Module 8: Composting
Turning “waste” into black gold.
Introduction
I'll never forget the first time I made my own "compost." The gardening bug had bitten hard and I was obsessed with my first garden, a tiny patch of dirt bordering the back patio of my raffish English basement apartment. I tore out the weeds and planted a hodgepodge of pretty and good-smelling things: basket-of-gold, sedum, yarrow, parsley, sage, rosemary, and thyme. I had no system or clue, but I was so happy digging in that junky little spit of soil. And poor soil it was — clay mixed with rubble and broken bricks, typical construction backfill. This soil needs a boost, I thought. I'll make compost!
I punched a bunch of holes in an empty storage bin — my knowledge level was close to zilch, but at least I knew compost needed air. I cooked up a big veggie stir-fry so I would have plenty of broccoli stems and carrot peels to start the pile. The next morning I added a banana peel and dumped my coffee grinds on the mix. This is gonna be awesome!
A week passed, then two. I added every food scrap I could. I shook the bin. It didn't smell very good. Actually, it smelled awful. And it didn't look anything like the compost I bought from the nursery. It looked like a bunch of slimy carrot peels, broccoli stems, banana peels and coffee grinds.
I showed my food scrap slime to my friend Deana. She was a landscape architect and naturalist, she would know. She looked at it, wrinkling her nose. "You can't just compost food," she told me. "You need some dry materials. Put some leaves in there. And dirt with worms in it, some critters to eat all that stuff."
My friend's sage advice taught me an important lesson:
While a compost pile is a great place to re-purpose your food scraps, food scraps alone are not compost.
There's a lot of stuff you can put in a compost pile, but the basic three ingredients are:
Carbon. Dry brown materials like fall leaves, shredded bark, and straw
Nitrogen. Fresh moist materials like manure, food scraps, and grass clippings
And the most important thing people often don't know about: MICROBES. Microbes are found in healthy living soil. You can also add microbe boosters, which you'll also learn about in this module.
Apparently, my first misadventure with compost reflects a common error. Luke recently signed on to help get a compost pile started at his community garden in Winchester VA. People show up with slimy food scraps and honestly believe they will just turn into beautiful soil, just like I did.
Well, we are here not only to sweep away any misconceptions about compost, but also to teach you exactly how to make your own fertile growing medium with easily sourced dry materials, microbes, and yes, food scraps too.
First, let's take a look at what makes compost a go-to for successful home gardeners.
Benefits of Compost
Compost is whole nutritious food for your plants.
What's better for your body: A diet of nutritious whole food? Or a diet of junk food and vitamin pills? Compost is whole food. Plants grown in compost-enriched soil are able to funnel out the nutrients they need — when they need them — via a wonderfully intricate exchange system facilitated by soil microbes.
In comparison, commercial fertilizers flood the soil with absurdly high concentrations of nutrients (just like many vitamin pills) that plants can't use all at once. As much as 90% of chemical fertilizer washes out of the soil when it rains, eventually finding its way into the water supply. In fact, chemical fertilizers are a major source of water contamination.
Compost is cheap.
I won't say "free" because there is an initial cost associated with making the composting system that suits you and your space/time conditions. But whether you use a small worm container under the kitchen sink or a large wire mesh bin in the backyard, making your own compost is a MUCH smaller expense than buying nursery compost or commercial fertilizers.
Compost reduces waste.
Over one-third of food (1.3 billion tons) produced annually for human consumption is wasted. In developed countries, more than half of the waste happens at the household level. Having a compost pile gives you the opportunity to feed beneficial microbes, earthworms and other beneficial insects in soil simply using it as a receptacle for kitchen scraps.
Composting FAQ
Q: Do I need a lot of space to compost?
A: You can compost in a small space, like a cabinet under the kitchen sink. It all depends on what system you use and your willingness to adapt to your circumstances. Right now, humans need to evolve in order to survive. Adaptation is key to evolution. It's up to you.
