BMP testingEnergy crops and whole-crop plants (WCS)
Sorghum, whole crop — BMP: 19 studies, weighted mean 351 m³ CH₄/t VS
Sorghum (sweet, forage, grain) is a heat-loving, drought-resistant energy crop. The dataset covers many varieties and harvest dates from several studies.
Photo Zarate123 / Wikimedia Commons, licence CC BY-SA 4.0, source file; changes: cropping
- Weighted mean
- 351m³ CH₄/t VS
- Range
- 269–538m³ CH₄/t VS
- Records
- 19studies
- Publications
- 5sources
- Temperatures
- 35 °C, 38 °C, 40 °Cof the test
Methane in biogas
Medium methane content · ≈ 5.8 kWh/m³ of biogas
measured mean of 3 studies BMP, range 56.9–59.6 %; in a batch test the CH₄ share tends to be higher than in a plant.
Rating for biogas plants
good — editorial rating for biogas plantsStable, usually accepted without a fee
Potential per tonne of fresh matter: high (78 m³ CH₄/t); process risk: acidification. No additional handling requirements.
Why? Rating factors
Potential per tonne +2
- +2potential 78 m³ CH₄/t fresh matter (BMP 351 × DM 24.1 % × VS 92 %)
Process stability −0.5
- −0.5acidification: rapid degradation / acidic pH, risk of VFA accumulation, needs buffering
Handling and costs 0
- 0no factors
Total points: 1.5 · thresholds: ≥ 2.5 very good, ≥ 1 good, below — neutral; negative with cumulative process risk.
Add to the co-digestion calculator CSV data
BMP curves from 19 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 (351); 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.
Show the remaining records in the legend (7)
Records and sources
Download CSV| Source | BMP m³ CH₄/t VS | CH₄ in biogas % vol., measured | Temperature | Sample | Curve |
|---|---|---|---|---|---|
| Pouech (b.r.) · 1 | 295 | 56.9 % | 40 °C · mesophilic | Forage sorghum | end point (model curve) |
| Pouech (b.r.) · 2 | 352 | 58.5 % | 40 °C · mesophilic | Sweet sorghum | end point (model curve) |
| Pouech (b.r.) · 3 | 372 | 59.6 % | 40 °C · mesophilic | Grain sorghum | end point (model curve) |
| Chynoweth et al. (1993) · 1 DOI | 311 | — | 35 °C · mesophilic | Sorghum | end point (model curve) |
| Chynoweth et al. (1993) · 2 DOI | 410 | — | 35 °C · mesophilic | Sorghum | end point (model curve) |
| Chynoweth et al. (1993) · 3 DOI | 420 | — | 35 °C · mesophilic | Sorghum | end point (model curve) |
| Gunaseelan (2004) · 1 DOI | 367 | — | 35 °C · mesophilic | Sorghum bicolor Lamina | end point (model curve) |
| Gunaseelan (2004) · 2 DOI | 407 | — | 35 °C · mesophilic | Sorghum bicolor Sheath | end point (model curve) |
| Gunaseelan (2004) · 3 DOI | 480 | — | 35 °C · mesophilic | Sorghum bicolor Inflorescence with flowers | end point (model curve) |
| Gunaseelan (2004) · 4 DOI | 538 | — | 35 °C · mesophilic | Sorghum bicolor Inflorescence with Grains | end point (model curve) |
| Lallement et al. (2023) · 1 DOI | 273 | — | 38 °C · mesophilic | Sorghum | end point (model curve) |
| Lallement et al. (2023) · 2 DOI | 286 | — | 38 °C · mesophilic | sorghum | end point (model curve) |
| Lallement et al. (2023) · 3 DOI | 290 | — | 38 °C · mesophilic | Sorghum | end point (model curve) |
| Lallement et al. (2023) · 4 DOI | 305 | — | 38 °C · mesophilic | Sorghum | end point (model curve) |
| Lallement et al. (2023) · 5 DOI | 333 | — | 38 °C · mesophilic | sorghum | end point (model curve) |
| Lallement et al. (2023) · 6 DOI | 351 | — | 38 °C · mesophilic | sucro variety | end point (model curve) |
| Lallement et al. (2023) · 7 DOI | 360 | — | 38 °C · mesophilic | vega sorghum | end point (model curve) |
| Lallement et al. (2023) · 8 DOI | 362 | — | 38 °C · mesophilic | sorghum | end point (model curve) |
| Sambusiti et al. (2013) DOI | 269 | — | 35 °C · mesophilic | ensiled sorgum forage | end point (model curve) |
| Weighted mean | 351 | 58.3 % | arithmetic mean 357, SD 71 | ||
Typical composition
- Dry matter (DM)
- 24.1% (range 15.5–93)
- Volatile solids (VS)
- 92 % DM (range 86.6–97.1)
- Nitrogen
- 1.6 % DM
- C/N ratio
- 44.5
Median and range of the determinations reported in the publications behind this substrate's BMP records (read from: CROPGEN D4, MY-D); dry matter: 12 determinations, volatile solids: 14 determinations. C/N was calculated as the ratio of C and N content (% DM) from the same source. The DM range includes fresh samples as well as samples partly dried or dried before the test – for fresh material the lower part of the range applies, ideally your own measurement.
