kSIST FprEN 16087-1:2026

• Abstract:

  This document describes a method to determine the stability of materials (e.g. compost, digestate) used as components (ingredients) in growing media, soil improvers and organic fertilizers by measuring the oxygen uptake rate (OUR). It can also be used for growing media and soil improvers. The oxygen uptake rate is a direct parameter for the degradation rate of biodegradable organic matter that is being broken down within a specified time period. The method is not suitable for materials with a content of particle sizes > 20 mm exceeding 20 % by volume.; NOTE 1 The relation between the degradation rate and the oxygen uptake rate under the same conditions is depending on the type of material, for example by the C/N ratio. So it is important for the interpretation and limit values to be set based on the type of material.; NOTE 2 This method has been validated in an interlaboratory study with specific products that were present on the market during the study (as included in Annex C, being biowaste compost, green compost, solid digestate and liquid digestate).

• Status: Not Published
• Public Enquiry End Date: 19-Dec-2025
• ICS: 65.080 - Fertilizers
• Technical Committee: KAT - Soil quality
• Current Stage: 5020 - Formal vote (FV) (Adopted Project)
• Start Date: 13-Oct-2026
• Due Date: 01-Dec-2026
• Directive: 2019/1009 - Regulation (EU) 2019/1009 of the European Parliament and of the Council of 5 June 2019 laying down rules on the making available on the market of EU fertilising products and amending Regulations (EC) No 1069/2009 and (EC) No 1107/2009 and repealing Regulation (EC) No 2003/2003 (Text with EEA relevance)
• Mandate: M/564 - Fertilising products in support of Regulation (EU) 2019/1009
• Mandate: M/564 AMD 1 - amending Implementing Decision C(2020) 612 as regards certain harmonised standards and standardisation deliverables, deadlines for their adoption and the duration of the validity of the standardisation request
• Mandate: M/564 AMD 2 - Commission Implementing decision amending Implementing Decision C(2020)612 as regards harmonised standards, the deadlines for the adoption of those standards and the duration of the validity of the standardisation request to the European Committee for Standardisation as regards the EU fertilising products in support of Regulation (EU) 2019/1009 of the European Parliament and of the Council
• Mandate: M/XXX - M/XXX
• Ref Project: FprEN 16087-1 - Soil improvers and growing media - Determination of the aerobic biological degradation rate of organic matter - Part 1: Oxygen uptake rate (OUR)

• Revises: SIST EN 16087-1:2020 - Soil improvers and growing media - Determination of the aerobic biological activity - Part 1: Oxygen uptake rate (OUR)
• Effective Date: 01-Dec-2025

kSIST FprEN 16087-1:2026 is a draft European standard for measuring the aerobic biological degradation rate of organic matter in soil improvers and growing media by the oxygen uptake rate (OUR) method. It is aimed at materials such as compost and digestate, and it is used to judge how stable a material is under defined laboratory conditions.

What does kSIST FprEN 16087-1:2026 specify?

kSIST FprEN 16087-1:2026 specifies a laboratory method for determining the stability of materials used as ingredients in growing media, soil improvers and organic fertilizers by measuring OUR. The method is not suitable for materials with more than 20 % by volume of particles larger than 20 mm.

The document is organized into clauses on scope, references, terms, principle, apparatus, reagents, sampling, procedure, calculations, test report and validation, followed by three informative annexes.

Annex	What it covers
Annex A	Specific information on the OUR test, including the reaction vessel and typical pressure curve
Annex B	Incubation temperature and why 20 °C and 30 °C give different results
Annex C	Performance characteristics from the interlaboratory study

What are the key requirements of kSIST FprEN 16087-1:2026?

The core requirement in Clause 4 is to suspend the material in water, measure pressure drop in the headspace of a closed vessel, and use a CO2 absorbent so that the pressure change reflects oxygen use. In practice, the result is a respiration-based stability value, so the setup must stay gas-tight and the absorbent must work properly.

Clause 5 sets out the equipment needed for a controlled test, including a temperature-controlled room or bath, pressure transducer, reaction vessel, mixing device, balance, pH meter, sieves and glassware. This matters because the method depends on stable temperature, accurate weighing and consistent mixing.