Q: Won't it smell bad?
A: Not if you do it right! A common misconception about compost is that it "rots down." This is untrue. If it were, landfills would be filled with compost, not slimy piles of food waste. Compost is the result of waste that is broken down and digested by bacteria, fungi, amoebas, insects, and other life forms. A properly mixed pile will actually emit a good, warm earthy smell. If it smells bad, that's a signal that the pile needs an adjustment. We'll get into specific composting ingredients and how to combine them effectively in the next section.
Q: How long does it take to make?
A: Homemade compost does take time. Depending on what method you employ, it can take anywhere from 3 months to a year for your compost to be ready to use once the materials are mixed. Don't let this stop you. It's well worth the wait. Plus, compost can be started at any time of year, even in winter.
Q: I live in the city. Won't my compost attract rats and other pests, like squirrels?
A: Again, it depends. I had outdoor compost bins in three different urban scenarios, a tiny patio, a back alley, and a narrow row house yard. I never had rats or mice get into the bins because:
I pest-proofed them with sturdy mesh wire OR used a closed bin with air-holes
and
There were were dumpsters around filled with restaurant waste, pizza boxes, and the like to entice rodents.
In one instance where my back patio was directly across from the Don Juan Salvadoran carry-out, I even left my compost bin uncovered sometimes. No rats. If you were a rat what would you go after? Half-eaten tacos de lengua or some tough broccoli stems splashed with coffee grinds? As for squirrels, get over it. They're everywhere.
Q: Is there anything I shouldn't compost?
A: There are some forms of waste that don't make good compost. It also depends on what system you use. Examples include citrus peels, meat scraps and bones, and dairy foods. Some materials, like heavy cardboard and newspapers can be composted, but it's a lot of work for a small home compost pile. A better way to use bulky materials is sheet mulching which we already explored back in Module 2: Black Gold.
How Compost Works
It's alive
As we learned in our section on Soil, organic matter — food scraps, leaves, paper, what have you — doesn't break down by itself. Decomposition is a process of digestion by insects, bacteria, and other microbes.
Like any other living thing, a compost pile needs food, air, and water. The food is what you feed the microbes. They also need air to breathe so don't try to compost in a sealed bin without air flow. And microbes need water, but too much will drown them. A compost pile should be damp like a wrung-out towel. So if your bin is outside, make sure it has a lid or is under a roof and out of the rain.
Chemistry Counts
One of the most common mistakes novice composters make (including yours truly in my beginner days) is putting only food scraps in the compost bin. Or stacks of newspaper with some banana peels and broccoli stems. Months later, the "compost" is still banana peels, broccoli stems, and perfectly legible newspaper. What happened? Or, more accurately, what didn't?
When you build a fire, you make a base of thick slow-burning pieces of wood, strategically place some fast-burning twigs in between, and light it with a flame or spark. A compost pile is just like that. Materials high in carbon form the base, nitrogen-rich materials serve as the twigs, and microbes provide the spark. For a good steady heat to break down the pile, in addition to microbes, you need the right ratio of carbon to nitrogen-rich materials.
You're losing me here. This sounds complicated.
Rest easy. Nature is very flexible and will work with you. The right ratio is 30 parts carbon to 1 nitrogen. But it's perfectly fine to guess-timate and adjust later. And look! Your gentle writer has provided this handy guide to common compost materials. All you need to do is mix approximately half and half from each column, toss in a few cupfuls of healthy soil to incorporate microbes, and your pile is good to go.
Use your senses
First, give your pile about ten days to get "fired up." Give it a gentle stir every other day. Then LOOK at it. Put your hands close to the pile and FEEL the temperature. SMELL it. If the pile isn't emanating heat, doesn't smell good, and the materials look exactly the same as when you compiled them, your pile needs more nitrogen-rich materials and possibly microbes. Incorporate another cup of soil from your garden or yard. The best soil will be under a tree or shrub where microbes are feeding on fallen leaves. Put those decomposing leaves in your pile too--they are microbe magnets.
