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BMP testingFruit, vegetables and their residues

Taro (corms) — BMP: 5 studies, weighted mean 342 m³ CH₄/t VS

Taro (cocoyam) tubers are a starchy material with a lot of water, readily fermentable; results for the varieties studied are very similar and stable.

rating: goodCH₄ ≈ 52 % (estimate)

Published Updated 3 min readFeedstockData Editorial Team

Photo Yongxinge / Wikimedia Commons, licence CC BY-SA 3.0, source file; changes: cropping

Weighted mean
342m³ CH₄/t VS
Range
314–355m³ CH₄/t VS
Records
5studies
Publications
2sources
Temperatures
35 °C, 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 (protein from total nitrogen (N 1 % 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: high (71 m³ CH₄/t); process risk: acidification. No additional handling requirements.

Why? Rating factors

Potential per tonne +2

  • +2potential 71 m³ CH₄/t fresh matter (BMP 342 × DM 21.1 % × VS 98 %)

Process stability −0.5

  • −0.5acidification: rapid degradation / acidic pH, risk of VFA accumulation, needs buffering

Handling and costs 0

  • 0no factors

Total points: 1.5 · 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 5 studies

Weighted mean Individual records

BMP curves: Taro (corms)Cumulative methane production over time for 5 records and the weighted mean of 342 m³ CH₄/t VS. 5 of the curves are model curves (first-order kinetics).01002003004000510152025303540time [d]m³ CH₄/t VSChynoweth et al. (1993) · 1: 314 m³ CH₄/t VS (model curve)Chynoweth et al. (1993) · 2: 321 m³ CH₄/t VS (model curve)Chynoweth et al. (1993) · 3: 344 m³ CH₄/t VS (model curve)Chynoweth et al. (1993) · 4: 355 m³ CH₄/t VS (model curve)Ge et al. (2014): 350 m³ CH₄/t VS (model curve)mean342

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 (342); 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 DOI31435 °C · mesophilicBun-long taroend point (model curve)
Chynoweth et al. (1993) · 2 DOI32135 °C · mesophilicChin-Sen taroend point (model curve)
Chynoweth et al. (1993) · 3 DOI34435 °C · mesophilicChin-Sen taroend point (model curve)
Chynoweth et al. (1993) · 4 DOI35535 °C · mesophilicBun-long taroend point (model curve)
Ge et al. (2014) DOI35037 °C · mesophilicTaro fleshend point (model curve)
Weighted mean342arithmetic mean 337, SD 18

Typical composition

Dry matter (DM)
21.1% (range 21.1–21.1)
Volatile solids (VS)
98 % DM (range 98–98)
Nitrogen
1 % DM
C/N ratio
47.9

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: 1 determination. C/N was calculated as the ratio of C and N content (% DM) from the same source. DM from a single determination – indicative value.

Sources: Ge et al. (2014).

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. Biochemical methane potential of biomass and waste feedstocks
  4. Biogas energy production from tropical biomass wastes by anaerobic digestion
  5. Lab-scale anaerobic digestion of cassava peels: the first step of energy recovery from cassava waste and water hyacinth
  6. Effects of size and thermophilic pre-hydrolysis of banana peel during anaerobic digestion, and biomethanation potential of key tropical fruit wastes
  7. 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

Taro (Colocasia esculenta) is a tropical tuber crop grown in Asia, Oceania and Africa as a staple source of starch. The tubers are peeled, cooked and processed into flour, chips or pastes. The waste is tubers that do not meet commercial standards, damaged or surplus, and also peelings. In Poland taro is a rarely encountered plant, so the data concern mainly production regions, and the usefulness is comparative for other starchy materials, such as potatoes or cassava.

Properties relevant to digestion

The tubers contain a lot of water, and in the dry matter starch predominates, with a small share of protein, fat and fibre. There is little lignin. Taro starch has small granules, which eases enzymatic hydrolysis, and degradation proceeds quickly. The consequence is a risk of accumulation of fatty acids and a drop in pH if the dose is too high relative to the buffering capacity of the feed. Taro contains calcium oxalate crystals, which cause irritation on raw contact, but in the digester they are not a known barrier to methanogenesis. The high C/N ratio encourages mixing with slurry or sludge.

How to read the spread of results

The dataset contains several records from several sources, concerning the varieties Bun-long and Chin-Sen, all under mesophilic conditions. The spread is small, which fits a homogeneous, starchy material. Nevertheless, differences may arise from the maturity of the tubers, variety, the way the sample was prepared (fresh, cooked, dried), chopping and inoculum. Because there are few sources, not much can be said about variability between laboratories.

In biogas plant practice

Taro is a typical starchy feedstock which tolerates chopping well and can be dosed together with slurry or manure. Because of its easy hydrolysis, doses should be spread over time and pH and volatile acids monitored. Storage of tubers in tropical conditions is limited by spoilage, so the material is used quickly. For plants in Poland taro has no practical significance, but it helps in assessing the behaviour of similar tubers. If the material is imported as a processing waste, it is subject to waste regulations.

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. 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. Ge, X.; Matsumoto, T.; Keith, L.; Li, Y. (2014). Biogas energy production from tropical biomass wastes by anaerobic digestion. Bioresource Technology 169, 38–44. DOI: 10.1016/j.biortech.2014.06.067 DOI

All sources of the site: bibliography.

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