Is it waste? – Understanding your digestate or digestate-derived material

The regulation of digestates in the UK can appear confusing, with different environmental regulators taking slightly different approaches to different types of digestate. Ultimately, these approaches are driven by the underlying regulations – and particularly the Waste Framework Directive (Directive 2008/98/EC). This defines wastes (Article 3), end-of-waste (Article 6), and by-products (Article 5). The Animal By-Products Regulation (Regulation (EC) 1069/2009) is also important where manures, slurries, food waste and other animal by-products are processed via AD.

Whether the input(s) to an Anaerobic Digestion process are classified as wastes (or not) informs the regulatory approaches to both the processing of those inputs and the resulting digestates. Guidance on deciding whether a material is waste or not is available for England, Wales and Northern Ireland, with separate guidance for Scotland. Bear in mind that mixing a waste with a non-waste will render the mixture a waste. The classification outlined in Table 1 is generally applied to common AD feedstocks.

Table 1: Regulatory approach to AD of different feedstocks

Feedstock

Waste?

Comments

Purpose-grown / energy crops No These are grown for the specific purpose of generating biogas in an AD plant.
Crop residues Yes and No In England, the Environment Agency consider some crop residues to be by-products.

In Scotland, Wales and Northern Ireland, crop residues are likely to be considered wastes.

Livestock manures and slurries Yes Manures and slurries are Animal By-Products, and as such fall into the scope of the Waste Framework Directive and are considered wastes when used as feedstocks for AD.
Source-segregated biodegradable wastes Yes
Mechanically recovered organic fraction of mixed waste Yes
Sewage sludge Yes

 

Table 2: Regulatory approach to the use of various digestates

Feedstock

Are waste regulatory controls applied to the resulting digestate?

Digestate uses allowed

Purpose-grown / energy crops No This digestate is a product and no market restrictions are imposed.
Crop residues Not in England, provided EA guidance is followed

Not in Scotland, provided SEPA guidance is followed

England: this digestate is considered a product and no market restrictions are imposed.

Scotland: digestate used as fertiliser on agricultural land.

Livestock manures and slurries Not in England, provided EA guidance is followed[1]

Not in Wales, provided (draft) NRW guidance is followed

Not in Scotland, provided SEPA guidance is followed

Not in Northern Ireland, provided NIEA guidance is followed

As a fertiliser on agricultural land in the same way as un-processed manures and slurries.

Note that ABP restrictions may still apply.[2]

Source-segregated biodegradable wastes Not in England, Wales or Northern Ireland – providing that the requirements of the AD Quality Protocol are followed

Not in Scotland – provided that the SEPA requirements are followed

Note that the requirements for the UK as a whole are covered by the Biofertiliser Certification Scheme, which incorporates the separate requirements of the ADQP and SEPA position statement

England, Wales and Northern Ireland: Whole, Separated Liquid and Separated Fibre digestates can be used in Agriculture, Field Horticulture and Forestry; Separated Fibre digestates can be used in land restoration.

Scotland: Digestates can be applied ‘to land’.

Note that ABP restrictions may still apply.[2]

Mechanically recovered organic fraction of mixed waste Yes These digestates may be used on non-agricultural land under waste regulatory controls only.
Sewage sludge Not when applied to agricultural land under the requirements of the Sludge (Use in Agriculture) Regulations.

Note that – in addition to the regulatory requirements – there are several important good practices associated with the use of this material. These are covered by the Biosolids Assurance Scheme.

At the time of writing, the regulatory approach to the use of sewage sludges is under review.

UK: agriculture.

These digestates may be used on non-agricultural land under.

Important points to bear in mind

1. The various digestate uses outlined in Table 2 are the prescribed market end points for those digestates. This means that (for example), while source segregated fibre digestate can be considered a product when produced and used on agricultural land in the ways prescribed – it cannot be considered a product for other markets such as biomass combustion or as a growing media ingredient;

2. The waste status of digestate-derived materials (such as ammonium sulphate stripped f rom digestate) must be determined by producers, using the guidance highlighted above for England, Wales and Northern Ireland, and Scotland. There are no standard end-of-waste positions or guidance for these derivatives, where they are classified as wastes. For example:

a. Ammonium sulphate recovered from a crop-only (non-waste) AD system could be classified as a by-product and supplied to the market without waste regulatory control;

b. Ammonium sulphate recovered from a manure / slurry or other waste AD system could be classified as waste and therefore subject to waste regulatory control;

3. It is hoped that additional clarity and/or markets for digestate-derived materials will result from the up-coming review of the AD Quality Protocol, and the development of new UK fertiliser regulations that may mirror some of the requirements of the new EU Fertilising Product Regulations.

Footnotes

[1] This guidance is no longer available online.

[2] These include restrictions on grazing and harvesting fodder crops from land treated with ABP materials , as well as associated record-keeping requirements. At the time of writing there is no authoritative document that clearly outlines these requirements.

By David Tompkins (3 July 2020)

Send this to a friend