BMP testingFruit, vegetables and their residues
Chinese cabbage — BMP: 2 studies, weighted mean 148 m³ CH₄/t VS
Chinese cabbage is a delicate leafy vegetable of very high moisture content, readily hydrolysed, with the H₂S risk typical of brassicas.
Photo Krzysztof Ziarnek, Kenraiz / Wikimedia Commons, licence CC BY-SA 4.0, source file; changes: cropping
- Weighted mean
- 148m³ CH₄/t VS
- Range
- 129–167m³ CH₄/t VS
- Records
- 2studies
- Publications
- 2sources
- Temperatures
- —of the test
Methane in biogas
Medium methane content · ≈ 5.9 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 5.5 % DM × 6.25)) and the yields of compound groups according to FNR.
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.
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 (148); 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 |
|---|---|---|---|---|
| Yan et al. (2017) DOI | 129 | — | Chinese cabbage (Brassica pekinensis) | end point (model curve) |
| Cai et al. (2019) DOI | 167 | — | Chinese cabbage (Brassica chinensis) | end point (model curve) |
| Weighted mean | 148 | arithmetic mean 148, SD 27 | ||
Typical composition
- Volatile solids (VS)
- 76 % DM (range 69.6–82.4)
- Nitrogen
- 5.5 % DM
- C/N ratio
- 6.2
Median and range of the determinations reported in the publications behind this substrate's BMP records (read from: BCBPD); dry matter: 0 determinations, volatile solids: 2 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); Cai et al. (2019).
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
- Improvement of fruit and vegetable waste anaerobic digestion performance and stability with co-substrates addition
- Study on biomethane production and biodegradability of different leafy vegetables in anaerobic digestion
- Prediction of methane production performances based on determination of organic components for different vegetable wastes
- Effects of size and thermophilic pre-hydrolysis of banana peel during anaerobic digestion, and biomethanation potential of key tropical fruit wastes
- Effect of particle size on biogas generation from biomass residues
The co-digestion calculator will assess a specific mixture containing this substrate.
What it is and where it comes from
Chinese cabbage (Brassica rapa subsp. pekinensis) is a leafy vegetable with elongated heads, grown in Poland on a smaller scale than head cabbage, but popular in catering. Waste arises in the processing of salads and vegetable semi-finished products, in trade and on farms. In the literature, results of studies on "Chinese cabbage" are sometimes described for different subspecies, which affects how they should be interpreted.
Properties relevant to digestion
The plant has a very high water content and a low dry matter content, in which soluble sugars, pectins, hemicellulose and protein predominate. Lignin is present only in traces. Easy hydrolysis means rapid formation of acids, so introducing large portions at once threatens acidification. Sulphur compounds from the brassica family promote the formation of hydrogen sulphide, and protein may add ammonium nitrogen. The absence of woody fibre means that the material does not form scum, but it spoils quickly.
How to read the spread of results
The dataset contains several records from several sources, and it is not known at what temperature these tests were carried out, because the source does not state it. The descriptions indicate that they concern different species or subspecies of Chinese cabbage, which is enough to explain part of the differences. In addition, the stage of maturity, the share of outer leaves, size reduction, moisture content and the inoculum have an effect. With so little data, conclusions about the stability of the material should not be drawn.
In biogas plant practice
Chinese cabbage can supplement the feed together with more structural materials: slurry, manure or silage. Slight size reduction is sufficient, but doses should be moderate and spread over time. Storage is not possible for longer than a few days without losses and odours. The installation should monitor the hydrogen sulphide concentration in the biogas. Waste from trade and processing is subject to the waste regulations.
With so little data, it is sensible to treat Chinese cabbage in the same way as other watery brassicas and to draw on experience with head cabbage, while taking into account its greater delicacy and faster spoilage after harvest and sorting.
It is good practice to determine the dry matter and volatile solids of each delivery, because with very watery leafy waste even small differences in moisture translate into large differences in organic load.
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.
Bibliography
- Yan, H.; Zhao, C.; Zhang, J.; Zhang, R.; Xue, C.; Liu, G.; Chen, C. (2017). Study on biomethane production and biodegradability of different leafy vegetables in anaerobic digestion. AMB Express 7(1), 27. DOI: 10.1186/s13568-017-0325-1 DOI
- Cai, F.; 1. Biomass Energy and Environmental Engineering Research Center, College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, China; Yan, H.; Zhang, R.; Liu, G.; Chen, C.; 2. Department of Biological and Agricultural Engineering, University of California, Davis, CA 95616, USA (2019). Prediction of methane production performances based on determination of organic components for different vegetable wastes. International Journal of Agricultural and Biological Engineering 12(3), 154–159. DOI: 10.25165/j.ijabe.20191203.4705 DOI
All sources of the site: bibliography.
Other substrates in the group “Fruit, vegetables and their residues”
Fruit and vegetable waste (mixed) — BMP: 5 studies, weighted mean 305 m³ CH₄/t VS
305 m³ CH₄/t VS weighted mean from 5 studies
neutral — editorial rating for biogas plants≈55 %
Banana peels — BMP: 17 studies, weighted mean 330 m³ CH₄/t VS
330 m³ CH₄/t VS weighted mean from 17 studies
good — editorial rating for biogas plants≈52 %
Mango peels — BMP: 13 studies, weighted mean 448 m³ CH₄/t VS
448 m³ CH₄/t VS weighted mean from 13 studies
≈52 %
Lettuce — BMP: 6 studies, weighted mean 256 m³ CH₄/t VS
256 m³ CH₄/t VS weighted mean from 6 studies
≈57 %