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BMP testingFruit, vegetables and their residues

Turnip — BMP: 2 studies, weighted mean 304 m³ CH₄/t VS

Turnip (tubers and fodder turnip) is a watery root of the Brassicaceae family, easily fermentable and rich in sugars, with the elevated H₂S risk typical of Brassica.

rating: neutralCH₄ ≈ 53 % (estimate)

Published Updated 3 min readFeedstockData Editorial Team

Photo thebittenword.com / Wikimedia Commons, licence CC BY 2.0, source file; changes: cropping

Weighted mean
304m³ CH₄/t VS
Range
237–372m³ CH₄/t VS
Records
2studies
Publications
2sources
Temperatures
38 °Cof the test

Methane in biogas

Medium methane content · ≈ 5.3 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 2 % 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

neutral — editorial rating for biogas plantsNo clear advantages — worth charging a fee for accepting it

Potential per tonne of fresh matter: moderate (29 m³ CH₄/t); process risk: acidification. Handling costs: fibres, floating layer.

Why? Rating factors

Potential per tonne +1

  • +1potential 29 m³ CH₄/t fresh matter (BMP 304 × DM 10.3 % × VS 92.1 %)

Process stability −0.5

  • −0.5acidification: rapid degradation / acidic pH, risk of VFA accumulation, needs buffering

Handling and costs −0.5

  • −0.5fibres, floating layer — shredding and intensive mixing

Total points: 0 · thresholds: ≥ 2.5 very good, ≥ 1 good, below — neutral; negative with cumulative process risk.

Editorial rating per the methodology · confidence of the rating: low · excluding market prices

Add to the co-digestion calculator CSV data

BMP curves from 2 studies

Weighted mean Individual records

BMP curves: TurnipCumulative methane production over time for 2 records and the weighted mean of 304 m³ CH₄/t VS. 2 of the curves are model curves (first-order kinetics).0100200300400051015202530time [d]m³ CH₄/t VSYan et al. (2021): 237 m³ CH₄/t VS (model curve)Kolbl et al. (2014): 372 m³ CH₄/t VS (model curve)mean304

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 (304); 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
SourceBMP
m³ CH₄/t VS		TemperatureSampleCurve
Yan et al. (2021) DOI237—Turnip (Brassica rapa) – Wholeend point (model curve)
Kolbl et al. (2014) DOI37238 °C · mesophilicForage Turnipsend point (model curve)
Weighted mean304arithmetic mean 304, SD 96

Typical composition

Dry matter (DM)
10.3% (range 10.3–10.3)
Volatile solids (VS)
92.1 % DM (range 91.6–92.7)
Nitrogen
2 % DM
C/N ratio
20.4

Median and range of the determinations reported in the publications behind this substrate's BMP records (read from: BCBPD, MY-D); dry matter: 1 determination, volatile solids: 2 determinations. C/N was calculated as the ratio of C and N content (% DM) from the same source. DM from a single determination – indicative value.

Sources: Yan et al. (2021); Kolbl et al. (2014).

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
carbon-rich
high C/N → nitrogen deficiency; combine well with nitrogen-rich substrates
low in nitrogen
high C/N → nitrogen deficiency; combine well with nitrogen-rich substrates
poor in trace elements
poor in trace elements — mono-digestion requires supplementation
seasonal
seasonal availability — requires storage
fibrous
lignocellulose, long fibres → floating layer, harder mixing, slow degradation

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

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

  1. Improvement of fruit and vegetable waste anaerobic digestion performance and stability with co-substrates addition
  2. Biochemical methane potential and biodegradability of complex organic substrates
  3. Compositional components and methane production potential of typical vegetable wastes
  4. Addressing case specific biogas plant tasks: Industry oriented methane yields derived from 5L Automatic Methane Potential Test Systems in batch or semi-continuous tests using realistic inocula, substrate particle sizes and organic loading
  5. Lab-scale anaerobic digestion of cassava peels: the first step of energy recovery from cassava waste and water hyacinth
  6. Effects of size and thermophilic pre-hydrolysis of banana peel during anaerobic digestion, and biomethanation potential of key tropical fruit wastes
  7. 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

Turnip (Brassica rapa subsp. rapa) is a root crop of the Brassicaceae family, formerly widely grown as a vegetable and a fodder plant. Fodder turnip and stubble turnip are sometimes sown as a catch crop, that is, a crop grown after the cereal harvest to obtain green forage and roots. In Poland it is a crop of little production importance, so as a biogas substrate it occurs mainly on farms that grow it themselves, or as a vegetable surplus.

Properties relevant to digestion

Turnip tubers contain a great deal of water, and in the dry matter soluble sugars, pectins and hemicellulose predominate, with a low content of lignin and fat. As a result, the material hydrolyses quickly, which at a high dose may acidify the digester. Like other Brassicaceae, turnip contains glucosinolates and sulphur compounds that are converted into hydrogen sulphide, so plants without efficient desulphurisation should monitor its concentration in the biogas. Roots pulled out of the ground also carry sand, which settles in the digester. The green tops have a different composition from the root: more fibre and protein.

How to read the spread of results

The dataset contains several records from several sources, including records without a stated test temperature and mesophilic ones (among others from fodder turnip). The differences result from cultivar, harvest date and root size, and from whether the sample included the tops. Chopping and the way the sample was prepared (fresh, frozen, dried), the inoculum and the substrate-to-inoculum ratio complete the picture. With so little data, the spread is information about caution, not about the precision of the estimate.

In biogas plant practice

Turnip is used as a seasonal supplement to the feed, after the roots have been washed and chopped, to limit sand and avoid blocking the pumps. It is best combined with slurry or maize silage, which provide buffering and structure. Dosing should be even and the hydrogen sulphide concentration monitored. Storage in clamps is possible for a limited time, but rotting roots give off unpleasant odours. If the turnip comes from the farm's own crops, it is treated as an agricultural product; waste from processing and trade is subject to waste regulations.

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

  1. Yan, H.; Cai, F.; Wang, L.; Chen, C.; Liu, G. (2021). Compositional components and methane production potential of typical vegetable wastes. Environmental Science and Pollution Research 28(38), 54177–54186. DOI: 10.1007/s11356-021-15798-y DOI
  2. Kolbl, S.; Paloczi, A.; Panjan, J.; Stres, B. (2014). Addressing case specific biogas plant tasks: Industry oriented methane yields derived from 5L Automatic Methane Potential Test Systems in batch or semi-continuous tests using realistic inocula, substrate particle sizes and organic loading. Bioresource Technology 153, 180–188. DOI: 10.1016/j.biortech.2013.12.010 DOI

All sources of the site: bibliography.

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