Clause 6 specifies the reagents and solutions: water, pH buffer, macronutrient and micronutrient solutions, complete nutrient solution, nitrification inhibitor (ATU), CO2 absorbent, acid and alkali, and an inoculum for materials with little microbial activity. The practical point is that the test is not just a respiration measurement - it also controls nutrients, pH and unwanted oxygen use by nitrification.

Clause 7 says sampling follows EN 12579. The laboratory therefore needs a representative sample that has not been altered during transport or storage.

Clause 8 gives separate preparation paths for solid materials < 10 mm, solid materials < 20 mm and liquid materials. Samples are sieved, oversized particles are removed, storage is limited to refrigerated conditions, and moisture content and organic matter content are measured before the test.

Clause 8 also fixes the starting conditions for the vessel: calculate the sample amount from organic matter content, add water, nutrient solution, pH buffer and ATU, check that pH is between 6,5 and 7,5, then mix and run the test, normally in duplicate. If early pressure drop is too small or too large, the sample mass is adjusted; this keeps the measurement in a usable range.

Clause 8.7 and Clause 9 define the respiration measurement and the calculation path. Pressure is recorded over seven days, oxygen consumption is calculated from pressure drop and gas volume, and OUR is obtained from oxygen consumption over time. This is the step that turns raw pressure data into a comparable stability result.

Clause 10 requires the test report to identify the sample, state the mean OUR and testing temperature, and record any optional work cycles or influences on the result.

What terms does kSIST FprEN 16087-1:2026 define?

• Oxygen uptake rate (OUR) - the rate at which the sample consumes oxygen, expressed per mass of organic matter and time.
• Organic matter (OM) - the organic fraction used to normalize the result after measuring content on the dried sample.
• Dry matter (DM) - the solid fraction of the fresh sample used in the calculation of sample mass.
• Headspace - the gas phase above the liquid suspension in the closed reaction vessel where the pressure change is measured.
• Nitrification inhibitor - ATU added so oxygen use by nitrification does not distort the respiration result.
• Inoculum - an extract from active compost used when the sample has very low microbial activity.

Who uses kSIST FprEN 16087-1:2026?

kSIST FprEN 16087-1:2026 is used by laboratories, compost and digestate producers, manufacturers of growing media and soil improvers, and organizations checking material quality or product performance. It is also relevant for technical staff who compare materials, document stability, or support conformity assessment for fertiliser-related products.

What changed in kSIST FprEN 16087-1:2026 from the previous edition?

The foreword states that this draft will supersede EN 16087-1 and lists these changes compared with EN 16087-1:2011: balance requirements were added, sample preparation was clarified, formulas were corrected, the figures in Annex A were updated, the bibliography was corrected, and the test temperature was revised so products may be tested at 20 °C or 30 °C. Annex B explains why temperature choice matters.

Which standards are used with kSIST FprEN 16087-1:2026?

• CEN/TS 17732:2022 - provides the terminology used in Clause 3.
• EN 12579:2024 - gives the sampling approach to obtain a representative sample.
• prEN 13040-1:2025 - covers sample preparation and determination of dry matter content and moisture content.
• prEN 13039:2025 - covers determination of organic matter content and ash.
• EN 45501 - supports the weighing requirements for the balance.
• ISO 5725-2 - provides the basis for the validation, repeatability and reproducibility assessment.

What does the kSIST FprEN 16087-1:2026 document contain?

The document contains the test principle, apparatus list, reagent recipes, sampling note, detailed preparation steps for solids and liquids, calculation formulas, and the reporting requirements. It also includes a seven-day respiration measurement procedure and guidance on oxygen depletion and nitrification effects.

Annex A adds figures for the reaction vessel, stirrer and typical pressure-time curve. Annex B discusses how incubation at 20 °C or 30 °C changes results for different matrices. Annex C gives interlaboratory performance data for biowaste compost, green compost, solid digestate and liquid digestate, which helps laboratories understand the method’s repeatability and reproducibility.

