Making compost

It's a common mistake to use too much water -- it's probably the most common reason for failures. (Others are not enough nitrogen, and, more rarely, no aeration.) The overall moisture content of the assembled pile should be about 60--65%. They say it should be as moist as a wrung-out sponge, which is a good guide if you've put everything through a shredder so it's homogenized and the particle-size is small, but with the usual rough compost materials it's not very useful.

Midori filling a compost bin

This is typical advice: "Spray the mixed materials with a hose until wet like a sponge but not soggy. Fork it into the bin, spray more water to make sure it is wet enough."

Beginners read such things and end up with a disaster. When the stuff starts to decay it disintegrates into a slimy, stinking sludge, like what happens to grass clippings if you leave them in a big pile: it gets very hot, and then it dies into a dark green gunge -- much worse if there's manure and kitchen scraps in it! And it's difficult to repair the damage and get it working properly. That's often the end of that particular beginner's composting efforts.

Compost materials are often much wetter than they look at first. Fresh green leaves can be 95% water, but they don't look wet. Kitchen wastes are usually more than 85% water. Spreading fresh greens out and letting them wilt for a day loses a lot of the water, and probably quite a lot of the nitrogen too, unfortunately. Manure is a lot easier to handle if it's on the dry side, which also loses a bit of the nitrogen.

There's another way of going about this.

Greens and browns

Compost materials are assembled in the correct proportion of "Greens" (nitrogen-rich) and "Browns" (carbon-rich) to achieve an overall carbon/nitrogen ratio of 25-30:1 (Virtual composter, and Compost Calculations from Rodale). Put simply, fresh green matter such as grass clippings, vegetable wastes, fresh leaves, etc, contain a lot of nitrogen. So does manure, bloodmeal, kitchen scraps, alfalfa meal, and hay. Fallen leaves, straw, sawdust, shredded newspaper and cardboard, wood chips -- browns -- contain high proportions of carbon.

Keith turning compost at the Beach House

Instead of thinking in "greens" and "browns", think in terms of "wets" and dries". In fact wets are usually green, and browns are often dry. You can make sure the browns are dry -- collect fallen leaves when the weather's dry, for instance. Presume your compost materials will always be too wet, and always have lots of dry browns on hand to balance it with. Too much carbon? We'll deal with that in a minute.

The advantage of dry browns is that you can store them indefinitely, unlike wet greens. With a bit of foresight and effort you can always have a few garbage bags filled with dries ready for when you need them. Make a big effort in autumn -- collect enough leaves for the whole year.

Hints

1. Not enough water is better than too much water. Too much water is a usually a disaster, but if there's not enough, the pile will heat up and then stop. Empty it out, loosen it all up with the compost fork, add more moisture, and put it back in the box again, no big deal. Soon you'll learn how much water is enough. If your pile is too wet, try emptying it, fluff it out, add more dry stuff, and some dry greens if you have such a thing (bloodmeal, peanut cake, alfalfa meal), and rebuild it. It might work.

2. Too much nitrogen is better than not enough nitrogen. If there's not enough the pile will just sit there forever, nothing happens for a year or two. If there's too much the pile will heat up well and simply blow off the excess with the steam in the form of ammonia gas, until the balance is right. But isn't that a waste of precious nitrogen? No -- nitrogen's only precious if you're dumb enough to buy it from a chemical company (see below, Adding liquids). Again, this way you'll soon learn how much is enough.

3. Roots: shake as much soil as you can off clumped roots before putting them in the compost. Many people put much too much soil in the compost with the roots, and it clogs everything up. But always have some soil sprinkled throughout the pile. It helps to inoculate the compost with the beneficial soil microorganisms that make the process happen, especially if you're not using animal manure, and clay particles in the soil help to spread a thin film of moisture throughout the pile, which is just what you want.

4. Useful additions: Lime, or, better, ground limestone, the finer ground the better. Liquid seaweed emulsion, such as Maxicrop, SM-3 or equivalent -- all the minerals for all the soilbugs, in easily digestible forms. Compost or compost siftings from the previous batch to inoculate the pile. Sprinklings of ground rock powders are useful.

5. Newsprint: Modern printing inks are almost always non-toxic and biodegradeable, particularly black ink, so don't be shy of using shredded newspaper (very "brown").

Compost containers

If you have really big supplies of organic wastes, make windrows, 8ft at the base, 5-6ft high, with sloping sides, and as long as you like. Otherwise prefer boxes or bins to heaps. If you're expert enough you can make a steep-sided heap, even a sheer-sided one, otherwise it degenerates into a mound, which is not efficient -- unless you're making an expert Biodynamic compost heap, that is.

Boxes and bins have sheer sides, and protect the compost from the elements. There are endless different designs -- see HDRA -- Building a compost bin for instructions on making a simple, flexible box system.

