BMP testingEnergy crops and whole-crop plants (WCS)single study (4 samples)

Sudan grass — BMP: 4 studies, weighted mean 250 m³ CH₄/t VS

Sudan grass (Sudanese sorghum) is a fast-growing, heat-loving fodder grass, considered as an energy crop. The dataset covers several silage records from one study.

rating: good CH₄ ≈ 52 % (estimate)

Published 30 November 2025Updated 29 October 20263 min readFeedstockData Editorial Team

Photo Victor M. Vicente Selvas / Wikimedia Commons, licence CC BY-SA 3.0, source file; changes: cropping

Weighted mean: 250m³ CH₄/t VS
Range: 123–336m³ CH₄/t VS
Records: 4single study (4 samples)
Publications: 1source
Temperatures: 37 °Cof the test

Methane in biogas

≈51–54% CH₄

Medium methane content · ≈ 5.2 kWh/m³ of biogas

estimate from the substrate type The collected studies contain no measurement. The interval follows from the approximate composition (carbohydrate-dominated (no protein or fat characteristics)) and the yields of compound groups according to FNR.

How we calculate it and what the zones mean

Rating for biogas plants

good — editorial rating for biogas plantsStable, usually accepted without a fee

Potential per tonne of fresh matter: high (76 m³ CH₄/t); no particular threats to stability. Handling costs: fibres, floating layer.

Why? Rating factors

Potential per tonne +2

+2potential 76 m³ CH₄/t fresh matter (BMP 250 × DM 32.4 % × VS 94 %)

Process stability 0

0no factors

Handling and costs −0.5

−0.5fibres, floating layer — shredding and intensive mixing

Total points: 1.5 · 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 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 (250); 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
Kaiser (2007) · 1	123	37 °C · mesophilic	Sudangrass silage	end point (model curve)
Kaiser (2007) · 2	262	37 °C · mesophilic	Sudangrass silage	end point (model curve)
Kaiser (2007) · 3	279	37 °C · mesophilic	Sudangrass silage	end point (model curve)
Kaiser (2007) · 4	336	37 °C · mesophilic	Sudangrass silage	end point (model curve)
Weighted mean	250	arithmetic mean 250, SD 90

Typical composition

Dry matter (DM): 32.4% (range 27.2–37.2)
Volatile solids (VS): 94 % DM (range 89.3–95.2)

Median and range of the determinations reported in the publications behind this substrate's BMP records (read from: MY-D); dry matter: 4 determinations, volatile solids: 4 determinations.

Sources: Kaiser (2007).

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.

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

combines well
group: Animal excreta (slurry, manure, poultry litter)
Co-digestion with excreta (slurry/solid manure) is the standard arrangement for plant biomass: they supply alkalinity and microflora.^[1][2]

Dosing

No source-based dose limits.

Practical requirements

Ensiling makes it possible to store seasonal biomass; properly ensiled plants (in the study maize, sorghum, forage rye, triticale) can be stored for up to a year without loss of methane production (Herrmann et al. 2011).

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

Sudan grass is a hybrid of sorghum and Sudan grass, grown as a fodder plant and green manure. It is heat-loving, grows quickly and can give more than one cut per season. It is drought-resistant, so it is sometimes considered as an energy crop in regions where maize is risky. The dataset contains several silage records from one study, carried out under mesophilic conditions.

Properties relevant to digestion

The composition is similar to other C4 grasses: low protein content, a high share of fibre and a wide C to N ratio. Harvest at the vegetative stage gives biomass that is better digestible than after heading. Like sorghum, Sudan grass contains cyanogenic compounds (dhurrin) in young plants, the significance of which at typical plant shares in the digester is small, but harvest after frost or under stress requires caution in animal feeding. Ensiling is possible with a suitable dry matter content. The material must be chopped, and mixing with slurry improves the nitrogen balance.

How to read the spread of results

The records come from one publication and concern silage, so the spread mainly reflects differences between cuts, varieties or batches within one experiment. It does not capture differences between laboratories, years and regions. In addition, the mowing date, fertilisation, the method of ensiling and sample preparation and the test parameters have an effect. The results should be treated as indicative for silage under typical test conditions.

In biogas plant practice

Sudan grass can be a seasonal supplement on farms that grow it for fodder or have surplus green forage. It is harvested with a forage harvester, ensiled and added to the mix in a limited share. In the Polish climate it depends on the summer, because it requires warmth, so yield is variable. Before it becomes a regular component of the ration, it is worth carrying out a BMP test of your own silage and comparing the costs with other crops. It should also be noted that results for silage are not a simple equivalent of the result for fresh green forage. Ensiling changes the content of sugars and organic acids, so when planning the dose one should rely on testing the material in the form in which it will be fed to the digester.

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 = 0.085 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

Kaiser, F.L. (2007). Einfluss der stofflichen Zusammensetzung auf die Verdaulichkeit nachwachsender Rohstoffe beim anaeroben Abbau in Biogasreaktoren. Dissertation, Technische Universität München, Wissenschaftszentrum Weihenstephan. https://mediatum.ub.tum.de/631394 source

All sources of the site: bibliography.