BMP testingFruit, vegetables and their residues

Head cabbage — BMP: 4 studies, weighted mean 260 m³ CH₄/t VS

Head cabbage (white and red) is a watery brassica vegetable, readily fermentable; it requires size reduction and control of the H₂S concentration in the biogas.

CH₄ ≈ 56 % (estimate)

Published 8 September 2022Updated 29 October 20263 min readFeedstockData Editorial Team

Photo Elrond / Wikimedia Commons, licence CC BY-SA 4.0, source file; changes: cropping

Weighted mean: 260m³ CH₄/t VS
Range: 204–305m³ CH₄/t VS
Records: 4studies
Publications: 3sources
Temperatures: 35 °Cof the test

Methane in biogas

≈54–58% CH₄

Medium methane content · ≈ 5.6 kWh/m³ of biogas

estimate from the substrate type The collected studies contain no measurement. The interval follows from the approximate composition (protein from total nitrogen (N 4 % DM × 6.25)) 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 4 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 (260); 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

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Source	BMP m³ CH₄/t VS	Temperature	Sample	Curve
Yan et al. (2017) · 1 DOI	204	—	Cabbage (Brassica oleracea var. Capitata)	end point (model curve)
Yan et al. (2017) · 2 DOI	233	—	Purple cabbage (Brassica campestris var. Purpuraria)	end point (model curve)
Kouas et al. (2017) DOI	305	35 °C · mesophilic	green cabbage	end point (model curve)
Labatut et al. (2011) DOI	256	35 °C · mesophilic	Cabbage	end point (model curve)
Weighted mean	260	arithmetic mean 250, SD 43

Typical composition

Volatile solids (VS): 91.3 % DM (range 90.2–92)
Nitrogen: 4 % DM
C/N ratio: 10.2

Median and range of the determinations reported in the publications behind this substrate's BMP records (read from: BCBPD, MY-D); dry matter: 0 determinations, volatile solids: 3 determinations. C/N was calculated as the ratio of C and N content (% DM) from the same source. No DM in the sources – the calculator has to ask for a value.

Sources: Yan et al. (2017); Labatut et al. (2011).

The composition of the raw material varies between batches — for plant calculations use an analysis of your own sample. The calculator inserts typical values automatically.

Process properties

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.

No published process studies

The literature we use does not describe the advantages or drawbacks of digesting this substrate beyond the BMP test results. Below are process characteristics assigned on the basis of the type of material — an editorial classification, not a study result.

easily degradable: sugars, starch, glycerol → fast hydrolysis and acidification (VFA), needs buffering
acidic: low pH of the substrate (silages, stillage, whey, fruit)
dilutes the feed (low DM): low dry matter, dilutes the feed
seasonal: seasonal availability — requires storage
variable composition: high variability of composition between batches

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

combines well
substrates: nitrogen-rich — e.g. Pig slurry, Poultry manure, Waste activated sludge (secondary sludge), Chlorella vulgaris, Nannochloropsis salina
A nitrogen-rich co-substrate balances the low C/N of fruit and vegetable waste (Bouallagui et al. 2009).^[1]

Dosing

No source limits on the dose for this substrate.

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

Head cabbage (Brassica oleracea var. capitata) is one of the basic vegetables grown in Poland, and its waste arises in processing plants (sauerkraut, freezing, salads), on markets and with surplus production. This description concerns heads, white and red. Outer leaves and cores are described separately as waste from cleaning the heads.

Properties relevant to digestion

Cabbage contains a lot of water, and the dry matter is rich in soluble sugars, pectins, hemicellulose and protein, with a low lignin content. As a result the material hydrolyses quickly, which at high dosing can lead to temporary acidification. A phenomenon typical of brassicas is the presence of glucosinolates and sulphur compounds, from which hydrogen sulphide arises. Sauerkraut additionally contains lactic acid and salt, which should be taken into account if the waste comes from fermented products. Otherwise the material does not create major mechanical problems after size reduction.

How to read the spread of results

The dataset contains several records from several sources, covering white cabbage, red cabbage and green cabbage. The varieties differ in dry matter and sugar content, and in addition the result depends on the stage of maturity, storage time, size reduction and whether the sample was fresh or frozen. Some studies do not state the test temperature, the others indicate mesophilic conditions. The inoculum and the substrate-to-inoculum ratio also affect the result, particularly for material of rapid hydrolysis.

In biogas plant practice

Cabbage works as a seasonal supplement to the feed together with slurry and silage. The heads must be size-reduced, and the dose set carefully because of volatile acids and hydrogen sulphide. The installation should have effective desulphurisation. Storage in warm conditions is not advisable, because the material quickly spoils and gives off odours; in the case of surpluses, ensiling is considered. Waste from vegetable processing and trade is waste and requires the appropriate legal status of the installation.

When planning deliveries, it is worth taking into account that cabbage from storage, previously chilled or partly spoiled, has a different content of sugars and acids from fresh cabbage, and its waste is often strongly contaminated with juices, which further accelerates acidification of the feed.

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 = 0.245 d⁻¹ was assumed (median of rate constants k reported in the sources and/or fitted to the mean measured curves).

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.