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BMP testingFruit, vegetables and their residues

Potatoes (tubers) — BMP: 5 studies, weighted mean 376 m³ CH₄/t VS

Potatoes (tubers) are a starchy agricultural and processing waste, easily fermentable and prone to acidification; results from several sources are fairly consistent.

CH₄ ≈ 53 % (estimate)

Published Updated 3 min readFeedstockData Editorial Team

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

Weighted mean
376m³ CH₄/t VS
Range
289–515m³ CH₄/t VS
Records
5studies
Publications
5sources
Temperatures
35 °C, 38 °C, 55 °Cof the test

Methane in biogas

Medium methane content · ≈ 5.3 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 1.6 % 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

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 5 studies

Weighted mean Individual records

BMP curves: Potatoes (tubers)Cumulative methane production over time for 5 records and the weighted mean of 376 m³ CH₄/t VS. 5 of the curves are model curves (first-order kinetics).0200400600051015202530time [d]m³ CH₄/t VSYan et al. (2021): 315 m³ CH₄/t VS (model curve)Buffiere et al. (2006): 427 m³ CH₄/t VS (model curve)Dubrovskis et al. (2018): 515 m³ CH₄/t VS (model curve)Kouas et al. (2017): 289 m³ CH₄/t VS (model curve)Labatut et al. (2011): 334 m³ CH₄/t VS (model curve)mean376

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 (376); 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
Yan et al. (2021) DOI315—Potato (Solanum tuberosum) – Wholeend point (model curve)
Buffiere et al. (2006) DOI42755 °C · thermophilicPotatoend point (model curve)
Dubrovskis et al. (2018) DOI51538 °C · mesophilicPotatoes Vineta wasteend point (model curve)
Kouas et al. (2017) DOI28935 °C · mesophilicpotatoend point (model curve)
Labatut et al. (2011) DOI33435 °C · mesophilicPotatoesend point (model curve)
Weighted mean376arithmetic mean 376, SD 93

Typical composition

Volatile solids (VS)
93.3 % DM (range 92–94.7)
Nitrogen
1.6 % DM
C/N ratio
26

Median and range of the determinations reported in the publications behind this substrate's BMP records (read from: BCBPD, MY-D); dry matter: 0 determinations, volatile solids: 2 determinations. C/N was calculated as the ratio of C and N content (% DM) from the same source. No DM in the sources – the calculator has to ask for a value.

Sources: Yan et al. (2021); Labatut et al. (2011).

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.

easily degradable
sugars, starch, glycerol → fast hydrolysis and acidification (VFA), needs buffering
carbon-rich
high C/N → nitrogen deficiency; combine well with nitrogen-rich substrates
low in nitrogen
high C/N → nitrogen deficiency; combine well with nitrogen-rich substrates
poor in trace elements
poor in trace elements — mono-digestion requires supplementation
seasonal
seasonal availability — requires storage

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

Dosing

No source limits on the dose for this substrate.

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

Sources of the process data

  1. Improvement of fruit and vegetable waste anaerobic digestion performance and stability with co-substrates addition
  2. Biochemical methane potential and biodegradability of complex organic substrates
  3. Compositional components and methane production potential of typical vegetable wastes
  4. Towards new indicators for the prediction of solid waste anaerobic digestion properties
  5. Methane production from bread Kursu and potatoes Vineta waste and effect of catalyst metaferm
  6. Robust assessment of both biochemical methane potential and degradation kinetics of solid residues in successive batches
  7. Lab-scale anaerobic digestion of cassava peels: the first step of energy recovery from cassava waste and water hyacinth
  8. Effects of size and thermophilic pre-hydrolysis of banana peel during anaerobic digestion, and biomethanation potential of key tropical fruit wastes
  9. Effect of particle size on biogas generation from biomass residues

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

What it is and where it comes from

The potato (Solanum tuberosum) is one of the main root crops in Poland. Waste tubers come from sorting plants (green, cracked, too small tubers), storage facilities (diseased and rotten ones), processing (chips, crisps, starch) and from fields after harvest. They are also considered as a raw material for agricultural biogas plants when there is surplus production. Peelings and pulp from processing are treated separately.

Properties relevant to digestion

Tubers contain about eighty per cent water, and the dry matter is mainly starch. The content of protein, fat and fibre is low, and there is practically no lignin. As a result hydrolysis proceeds quickly and supplies a lot of readily available carbon, but there is a risk of acidification of the digester if the dose is too high or too abrupt. The C/N ratio is high, so combining with nitrogen-rich material is advantageous. Green and sprouting tubers contain glycoalkaloids (solanine and chaconine), but their effect on digestion at typical shares is not considered significant. Soil adhering to the tubers brings in sand.

How to read the spread of results

The set contains several records from several sources, including thermophilic tests and tests with no temperature stated, the others being mesophilic. The spread is moderate. The result depends on the variety and starch content, the condition of the tubers (healthy, diseased, sprouting), particle size, the method of sample preparation, and the inoculum and loading. With starchy materials, a short test or too high a load can understate the result through acidification.

In biogas plant practice

Potatoes must be shredded and washed, or the sand screened out, because a whole tuber can clog feeding systems. Dosing should be gradual, in a mixture with slurry or silage. Spoiled tubers ferment quickly in clamps, give off odours and juices, so they should not be left for long. Waste from processing and trade is waste, so its acceptance requires appropriate permits; tubers from one's own farm are treated as an agricultural product. In mixtures with a large share of starch, continuous control of volatile acids is important.

In agricultural biogas plants, potato tubers are sometimes treated as an emergency substrate in the event of surplus or after frosts, when a batch loses its commercial value. Its quality is then very variable, and it is safer to measure the dry matter of each delivery and adjust the dose to the current state of the digester.

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 = 0.245 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. Yan, H.; Cai, F.; Wang, L.; Chen, C.; Liu, G. (2021). Compositional components and methane production potential of typical vegetable wastes. Environmental Science and Pollution Research 28(38), 54177–54186. DOI: 10.1007/s11356-021-15798-y DOI
  2. Buffiere, P.; Loisel, D.; Bernet, N.; Delgenes, J.P. (2006). Towards new indicators for the prediction of solid waste anaerobic digestion properties. Water Science and Technology 53(8), 233–241. DOI: 10.2166/wst.2006.254 DOI
  3. Dubrovskis, V.; Plume, I.; Straume, I. (2018). Methane production from bread Kursu and potatoes Vineta waste and effect of catalyst metaferm. Engineering for Rural Development. DOI: 10.22616/erdev2018.17.n414 DOI
  4. Kouas, M.; Torrijos, M.; Sousbie, P.; Steyer, J.P.; Sayadi, S.; Harmand, J. (2017). Robust assessment of both biochemical methane potential and degradation kinetics of solid residues in successive batches. Waste Management 70, 59–70. DOI: 10.1016/j.wasman.2017.09.001 DOI
  5. Labatut, R.A.; Angenent, L.T.; Scott, N.R. (2011). Biochemical methane potential and biodegradability of complex organic substrates. Bioresource Technology 102(3), 2255–2264. DOI: 10.1016/j.biortech.2010.10.035 DOI

All sources of the site: bibliography.

Other substrates in the group “Fruit, vegetables and their residues”