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BMP testingEnergy crops and whole-crop plants (WCS)single study (2 samples)

Hops, whole plant — BMP: 2 studies, weighted mean 161 m³ CH₄/t VS

Hop as a whole plant is the biomass remaining after cone harvest or considered as an energy crop. In the compilation it appears in fresh form and as silage from a single study.

rating: neutralCH₄ ≈ 52 % (estimate)

Published Updated 3 min readFeedstockData Editorial Team

Photo Hejnjahns / Wikimedia Commons, licence CC BY-SA 4.0, source file; changes: cropping

Weighted mean
161m³ CH₄/t VS
Range
141–181m³ CH₄/t VS
Records
2single study (2 samples)
Publications
1source
Temperatures
37 °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

neutral — editorial rating for biogas plantsNo clear advantages — worth charging a fee for accepting it

Potential per tonne of fresh matter: moderate (43 m³ CH₄/t); no particular threats to stability. Handling costs: fibres, floating layer.

Why? Rating factors

Potential per tonne +1

  • +1potential 43 m³ CH₄/t fresh matter (BMP 161 × DM 30.5 % × VS 87.9 %)

Process stability 0

  • 0no factors

Handling and costs −0.5

  • −0.5fibres, floating layer — shredding and intensive mixing

Total points: 0.5 · thresholds: ≥ 2.5 very good, ≥ 1 good, below — neutral; negative with cumulative process risk.

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

Add to the co-digestion calculator CSV data

BMP curves from 2 studies

Weighted mean Individual records

BMP curves: Hops, whole plantCumulative methane production over time for 2 records and the weighted mean of 161 m³ CH₄/t VS. 2 of the curves are model curves (first-order kinetics).0501001502000510152025303540time [d]m³ CH₄/t VSKaiser (2007) · 1: 141 m³ CH₄/t VS (model curve)Kaiser (2007) · 2: 181 m³ CH₄/t VS (model curve)mean161

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 (161); 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
Kaiser (2007) · 114137 °C · mesophilicHumulus freshend point (model curve)
Kaiser (2007) · 218137 °C · mesophilicHumulus silageend point (model curve)
Weighted mean161arithmetic mean 161, SD 28

Typical composition

Dry matter (DM)
30.5% (range 29.9–31.1)
Volatile solids (VS)
87.9 % DM (range 86–89.9)

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

Sources: Kaiser (2007).

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

Low confidence: the description is based on general characteristics of the substrate group, not on studies of this material. Treat it as a hint to be verified.

No published process studies

The literature we use does not describe the advantages or drawbacks of digesting this substrate beyond the BMP test results. Below are process characteristics assigned on the basis of the type of material — an editorial classification, not a study result.

seasonal
seasonal availability — requires storage
fibrous
lignocellulose, long fibres → floating layer, harder mixing, slow degradation

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

Dosing

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

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

  1. Kaiser, F.L. (2007) Einfluss der stofflichen Zusammensetzung auf die Verdaulichkeit nachwachsender Rohstoffe beim anaeroben Abbau in Biogasreaktoren. Dissertation, Technische Universität München, Wissenschaftszentrum Weihenstephan
  2. Weiland, P. (2010) Biogas production: current state and perspectives. Applied Microbiology and Biotechnology
  3. Hendriks, A.T.W.M.; Zeeman, G. (2009) Pretreatments to enhance the digestibility of lignocellulosic biomass. Bioresource Technology
  4. 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

Common hop (Humulus lupulus) is a perennial plant grown on special structures in order to harvest cones, used in brewing. After the cones are harvested, bines and leaves remain, which are collected and managed, and in Poland there are regions specialising in hop growing. In biogas research, hop has been considered as a whole plant. The compilation contains several records from a single study: hop as fresh mass and as silage.

Properties relevant to digestion

Hop is a plant with a large green mass, with fibrous bines and leaves. It also contains secondary compounds, including resins and essential oils, which at high concentrations have antimicrobial activity, but their real effect on digestion at typical plant shares in the mix is the subject of research and should not be prejudged. The material is moist and requires size reduction and ensiling or prompt use. The bines may contain residues of the twine and wires used in cultivation, which must be removed.

How to read the spread of results

Records from a single study compare fresh mass with silage, so their difference shows the effect of ensiling, not the uncertainty of the method. The actual variability depends on the hop variety, the harvest date, the share of leaves and bines, contamination with twine and the method of size reduction. There are also test parameters, such as the inoculum and the substrate-to-inoculum ratio. A single publication does not reflect the full variability that will be encountered in practice.

In biogas plant practice

Hop residues are a seasonal and local material, available once after cone harvest. In hop-growing regions they can supplement the mix if harvesting and transport can be organised. It is necessary to remove structural elements (twine, wires), size-reduce and ensile or use promptly. The share in the ration should be moderate, and the behaviour of the digester should be observed after introduction. Before regular use, your own BMP test must be carried out. If a region has large hop plantations, organising a joint collection from several producers can improve profitability. However, it is important to establish who is responsible for cleaning the material of wires and twine, because it is these that most often cause failures in the feeding system.

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.

Full methodology and correction policy

Bibliography

  1. Kaiser, F.L. (2007). Einfluss der stofflichen Zusammensetzung auf die Verdaulichkeit nachwachsender Rohstoffe beim anaeroben Abbau in Biogasreaktoren. Dissertation, Technische Universität München, Wissenschaftszentrum Weihenstephan. https://mediatum.ub.tum.de/631394 source

All sources of the site: bibliography.

Other substrates in the group “Energy crops and whole-crop plants (WCS)”