dialogue. First, the book recommends using stove paint on the metal heat collector. While this paint is good to 1,200°F, it is faaar from environmentally friendly. Plus it's $13 a can. This time I used a few coats of black tempura paint, which is not as durable, but is much cheaper and much less toxic. Second, this time I had to actually go out and buy a piece of metal for the heat collector, and found sheets of galvanized steel for something around $22. But galvanized ductwork was more like $13 for the same area, so I got that and banged it flat. And finally, the screen that the food sits on to dry: I like cheap, but this time I bought the stuff that the book recommends instead of using free (but icky) aluminum or fiberglass screen. And you know what? The dried food comes off like a dream! Well worth the $18-$20.
Without going into great depth on cooking pointers, the basics to solar cooking are as follows: It generally takes more time to cook with the sun, and this is the only downside. The upsides are many. Since there is no danger of your food (or your house) burning if you leave solar cooking food unattended, you can put out a dish in the morning and leave it till lunch or supper. Because of the nature of solar cooking your food will not dry out, and will often be much more moist and flavorful than food cooked on a stove or in a standard oven. And the cardboard box cookers (at left) are very inexpensive to build, so by making a few of them you'd have the capacity to cook for a great many people at once, with no fuel, while you are yourself working somewhere else the whole day long! Even in our climate, with the presence of cloudy days, solar cooking is tremendously practical. It merely takes an understanding of the principles and a willingness to work with the weather.
The solar food dryer, too, is dreamy. In its very first batch, our new one simultaneously dried tomatoes, basil, and bananas (see the close-up at top). The tomatoes and basil have been gracing our sourdough bread for the past couple of months, but I must confess that the bananas didn't last a day before being consumed. I don't have as much experience as others in its use yet, but the aforementioned Gardenerd blog has advice on making Flax Chips and Kale Chips, and drying mint and leeks with the solar dryer. I can tell you, though, that even in this humid climate this simple dryer works well.
I'd encourage anyone interested to give it a shot. In the worst case you'll come out with a conversation piece. In the best case you will change your diet, cut your fuel costs drastically, and become a calmer, happier, and more charmingly eccentric person!

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