Table 2 Impact of species and pre-treatments on the methane yields of anaerobic digestion of European seaweeds
From: A review of the current potential of European brown seaweed for the production of biofuels
Seaweed species | Location details | Pre-treatments | Inoculum/Co-digestion | Inoculum to Sludge ratio | Process conditions | Methane yield | References |
|---|---|---|---|---|---|---|---|
Phaeophyta | |||||||
 Alaria esculenta | Cork, South of Ireland July | Macerated to < 4 mm | Combination of lab-scale reactors processing grass silage, dairy slurry & macroalgae | 2:1 | Batch, 37 °C, 30 days | 226.0 L CH4 kg−1 VS | [52] |
 Alaria esculenta | Trondheim, Norway Aug/Oct 2014 & May 2015 | Stored at 10 °C in seawater tanks. Epiphytes removed manually. Stored at − 80 °C. Cut to ≤ 1 cm2 | Wastewater sludge (mixed primary and waste active sludge) | n/k | Batch, 37 °C, 60 days | Between 187 N mL CH4 g−1 VS (Aug. 2014) and 254 N mLCH4 g−1 VS (May 2015) | [9] |
 Laminaria digitata | USA | Coarsely shredded | Digester slurry | n/k | Batch, 35 °C, 30 days | 280 mL CH4 g−1 VS | [98] |
 Laminaria digitata | Aberystwyth, Wales Jan–Dec. 2008 | Frozen, dried at 70–80 °C. Milled to produce flour to < 1.0 mm | Digested sludge | n/k | Batch, 35 °C, 36 days | 254.14 L CH4 kg−1 VS (July) 196.33 L CH4 kg−1 VS (March) | [149] |
 Laminaria digitata (Fronds) | Aberystwyth, Wales July 2009 & Jan. 2010 | Unwashed Washed with tap water up to 1 min Oven-dried 70 °C, 72 h Frozen at 20 °C, oven dried 70 °C, 72 h Shock frozen with liquid nitrogen, freeze-dried Material milled to < 1 mm | Digested sludge | n/k | Batch, 35 °C, 35 days | 257.7 mL CH4 g−1 VS (Freeze-dried, washed) | [90] |
 Laminaria digitata at 15, 24 & 41% | Denmark | Stored at − 18 °C after collection Washed with tap water, chopped for 30 min. to ~ 10 × 10 mm | Cattle manure | n/a | 5L reactors, semi-continuous, 80 days Mesophilic (35 °C) Thermophilic (50 °C) | 165 L CH4 kg−1 VS mesophilic (41% L. digitata) 198 L CH4 kg−1 VS thermophilic (41% L. digitata) | [112] |
 Laminaria digitata | Co. Sligo, Ireland Sept. 2011 | Washed, dried at room temp. for 48 h. Milled to < 1.0 mm | Co-digested with Cattle manure | 1:1 | Batch, 35 °C, 109 days | 246 mLCH4 g−1 VS | [101] |
 Laminaria digitata (Frond only) | Culler Coats, Tyne & Wear Dec. 2013 | Washed. Fronds roughly chopped to approx. 10 mm. Two pre-treatments, fresh and dried Fresh: fronds roughly chopped to approx. 10 mm, macerated to consistency of thick slurry (< 2 mm) Dried: feedstock dried at 104 °C for 24 h, milled to max. 1 mm | Lab scale mesophilic digester | 3:1 | Batch, 35 °C, 32 days | 141.45 L CH4 kg−1 VS (washed & dried) 93.35 L CH4 kg−1 VS (washed & fresh) | [76] |
 Laminaria digitata | Cork, South of Ireland August | Macerated to < 4 mm | Lab-scale reactors processing grass silage, dairy slurry & macroalgae | 2:1 | Batch, 35 °C, 35 days | 218 L CH4 kg−1 VS | [52] |
 Laminaria digitata + dairy slurry | West Cork, South of Ireland | Washed with tap water, macerated to < 4 mm, stored at − 20 °C | Originating from digester treating grease trap waste and slurry | 2:1 | Batch 37 °C, 30 days | 232 L CH4 kg−1 VS (66.6% L. digitata + 33.3% dairy slurry) | [77] |