A chickenwire compost bin (Beach House style) on the left. When cooked, you can open the wire mesh and work on the pile (centre). Cardboard boxes (right) also make a good compost bin

Here's how to make a wire mesh bin.

Make a "tube" of chickenwire, 3ft in diameter. Leave about 8-10" overlap, and connect the ends with four twists of wire each. You'll need about 10.5ft of 3ft-wide mesh, and two more pieces each 3ft long -- total 16.5ft.

Line the bin with a garbage bag, or two bags, with the bottoms cut off, to keep the moisture in. Have the liner flush with one end, and overlapping the other (that's the top).

Make a 3ft square of four bricks, one at each corner, with a fifth in the middle, and put a 3ft square of tough wire grille such as pig fencing on the bricks. Put one of the two 3ft-square pieces of chickenwire on top of that. Stand the mesh bin on end on top of this aerated base. Now you can fill it with compost material.

When it's full, depending on the weather, you can close it loosely with the garbage bag overlap, again to keep the moisture in; when it starts steaming, open the bag, if it seems to be getting dry, close it again.

Cover the top with the second 3ft-square piece of chickenwire, and clip it on, to dissuade wildlife. If it's in the open, cover the top with a garbage bag to keep the rain out.

You'll need two of these bins -- you always need at least two compost bins/boxes: when one's full, you start filling the next one. By the time that one's full, the first one is finished and can be emptied.

Assembling the materials

It's easier to make good compost if you have enough materials to fill the box at one go. If not, see below, Batches. See HDRA -- How to make compost, for good information on which materials to use and how to use them. Basically, anything that was once alive or part of something alive can be composted. This is the recipe: the assembled pile should have 60--65% moisture content, good aeration, acid-alkaline level about neutral (pH 7) or slightly acid (pH 6-6.5), carbon/nitrogen ration 25-30:1 (Virtual composter, and Compost Calculations from Rodale).

First, collect all the greens together and mix them thoroughly with a compost fork. If anything's too big to mix, chop it up into 4-6" lengths with the edge of a spade or a chopper.

A compost fork -- the perfect tool for composting, 4-tined or 5-tined

Up to 10% of the material can be rough material like small sticks and prunings -- they probably won't break down but they'll help with aeration and prevent the material packing down and clogging up too much.

Assemble all the ingredients in a sort of big pancake (5-6ft diameter) in front of the open box (leave yourself enough room around it to work).

Put wet greens on top of dry browns. Use a 5-gallon bucket or a basket. Spread out two buckets of browns (pack it in) and then one bucket of greens on top.

Do that twice, then add some sprinklings: a handful of ground limestone or wood ash (sprinkle it like icing sugar on a sponge cake), some bonemeal if you have it, a handful or two of soil, and a couple of handsful of compost (unless you're using the siftings from the previous batch -- mix with the browns if they're dry enough). Scuff over the surface to bury the sprinklings a bit, then add liquid (see below, Adding liquids) -- 1-2 litres, with a sprinkling can. If you must use a hose, set the nozzle to a fine mist.

Mixing the layered material before putting it in the bin

Repeat this whole layering process two or three more times or until you've used all the materials.

Now work from the edge of the layered pancake: rake off about 1ft with the compost fork, mix it up well, and fork it into the box, spreading it evenly and tamping it down firmly (but not too tight). Layering it and then mixing vertical slices this way gets it thoroughly mixed and evenly distributed. Then do the next foot, and continue until it's all in. Sweep up fines as you go, sprinkling them into the box with a shovel.

Aeration
Compost needs air from underneath. You can put the box on the soil, if it's good soil that breathes well. Even then, loosen it well with a fork to a depth of about 12 inches. An advantage of this is that if the pile is too wet some of the excess water might drain off into the soil. (Or it might not.)

Turning the pile aerates and mixes it thoroughly to burn a second time

Alternatively make a base like that for the wire mesh bin described above: make a 3ft square of four bricks, one at each corner, with a fifth in the middle, and put a 3ft square of tough wire grille such as pig fencing on the bricks. Put a 3ft-square piece of chicken wire on top of that, and stand the box on this base.

When filling the box, stand a 5ft length of bamboo or a broomstick upright in the middle until the box is full. Then shake it from side to side a bit (an inch or two) and pull it out. Or make vertical holes every 6" or so across the top with a piece of rebar, push it right down until you hit the wire mesh at the bottom. Now your compost can breathe easily.

Put a lid on the box when it's full, not airtight, but wildlife-proof, and waterproof if it's in the open.

That's it. By the next day the temperature should be above 50 deg C, and it should climb to 60 deg or higher. You can turn it after a week or two when the temperature's fallen to about 40 deg, or just leave it for another couple of weeks instead.

Get a soil thermometer, or any long thermometer that will reach the centre of the pile to monitor the temperature. Or just put your hand in -- if it's too hot to keep it there, it's fine.

Adding liquids