Glossary

Anaerobic digestion is a series of processes by which microorganisms break down biodegradable material in the absence of oxygen. Such processes are used for industrial or domestic purposes to manage waste, or to produce fuel (methane also known as biogas), and compost.

Batch composting simply involves mixing all your organic waste together at once and then letting it decompose without adding any more material (except water), until it turns into compost.

Biodegradable plastic can be broken down into water, biomass, and gases such as carbon dioxide and methane. Biodegradability depends on environmental conditions such as temperature, humidity, the presence of oxygen, and microorganisms.

Bioplastics is a rather confusing term that encompasses a range of different materials that are either bio-based, biodegradable, or both. Bio-based bioplastics are made using polymers derived from plant-based or microorganism sources such as starch, cellulose, lignin, or polylactate. Bio-based bioplastics can be engineered to be biodegradable; equally they can be engineered to be chemically identical to petroleum-based plastics such as non-biodegradable polyethylene.

Biogasification is an industrial process whereby biomass is converted into biogas, which can then be used as fuel.

Carbon sequestration is the removal and storage of carbon dioxide from the atmosphere by natural or artificial processes.

Cold or passive composting uses many of the same ingredients as hot composting, but requires less maintenance and effort, i.e. no digging or aeration of the heap. The resulting internal temperature of your compost heap or bin is therefore much cooler, and so it takes longer for the organic waste to decompose into compost.

Compost is organic matter that has been decomposed in a process called composting. This process recycles various organic materials otherwise regarded as waste products and produces a soil conditioner (the compost).

Compostable materials are a subset of biodegradable plastics that break down safely into water, biomass, and gases under composting conditions. Industrial composting conditions are the most favourable: temperatures of 55-70℃, high humidity, and oxygen. Materials that break down in industrial composters may not break down under home composting conditions.

Continuous composting involves adding organic waste to a compost heap or bin continuously in an ongoing process. Commonly, continuous compost heaps consists of highly decomposed matter with compost underneath and fresh waste on top.

End-of-life is a term used to indicate the stage of a product, process, or system when it is disposed of and/or recycled.

Global warming potential (GWP) is a measure of greenhouse gas emissions in terms of their potential to trap heat in the earth’s atmosphere, relative to carbon dioxide, in a specific time horizon.

Home composting is a general term for the process by which biodegradable garden waste or domestic food waste is collected and placed in either a container or heap to allow natural processes to turn it into compost. It is a manual process whereby the composition and process temperatures remain largely unregulated. Both aerobic and anaerobic conditions can occur in home composting, although aerobic conditions are more normal. The time frame for home composting depends on personal preference and the use to which the compost is put, but 3-12 months is typical.

Hot or active composting is a method whereby microbial activity within the compost pile is at its optimum level, resulting in a higher internal temperature of your compost heap or bin, and the quick decomposition of organic matter into compost.

In-vessel composting (IVC) generally describes a group of methods that confines the composting materials within a building, container, or vessel. In-vessel composting systems can consist of metal or plastic tanks or concrete bunkers in which air flow and temperature can be controlled, using the principles of a ‘bioreactor’. Generally the air circulation is metered in via buried tubes that allow fresh air to be injected under pressure, with the exhaust being extracted through a biofilter, with temperature and moisture conditions monitored using probes in the mass to allow maintenance of optimum aerobic decomposition conditions.

In agriculture, windrow composting is the production of compost by piling organic matter or biodegradable waste such as animal manure and crop residues in long rows (windrows). This method is suited to producing large volumes of compost. These rows are generally turned to improve porosity and oxygen content, mix in, or remove moisture, and redistribute cooler and hotter portions of the pile. Windrow composting is a commonly used farm-scale composting method. Composting process control parameters include: the initial ratios of carbon- and nitrogen-rich materials, the amount of bulking agent added to assure air porosity, the pile size, moisture content, and turning frequency.

Life cycle assessment (LCA) is an environmental assessment methodology used to analyse the environmental impacts associated with resource utilisation and emissions at each stage of a product, process, or system’s life cycle.