SLOVENSKI STANDARD
oSIST prEN 16087-1:2025
01-december-2025
Izboljševalci tal in rastni substrati - Določanje aerobne biološke razgradljivosti
organskih snovi - 1. del: Stopnja porabe kisika (OUR)
Soil improvers and growing media - Determination of the aerobic biological degradation
rate of organic matter - Part 1: Oxygen uptake rate (OUR)
Bodenverbesserungsmittel und Kultursubstrate - Bestimmung der aeroben biologischen
Abbaurate organischer Substanz - Teil 1: Sauerstoffaufnahme (OUR)
Amendements du sol et supports de culture - Détermination de la cinétique de
dégradation biologique aérobie de la matière organique - Partie 1 : Cinétique
d’absorption de l’oxygène (OUR)
Ta slovenski standard je istoveten z: prEN 16087-1
ICS:
65.080 Gnojila Fertilizers
oSIST prEN 16087-1:2025 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN 16087-1:2025
oSIST prEN 16087-1:2025
DRAFT
EUROPEAN STANDARD
prEN 16087-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2025
ICS 65.080 Will supersede EN 16087-1:2020
English Version
Soil improvers and growing media - Determination of the
aerobic biological degradation rate of organic matter - Part
1: Oxygen uptake rate (OUR)
Amendements du sol et supports de culture - Bodenverbesserungsmittel und Kultursubstrate -
Détermination de la cinétique de dégradation Bestimmung der aeroben biologischen Abbaurate
biologique aérobie de la matière organique - Partie 1 : organischer Substanz - Teil 1: Sauerstoffaufnahme
Cinétique d'absorption de l'oxygène (OUR) (OUR)
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 223.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 16087-1:2025 E
worldwide for CEN national Members.

oSIST prEN 16087-1:2025
prEN 16087-1:2025 (E)
Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Principle . 4
5 Apparatus . 4
6 Reagents . 5
7 Sampling . 6
8 Procedure . 6
8.1 Safety . 6
8.2 Sample preparation for solid materials < 10 mm . 6
8.3 Sample preparation for solid materials < 20 mm . 7
8.4 Sample preparation for liquid materials . 7
8.5 Determination of moisture content and organic matter content . 7
8.6 Starting the procedure . 7
8.7 Respiration measurement . 8
9 Calculations . 9
9.1 Theoretical background . 9
9.2 Calculations . 9
10 Test report . 10
11 Validation of the method . 10
11.1 Validation in accordance with ISO 5725-2. 10
11.2 Performance characteristics. 10
Annex A (informative) Specific information on the OUR-test . 11
Annex B (informative) Incubation temperature. 13
Annex C (informative) Performance characteristics of the method . 14
Bibliography . 18

