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BMP testingStraws and crop residuessingle study (9 samples)

Sorghum straw (stover) — BMP: 9 studies, weighted mean 334 m³ CH₄/t VS

Sorghum straw (stalks and leaves after grain harvest) gave 277-413 m³ CH₄/t VS in one Spanish study depending on variety; these are data from a single publication, so the spread concerns varieties and not many independent studies.

rating: goodCH₄ ≈ 52 % (estimate)

Published Updated 4 min readFeedstockData Editorial Team

Illustration: FeedstockData (AI, Google Gemini)

Weighted mean
334m³ CH₄/t VS
Range
277–413m³ CH₄/t VS
Records
9single study (9 samples)
Publications
1source
Temperatures
35 °Cof the test

Methane in biogas

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: very high (279 m³ CH₄/t); no particular threats to stability. Handling costs: fibres, floating layer, slow degradation.

Why? Rating factors

Potential per tonne +3

  • +3potential 279 m³ CH₄/t fresh matter (BMP 334 × DM 91.8 % × VS 90.9 %)

Process stability 0

  • 0no factors

Handling and costs −1

  • −0.5fibres, floating layer — shredding and intensive mixing
  • −0.5slow degradation — long retention time

Total points: 2 · thresholds: ≥ 2.5 very good, ≥ 1 good, below — neutral; negative with cumulative process risk.

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

Add to the co-digestion calculator CSV data

BMP curves from 9 studies

Weighted mean Individual records

BMP curves: Sorghum straw (stover)Cumulative methane production over time for 9 records and the weighted mean of 334 m³ CH₄/t VS. 0 of the curves are model curves (first-order kinetics).010020030040050005101520253035time [d]m³ CH₄/t VSde la Lama‐Calvente et al. (2023) · 1: 277 m³ CH₄/t VS (measurement)de la Lama‐Calvente et al. (2023) · 2: 287 m³ CH₄/t VS (measurement)de la Lama‐Calvente et al. (2023) · 3: 302 m³ CH₄/t VS (measurement)de la Lama‐Calvente et al. (2023) · 4: 304 m³ CH₄/t VS (measurement)de la Lama‐Calvente et al. (2023) · 5: 318 m³ CH₄/t VS (measurement)de la Lama‐Calvente et al. (2023) · 6: 344 m³ CH₄/t VS (measurement)de la Lama‐Calvente et al. (2023) · 7: 376 m³ CH₄/t VS (measurement)de la Lama‐Calvente et al. (2023) · 8: 386 m³ CH₄/t VS (measurement)de la Lama‐Calvente et al. (2023) · 9: 413 m³ CH₄/t VS (measurement)mean334

All curves are measurements from the publications.

Cumulative methane production over the test [m³ CH₄/t VS]. The thick line is the weighted mean of all records (334); 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
de la Lama‐Calvente et al. (2023) · 1 DOI27735 °C · mesophilicSorghum straw PAN (mean of 3 reactors, BMP 5 sheet, day 30.9)measurement (27 pts)
de la Lama‐Calvente et al. (2023) · 2 DOI28735 °C · mesophilicSorghum straw PR88 (mean of 3 reactors, BMP 5 sheet, day 30.9)measurement (27 pts)
de la Lama‐Calvente et al. (2023) · 3 DOI30235 °C · mesophilicSorghum straw PR87 (mean of 3 reactors, BMP 5 sheet, day 30.9)measurement (27 pts)
de la Lama‐Calvente et al. (2023) · 4 DOI30435 °C · mesophilicSorghum straw ZHG (mean of 3 reactors, BMP 5 sheet, day 30.9)measurement (27 pts)
de la Lama‐Calvente et al. (2023) · 5 DOI31835 °C · mesophilicSorghum straw P89 (mean of 3 reactors, BMP 5 sheet, day 30.9)measurement (27 pts)
de la Lama‐Calvente et al. (2023) · 6 DOI34435 °C · mesophilicSorghum straw MP (mean of 3 reactors, BMP 5 sheet, day 30.9)measurement (27 pts)
de la Lama‐Calvente et al. (2023) · 7 DOI37635 °C · mesophilicSorghum straw TG (mean of 3 reactors, BMP 5 sheet, day 30.9)measurement (27 pts)
de la Lama‐Calvente et al. (2023) · 8 DOI38635 °C · mesophilicSorghum straw CÑ (mean of 3 reactors, BMP 5 sheet, day 30.9)measurement (27 pts)
de la Lama‐Calvente et al. (2023) · 9 DOI41335 °C · mesophilicSorghum straw ZH (mean of 3 reactors, BMP 5 sheet, day 30.9)measurement (27 pts)
Weighted mean334arithmetic mean 334, SD 48

Typical composition

Dry matter (DM)
91.8% (range 91.6–93.4)
Volatile solids (VS)
90.9 % DM (range 88.2–94)

Median and range of the determinations reported in the publications behind this substrate's BMP records (read from: tabele, tekst lub zbiór danych publikacji); dry matter: 9 determinations, volatile solids: 9 determinations. Samples were tested dried/air-dry – the DM refers to the material in the test, not to fresh material.

