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BMP testingStraws and crop residues

Oat straw — BMP: 2 studies, weighted mean 275 m³ CH₄/t VS

Oat straw is a lignocellulosic post-harvest waste with a high C/N ratio, available in small quantities. The dataset rests on a small number of records, so the result is indicative.

CH₄ ≈ 52 % (estimate)

Published Updated 3 min readFeedstockData Editorial Team

Illustration: FeedstockData (AI, Google Gemini)

Weighted mean
275m³ CH₄/t VS
Range
230–320m³ CH₄/t VS
Records
2studies
Publications
2sources
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

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 2 studies

Weighted mean Individual records

BMP curves: Oat strawCumulative methane production over time for 2 records and the weighted mean of 275 m³ CH₄/t VS. 2 of the curves are model curves (first-order kinetics).0100200300400051015202530time [d]m³ CH₄/t VSLehtomaki (2006): 320 m³ CH₄/t VS (model curve)Lehtomaki (2004): 230 m³ CH₄/t VS (model curve)mean275

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 (275); 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
Lehtomaki (2006)32035 °C · mesophilicStraw of oatsend point (model curve)
Lehtomaki (2004)23035 °C · mesophilicStraw of Oatsend point (model curve)
Weighted mean275arithmetic mean 275, SD 64

Typical composition

Dry matter (DM)
76.5% (range 63.4–89.6)
Nitrogen
0.7 % DM
C/N ratio
95

Median and range of the determinations reported in the publications behind this substrate's BMP records (read from: CROPGEN D4); dry matter: 2 determinations, volatile solids: 0 determinations.

Sources: Lehtomaki (2006); Lehtomaki (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

  • fibrous
  • slowly degrading
  • carbon-rich
  • low in nitrogen
  • seasonal
  • forms a floating layer
  • editorial classification

Advantages

  • Methane potential in the database: weighted mean 275 m³ CH₄/t VS (median 275; range 230–320; 2 records from 2 sources).

Drawbacks and risks

  • Lignin limits degradation; floating crust (review by Hendriks 2009).

Dosing

No source-based dose limits; like other cereal straws.

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. Lehtomaki, A. Viinikainen, T.A. Rintala, J.A (2006) Screening boreal energy crops and crop residues for methane biofuel production. Submitted to Biomass and Bioenergy
  2. Lehtomaki, A. Viinikainen, T.A. Ronkainen, O.M. Alen, R. Rintala, J.A. (2004) Effect of pretreatments on methane production potential of energy crops and crop residues. Proceedings Anaerobic Digestion Conference 1016-1021
  3. Dahunsi, S. (2019) Mechanical pretreatment of lignocelluloses for enhanced biogas production: Methane yield prediction from biomass structural components. Bioresource Technology 280, 18–26
  4. Hendriks, A.T.W.M.; Zeeman, G. (2009) Pretreatments to enhance the digestibility of lignocellulosic biomass. Bioresource Technology
  5. Weiland, P. (2010) Biogas production: current state and perspectives. Applied Microbiology and Biotechnology
  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

Oat straw is the residue left after the threshing of common oats (Avena sativa). Oats are grown in Poland on a smaller scale than wheat or rye, so there is less straw too. It is valued as bedding and roughage, which limits its availability to biogas plants. The dataset rests on a small number of records from several publications, carried out under mesophilic conditions.

Properties relevant to digestion

Like other straws, oat straw consists mainly of cellulose, hemicelluloses and lignin, with a low protein content and a high C to N ratio. Biological degradation is slow, particularly in the initial hydrolysis phase. The material is easy to store dry, but prone to dampening and mould. In the digester it tends to form scum, so it requires chopping and effective mixing. The influence of variety and growing conditions on digestibility is significant, but cannot be assessed from so small a number of records.

How to read the spread of results

The dataset contains few records, so the spread does not capture the full variability of the material. The result is affected by oat variety, the year and conditions of the growing season, harvest date and straw moisture, the way the sample was prepared (cutting, milling, drying) and the test parameters: inoculum, substrate-to-inoculum ratio and incubation time. With slowly degradable straws the length of the test is often key, and results from different studies are not always comparable.

In biogas plant practice

At agricultural plants, oat straw can be an occasional component of the mix when the farm has a surplus of it. Its share in the ration should be moderate because of scum and the need for mixing. Before use it should be chopped, and storage ensured in dry conditions. Because of competing uses, such as bedding, the economic balance often favours other destinations. Yield data should be supplemented with a test of your own batch. If there are doubts about the quality of a batch, for example dampness or mould, it is better not to use it, because biologically spoiled material lowers process stability and is sometimes a source of foaming problems. A simple visual inspection and moisture measurement at each delivery help.

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 = 0.136 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

Results after pretreatment (24) — excluded from the mean
SourceBMP
m³ CH₄/t VS		PretreatmentSample
Lehtomaki (2004)150—Straw of Oats
Lehtomaki (2004)190—Straw of Oats
Lehtomaki (2004)150—Straw of Oats
Lehtomaki (2004)70—Straw of Oats
Lehtomaki (2004)200—Straw of Oats
Lehtomaki (2004)200—Straw of Oats
Lehtomaki (2004)210—Straw of Oats
Lehtomaki (2004)140—Straw of Oats
Lehtomaki (2004)90—Straw of Oats
Lehtomaki (2004)140—Straw of Oats
Lehtomaki (2004)190—Straw of Oats
Lehtomaki (2004)110—Straw of Oats
Lehtomaki (2004)220—Straw of Oats
Lehtomaki (2004)170—Straw of Oats
Lehtomaki (2004)160—Straw of Oats
Lehtomaki (2004)160—Straw of Oats
Lehtomaki (2004)120—Straw of Oats
Lehtomaki (2004)180—Straw of Oats
Lehtomaki (2004)160—Straw of Oats
Lehtomaki (2004)160—Straw of Oats
Lehtomaki (2004)200—Straw of Oats
Lehtomaki (2004)240—Straw of Oats
Lehtomaki (2004)210—Straw of Oats
Lehtomaki (2004)210—Straw of Oats

Bibliography

  1. Lehtomaki, A. Viinikainen, T.A. Rintala, J.A (2006). Screening boreal energy crops and crop residues for methane biofuel production. Submitted to Biomass and Bioenergy.
  2. Lehtomaki, A. Viinikainen, T.A. Ronkainen, O.M. Alen, R. Rintala, J.A. (2004). Effect of pretreatments on methane production potential of energy crops and crop residues. Proceedings Anaerobic Digestion Conference 1016-1021.

All sources of the site: bibliography.

Other substrates in the group “Straws and crop residues”