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BMP testingGrain, bran, feed and fodder

Cereal grain and flour — BMP: 4 studies, weighted mean 350 m³ CH₄/t VS

Cereal grain and flour from waste batches are a concentrated, starchy substrate with rapid fermentation. They require careful dosing and good particle size reduction.

rating: very goodCH₄ ≈ 52 % (estimate)

Published Updated 3 min readFeedstockData Editorial Team

Photo Margaret Hoogstrate / Wikimedia Commons, licence CC BY 3.0, source file; changes: cropping

Weighted mean
350m³ CH₄/t VS
Range
247–386m³ CH₄/t VS
Records
4studies
Publications
3sources
Temperatures
36 °C, 38 °Cof the test

Methane in biogas

Low 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 (protein from total nitrogen (N 0.7 % 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

very good — editorial rating for biogas plantsWorth accepting even for free or with a payment to the supplier

Potential per tonne of fresh matter: very high (273 m³ CH₄/t); process risk: acidification. No additional handling requirements.

Why? Rating factors

Potential per tonne +3

  • +3potential 273 m³ CH₄/t fresh matter (BMP 350 × DM 87 % × VS 89.6 %)

Process stability −0.5

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

Handling and costs 0

  • 0no factors

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

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

Add to the co-digestion calculator CSV data

BMP curves from 4 studies

Weighted mean Individual records

BMP curves: Cereal grain and flourCumulative methane production over time for 4 records and the weighted mean of 350 m³ CH₄/t VS. 4 of the curves are model curves (first-order kinetics).0100200300400500051015202530time [d]m³ CH₄/t VSLallement et al. (2023) · 1: 247 m³ CH₄/t VS (model curve)Lallement et al. (2023) · 2: 325 m³ CH₄/t VS (model curve)Luna-delRisco et al. (2011): 386 m³ CH₄/t VS (model curve)Koch et al. (2020): 378 m³ CH₄/t VS (model curve)mean350

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 (350); 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
Lallement et al. (2023) · 1 DOI24738 °C · mesophilicmaize beansend point (model curve)
Lallement et al. (2023) · 2 DOI32538 °C · mesophilicmaize flourend point (model curve)
Luna-delRisco et al. (2011)38636 °C · mesophilicgrain mill - Flourend point (model curve)
Koch et al. (2020) DOI378—Wheat flourend point (model curve)
Weighted mean350arithmetic mean 334, SD 64

Typical composition

Dry matter (DM)
87% (range 42–91.2)
Volatile solids (VS)
89.6 % DM (range 87–98)
Nitrogen
0.7 % DM
C/N ratio
90.2

Median and range of the determinations reported in the publications behind this substrate's BMP records (read from: MY-D); dry matter: 3 determinations, volatile solids: 3 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: Lallement et al. (2023); Luna-delRisco et al. (2011).

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

  • easily degradable
  • carbon-rich
  • high dry matter
  • variable composition
  • editorial classification

Advantages

  • Methane potential in the database: weighted mean 350 m³ CH₄/t VS (median 352; range 247–386; 4 records from 3 sources).
  • Waste batches of grain and flour – a concentrated source of energy (Lunadelrisco 2011, Lallement 2023); flour assessed as a positive control (Koch 2020).

Drawbacks and risks

  • Spread of results in the database: standard deviation 64 at a mean of 334 m³ CH₄/t VS (4 records from 3 sources).

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

Dosing

No source-based dose limits.

Introduce gradually, starting with a small dose and monitoring the process (e.g. FOS/TAC, pH, gas composition).

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”).

Sources of the process data

  1. Chen, Y.; Cheng, J.J.; Creamer, K.S. (2008) Inhibition of anaerobic digestion process: A review. Bioresource Technology
  2. Weiland, P. (2010) Biogas production: current state and perspectives. Applied Microbiology and Biotechnology
  3. 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
  4. Luna-delRisco, M.; Normak, A.; Orupõld, K. (2011) Biochemical methane potential of different organic wastes and energy crops from Estonia. Agronomy Research 9(1–2), 331–342
  5. Koch, K.; Hafner, S.; Astals, S.; Weinrich, S. (2020) Evaluation of Common Supermarket Products as Positive Controls in Biochemical Methane Potential (BMP) Tests. Water 12(5), 1223
  6. FNR (2010). Guía sobre el Biogás – Desde la producción hasta el uso (hiszp. wydanie „Leitfaden Biogas”, GIZ 2013)

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

What it is and where it comes from

Cereal grain and flour are basic products of the grain and milling industry. They reach biogas plants when batches have been spoiled, dampened, contaminated or classified as waste because of expiry or inadequate quality. The compilation contains several records from several studies: maize grain, maize flour, flour from a grain mill and wheat flour from a shop. These are materials of a similar starchy character, but of different physical form.

Properties relevant to digestion

Grain and flour consist mainly of starch, with some protein and a small amount of fat. Starch hydrolyses rapidly, which gives a fast rise in biogas production, but also a risk of overload and acidification if the dose is too high. Whole grain is hard and poorly accessible to microorganisms, so without crushing part of the starch degrades more slowly, and part may pass through the system unused. Flour is available immediately, but it dusts and sticks into lumps, so good mixing with a liquid substrate is needed. Because of the low content of trace elements, co-digestion with slurry is advantageous.

How to read the spread of results

The records describe different products (grain, maize flour, wheat flour, a mill product), so the spread results in part from different composition and degree of particle size reduction. Further factors are the cereal species, protein and fat content, moisture, spoilage and the test protocol: inoculum, substrate-to-inoculum ratio, duration and temperature (in one study it was not stated explicitly). For rapidly fermenting substrates the buffer in the inoculum is also important, because overload lowers the test result.

In biogas plant practice

Grain and flour from waste batches can be a convenient energy supplement, especially when biogas production needs to be raised quickly. They should be dosed gradually, with control of pH and volatile fatty acids, and the grain should be crushed before feeding. Flour requires dust control, including safety rules for organic dusts in loading rooms. When purchasing or accepting the waste, its classification and compliance with the installation's permit must be checked. The yield of a batch is confirmed by a BMP test.

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 = 0.257 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. 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
  2. Luna-delRisco, M.; Normak, A.; Orupõld, K. (2011). Biochemical methane potential of different organic wastes and energy crops from Estonia. Agronomy Research 9(1–2), 331–342. https://www.semanticscholar.org/paper/25cf2d7bba4758136830a9a02caf3ecd997173bb source
  3. Koch, K.; Hafner, S.; Astals, S.; Weinrich, S. (2020). Evaluation of Common Supermarket Products as Positive Controls in Biochemical Methane Potential (BMP) Tests. Water 12(5), 1223. DOI: 10.3390/w12051223 DOI

All sources of the site: bibliography.

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