BMP testingFruit, vegetables and their residues

Radish — BMP: 3 studies, weighted mean 286 m³ CH₄/t VS

Radish (roots) is a watery vegetable waste of the Brassicaceae family, with stable results between cultivars and the typical risk of hydrogen sulphide formation.

CH₄ ≈ 56 % (estimate)

Published 3 November 2022Updated 29 October 20263 min readFeedstockData Editorial Team

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

Weighted mean: 286m³ CH₄/t VS
Range: 273–304m³ CH₄/t VS
Records: 3studies
Publications: 2sources
Temperatures: 35 °Cof the test

Methane in biogas

≈54–58% CH₄

Medium methane content · ≈ 5.5 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 3.4 % 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 3 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 (286); 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. (2021) DOI	273	—	Red radish (Raphanus sativus) – Whole	end point (model curve)
Gunaseelan (2004) · 1 DOI	293	35 °C · mesophilic	radish yellow white	end point (model curve)
Gunaseelan (2004) · 2 DOI	304	35 °C · mesophilic	radish pale pink	end point (model curve)
Weighted mean	286	arithmetic mean 290, SD 16

Typical composition

Volatile solids (VS): 84.9 % DM (range 81.7–91.3)
Nitrogen: 3.4 % DM
C/N ratio: 12.5

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. (2021); Gunaseelan (2004).

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

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]
combines well
substrates: high alkalinity (buffer) — e.g. Cattle manure, Pig slurry, Cattle slurry, Duck slurry, Rumen and digestive tract content
Co-digestion of easily degradable substrates with dairy slurry increased the methane yield relative to slurry alone.^[2]

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

Radish (Raphanus sativus) is grown in Poland primarily as the spring radish, grown in the open field and under cover, and as the larger-rooted summer and winter radish. The waste arises in packing houses and on plantations (overgrown, cracked roots that do not meet commercial standards), and also in salad processing. The stream is small and strongly seasonal.

Properties relevant to digestion

The radish root contains more than ninety per cent water, and the dry matter is rich in soluble sugars, pectins and protein, with a low lignin content. As a result, the material hydrolyses quickly and supplies readily available carbon, but requires sensible dosing because of the risk of acidification. Radish contains glucosinolates responsible for its pungent taste; their breakdown products and other sulphur compounds promote the formation of hydrogen sulphide in the biogas. Sand and soil adhering at harvest also have a minor effect. The low dry matter content means that the energy density per tonne of fresh matter is small.

How to read the spread of results

The dataset contains several records from several sources, including records without a stated temperature and mesophilic ones, relating to the yellow-white and light pink cultivars and to the red one. The results are similar to one another, which suggests that, expressed per volatile solids, cultivar is not the dominant factor in variability. However, uncertainty remains owing to the small number of sources, the way the sample was chopped and prepared, and the inoculum. With a very watery material, the accuracy of the dry matter determination is also important.

In biogas plant practice

Radish is a marginal addition that makes sense mainly where it arises on site in larger quantities. After chopping, it is mixed with slurry or silage, and the dose is spread over time. The plant should have efficient desulphurisation. Storage is limited because the roots spoil quickly. Plant waste from trade and processing counts as waste and requires appropriate provisions in the permit, whereas residues from the farm's own holding are treated as agricultural products.

Because the stream is small, radish rarely requires separate planning; it is enough to include it in the balance of seasonal vegetable waste and to remember that, together with other Brassicaceae such as cabbage or turnip, it increases the load on the desulphurisation system.

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.