The Responsible Sourcing Scheme for Growing Media (RSS), working closely with the UK Growing Media Association (GMA), has launched Version 11 of its guidance notes, introducing greenhouse gas emissions as a core assessment criterion alongside changes to pollution risk assessments and ingredient scoring. 

The RSS helps growing media manufacturers assess how responsibly their ingredients are sourced. It looks at the environmental and social impacts of materials such as coir, wood fibre, bark and peat, taking account of where they come from and how they are produced and transported. Manufacturers gather evidence from their supply chains to support ingredient scores, which are checked through independent audits. 

This gives businesses a consistent way to compare sources of materials, identify where improvements are needed and demonstrate their approach to responsible sourcing. For growers and retailers, the scheme provides greater transparency around the responsible sourcing credentials of the growing media they buy and sell. 

The guidance notes set out the assessment methods, scoring requirements and evidence needed. 

Developed by the RSS Technical Committee, Version 11 is the latest update to those requirements. 

The main change in Version 11 is the replacement of the energy use criterion with greenhouse gas emissions. The amount of energy used tells only part of the story: its climate impact also depends on the source of that energy and the emissions associated with it. The revised approach converts fuel, electricity and transport data into carbon dioxide equivalents, providing a common basis for comparing ingredients and supply chains. 

The criterion also considers the emissions from other fossil and near-fossil carbon stores. Therefore, for peat, the assessment goes further, including emissions associated with draining the peatland to enable extraction and the eventual oxidation of the peat following use. This means the assessment considers peat-specific greenhouse gas emissions as well as those associated with energy use and transport. 

Other updates include a wider water pollution risk assessment, revised social compliance scoring and clearer guidance on water use. Changes to habitat and biodiversity assessments also refine how individual materials, including coir, wood and loam, are scored. 

Steve Harper, RSS Chair, said: “Every growing media ingredient has an environmental impact, but those impacts are different and need to be understood properly. Moving from a measure of energy use to greenhouse gas emissions gives us a much more meaningful picture of the climate impact associated with different materials and supply chains. 

The Technical Committee has put a great deal of work into this update. Their job is to keep questioning how we assess materials and where the guidance can be improved. That work will continue, alongside helping members put the changes into practice.” 

To help members apply Version 11, the RSS has released an updated calculator and supporting tools, alongside revised worked examples and a documentary evidence checklist. These resources will help members work through the calculations and prepare the information required for their audits. 

Members will also have the opportunity to attend a workshop in November 2026, covering the guidance notes and updated calculator in more detail. The session will provide an opportunity to ask questions and discuss how the changes apply to their materials and supply chains. Further details will be shared with members nearer the time. 

Version 11 takes effect immediately and should be used by members starting the audit process. 

Those already part-way through an audit may continue using Version 10 until 31 December 2026. From 1 January 2027, Version 11 will be the sole version in use. 

The guidance notes, calculator and supporting documents are available on https://responsiblesourcing.org.uk/resources.

Businesses interested in joining the scheme are encouraged to contact the RSS to discuss membership and the audit process.