 Laminaria digitata (Fresh fronds) | West Cork, South of Ireland March–Sept | 2 washing pre-treatments at 15 °C and 40 °C 2 mechanical pre-treatments cutting and maceration | Lab-scale reactors processing grass silage, dairy slurry & macroalgae | 2:1 | Batch, 37 °C, 30 days | 282 L CH4 kg−1 VS (Pre-treatments, washing at 40 °C and macerated) | [95] |
 Laminaria digitata | Denmark August 2013 | Stored at − 20 °C | Thermophilic inoculum from biogas plant | n/k | Batch, 55 °C, 30 days | 358.9 N mLCH4 g−1 VS | [134] |
 Laminaria digitata | Cork, Rep. of Ireland Sept. & Oct | Washed under tap water. Minced to 4–5 mm Hydrolysis reactor Methanogenesis reactors | AD plant treating dairy slurry, grease and food waste | n/k | Single-stage (reactor M3) & Two-stage (H1 + M1 + M2) systems 37 °C, 6 weeks | 234 L CH4 kg−1 VS at HRT of 14 days | [150] |
 Laminaria digitata (Frond only) | Northumberland, UK July 2015 | Washed to remove marine salts and sediments Roughly chopped to ~ 10 cm, dried at 70 °C for 24 and 48 h, blended to < 1 mm | Sludge obtaining for AD operating on grass silage, pig and cow manure | 3:1 | Batch at 25 °C, 35 °C, 45 °C & 55 °C for 40 days | 352 mL CH4 g−1 VS at 55 °C | [111] |
 Laminaria digitata (residue) | East & West coasts of Ireland, seasonal collections | Stored at − 20 °C Chopped < 0.5 cm Bioproducts extracted using ethanol, acetic acid, Na2CO3 | Sewage sludge (acclimatise and non-acclimatised) | 1:0.3 | Batch, 38 °C, 21 days | 523 mL CH4 g−1 VS | [151] |
 Laminaria digitata | West Coast Ireland Sept | Washed with tap water, cut into small pieces, oven dried 105 °C, ground to powder, cryo-stored at − 20 °C Hydrothermal Hydrothermal dilute acid Enzymolysis Combination of above | Inoculum from digester treating food waste | 2:1 | Batch, 35 °C, 21 days | 282.2 L CH4 kg−1 VS Hydrothermal pre-treatment (140 °C for 20 min) | [121] |
 Laminaria digitata Laminaria digitata + Phragmites australis | West Coast, Sweden July/Aug 2015 | Frozen. Cut to 100 mm prior to use | Granular sludge from WWTP | n/k | Two-stage pilot scale process L. digitata 70 days L. digitata + P. australis 100 days | 170 L CH4 kg−1 VS yperbo. L. digitata only L. digitata + P. australis no increase in methane yield and showed process instability | [152] |
 Laminaria hyperborean (Frond only) | Tyne & Wear, UK July 2009 | Frond material only, roughly chopped to 10 mm, blended to slurry | Mixed methanogenic sludge Paper:sugar:sewage (2:2:1) | Reactors inoculated to 28% wv | Continuous, 35 °C, 179 days 3 reactors | Average over 3 reactors 236.7 mL CH4 g−1 VS | [103] |
 Laminaria hyperborea | Firth of Forth, Edinburgh, Scotland | Washed with tap water to remove sand and dirt, minced to ~ 6 mm, stored at − 20 °C. Before use reduced to 2 mm size, blended and autoclaved | Seven different inocula and mix of these (inoculum 8) Sheep rumen contents (× 2), sheep faeces (× 2), mix of leachates, human sewage, marine sediments, mix of all seven | 1:1 | Semi-continuous single- and two-stage process, 37 °C, 28 days | Inoculum 8 (mix of 7 inocula) produced most methane at single-stage 253 mL CH4 g−1 VS | [38] |