On the other hand, if your pile is slimy and emitting a rank ammonia-ish smell, it has too much nitrogen. Toss in some shredded paper, sawdust, straw, or dried leaves until it balances out. Mix the new ingredients in well.
A well-balanced compost pile will LOOK like it's decomposing, FEEL warm, and SMELL good!
Size matters
A compost pile needs a certain "critical mass" to generate enough heat to break down organic matter. The problem with compost that doesn't get hot enough is that seeds in food waste don't get sterilized. An occasional germinated seed is fine, but imagine spreading your compost and a few weeks later having to pull out hundreds of rogue tomato plants springing up from undigested seed. In order to build up to the target temperature, your pile needs to be at least 3(ft)x3x3 or 80cm on a side.
Now, in order to figure out the best fit for your space and garden needs, I've outlined a few recommendations for home composting systems below.
Composting for your Space
Scenario #1:
Balcony and/or patio only
Garden: containers, trellises, 4 sqft or smaller boxes
Best Compost Method: closed worm bin
If compost piles were pets, a worm bin would be a quiet, well-behaved housecat. A worm bin is compact, clean, and low-maintenance—plus it doesn't shed and you only have to "take out the litterbox" once every three months or so. Like it's name suggests, a worm bin is a container small enough to fit under the sink where worms turn a good portion of your food waste into pure gold for gardening. It is the perfect method for composting in a small indoor space. And when you move to a new apartment, it's easy to take your worm friends too.
Worm bin composters don't produce a large bulk. They do produce highly nutrient dense fully digested compost for very little work. They are an ideal way to feed container and intensive small gardens and don't compromise a lifestyle on-the-go.
Scenario #2:
Small yard and patio/porch
Garden: containers, boxes, trellises, small raised beds, fruit tree or shrubs
Best Compost Method: closed worm bin indoors AND a bin or "composter" outdoors
With more space, you can have a worm bin indoors AND a larger bin outside. With an outdoor bin, you can be less selective about what goes in the pile--citrus peels and leftover take-out are ok as long as the materials are well-balanced.
Personally, I'm not the biggest fan of those enclosed polyplastic compost bins that you can turn with a handle. They are serviceable, but have a few big flaws. The air holes are usually too small and get gummed up with your compost so it doesn't get enough air. Also, the spinning action tends to glom the composting materials up into a ball so they aren't really getting mixed up properly.
The advantage to these bins is that they are sleek, pest-proof, and inconspicuous (especially if you have nosy neighbors or a HOA to contend with). If you do use one, make larger air-holes and line them with pieces of screen mesh so rodents and flies don't get in. Also from time to time, take the lid off or open the door to separate and "fluff up" the materials so they can decompose.
If you are blessed with neighbors who mind their own beeswax, you can make a simple wooden box, three feet on a side, with a few slats removed as air holes. Use a sturdy wire mesh to cover the spaces you've left for air to enter. You can also make a lid with a wood frame and the same mesh (like a screen window). Keep the bin covered with a waterproof tarp (an old tent tarp is perfect). This combo lets air in on several sides and keeps pests and flies out. Then all you need is a shovel to mix your compost from time to time.
Scenario #3:
Big yard plus patio/porch
Garden: containers, boxes, trellises, larger raised beds, fruit trees and shrubs
Best Composting Method: multiple bins or piles
If you have a larger yard and more garden soil to feed, I strongly encourage making a two-bin system. Because the compost cycle takes several months to complete, with two bins you can create a rotation. A few months after getting one bin started, start the second. This way you always have a supply of finished compost and another one on the way.
You can use commercial composting bins or make your own, as described in Scenario #2.
Rest assured, no matter which compost system you choose to invest in, you will be amply repaid in gardener's black gold.