BMP testingBy-products of the agri-food industry

Rapeseed meal and cake — BMP: 2 studies, weighted mean 368 m³ CH₄/t VS

Rapeseed meal and cake is a protein-and-fibre by-product of pressing rapeseed and of biodiesel production; it contains glucosinolates and phytates, and in excess gives ammonia.

CH₄ ≈ 66 % (estimate)

Published 6 November 2025Updated 29 October 20263 min readFeedstockData Editorial Team

Illustration: FeedstockData (AI, Google Gemini)

Weighted mean: 368m³ CH₄/t VS
Range: 239–497m³ CH₄/t VS
Records: 2studies
Publications: 2sources
Temperatures: 35 °C, 38 °Cof the test

Methane in biogas

≈60–69% CH₄

High methane content · ≈ 6.6 kWh/m³ of biogas

estimate from the substrate type The collected studies contain no measurement. The interval follows from the approximate composition (protein-rich (process classification); fat-rich (process classification)) and the yields of compound groups according to FNR.

How we calculate it and what the zones mean

Rating for biogas plants

not rated — editorial rating for biogas plants

Not rated: no dry matter or volatile solids in the data. We calculate the rating when the dry matter and volatile solids of the material are known.

Editorial rating per the methodology

Add to the co-digestion calculator CSV data

BMP curves from 2 studies

Weighted mean Individual records

Dashed lines are a model curve (first-order kinetics, B(t) = B₀·(1 − e^−kt)); the end point comes from the publication. All curves are model curves.

Cumulative methane production over the test [m³ CH₄/t VS]. The thick line is the weighted mean of all records (368); dots mark the end values given in the publications. Point at the chart to read values; click a legend item to hide or show a record.

Records and sources

Download CSV

Source	BMP m³ CH₄/t VS	Temperature	Sample	Curve
Dubrovskis i Plume (2024) DOI	497	38 °C · mesophilic	Rapeseed meal (biodiesel plant)	end point (model curve)
Kouas et al. (2017) DOI	239	35 °C · mesophilic	rape meal	end point (model curve)
Weighted mean	368	arithmetic mean 368, SD 182

Process properties

protein-rich
sulphur-rich
fibrous
fat-rich
editorial classification

Low confidence: the description is based on general characteristics of the substrate group, not on studies of this material. Treat it as a hint to be verified.

Advantages

Methane potential in the Substraty.pl BMP dataset: weighted mean 368.0 m³ CH₄/t VS (SD 182.4; 2 records, 2 sources).
Protein and residual oil; stores well (Hagos et al. 2017).

Drawbacks and risks

Protein raises NH4-N (Rajagopal et al. 2013).
Sulphur compounds from rapeseed raise H2S (Chen et al. 2008).
Digestion of rapeseed press cake produces very high H2S concentrations in the biogas, resulting from the protein and sulphur content (FNR 2010, ch. 4).

Co-digestion — what to combine it with, what to watch out for

combines well
substrates: high alkalinity (buffer) — e.g. Cattle manure, Pig slurry, Cattle slurry, Duck slurry, Rumen and digestive tract content
Slurry supplies N and alkalinity, balancing the high C/N of the material.^[1][2]
caution
substrates: protein-rich — e.g. Food waste, Municipal sewage sludge (mixed), Poultry manure, Organic fraction of municipal solid waste, Grass clippings
Meal + blood/meat: ammonia.^[3]

Dosing

No source-based threshold; monitor NH4-N, H2S.

Introduce gradually, starting with a small dose and monitoring the process (e.g. FOS/TAC, pH, gas composition).

Sources of the process data

The co-digestion calculator will assess a specific mixture containing this substrate.

What it is and where it comes from

Rapeseed is the main oil crop in Poland. After the oil is pressed, cake remains, and after additional solvent extraction, rapeseed meal, used mainly as a protein feed. Large quantities arise in oil mills and biodiesel plants. The dataset describes meal from a biodiesel plant and meal in general terms.

Properties relevant to digestion

The composition depends on the technology: cold-pressed cake contains more residual fat, and the post-extraction meal is defatted. In both cases the material contains a lot of protein, fibre from the seed husk (cellulose, hemicellulose, lignin), and glucosinolates and phytates. The high protein lowers the C/N ratio and at larger shares can raise the ammonia concentration. Sulphur compounds from Brassicaceae favour the formation of hydrogen sulphide. Residual fat raises the energy potential, but increases the risk of LCFA. The material is dry and stores well.

How to read the spread of results

The dataset contains several records from several sources (38 and 35 °C), and their results differ clearly. The causes are the technology of production (pressing, extraction, biodiesel plant), the residual fat content, the share of husks, chopping, the rapeseed variety and the inoculum. The substrate-to-inoculum ratio can also shift the result if the ammonia concentration rises in the test.

In biogas plant practice

Rapeseed meal and cake are easy to store and dose, but require a limited share because of ammonia and hydrogen sulphide. They combine well with carbohydrate material, such as maize silage, and with low-nitrogen slurry. Grinding improves availability. The fodder value of the meal limits the profitability of its use in a biogas plant. As a by-product of the food or fuel industry it is subject to the regulations on by-products or wastes, depending on its status.

In agricultural practice rapeseed meal is often used as a nitrogen supplement in feeds, so at a biogas plant its price and availability depend on the feed market. Dose limits and monitoring of ammonium nitrogen are more important here than the gas yield itself.

When assessing the results it must be remembered that defatted meal and cake with residual fat are materials with different properties, so their mean does not describe either of them exactly.

Methodology in brief

BMP is the amount of methane obtained from volatile solids (VS) in a batch test, given in m³ CH₄ per tonne of VS (numerically the same as NmL CH₄/g VS in the publications) and converted to normal conditions (0 °C, 101.325 kPa). The weighted mean gives each publication a total weight of 1, split equally between its results for the substrate — a paper testing twenty varieties does not outweigh a paper with a single sample. In inter-laboratory programmes the unit is the laboratory (total weight 1), and within it the weight of a test grows with the number of bottles (replicates). Results after pretreatment (e.g. thermal, chemical, enzymatic) are shown separately and are not included in the mean.

Solid lines are curves measured in the tests. Where a publication gives only the final result, we draw a first-order kinetic model, B(t) = B₀·(1 − e^−kt): only the end point comes from the publication, and the shape of the curve serves purely as visualisation — do not read the production on a particular day from it. For this substrate k = 0.091 d⁻¹ was assumed (no kinetic data for the group – the median of all available rate constants k (93 values) was used).

The statistics describe the spread of published results — a descriptive compilation, not a meta-analysis or a guarantee of plant yield.

Full methodology and correction policy

Bibliography

All sources of the site: bibliography.