Composting is an easy way to reuse organic materials and their by-products and generate rich soil. This process can minimize waste materials being thrown in landfills and at the same time provide a natural fertilizer at home. One popular type of composting is anaerobic composting.

What Is Anaerobic Composting?

Anaerobic composting is done by fermentation, using no or limited oxygen. It relies on anaerobic microbes, which survive without oxygen, to decompose the materials. This decomposition process produces methane and hydrogen sulfide gases which release a strong stinky smell. As anaerobic composting is a low-temperature process, pathogens and weed seeds are not killed in the process. The pathogens will disappear slowly over time in the unfavourable environment. Factors that determine the composting duration and success include the types of nitrogen-rich materials, the surface area used, the moisture content of the pile, and the amount of oxygen present.

Anaerobic Composting Materials

For anaerobic composting, you need to choose nitrogen-rich materials. For eg non-fatty kitchen scraps, houseplant clippings, tea bags, egg shells, human or pet hair, small amounts of wood ash or grass clippings, and untreated paper towels, napkins or tissue. It’s best to not include organic materials like meat, bones, animal fat or oil, and dairy products. Anaerobic composting also thrives with a limited amount of carbon-rich materials like leaves and wood yard trimmings.

Anaerobic Composting Process

Anaerobic composting requires little work as you need only to pile up the materials in the bin, wet the pile, cover it with a lid, and wait for the compost to be ready for use.

If you have yard space, you can set aside a small area for your anaerobic compost. The greater the surface area for the microorganisms to thrive in means the faster the decomposing process. Try and work with a large bin with a lid, preferably those that have more than a 135 litre capacity. Remove the bottom of the bin. Dig about 6-12 inches deep and place the bin firmly in the pit. You may fortify the bottom of the hole with bird wire to keep out scavengers but allow earthworms to enter and enrich your compost.

Once you have set up the bin, you can begin adding materials to your anaerobic compost pile. Add enough water to keep the moisture content at 40 – 75%. Cover the bin and refrain from opening and closing the bin frequently to promote the anaerobic microbe activity, limiting it to no more than twice a week. Maintain the moisture level by watering at least once a month. Unlike aerobic composting, do not turn the pile since this would be incorporating oxygen into the pile and only prolong the decomposing process.

Anaerobic composting generally takes about three months to fully mature. The resulting compost may look dark and slimy, but it is filled with nutrients that are beneficial for your soil and plants. Once the decomposing process has been completed, it should be allowed to dry and aerate for 6 months to a year to allow for the elimination of pathogens and promote ideal compost composition to be harvested.

Anaerobic Composting

To wrap up… here are the pluses and minuses:

Pluses of Anaerobic Composting
• Requires a lot less work than aerobic composting
• Produces more usable humus per volume of original composting ingredients compared to aerobic composting
• Finished product contains higher levels of ammonium, since anaerobic microbes tend to use less nitrogen than aerobic microbes
• Process of composting anaerobically produces biogas (e.g. methane and carbon dioxide), which can be captured and used for energy/fuel

Disadvantages of Anaerobic Composting
• Putrification of organic materials can lead to very unpleasant odors, due to release of sulfur-containing compounds such as hydrogen sulfide
• Process requires a lot more time to produce usable compost compared to aerobic composting
• If anaerobic compost is not allowed adequate time to breakdown, there are risks that the compost will contain pathogens. Since there is not enough heat generated in an anaerobic pile, you must rely on your microbes. That is, if your compost is given enough time to breakdown, any pathogens that may have been present will eventually be out-competed by more beneficial microbes.

Sources: www.Ecoevaluator.com and www.compostjunkie.com