About usContact

BMP testingWood and woody biomass

Hardwood — BMP: 8 studies, weighted mean 153 m³ CH₄/t VS

Hardwood (for example sweetgum, black locust, branches from green waste) has less lignin than softwood, but still degrades slowly without pretreatment.

rating: neutralCH₄ ≈ 52 % (estimate)

Published Updated 3 min readFeedstockData Editorial Team

Photo Anne LaBastille / Wikimedia Commons, public domain, source file; changes: cropping

Weighted mean
153m³ CH₄/t VS
Range
45–270m³ CH₄/t VS
Records
8studies
Publications
4sources
Temperatures
35 °C, 55 °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, but limited by the poor degradability of the organic matter (128 m³ CH₄/t); no particular threats to stability. Handling costs: fibres, floating layer, slow degradation.

Why? Rating factors

Potential per tonne +1

  • +1potential 128 m³ CH₄/t fresh matter (BMP 153 × DM 92.7 % × VS 89.8 %); low degradability of VS (BMP 153 m³ CH₄/t VS) — points capped

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

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

Add to the co-digestion calculator CSV data

BMP curves from 8 studies

Weighted mean Individual records

BMP curves: HardwoodCumulative methane production over time for 8 records and the weighted mean of 153 m³ CH₄/t VS. 8 of the curves are model curves (first-order kinetics).01002003000510152025303540time [d]m³ CH₄/t VSChynoweth et al. (1993) · 1: 210 m³ CH₄/t VS (model curve)Chynoweth et al. (1993) · 2: 240 m³ CH₄/t VS (model curve)Nallathambi Gunaseelan (1997): 134 m³ CH₄/t VS (model curve)Krause et al. (2018) · 1: 45 m³ CH₄/t VS (model curve)Krause et al. (2018) · 2: 49 m³ CH₄/t VS (model curve)Krause et al. (2018) · 3: 170 m³ CH₄/t VS (model curve)Krause et al. (2018) · 4: 270 m³ CH₄/t VS (model curve)Costa et al. (2019): 121 m³ CH₄/t VS (model curve)mean153

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 (153); 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
Chynoweth et al. (1993) · 1 DOI21035 °C · mesophilicSweetgumend point (model curve)
Chynoweth et al. (1993) · 2 DOI24035 °C · mesophilicBlack Locustend point (model curve)
Nallathambi Gunaseelan (1997) DOI13435 °C · mesophilicbranches (from municipal waste) (orig.: “Branches”): value quoted in a literature reviewend point (model curve)
Krause et al. (2018) · 1 DOI4535 °C · mesophilichardwoodend point (model curve)
Krause et al. (2018) · 2 DOI4955 °C · thermophilichardwoodend point (model curve)
Krause et al. (2018) · 3 DOI17055 °C · thermophilichardwoodend point (model curve)
Krause et al. (2018) · 4 DOI27035 °C · mesophilichardwoodend point (model curve)
Costa et al. (2019) DOI121—Birch (milled wood)end point (model curve)
Weighted mean153arithmetic mean 155, SD 83

Typical composition

Dry matter (DM)
92.7% (range 92.7–92.7)
Volatile solids (VS)
89.8 % DM (range 85.8–93.9)

Median and range of the determinations reported in the publications behind this substrate's BMP records (read from: MY-D); dry matter: 1 determination, volatile solids: 2 determinations. Samples were tested dried/air-dry – the DM refers to the material in the test, not to fresh material.

Sources: Nallathambi Gunaseelan (1997); Krause et al. (2018).

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
  • forms a floating layer
  • variable composition
  • editorial classification

Advantages

  • Methane potential in the database: weighted mean 153 m³ CH₄/t VS (median 152; range 45-270; 8 records from 4 sources).

Drawbacks and risks

  • Lignin limits conversion; mature wood degrades slowly (review by Hendriks 2009).
  • Spread of results in the database: standard deviation 83 at a mean of 155 m³ CH₄/t VS (8 records from 4 sources).

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

  • caution

    Softwood

    Mixing hardwood and softwood in one batch does not give a predictable BMP value: test the mixture.[1]

Dosing

No source dose limits; treat as a lignocellulosic additive in mixtures with excreta, after shredding. Carry out a BMP test for the specific batch.

