BMP testingStraws and crop residues

Rice straw — BMP: 12 studies, weighted mean 262 m³ CH₄/t VS

Rice straw is an enormous waste stream in Asia, rich in silica and lignocellulose. Practically absent in Poland, it is important as a reference point in research on straws.

rating: good CH₄ ≈ 52 % (estimate)

Published 12 May 2026Updated 29 October 20263 min readFeedstockData Editorial Team

Photo 池田正樹 (talk) masaki ikeda / Wikimedia Commons, public domain, source file; changes: cropping

Weighted mean: 262m³ CH₄/t VS
Range: 167–367m³ CH₄/t VS
Records: 12studies
Publications: 7sources
Temperatures: 35 °C, 37 °C, 40 °Cof the test

Methane in biogas

≈51–53% 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 (protein from total nitrogen (N 0.9 % 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

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

Potential per tonne of fresh matter: very high (205 m³ CH₄/t); no particular threats to stability. Handling costs: fibres, floating layer, slow degradation.

Why? Rating factors

Potential per tonne +3

+3potential 205 m³ CH₄/t fresh matter (BMP 262 × DM 88.7 % × VS 88.2 %)

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: high · excluding market prices

Add to the co-digestion calculator CSV data

BMP curves from 12 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 (262); 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

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Source	BMP m³ CH₄/t VS	Temperature	Sample	Curve
Saha et al. (2025) DOI	167	35 °C · mesophilic	rice straw (RS), 100%	end point (model curve)
Chanakya i Malayil (2012)	300	35 °C · mesophilic	(orig.: “rice straw”): value quoted in a literature review	end point (model curve)
Sharma et al. (1988) · 1 DOI	241	37 °C · mesophilic	Rice · pretreatment: Material were first dried in the sun and then in an oven at 90oC	end point (model curve)
Sharma et al. (1988) · 2 DOI	347	37 °C · mesophilic	Rice · pretreatment: Material were first dried in the sun and then in an oven at 90oC	end point (model curve)
Sharma et al. (1988) · 3 DOI	358	37 °C · mesophilic	Rice · pretreatment: Material were first dried in the sun and then in an oven at 90oC	end point (model curve)
Sharma et al. (1988) · 4 DOI	365	37 °C · mesophilic	Rice · pretreatment: Material were first dried in the sun and then in an oven at 90oC	end point (model curve)
Sharma et al. (1988) · 5 DOI	367	37 °C · mesophilic	Rice · pretreatment: Material were first dried in the sun and then in an oven at 90oC	end point (model curve)
Dinuccio et al. (2010) DOI	195	40 °C · mesophilic	Rice straw · pretreatment: particle size reduction/sample preparation (MY-D: physical treatment)	end point (model curve)
Li et al. (2013) DOI	281	37 °C · mesophilic	Rice Straw	end point (model curve)
López-Dávila et al. (2022) DOI	358	—	Rice straw	end point (model curve)
Menardo et al. (2012) · 1 DOI	197	40 °C · mesophilic	Rice Straw	end point (model curve)
Menardo et al. (2012) · 2 DOI	203	40 °C · mesophilic	Rice Straw · pretreatment: particle size reduction/sample preparation (MY-D: physical treatment)	end point (model curve)
Weighted mean	262	arithmetic mean 282, SD 78

Typical composition

Dry matter (DM): 88.7% (range 28.7–92.9)
Volatile solids (VS): 88.2 % DM (range 79.4–91.9)
Nitrogen: 0.9 % DM
C/N ratio: 73.5

Median and range of the determinations reported in the publications behind this substrate's BMP records (read from: CROPGEN D4, MY-D); dry matter: 3 determinations, volatile solids: 4 determinations. 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: Sharma et al. (1988); Dinuccio et al. (2010); Li et al. (2013); Menardo et al. (2012).

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 262 m³ CH₄/t VS (median 290; range 167–367; 12 records from 7 sources).
Co-digestion with cattle and poultry faeces improves results (Saha 2025).

Drawbacks and risks

Spread of results in the database: standard deviation 78 at a mean of 282 m³ CH₄/t VS (12 records from 7 sources).

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

combines well
group: Animal excreta (slurry, manure, poultry litter)
Cattle faeces and poultry excrement supply N and buffer (Saha 2025).^[1]

Dosing

The sources do not give a share limit; Saha 2025 studied co-digestion with cattle manure and poultry excrement in various proportions (values in the paper).

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

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

What it is and where it comes from

Rice straw is the residue left after the harvest of rice (Oryza sativa), one of the most important crops in the world. In Asian countries it arises in enormous quantities, and its management is a problem, because burning in the field pollutes the air. Methane fermentation is one of the alternatives being studied. In Poland rice straw does not occur as a local waste, but papers about it form an important element of the literature on biogas from straws.

Properties relevant to digestion

A characteristic feature of rice straw is its high silica content, which increases the ash content and the abrasiveness for equipment and hinders microorganisms' access to polysaccharides. Apart from this, the straw consists of cellulose, hemicelluloses and lignin, and has a high C/N ratio and low protein content. The material is bulky, and without chopping it floats and forms scum. For this reason its pretreatment is often described in the literature, although the records in this dataset concern material without such treatment. The content of plant protection product residues depends on the growing region.

How to read the spread of results

The dataset contains records from different decades, from papers of the 1980s to studies from 2025, and a value quoted in a literature review, marked as secondary data. In one of the studies, fractions of different chopping were examined, which gives a series of records from the same source. The differences arise from rice variety, region, maturity at harvest, chopping, inoculum parameters, S/I ratio and temperature. The spread is therefore not only a characteristic of the material, but also the result of different methodology from many eras.

In biogas plant practice

For Polish plants, rice straw is not a practical substrate; its description is of comparative significance. In rice-growing countries, dry or wet fermentation with co-digestion of animal excreta is studied. The most important issues are chopping, nitrogen supplementation, scum control and periodic removal of mineral sediments from the bottom of the chamber. Harvesting and transporting a bulky material is costly, so profitability depends on the distance of the plant from the fields. Should interest in such a material arise in Polish conditions, for example through imports or in research, separate analyses of residues, ash and silica content, and your own BMP tests will be needed. Data from the literature show the order of magnitude well, but do not replace measurement.

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 (2) — excluded from the mean

Source	BMP m³ CH₄/t VS	Pretreatment	Sample
Menardo et al. (2012)	207	unspecified	Rice Straw
Menardo et al. (2012)	261	unspecified	Rice Straw

Bibliography

All sources of the site: bibliography.