oSIST prEN 16087-1:2025
prEN 16087-1:2025 (E)
European foreword
This document (prEN 16087-1:2025) has been prepared by Technical Committee CEN/TC 223 “Soil
improvers and growing media”, the secretariat of which is held by NEN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 16087-1:2011.
prEN 16087-1:2025 includes the following significant technical changes with respect to
EN 16087-1:2011:
— For the balance (5.6) requirements have been added;
— Clarification of sample preparation (8.2) has been added;
— Formula (3) and 5 have been corrected;
— The figures in Annex A have been updated;
— The Bibliography has been corrected;
— The temperature of testing was for all products 30 °C but it has been changed. Products may be tested
at 20 or 30 °C. Background about the differences between the testing temperatures and the to choose
temperature can be found in Annex B.
This document has been prepared under a standardization request addressed to CEN by the European
Commission. The Standing Committee of the EFTA States subsequently approves these requests for its
Member States.
oSIST prEN 16087-1:2025
prEN 16087-1:2025 (E)
1 Scope
This document describes a method to determine the stability of materials (e.g. compost, digestate) used
as components (ingredients) in growing media, soil improvers and organic fertilisers by measuring the
oxygen uptake rate (OUR). The oxygen uptake rate is a direct parameter for the degradation rate of
biodegradable organic matter that is being broken down within a specified time period. The method is
not suitable for material with a content of particle sizes > 20 mm exceeding 20 % by volume.
NOTE The relation between the degradation rate and the oxygen uptake rate under the same conditions is
depending on the type of material, for example by the C/N ratio. So it is important for the interpretation and limit
values to be set based on the type of material.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
CEN/TS 17732:2022, Soil improvers and growing media — Terminology
EN 12579:2024, Soil improvers and growing media — Sampling
prEN 13039:2025, Soil improvers and growing media — Determination of organic matter content and ash
prEN 13040-1:2025, Soil improvers and growing media — Sample preparation — Part 1: Sample
preparation for chemical and physical tests, determination of dry matter content, moisture content and
laboratory bulk density
EN 45501, Metrological aspects of non-automatic weighing instruments
3 Terms and definitions
For the purposes of this document, the terms and definitions given in CEN/TS 17732:2022 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp/
— IEC Electropedia: available at https://www.electropedia.org/
4 Principle
The material is suspended in water. The respiration rate (i.e. oxygen uptake rate) is indirectly determined
by measuring the pressure drop in the headspace (i.e. gas phase in the closed space above the water
phase). The produced CO (carbon dioxide) is removed by a suitable alkaline absorbent. The
measurements are performed under defined conditions.
5 Apparatus
5.1 Testing facility
Temperature controlled room, climate cabinet or water bath, temperature adjustable to 20 °C ± 2 °C or
30 °C ± 2 °C.
5.2 Pressure transducer
oSIST prEN 16087-1:2025
prEN 16087-1:2025 (E)
Operating range 0 kPa to 20 kPa (accuracy ± 0,1 kPa) and record for measuring 2 to 4 times per hour for
seven days.
5.3 CO -absorbent containing unit
5.4 Reaction vessel
1 000 ml to 2 500 ml with a CO -absorbent containing unit (5.3) and the pressure transducer (5.2)
gastight connected (see Figure A.1).
5.5 Mixing device
Shaking Table 120 rpm ± 20 rpm or magnetic stirring unit and banded magnetic stirrer (see Figure A.2).
5.6 Balance
Meeting EN 45501 class II tolerances with a verification scale interval of 0,01 g.
5.7 pH meter
With slope adjustment and temperature control.
5.8 Dispenser
Dispensers or pipettes, adjustable units of 0,5 ml.
5.9 Glassware
Beakers and measuring cylinder.
5.10 Sieves
10 mm and 20 mm square aperture size.
5.11 Filter paper
Filter paper, with low ash content and high retentive properties.
6 Reagents
6.1 Water with a specific conductivity not higher than 0,2 mS/m at 25 °C
6.2 pH buffer
86 g/l KH PO , 89 g/l Na HPO ⋅ 2H O, mix ratio of 1:4 for pH 7; the solution is stable for 2 months if
2 4 2 4 2
stored at 1 °C to 5 °C. When a particulate precipitation is found a fresh solution is to be made.
Commercially available buffers may be used as well.
6.3 Macronutrient solution
Dissolve the following masses of chemical compounds in 1 000 ml water (6.1): 4,3 g NH Cl,
5,4 g CaCl ⋅ 2H O, 4,3 g MgSO ⋅ 7H O
2 2 4 2
The solution is stable for 2 months if stored at 3 °C ± 2°C. When a particulate precipitation is found a fresh
solution is to be made.
6.4 Micronutrient solution
oSIST prEN 16087-1:2025
prEN 16087-1:2025 (E)
Dissolve the following masses or volumes of chemical compounds in 1 000 ml water (6.1): 5,0 g EDDHA
iron chelate (60 g Fe/kg), 1,4 g MnSO , 1,1 g ZnSO , 4,2 g Na B O , 0,2 g CuSO , 0,13 g Na MoO ,
4 4 2 4 7 4 2 4
1 ml/l HCl (360 g/kg).