Sources: de la Lama‐Calvente et al. (2023).

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

  • fibrous
  • slowly degrading
  • carbon-rich
  • low in nitrogen
  • high dry matter
  • variable composition
  • seasonal
  • editorial classification

Advantages

  • Methane potential in one paper (9 varieties, 35 °C): from 276.9 to 412.8 m³ CH₄/t VS, mean 334 (de la Lama-Calvente et al. 2023).
  • Dry matter approx. 92% FM, and VS approx. 89-90% DM - little ash, high energy density per tonne of material (raw Zenodo data for de la Lama-Calvente et al. 2023).
  • High C/N complements nitrogen-rich substrates well, e.g. slurry (Weiland 2010).

Drawbacks and risks

  • All data come from one publication and one protocol; yield depends strongly on the variety (more than a 1.4-fold difference), so the mean is only indicative (de la Lama-Calvente et al. 2023).
  • The lignocellulosic structure limits degradation and requires size reduction or pretreatment (Hendriks and Zeeman 2009).
  • Very little nitrogen (C/N from approx. 50 to several hundred in the data sheet) - mono-digestion risks N deficiency (de la Lama-Calvente et al. 2023; Weiland 2010).

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

Dosing

No source-based dose limit. Dry, fibrous straw requires size reduction and dosing together with a liquid substrate (slurry); choose the share to suit the mixing capability of the digester and confirm with a BMP test for the specific variety.

Practical requirements

  • BMP test for a specific variety and batch (de la Lama-Calvente et al. 2023)

Sources of the process data

  1. Weiland, P. (2010) Biogas production: current state and perspectives. Applied Microbiology and Biotechnology
  2. Hendriks, A.T.W.M.; Zeeman, G. (2009) Pretreatments to enhance the digestibility of lignocellulosic biomass. Bioresource Technology
  3. de la Lama-Calvente et al. (2023). Valorization of different landrace and commercial sorghum (Sorghum bicolor (L.) Moench) straw varieties by anaerobic digestion. GCB Bioenergy 15(3), 332-345

The co-digestion calculator will assess a specific mixture containing this substrate.

What it is and where it comes from

Sorghum straw is the stalks and leaves of common sorghum (Sorghum bicolor) that remain in the field after the grain harvest. In Poland sorghum is grown on a small scale, so this stream is local and rather seasonal; it is of greater importance in Mediterranean countries, from which the data come. The dataset contains nine records from one publication: de la Lama-Calvente et al. (2023, GCB Bioenergy), whose authors made the raw data available in a Zenodo dataset. It compared local varieties (including Zahina, Zahina gigante, Trigomillo) and commercial ones (including PR88Y20). Each record is the mean of three reactors for one variety.

Properties relevant to digestion

The data sheets show that the material is very dry: dry matter was about 92% of fresh matter, and volatile solids about 82-83% of fresh matter, i.e. about 89-90% of dry matter. This is a typical lignocellulosic straw, so it degrades more slowly than starchy materials and requires chopping. The nitrogen content is very low: in the sheet with elemental analysis the C/N ratio comes out from about 50 to several hundred, and for one variety exceeds a thousand, which results from nitrogen close to the limit of quantification. These figures should be treated as indicative. In practice this means a nitrogen deficiency in mono-digestion, and mixing with a nitrogen-rich substrate (e.g. slurry) is the natural solution (Weiland 2010).

How to read the spread of results

This is the most important remark about this entry: all nine values come from one study, carried out by one team, under the same conditions (35 °C, mesophilic, about 31 days). The spread from 276.9 m³/t (variety Panizo) to 412.8 m³/t (local variety Zahina) therefore mainly reflects differences between varieties, and not between laboratories, and it is not known how straw from another year, soil or harvest date would behave. The mean of 334 m³/t (SD 48) is only indicative. The dataset also contains sheets in which values calculated in a different way deviate from the means of the last measurement used here, so these figures should not be compared with other compilations without checking the method.

In biogas plant practice

For an agricultural plant, sorghum straw is a supplementary substrate, not a primary one. The dose must be matched to the mixing capability in the chamber: a dry, long-fibre mass can form scum, so chopping and dosing together with a liquid substrate are needed. Methane yield depends on the variety, and there is no source giving a safe dose limit, so the calculator applies no threshold for it. If you are planning a contract for sorghum straw, commission your own BMP test for the specific variety; pretreatment (chopping, possibly chemical) can raise the yield, but this entry does not cover it (Hendriks and Zeeman 2009).

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.

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. de la Lama‐Calvente, D.; Fernández‐Rodríguez, M.J.; Gandullo, J.; Desena, I.; de la Osa, C.; Feria, A.B.; Jiménez‐Rodríguez, A.; Borja, R. (2023). Valorization of different landrace and commercial sorghum (Sorghum bicolor (L.) Moench) straw varieties by anaerobic digestion. GCB Bioenergy 15(3), 332–345. DOI: 10.1111/gcbb.13025 DOI

All sources of the site: bibliography.

Other substrates in the group “Straws and crop residues”