BMP testingEnergy crops and whole-crop plants (WCS)
Barley, whole crop — BMP: 6 studies, weighted mean 419 m³ CH₄/t VS
Barley as a whole plant (GPS) is green forage harvested before full grain maturity. The compilation covers several development stages from different studies and conditions.
Photo Sandy Gerrard / Wikimedia Commons, licence CC BY-SA 2.0, source file; changes: cropping
- Weighted mean
- 419m³ CH₄/t VS
- Range
- 353–658m³ CH₄/t VS
- Records
- 6studies
- Publications
- 2sources
- Temperatures
- 35 °C, 40 °Cof the test
Methane in biogas
High methane content · ≈ 6.1 kWh/m³ of biogas
measured mean of 6 studies BMP, range 57–68 %; in a batch test the CH₄ share tends to be higher than in a plant.
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 (103 m³ CH₄/t); no particular threats to stability. Handling costs: fibres, floating layer.
Why? Rating factors
Potential per tonne +3
- +3potential 103 m³ CH₄/t fresh matter (BMP 419 × DM 26.4 % × VS 93.4 %)
Process stability 0
- 0no factors
Handling and costs −0.5
- −0.5fibres, floating layer — shredding and intensive mixing
Total points: 2.5 · 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 6 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 (419); 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| Source | BMP m³ CH₄/t VS | CH₄ in biogas % vol., measured | Temperature | Sample | Curve |
|---|---|---|---|---|---|
| Pouech (b.r.) | 356 | 58.7 % | 40 °C · mesophilic | Barley | end point (model curve) |
| Heiermann (2002) · 1 | 353 | 57.0 % | 35 °C · mesophilic | Barley | end point (model curve) |
| Heiermann (2002) · 2 | 438 | 65.0 % | 35 °C · mesophilic | Barley | end point (model curve) |
| Heiermann (2002) · 3 | 462 | 64.0 % | 35 °C · mesophilic | Barley · pretreatment: Silage in 1L glass vessels packed and sealed for 3 month period | end point (model curve) |
| Heiermann (2002) · 4 | 503 | 63.0 % | 35 °C · mesophilic | Barley | end point (model curve) |
| Heiermann (2002) · 5 | 658 | 68.0 % | 35 °C · mesophilic | Barley · pretreatment: Silage in 1L glass vessels packed and sealed for 3 month period | end point (model curve) |
| Weighted mean | 419 | 61.1 % | arithmetic mean 462, SD 113 | ||
Typical composition
- Dry matter (DM)
- 26.4% (range 18.8–46.5)
- Volatile solids (VS)
- 93.4 % DM (range 90.2–94.7)
- Nitrogen
- 2.7 % DM
Median and range of the determinations reported in the publications behind this substrate's BMP records (read from: CROPGEN D4); dry matter: 6 determinations, volatile solids: 5 determinations.
Sources: Pouech, P. Fruteau, H. Bewa, H.. Agricultural crops for…; Heiermann (2002).
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 419 m³ CH₄/t VS (median 450; range 353-658; 6 records from 2 sources).
Drawbacks and risks
- Spread of results in the database: standard deviation 113 at a mean of 462 m³ CH₄/t VS (6 records from 2 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 dose limits; whole-crop cereal silage is used as an element of crop rotation alongside maize.
Practical requirements
- 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
- Heiermann, M. Plöchl, M. Linke, B. Schelle, H. (2002) Preliminary evaluation of some cereals as energy crops for biogas production. World Renewable Energy Congress VII
- Weiland, P. (2010) Biogas production: current state and perspectives. Applied Microbiology and Biotechnology
- Pouech, P. Fruteau, H. Bewa, H. (None) Agricultural crops for biogas production on anaerobic digestion plants. Biomass for energy and industry 163-165
- Hendriks, A.T.W.M.; Zeeman, G. (2009) Pretreatments to enhance the digestibility of lignocellulosic biomass. Bioresource Technology
- Herrmann, C. et al. (2011) Effects of ensiling, silage additives and storage period on methane formation of biogas crops. Bioresource Technology
The co-digestion calculator will assess a specific mixture containing this substrate.
What it is and where it comes from
The abbreviation GPS stands for the whole plant harvested for silage (whole crop silage). Barley harvested in this form is not an ordinary grain harvest, but the cutting and ensiling of stems, leaves and immature ears. Earlier harvest than in the case of maize makes it possible to use the field for a catch crop or the next crop. The compilation contains records for the whole barley plant at different development stages: from flowering to milk and wax ripeness, from studies conducted under mesophilic conditions.
Properties relevant to digestion
As the plant matures, the share of starch in the grain rises, and at the same time the fibre content in the straw rises. As a result, the composition of the silage changes depending on the stage: a younger plant has more protein and readily available compounds, an older one more starch and woody structures. Ensiling cereals is usually easy, provided that the dry matter content lies within the right range. Material that is too mature is dry and more difficult to compact, and unground grains may partly pass through the system. Barley has a lower C/N ratio than straw, so it combines more easily with other substrates.
How to read the spread of results
The spread results primarily from the development stage at harvest, which in the records covers flowering, milk and wax ripeness. In addition, the variety (spring, winter), fertilisation, the year, the form of the material and the degree of size reduction have an effect. Some of the records come from a single series of studies, so they are not independent. There are also test parameters: inoculum, the substrate-to-inoculum ratio and test length. The result for one stage therefore does not describe the whole category.
In biogas plant practice
Barley GPS works well as a supplementary substrate, particularly where maize is less productive. Harvest at milk or wax ripeness gives a compromise between yield and digestibility. The material requires size reduction, compaction and a tight cover. Yield and profitability depend on local conditions, so before planning crops they should be compared with maize and other options. A BMP test with the harvest stage specified makes it possible to choose the dose. When comparing barley with other cereals for GPS, such as wheat, rye and triticale, cultivation requirements and harvest dates must be taken into account, because differences between species often result from the stage of maturity at the time of cutting, and not from the species itself.
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.
Bibliography
- Pouech, P. Fruteau, H. Bewa, H.. Agricultural crops for biogas production on anaerobic digestion plants. Biomass for energy and industry 163-165.
- Heiermann, M. Plöchl, M. Linke, B. Schelle, H. (2002). Preliminary evaluation of some cereals as energy crops for biogas production. World Renewable Energy Congress VII.
All sources of the site: bibliography.
Other substrates in the group “Energy crops and whole-crop plants (WCS)”
Jerusalem artichoke biomass — BMP: 11 studies, weighted mean 384 m³ CH₄/t VS
384 m³ CH₄/t VS weighted mean from 11 studies
good — editorial rating for biogas plants65 %
Maize silage (whole crop) — BMP: 82 studies, weighted mean 341 m³ CH₄/t VS
341 m³ CH₄/t VS weighted mean from 82 studies
very good — editorial rating for biogas plants59 %
Hops, whole plant — BMP: 2 studies, weighted mean 161 m³ CH₄/t VS
161 m³ CH₄/t VS weighted mean from 2 studies
neutral — editorial rating for biogas plants≈52 %
Rapeseed, green biomass — BMP: 4 studies, weighted mean 367 m³ CH₄/t VS
367 m³ CH₄/t VS weighted mean from 4 studies
good — editorial rating for biogas plants66 %