Practical requirements

  • Control floating crust and sediment: when solids are fed directly into the digester, the risk of their formation depends on the substrate (FNR 2010, Ch. 3).
  • Shredding (the finer, the faster the degradation; the effect of particle size is studied by Krause 2018)

Sources of the process data

  1. Krause, M.J.; Chickering, G.W.; Townsend, T.G.; Pullammanappallil, P. (2018) Effects of temperature and particle size on the biochemical methane potential of municipal solid waste components. Waste Management 71, 25–30
  2. Chynoweth, D.; Turick, C.; Owens, J.; Jerger, D.; Peck, M. (1993) Biochemical methane potential of biomass and waste feedstocks. Biomass and Bioenergy 5(1), 95–111
  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. Nallathambi Gunaseelan, V. (1997) Anaerobic digestion of biomass for methane production: A review. Biomass and Bioenergy 13(1-2), 83–114
  5. Hendriks, A.T.W.M.; Zeeman, G. (2009) Pretreatments to enhance the digestibility of lignocellulosic biomass. Bioresource Technology
  6. Costa, T.H.F.; Eijsink, V.G.H.; Horn, S.J. (2019) The use of lytic polysaccharide monooxygenases in anaerobic digestion of lignocellulosic materials. Biotechnology for Biofuels 12(1), 270
  7. Weiland, P. (2010) Biogas production: current state and perspectives. Applied Microbiology and Biotechnology
  8. 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

Hardwood includes species such as beech, oak, birch, black locust, sweetgum and alder. It comes from forestry, the wood industry and green space maintenance. The dataset includes samples of specific species, branches from municipal waste and samples described as hardwood, tested under mesophilic and thermophilic conditions. Fast-growing poplars and willows have been separated into their own substrates, because in practice they occur as energy crops.

Properties relevant to digestion

The composition of hardwood is cellulose, hemicelluloses (with a larger share of xylan than in softwood) and lignin. The lignin contains syringyl units and is somewhat less compact than in softwood, which eases hydrolysis but does not remove the main limitation. Young shoots and branches with a large share of bark and soft tissues degrade better than old, woody timber. Extractives are usually less troublesome than conifer resins. There is little nitrogen, so the C/N ratio is high.

How to read the spread of results

The spread is large, because the group combines very different materials: mature wood, young branches, fast-growing species and green waste. The result is determined by the species, age and part of the tree (heartwood, sapwood, bark), size reduction (dust or wood chips), temperature and test length, and any pretreatment. The dataset also includes a value quoted in a literature review, which means that the conditions under which it was obtained are known in less detail than in primary studies.

In biogas plant practice

Hardwood can be treated as a structural material or a contaminant, and not as a main substrate. In agricultural installations its use is limited by low yield relative to the cost of size reduction. If use is being considered, fine milling and an extended retention time must be thought through. Pretreatment (steam, alkaline, mechanical) is being researched, but is not standard in biogas plants. Wood waste is usually more cost-effective as a solid fuel.

Ultimately, if the use of green waste with branches is being considered, it is more justified to remove the coarser woody fraction beforehand and send it for composting or combustion, and to send only leaves and young shoots for digestion.

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 = 0.039 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. Chynoweth, D.; Turick, C.; Owens, J.; Jerger, D.; Peck, M. (1993). Biochemical methane potential of biomass and waste feedstocks. Biomass and Bioenergy 5(1), 95–111. DOI: 10.1016/0961-9534(93)90010-2 DOI
  2. Nallathambi Gunaseelan, V. (1997). Anaerobic digestion of biomass for methane production: A review. Biomass and Bioenergy 13(1-2), 83–114. DOI: 10.1016/s0961-9534(97)00020-2 DOI
  3. Krause, M.J.; Chickering, G.W.; Townsend, T.G.; Pullammanappallil, P. (2018). Effects of temperature and particle size on the biochemical methane potential of municipal solid waste components. Waste Management 71, 25–30. DOI: 10.1016/j.wasman.2017.11.015 DOI
  4. Costa, T.H.F.; Eijsink, V.G.H.; Horn, S.J. (2019). The use of lytic polysaccharide monooxygenases in anaerobic digestion of lignocellulosic materials. Biotechnology for Biofuels 12(1), 270. DOI: 10.1186/s13068-019-1611-8 DOI

All sources of the site: bibliography.

Other substrates in the group “Wood and woody biomass”