The solution is stable for 2 months if stored at 3 °C ± 2°C. When a particulate precipitation is found a fresh
solution is to be made.
6.5 Complete nutrient solution
Add 1 ml of micronutrient solution (6.4) to 1 000 ml of macronutrient solution (6.3). The solution is
stable for 2 months if stored at 3 °C ± 2°C. When a particulate precipitation is found a fresh solution is to
be made.
6.6 Nitrification inhibitor
4 g/l N-Allylthiourea, C H N S (ATU).
4 8 2
Store the solution in a closed container at 1 °C to 5 °C. The solution is stable for not more than 2 weeks.
6.7 CO -absorbent
Such as NaOH-pellets, KOH-pellets or soda lime (mixture of Ca(OH) , NaOH, KOH and water), preferably
with colour indicator.
NOTE Based on experience, 4,0 g of pellets (carbon dioxide absorption capacity > 200 g/kg) per container is
sufficient.
6.8 NaOH (0,5 mol/l)
6.9 HCI (0,5 mol/l)
6.10 Inoculum (to be added for materials without or low microbial activity)
–1 −1
Prepare an extract by shaking an active compost (OUR level 25 to 30 mmol O · kg · OM · hour ) with
water at mass:volume, 1:10 and filter it over a filter paper (5.11).
7 Sampling
Sampling is not part of the method specified in this document. Follow EN 12579:2024 dealing with soil
improvers and growing media. It is important that the laboratory receives a sample that is representative
of the product under consideration. The sample should not have been damaged or changed during
transport or storage.
8 Procedure
8.1 Safety
SAFETY PRECAUTIONS — Care should be taken when handling substances of caustic nature or samples
that may contain sharps or is of a dusty nature.
8.2 Sample preparation for solid materials < 10 mm
Take minimally 1 l of material. Manually, but carefully, break up lumps and agglomerates only that have
been caused by, for example, compress ion during transport. Break up lumps and agglomerates only and
pass the sample through a 10 mm sieve (5.10), gently agitating the material if required. Particles > 10 mm
shall not be broken up and shall be removed. Record the % mass of particles > 10 mm. If this amount
oSIST prEN 16087-1:2025
prEN 16087-1:2025 (E)
is > 20 % of the total fresh mass the procedure for materials < 20 mm (8.3) is to be followed. The moist
sample shall be stored at 3 °C ± 2 °C (total storage time max. 2 weeks).
8.3 Sample preparation for solid materials < 20 mm
Take minimally 1 l of material. Manually, but carefully, break up lumps and agglomerates only that have
been caused by, for example, compression during transport. Break up lumps and agglomerates only and
pass the sample through a 20 mm sieve (5.10), gently agitating the material if required. Particles > 20 mm
shall not be broken up and shall be removed. Record the % mass of particles > 20 mm. If this amount
is > 20 % of the total fresh mass, the test is not applicable. The moist sample shall be stored at 3 °C ± 2°C
(total storage time max. 2 weeks).
8.4 Sample preparation for liquid materials
Take minimally 1 l of material. Homogenize the sample by stirring. Break up lumps and agglomerates
only and pass the sample through a 10 mm sieve (5.10), gently agitating the material if required.
Particles > 10 mm shall not be broken up and shall be removed. Record the % mass of particles > 10 mm.
If this amount is > 20 % of the total fresh mass, the test is not applicable. The sample shall be stored at
3 °C ± 2 °C (total storage time max. 2 weeks). Stir the sample just before using it again.
8.5 Determination of moisture content and organic matter content
The moisture content shall be determined according to prEN 13040-1:2025 and the organic matter
content according to prEN 13039:2025, both determinations should take place after the sample
preparation.
8.6 Starting the procedure
For solid materials < 10 mm and liquid materials (8.2 and 8.4), calculate the mass of fresh material (EOM)
to be added to the reaction vessel based on 2 g of organic matter per litre according to Formula (1).
EOM g = (1)
( )
WW×
om d
where
W is the organic matter content, in % mass of the dried sample according to prEN 13039:2025;
om
W is the dry matter content, in % mass of the fresh sample according to prEN 13040-1:2025.
d
Calculate the required mass of sample (W ) to perform the test according to Formula (2).
S
W g EOM× C (2)
( )
S V
where
C is the capacity of the vessel in litres.
V
Place the calculated quantity of the sample in the clean reaction vessel (5.4). Add 180 ml water (6.1) and
10 ml complete nutrient solution (6.5) using a dispenser (5.8). Add 10 ml pH buffer (6.2) using a
dispenser (5.8). Add 2,5 ml nitrification inhibitor (6.6) using a dispenser (5.8). For materials without or
low microbial activity (e.g. wood fibre directly after production), 5 ml inoculum (6.10) can be added.
Then, measure the pH of the suspension. The value should be between 6,5 and 7,5. If this is not the case,
base or acid should be added (see 6.8 and 6.9). Place the sample on the mixing device (5.5) and start the
mixing for 4 h to 8 h in the conditioned room (5.1).
The analyses shall be performed at least
...