Anaerobic Composting has to occur in a warmed, sealed airless container, referred to as the digester, which creates the best conditions for the bacteria to grow and ferment the organic material in the oxygen-free conditions.

We have seen that grass cutting left in a plastic bag in the garden can begin to decompose anaerobically very quickly, making a slimy mass emitting strong odors, which is “anaerobic composting”. The “anaerobic digester” used for composting can be any kind of air-tight container, barrel or bucket with a lid, or as easy as a plastic bag. There are 2 forms of anaerobic digesters: Dry Digesters and Wet Digesters.

Dry Anaerobic Digesters as its name suggests uses no additional water or liquids to push the biological process. The compostable materials that contain sufficient water content, for example, cut grass, fleshy plants, and stems, or food waste are finely chopped and shredded, sealed in their respective airtight containers and left for several weeks or months to naturally decompose.

The decomposition time of the solid waste feedstock, likewise because the quantity of biogas produced, is significantly affected by the kind of waste materials used and the external temperature during fermentation. Once choosing solid wastes for dry anaerobic digestion, the carbon to nitrogen ratio, C/N ratio and the biodegradability of the feedstock materials need to be carefully considered.

If you do not have an anaerobic composter, another approach to dry anaerobic composting is to bury it underground. This kind of passive anaerobic composting process referred to as pit composting, seals the solid feedstock waste from exposure to the air and oxygen by burying underground. This is the simplest approach to compost if you do not mind digging. A dugout pit or trench in the ground is filled and tightly compressed with the organic matter and sealed from the surrounding air by a layer of topsoil.

The anaerobic de-composting occurs underground and doesn’t produce compost to spread around the garden, however, it will improve the soil in this spot. Additionally, with pit composting, there are no sightly compost heaps, containers or fermentation barrels visible above ground. Another advantage of this kind of anaerobic composting is that the pit or trench can be dug around the roots of trees, bushes, and alternative such larger garden plants rising their soil conditions to assist develop stronger roots.

As anaerobic organisms decompose the solid waste at a slower rate than their aerobic counterparts, sometimes it can be difficult to monitor their progress without digging out the pit or opening the containers to look permitting oxygen to enter. However, once completed, the dry anaerobic compost ought to be odor free with little or no liquid effluent made. Also, anaerobically digested manures retain most of their nutrient and fertilizer value that is good for the growing plants.

Wet Anaerobic Digesters: using animal and poultry manures, slurries, effluent’s and inexperienced organic materials mixed with water as a type of liquid composting. The water content of the liquid feedstock is extremely high at over 80th of the volume. Wet Anaerobic Compostingconverts liquid organic waste into a fashionable source of renewable energy in the variety of “Biogas”. This biogas contains methane and greenhouse emission which can be used for energy generation directly, still as a stable semi-solid digested material referred to as the “digestate”.

This digestate can be separated into a liquid compost, affectionately referred to as “compost tea” which can be used as a liquid fertilizer high in water-soluble nutrients and a nutrient-rich solid fraction as a soil conditioner. Liquid composting and liquid anaerobic fertilizers can be cheaply created at home by using a standard watering pot as a wet anaerobic digester.

Another method of making anaerobic compost involves keeping the compost submerged underwater. This method doesn't need to be sealed against the ingress of oxygen however a large tank, plastic pool or a shallow pit is required to hold the compost that is then filled with water. Since the compost decomposes, the odors are trapped in the water. this type of passive composting takes a great deal longer to finish because the water temperature is usually cold and therefore the micro-organisms don't have as high a metabolism.

One of the principal disadvantages of wet anaerobic composting by the direct use of animal manures and sludges is the risk of plant and human contamination by pathogens like ecoli and salmonella. Heating of the liquids and/or solids produced above 55oC would destroy these pathogens yet an additional energy resource is needed to do this.