In the context of greenspace, waste materials (as defined by European and national legislation) encompass three main groups:
- Soil materials that arise from industrial processes, such as sugar beet washing
- Industrial mineral wastes suitable for use as soil-forming materials, such as colliery spoil or pulverised fuel ash
- Organic wastes, such as composts or biosolids, which are valuable as amendments to mineral soil-forming materials.
Using wastes for establishment of vegetation is a useful and potentially cheaper option than importing soil materials from donor sites, and in many cases may be the only practicable option. Certain types of mineral and organic wastes (singly or in combination) are useful in reducing the availability and mobility of contaminants. Many organic wastes also improve fertility and water-holding capacity.
It is vital to identify and characterise waste materials for use in urban greenspace – both materials that are suitable for use as soil-forming materials, and those on site that are not, and therefore are a potential hazard. On-site wastes should be identified by a site survey, and sufficient samples taken to establish basic chemical and physical characteristics through laboratory analysis. Wastes considered worth importing on site to support artificial soil formation must be characterised in the same way. Suppliers of some organic wastes will be able to supply general analytical data, but if possible it is advisable to seek supplementary information from samples representative of the material to be imported.
Importation of designated wastes will be subject to control under the Waste Management Licensing Regulations 1994. Only specified wastes are exempt from full licensing if used during land restoration. The amounts allowed are specified in the Regulations and subsequent amendments. It is advised to consult with Waste Regulation Authorities if waste importation is being considered.
Creating an artificial soil from more than one source material will require appropriate mixing and blending of materials. It is also important to consider the depth of incorporation of organic-rich wastes.
On-site waste surveying should establish the gross amounts of suitable waste materials for soil creation. Types of waste may be visually distinguishable and the history of the site well known; or waste may be stratified if the site has a complex history, for example after industrial contamination (see Doick and Hutchings, 2007).
On-site wastes may be considered as suitable for particular vegetation establishment on the basis of their chemical and physical properties, or suitable after amendment with imported organic wastes in situ. Alternatively, certain wastes may be considered for placement elsewhere on site to meet particular design objectives.
It is important to remember that an adequate thickness of waste material should be provided to supply the water requirements of the mature vegetation type. If addition of organic wastes as amendments is warranted, it will require calculation of the appropriate addition rate, taking into account the possible risk of nitrogen and phosphorus pollution if too much is added. Guidance on this aspect of artificial soil formation using wastes is contained in the roots™ software. It is vital that secondary pollution caused by importing inappropriate or excessive amounts of wastes is avoided.
Forest Research offers professional help in identifying and characterising wastes potentially suitable in greenspace projects through on-site surveying and laboratory analysis, and in tailoring the use of wastes to form soil materials for particular vegetation types. It is well placed to undertake research to test particular waste products for their suitability for vegetation establishment, for example through nursery- or field-scale experimentation.
Forest Research Best Practice Guidance
Foot, K. and Sinnett, D. (2006). Imported Soil or Soil-Forming Materials Placement (PDF-191K). Best Practice Guidance for Land Regeneration, BPG Note 5. Forest Research, Farnham.
van Herwijnen, R. and Hutchings. A. (2006). Laboratory Analysis of Soils and Spoils (PDF-294K). Best Practice Guidance for Land Regeneration, BPG Note 2. Forest Research, Farnham.
Kilbride, C. (2006). Application of Sewage Sludges and Composts (PDF-317K). Best Practice Guidance for Land Regeneration, BPG Note 6. Forest Research, Farnham.
DETR (1999). Soil-forming Materials: Their Use in Land Reclamation. London: Department for the Environment, Transport and the Regions/Stationery Office.
Doick, K. and Hutchings, T. (2007). Greenspace Establishment on Brownfield Land: The Site Selection and Investigation Process (PDF-1060K). Information Note 91. Forestry Commission, Scotland.
Muddy Boots et al. (2005). roots: The Definitive Software Tool for Land Reclamation. Muddy Boots Software Ltd/Progressive Restoration, Ross-on-Wye.