Knowledge Base

Both anaerobic digestion and composting process organic material into useful outputs, but they work in fundamentally different ways. Composting is an aerobic process: it requires oxygen, takes place in open or semi-open systems, and produces compost as its primary output. Anaerobic digestion takes place without oxygen in a sealed tank, and its primary output is biogas (an energy carrier), alongside digestate. This makes AD the more energy-productive route: organic waste becomes a source of renewable electricity, heat, or gas, rather than solely a soil amendment. The thick fraction of the digestate can, with additional post-treatment, also be turned into compost, so the two routes are not mutually exclusive.

For organizations looking to extract energy value from organic waste, anaerobic digestion is the more powerful option: composting does not capture the energy locked in organic material, while AD does. The biogas produced can replace fossil fuels across heat, power, and transport applications, and the digestate produced by AD is comparable in fertilizing value to compost, retaining the key nutrients (nitrogen, phosphorus, and potassium) from the input material. AD therefore delivers a dual return: renewable energy and a circular nutrient product, from waste streams that would otherwise require costly disposal.