 Laminaria hyperborean (Stipe only) | Culler Coats, Tyne & Wear Dec. 2013 | Washed to remove marine salts and sediments. Stipes broken to < 5 mm pieces. Two pre-treatments, fresh and dried Fresh: stipes roughly chopped to approx. 10 mm, macerated to consistency of thick slurry (< 2 mm) Dried: stipes dried in oven at 104 °C for 24 h | Lab scale mesophilic AD | 3:1 | Batch, 35 °C, 32 days | Fresh—105.06 L CH4 kg−1 VS Dried—113.28 L CH4 kg−1 VS | [76] |
 Laminaria spp. mix (L. digitata, S. latissima, L. hyperborea) | Dublin, Ireland May 2014 | Roughly cut, no washing Mechanical pre-treatment—beaten for 5, 10, 15 min. producing pulp of different consistencies VS concentrations 1, 2.5, 4% | Sewage sludge from WWTP | n/k | Batch, 38 °C, 14 days | 240 L CH4 kg−1 VS (15 min, 2.5% VS) | [99] |
 Laminaria sp. (mix of L. digitata, S. latissima, L. hyperborea) | Dublin, Ireland November 2013 | Beaten—pulped Ball milled—dried for 24 h at 80 °C, milled, sieved to 1 and 2 mm particle size Microwaved—rough cut | Sewage sludge from WWTP | 1:1 | Batch, 38 °C, 25 days | 335 N mL CH4 g−1 VS (with beaten pre-treatment) | [108] |
 Saccharina latissima | Trondheimsfjord, Norway Spring—March 1982, 1989 Autumn—Sep. & Nov. 1988 | Fresh algae milled to < 4 mm, stored at − 25 °C | Batch—inoculum from semi-continuous digestion Semi-continuous- fermented spring kelp | n/k | Batch, 32, 35 days Semi-continuous, 35 °C, 40 days | Spring—25 mL CH4 g−1 VS Autumn—51 mL CH4 g−1 VS Spring—220 mL CH4 g−1 VS Autumn—270 mL CH4 g−1 VS | [153] |
 Saccharina latissima | Brittany, France July 2010 | Dried at 40 °C for 24 h. Roughly chopped to ~ 2 cm | Sludge | 2:1 | Batch, 35 °C, 60 days SCSTR, 35 °C, 182 days | 210 mL CH4 g−1 VS 270 mL CH4 g−1 VS | [154] |
 Saccharina latissima | Brittany, France May–August 2011 | Washed with seawater, dried at 40 °C for 24 h Roughly chopped | Anaerobic sludge | 2:1 | Batch, 35 °C, 40 days | 209 mL CH4 g−1 VS | [96] |
 Saccharina latissima | Cork, South of Ireland July | Macerated to < 4 mm | Combination of lab scale reactors processing grass silage, dairy slurry & macroalgae | 2:1 | Batch, 37 °C, 30 days | 341.7 L CH4 kg−1 VS | [52] |
 Saccharina latissima (cultivated) + Dairy slurry | West Cork, Ireland | Washed with tap water, macerated to < 4 mm, stored at − 20 °C | Originating from digester treating grease trap waste and slurry | 2:1 | Batch 37 °C, 30 days | 252 L CH4 kg−1 VS (66.6% S. atissimi + 33.3% dairy slurry) | [77] |
 Saccharina latissima | Denmark 2012, 2013 | Stored at − 20 °C | Thermophilic inoculum from biogas plant | n/k | Batch, 55 °C, 30 days | 285.0 N mL CH4 g−1 VS (August 2013) | [134] |
 Saccharina latissima (residue) | East & West coasts of Ireland, seasonal collections | Stored at − 20 °C Chopped < 0.5 cm Bioproducts extracted using ethanol, acetic acid, Na2CO3 | Sewage sludge (acclimatise and non-acclimatised) | 1:0.3 | Batch, 38 °C, 21 days | 535 mL CH4 g−1 VS | [151] |
