Domestic waste consists in about 30% of organic compounds as food waste from kitchens and vegetable waste from gardens. Besides a certain fraction of paper difficult to recycle can be added, such as household paper, food paper wrappings and tissues. All these components are «biodegradable», as to say they can be the subject of a biological treatment.
Two types of treatment are to be considered, according to the waste composition: Composting and Methanisation.
Composting is the decomposition of biodegradable organic matter by oxidation, producing compost, a product that can be used as a fertilizer or soil conditioner, thanks to the work of aerobic microorganisms (organisms who require oxygen to live). The process is best applicable for vegetable waste containing a high concentration of ligneous (woody) structured components as wood, branches and straws. The latter enhances the diffusion of oxygen inside the mass, essential for the activity of the microorganisms.
Methanisation is the decomposition of biodegradable organic matter by digestion, producing compost (after a finishing stage). Besides that it produces also a renewable energy in the form of biogas. The digestion is an anaerobic process, which takes place in the absence of oxygen. The process is best applicable for humid to liquid waste and/or for waste easily fermenting while producing foul-smelling emissions as well as waste containing a high energy potential (sugars, starch, greases, cellulose paper).
Composting and methanisation allow the recycling of organic matter back to the soil. Only the digestion process can produce renewable energy. Recovery of by-products, energy and compost, is an essential aspect for a successful project.
Type of treatment, waste composition, type of collection and final recovery: the overall waste management chain must be consistent.