Sources: Pouech, P. Fruteau, H. Bewa, H.. Agricultural crops for…; Gunaseelan (2004); Lallement et al. (2023); Sambusiti et al. (2013).
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
Advantages
- Methane potential in the database: weighted mean 351 m³ CH₄/t VS (median 352; range 269–538; 19 records from 5 sources).
Drawbacks and risks
- Spread depends on the variety and harvest date (19 records).
- Spread of results in the database: standard deviation 71 at a mean of 357 m³ CH₄/t VS (19 records from 5 sources).
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
- Shred: shredding increases the surface available for degradation and speeds it up, but does not necessarily raise the final gas yield (FNR 2010, Ch. 3 “Triturado”).
- 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
- Pouech, P. Fruteau, H. Bewa, H. (None) Agricultural crops for biogas production on anaerobic digestion plants. Biomass for energy and industry 163-165
- Weiland, P. (2010) Biogas production: current state and perspectives. Applied Microbiology and Biotechnology
- Chen, Y.; Cheng, J.J.; Creamer, K.S. (2008) Inhibition of anaerobic digestion process: A review. Bioresource Technology
- Chynoweth, D.; Turick, C.; Owens, J.; Jerger, D.; Peck, M. (1993) Biochemical methane potential of biomass and waste feedstocks. Biomass and Bioenergy 5(1), 95–111
- Gunaseelan, V. (2004) Biochemical methane potential of fruits and vegetable solid waste feedstocks. Biomass and Bioenergy 26(4), 389–399
- Lallement, A.; Peyrelasse, C.; Lagnet, C.; Barakat, A.; Schraauwers, B.; Maunas, S.; Monlau, F. (2023) A Detailed Database of the Chemical Properties and Methane Potential of Biomasses Covering a Large Range of Common Agricultural Biogas Plant Feedstocks. Waste 1(1), 195–227
- Sambusiti, C.; Monlau, F.; Ficara, E.; Carrère, H.; Malpei, F. (2013) A comparison of different pre-treatments to increase methane production from two agricultural substrates. Applied Energy 104, 62–70
- FNR (2010). Guía sobre el Biogás – Desde la producción hasta el uso (hiszp. wydanie „Leitfaden Biogas”, GIZ 2013)
- Herrmann et al. (2011). Effects of ensiling, silage additives and storage period on methane formation of biogas crops. Bioresour. Technol.
The co-digestion calculator will assess a specific mixture containing this substrate.
What it is and where it comes from
Sorghum (Sorghum bicolor) is a heat-loving C4 grass, grown around the world as a cereal (grain sorghum), fodder (forage sorghum) and sugar crop (sweet sorghum). In countries with a cooler climate it is studied as an alternative to maize, because it is more drought-resistant. In Poland cultivation is possible, but limited by spring temperature and the length of the season. The dataset comprises over a dozen records for forage, sweet and grain sorghum from several studies, under mesophilic conditions.
