Composting

Composting is the aerobic decomposition of biodegradable organic matter, producing compost. (Or in a simpler form: composting is the decaying of food, plant matter or manure.) The decomposition is performed primarily by facultative and obligate aerobic bacteria, yeasts and fungi, helped in the cooler initial and closing phases by a number of larger organisms, such as springtails, ants, nematodes and oligochaete worms.

Composting can be divided into home composting and industrial composting. Essentially the same biological processes are involved in both scales of composting; however techniques and different factors must be taken into account.

Home composting

Home composting is a way for householders to treat their garden waste and produce a compost they can use in their own gardens. Separating and composting vegetable peelings, tea bags along with plant and green garden waste (grass clippings, plant and hedge trimmings, etc), not only reduces the amount of household waste that is generated for collection but adds vital nutrients and structure back in to the soil. Most kitchen and garden waste can be recycled back into the soil, via a home compost bin.

Industrial composting

Industrial composting is the name given to large scale composting that occurs on farms in windrows or under cover in In-vessel composting that allows food waste to be composted along with non-food waste. If food waste is included the facility has to be conform to Animal By-Products Regulations 2013 . Material collected at a civic amenity site will usually be processed in a windrow as there has been no contact with food waste. Compost from large scale composting can be applied in many ways, including as mulch, in planting beds, as a soil improver in general landscaping, in topsoil manufacturing, and for tree, shrub and herbaceous plantings.

Quality Protocol

There is a quality protocol for compost and a public available standard (PAS) 100 which sets out criteria for the production of quality compost. The quality protocol identifies the point at which compost has reached end of waste status and no longer needs to adhere to waste regulations. This allows QP compost to be spread without a permit. It helps provide users with confidence that the compost they use conforms to an approved standard and helps protect the environment and human health.

BSI PAS 100

PAS 100 was prepared and published by the British Standards Institution (BSI) and developed following extensive consultation across the compost industry. It only covers biodegradable materials that have been kept separate from non-biodegradables, and applies to composted materials produced at centralised, on-farm and community composting facilities. It does not cover end products of home composting for self-use. It was updated in 2011 and again in 2018. PAS 100:2018. Having a PAS improves confidence in composted materials among end-users, specifiers and blenders, and helps producers differentiate products that are safe, reliable and of high performance. The Organics Recycling Group (ORG) is part of REA (Renewables Energy Association and they manage the compost certification scheme through REAL.

Quality Protocol Compost

In England, Wales and Northern Ireland the quality protocol for the production and use of quality compost from source-segregated biodegradable waste has been recognised by the Environment Agency.

In Scotland, SEPA issued a position statement in 2017 stating the level of plastic allowed in compost.

From 1 Dec 2018 0.08% (which is 66% of PAS 100: 201)
From 1 Dec 2019 0.06% (which is 50% of PAS 100:2011)

The quality protocol for compost has been developed so that materials produced in accordance with the quality protocol will no longer be considered as waste. It was also developed to try and help reduce the regulatory burden for the production and use of quality compost. It provide users with confidence that the compost they purchase conforms to an approved standard and helps to protect the environment and human health.

Ireland produced a National Biodegradable Waste Strategy in 2006 which set out the use of quality source segregated compost for use in horticulture, agriculture, forestry and other uses.

Zero Waste Scotland published the Compost Good Practice Guide in 2011 for the use of quality compost use in building, civil engineering, landscaping and land regeneration projects.

Brownfield Sites

WRAP have a number of guides and case studies on compost being used on land regeneration and landscaping .

Horticulture

There are a number of benefits in using compost whether a grower of fresh produce or pot plants, bedding or nursery stock:

Reduces the need for inorganic fertilisers
Can increase yield
Improves soil structure
Raises water retention capacity
Reduces soil erosion
Contains valuable micro-organisms
Reduces cost

Agriculture

The benefits of using quality compost in agriculture and field horticulture are multiple. European and UK studies show that compost made from garden and food waste can significantly benefit soils and crops by:

Maintaining and enhancing soil organic matter levels.
Supplying major crop available nutrients such as Nitrogen, Potash, Phosphorous, Sulphur, Magnesium and trace elements.

The use of quality compost can therefore improve crop establishment and increase yields. Quality compost can be used in a variety of agricultural applications:

Arable crops
Top and soft fruit
Root crops & vegetables
Grassland
In organic farming

Legislation

Composting in a waste facility requires permitting and it is also covered by the BREF for Waste Treatment .

Composting permits include those for:

500 tonnes specified biodegradable waste open or in-vessel composting SR2010 No 14 or SR2011 No 1
Open systems with under 75 tonnes a day (existing permits before 1 March 2016) SR2012 No 7
Closed systems with under 75 tonnes a day (existing permits before 1 March 2016) SR2012 No 3

There is a composting exemption T23 available but this is for small amounts for use by schools or community groups.