The Different Kinds of Compost

Fresh compost from a compost bin

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You might know about composting if your town collects a special bin for yard waste and food scraps, and if you know any gardeners, you know how passionate they can be on the topic. But what is composting all about, and what are the different kinds of compost?

What Is Compost?

Compost is organic matter that's been broken down by bacteria, fungi, insects, and other organisms. The reason compost is such a boon for gardeners is that it adds nutrients to the soil, which are then absorbed by the plants growing in it. 

Compost also fights plant diseases, helps soil retain water, and reduces the need for chemical fertilizers. And if you make your own compost at home, it's a great way to derive some benefit from food scraps you would otherwise just throw away. Fruit and vegetable peels, trimmings, stems, and pulp from juicing, as well as coffee grounds, tea bags, and stale bread, can all be composted.

There are several methods of composting that people use at home. Some require more effort and specialized equipment than others. But mainly, you just need to set aside some space to add your food scraps, a little at a time. It might be easier than you think, and the results are definitely worth it.

Bokashi Composting

Bokashi composting is an indoor type of composting, and it has a few advantages. One, you can compost all your kitchen scraps, even meat, fats, oils, and dairy products, which you can't do with any other composting systems. Two, it can be done indoors. And three, it doesn't smell as bad as other systems. 

Here's how it works. You have a large bucket, about 5 gallons, with a tight-fitting lid and a spigot at the bottom. You also need some sort of host medium, such as bran, or some other organic material, that has been inoculated with beneficial yeasts and bacteria such as lactobacillus— that's the bacteria that makes yogurt and sourdough bread. You add your food scraps to the bucket each day and cover it with a layer of bran, which starts a fermentation process triggered by the organisms in the host medium. 

When the bucket is full, place it somewhere indoors, so you can ensure it is out of direct sunlight (and also away from heaters and other heat sources) for around ten days to two weeks, during which you will use the spigot to drain the mixture of liquid every other day. Diluted by a factor of 100 parts water to one part bokashi juice, this liquid can be used as a plant fertilizer.

After this, what you have can be described as "pre-compost." It's too acidic to come into contact with plant roots at this point. Instead, it goes into an empty patch in your garden, and in another two weeks, it will be ready to be fully incorporated into your soil. 

Vermiculture Composting

Vermiculture is worm composting, which transforms your kitchen scraps into dark, nutrient-rich soil that's perfect for blending with garden soil, potting soil, or dressing the tops of garden beds.

For worm composting, you need a container, some sort of bedding (often made of shredded newspaper, paper grocery bags, or cardboard), and the worms themselves. After preparing the bedding by wetting it with water, adding a bit of dirt and maybe a few eggshells, and fluffing up the mixture, you add your worms. They'll burrow into the bedding and, after a week or so, you're ready to start adding your kitchen scraps. 

Other than meat and dairy, all your kitchen scraps can go in, along with tea bags, coffee grounds, and unbleached coffee filters. Chopping up the scraps can help make it easier for the worms to digest everything.

You can keep the bins outside or inside. The ideal temperature for the worms is between 55 and 77 F. Depending on where you live, you may want to bring the bin inside during the summer, winter, or both. Some people or keep it in the basement year-round, as basements tend to keep a fairly steady temperature. In three to six months, you're ready to harvest your vermicompost.

Outdoor Composting

There are two types of outdoor composting: aerobic which means there is air in the compost, and anaerobic, which means the opposite. 

With aerobic composting, you're basically building a pile of compost all at once, made up of yard trimmings, leaves, and kitchen scraps, and letting it decompose. You'll need to turn the mixture a few times a week, using a pitchfork or shovel. That's because this process generates a lot of heat and the compost pile will heat up in the center, which accelerates the process of decomposition. Turning the compost regularly helps this process happen evenly throughout the pile. 

This method is sometimes referred to as hot composting because the temperatures in the pile can reach 110 to 160 F, or batch composting, because you make a batch all at once, rather than adding to it over time. This means you might have more than one pile going at a time. A given batch will be ready within four weeks.

The easiest composting method, however, is anaerobic composting. It also involves an outdoor pile, but you add your scraps, yard trimmings, and fallen leaves, to the top, a little at a time, and shovel out the finished compost from the bottom. This method requires almost no work, other than adding a bit of water from time to time to ensure that the pile doesn't dry out. This method is sometimes called cold, or continuous composting. It's much slower than hot composting, yielding a finished compost in six to 12 months.

As with vermicomposting, you can't add meat or dairy to outdoor composting, either aerobic or anaerobic.