Properties relevant to digestion
Sweet sorghum contains a lot of soluble sugars in the stalk, which ease ensiling and ferment quickly. Forage sorghum has more fibre, and grain sorghum contributes starch from the grain. The composition depends on the variety and harvest stage: with time the share of fibre and lignin rises. Ensiling is usually easy, provided the dry matter content is suitable. Sorghum plants contain secondary compounds, such as dhurrin in young plants, which can be toxic to animals, but are not significant in the biogas industry at typical shares. The C/N ratio is usually high, which favours co-digestion with slurry.
How to read the spread of results
The main sources of spread are the type of sorghum (sweet, forage, grain), variety, harvest date, length of the growing period and growing conditions. To these are added the form of the material (green forage, silage), chopping and the test protocol. The dataset combines studies from different decades and regions (from the 1990s to the present day). The spread is therefore much wider than in the case of a single experiment.
In biogas plant practice
Sorghum is sometimes considered as a supplement to or replacement for maize in dry regions. It is harvested with a forage harvester, ensiled and mixed with other substrates. In choosing a variety, maturation under the given climatic conditions and biomass yield count. The quality of ensiling and the dry matter content should be checked. Because of the great variability of varieties, a BMP test and a trial crop are advisable before wider implementation. Before taking up sorghum it is good to check the availability of varieties adapted to the Polish climate and the sowing requirements, because heat-loving means a risk of poor establishment in a cool spring. In the balance it is worth setting biomass yield against the costs of seed and harvest.
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.
Results after pretreatment (2) — excluded from the mean
| Source | BMP m³ CH₄/t VS | Pretreatment | Sample |
|---|---|---|---|
| Sambusiti et al. (2013) | 346 | chemical-unspecified | ensiled sorgum forage |
| Sambusiti et al. (2013) | 361 | chemical-unspecified | ensiled sorgum forage |
Bibliography
- Pouech, P. Fruteau, H. Bewa, H.. Agricultural crops for biogas production on anaerobic digestion plants. Biomass for energy and industry 163-165.
- Chynoweth, D.; Turick, C.; Owens, J.; Jerger, D.; Peck, M. (1993). Biochemical methane potential of biomass and waste feedstocks. Biomass and Bioenergy 5(1), 95–111. DOI: 10.1016/0961-9534(93)90010-2 DOI
- Gunaseelan, V. (2004). Biochemical methane potential of fruits and vegetable solid waste feedstocks. Biomass and Bioenergy 26(4), 389–399. DOI: 10.1016/j.biombioe.2003.08.006 DOI
- Lallement, A.; Peyrelasse, C.; Lagnet, C.; Barakat, A.; Schraauwers, B.; Maunas, S.; Monlau, F. (2023). A Detailed Database of the Chemical Properties and Methane Potential of Biomasses Covering a Large Range of Common Agricultural Biogas Plant Feedstocks. Waste 1(1), 195–227. DOI: 10.3390/waste1010014 DOI
- Sambusiti, C.; Monlau, F.; Ficara, E.; Carrère, H.; Malpei, F. (2013). A comparison of different pre-treatments to increase methane production from two agricultural substrates. Applied Energy 104, 62–70. DOI: 10.1016/j.apenergy.2012.10.060 DOI
All sources of the site: bibliography.
Other substrates in the group “Energy crops and whole-crop plants (WCS)”
Tall wheatgrass (Szarvasi grass) — BMP: 8 studies, weighted mean 313 m³ CH₄/t VS
313 m³ CH₄/t VS weighted mean from 8 studies
good — editorial rating for biogas plants≈52 %
Energy dock — BMP: 5 studies, weighted mean 271 m³ CH₄/t VS
271 m³ CH₄/t VS weighted mean from 5 studies
≈52 %
Napier grass — BMP: 35 studies, weighted mean 253 m³ CH₄/t VS
253 m³ CH₄/t VS weighted mean from 35 studies
good — editorial rating for biogas plants≈54 %
Pennisetum hybrid grass — BMP: 18 studies, weighted mean 266 m³ CH₄/t VS
266 m³ CH₄/t VS weighted mean from 18 studies
neutral — editorial rating for biogas plants≈52 %