 Saccharina latissima | West Cork, Rep. of Ireland June | Washed with tap water, minced to ~ 5 mm, dried at 105 °C, pulverised to 0.02 mm mesh size Hydrothermal pre-treatment from 100, 120,140, 160, 180 °C for 30 min | Lab digester using cellulose as substrate | 2:1 | Batch, 35 °C, 11 days | 281.4 mL CH4 g−1 VS untreated 345.1 mL CH4 g−1 VS treated at 140 °C | [78] |
 Saccharina latissima | Beadnell Bay, Northumberland, UK June 2017 | Freeze-dried, stored under nitrogen gas, ground to < 1 mm Hydrothermal pre-treatment (HTC) at 150, 200, 250 °C for 60 min | Sludge from WWTP | 2:1 | Batch, 37 °C, 30 days | Untreated—~ 200 mL CH4 g−1 VS Slurry 150 °C–217 mL CH4 g−1 VS Slurry 200 °C–202 mL CH4 g−1 VS Slurry 250 °C–196 mL CH4 g−1 VS | [35] |
 Saccharina latissima | Dunstaffnage, West Coast of Scotland August 2012 | Freeze dried, manually grinded to < 1 mm | Anaerobic digested sludge Anoxic surface sediment (SS) | 1:1 | Batch, 37 °C, 50 days | 230 dm3 kg−1 VS (DG) 175 dm3 kg−1 VS (SS) | [106] |
 Saccharina latissima | Coast of Frederikshavn, Denmark | Washed Unwashed Chopped to ~ 2 × 2 cm) Macerated to homogenised paste | Cattle manure | n/k | Batch, 53 °C, 34 days | 340 mL CH4 g−1 VS (washed, chopped) 333 mL CH4 g−1 VS (washed, macerated) | [81] |
 Saccharina latissima | Co. Sligo, Ireland Sept. 2011 | Washed, dried at room temp. for 48 h. Milled to < 1.0 mm | Co-digested with cattle manure | 1:1 | Batch, 35 °C, 109 days | 335 mL CH4 g−1 VS | [101] |
 Saccharina latissima | Trondheim, Norway Aug/Oct 2014 & Feb/May 2015 | Stored at 10° in seawater tanks. Epiphytes removed manually. Stored at − 80°. Cut to ≤ 1 cm2 | Wastewater sludge (mixed primary and waste active sludge) | n/k | Batch, 37 °C, 60 days | 195 NmL CH4 g−1 VS (Feb. 2015) 352 NmL CH4 g−1 VS (May 2015) | [9] |
 Saccharina latissima + wheat straw | Trondheimsfjord, Norway August 2010 | Frozen, ground to finely shredded slurry Steam explosion: L. saccharina 130 & 160 °C, 10 min Wheat straw 210 °C, 10 min | Anaerobic sludge | n/k | Batch, 37 °C, 119 days | 223 mL CH4 g−1 VS (untreated) 268 mL CH4 g−1 VS (130 °C, 10 m) 260 mL CH4 g−1 VS (160 °C,10 m) 270 mL CH4 g−1 VS (Co-digested with steam exploded wheat straw) | [114] |
 Saccharina latissima | Trondheimsfjord, Norway August 2017 | Washed with tap water, milled to pulp, dried at 30 °C for 48 h Enzyme hydrolysis | Large-scale continuous mesophilic multifuel anaerobic digester | 2:1 | Batch, 39 °C, 40 days | With hydrolysis 257 mL CH4 g−1 VS No hydrolysis 208 mL CH4 g−1 VS | [119] |
 Saccorhiza polyschides | Brittany, France May–August 2011 | Washed with seawater, dried at 40 °C for 24 h. Roughly chopped | Anaerobic sludge | 2:1 | Batch, 35 °C, 40 days | 216 mL CH4 g−1 VS | [96] |
 Saccorhiza polyschides | Cork, South of Ireland July | Macerated to < 4 mm | Lab scale reactors processing grass silage, dairy slurry & macroalgae | 2:1 | Batch, 37 °C, 30 days | 263.3 L CH4 kg−1 VS | [52] |
 Saccorhiza polyschides | Co. Sligo, Ireland Sept. 2011 | Washed, dried at room temp. for 48 h. Milled to < 1.0 mm | Co-digested with cattle manure | 1:1 | Batch, 35 °C, 109 days | 225 mL CH4 g−1 VS | [101] |