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Biogas production from sugar beet silage
Jin Mi Triolo University of Southern Denmark
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Why sugar beet silage? Dedicate energy crop for biogas production: prohibited until 2011 New regulation since 2012: up to 25% of dedicate energy crop allowed as co-feedstock (at least 75% must be animal manure) Sugar beet : Highest dry matter yield per. ha : Easily degradable, high methane potential : Ensilaging produce alcohols and organic acids (quick biogas production)
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Influence of ensilage
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Ensilage effect of beets pulps
DM DM loss VS VS loss Total VFA Total Alcohol pH BMP g kg-1 % g kg -1 (%) % of VS NL CH4 kg VS-1) CH4 NL kg -1 Fresh silage 194,6 153,4 78,8 0,46 0,00 4,5 342,1 52,5 Silage 1 146,7 24,6 109,8 28,41 74,9 8,48 4,60 3,6 490,3 53,8 Silage 2 157,6 19,0 116,8 23,84 74,1 8,63 4,50 499,8 58,4 Silage 3 163,5 16,0 121,1 21,05 6,01 4,66 456,3 55,3 Silage 4 173,7 10,8 114,2 25,52 65,8 6,78 4,95 478,0 54,6 Silage 5 135,5 30,4 106,0 30,90 78,2 8,77 4,84 3,7 493,9 52,3
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Further Study 1 Grøngas A/S (Hjørring)
Long term monitering of beet ensilage (Harvested in Nov Ensilaging until December 2014) (6 silos with different scenarios) GHG emission Biogas potentials Optimising high rate biogas production Organic composition
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Further study 2 1 Spring barley straw
2 Spring barley straw in the swath, 21/10 3 Spring barley straw + aftermath, fresh 4 Spring barley straw + aftermath, ensiled 5 Grass seed straw, fresh 6 Grass seed straw, silage 7 Grass seed straw, silage grass juice 8 Grass seed aftermath, fresh 9 Grass seed after forage ensiled 10 Maise silage
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Further study 3 Beet top Straw with 30% water Roerod knust
Grøngas A/S (Hjørring) Beet top Straw with 30% water Roerod knust Beet top and straw with different mixing ratios Beet top + Straw 100 75 25 80 20 85 15 90 10
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Examples of concept model work
Biogas production of sugar beet in Energy production and Greenhouse Gas Reduction Field Post -storage Biogas production Ensilage Cleaning Harvest Harvest in October Beet top for animal feed Beet root for bigas production Dry Cleaning in the field Removing soil, sand, stones, etc. Ensilage for 8 months Whole beet root, fermentation Covered Cattle manure Co-digestion with cattle manure 1200m3, 6ton/day, 37°C, HRT 20days PVC roof (avoid dilution), until field application Applied in October or April
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Flow chart of Reference Scenario
7 process units and sub-systems with a total of 15 process streams Top harvested m2g x2 H2O g x6 CO2 g Soil m4g Emission m6g x2 DM g x6 CH4 g Root harvested m3g Sugar beet in field Washed root m5g m1g Unit 1. Harvest Unit 2. Cleaning Unit 3. Storage x1top g x3root g x5 H2O g x1root g x3soil g x5DM g x1 soil g x5 ash g x5VS g Biogas (emitted) m11g x11 CH4 g x11 CO2 g x10 CH4 g x11NH3 g x7 H2O g x13 CH4 g Silage m7g Gas m13g x10 H2O g x10 CO2 g x7 DM g x13 CO2 g Biogas (obtained) m10g x13 NH3 g x10 NH3 g x7VS g x10 H2O g x7 ash g Mixed substrate m9g Digestate m12 g Unit 4. Mixing Cattle slurry m8 g Unit 6. After-storage Unit 5. Anaerobic digestion x12 H2O g x9 H2O g x8 H2O g x12 DM g x12 ash g x9 DM g x8 DM g x12VS g x9 ash g Gas m15g x8 VS g x14 H2O g x9VS g x8 ash g Fertilizer m14 g x14 DM g x14 ash g m15 N2O g x14VS g m15 CO2 g m15 NH3 g Unit 7 Field Model 1 (Basis unit :1000g beet) Model 2 (Basis unit : ton/ha)
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Process unit 1. Harvest 2 Top for animal feed
Removed 2 221.4 H2O g 255.6g 34.2 DM g Sugar beet in field Root harvested Top for animal feed Root for biogas production Soil : 22% of beet’s dry matter 1 1000g Unit 1. Harvest 744.4g 744.4g Total Dry matter 192.0g 152.7g VS 14.4g VSND 138.3g VSED Carbohydrate 129.8 g 0.8g Lipid 7.8g Protein 39.3g Ash 552.4g Water 706.9root g 706.9root g 3 37.5 soil g 37.5soil g Composition of root +soil (stream 3)
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Process unit 2. Cleaning 5 Soil residue 4 6
Removed 5 4.5 H2O g 35.3g 30.8 DM g Cleaned root Root harvested Soil residue 3.4% (dry cleaning) 2.1% (wet washing) Root cleaned 4 744.4g Unit 2. Cleaning 709.1g 152.7g VS 138.3g VSD Carbohydrate 129.8g Sucrose 101.2g Cellulose 6.5g Hemicelluloe 15.6g Pectins VSD Lipid 0.8 VSD protein 7.8g 14.4g VSND 706.9root g 547.9 g H2O 6 37.5 soil g 161.2 g DM AgroTech (Jørgen Pedersen) 8.5 g ash 151.7 g ash VS Composition of cleaned root (Stream 6)
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Process unit 3. Ensilage GHG VS and BMP loss during ensilage
CO2 emission through ensilage : 12.7 L /kg beet CH4 emission during first period ( 2-3 weeks) : 1.24 L/kg beet 2.5% (Agrotech) VS and BMP loss during ensilage German study (Weißbach et al., 2011) VS (g/kg w.w) BMP (L/kg VS) BMP (L /kg w.w) Fresh beet 231 361 83 Ensilage 8 months 212 383 81 Our study VS (g/kg w.w) BMP (L/kg VS) BMP (L /kg w.w) Fresh beet 215 324 70 Ensilage 8 months 187 359 67 High BMP of alcohol TBMP per kg VS TBMP Before ensilage TBMP After ensilage CH4 NL kg VS-1 CO2 NL kg VS-1 g CH4 NL CO2 NL Sucrose 393 (50%) 393(50%) 101 40 31 12 Ethanol 730(75%) 244(25%) 21 15 5
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Process unit 3. Ensilage 8 VS loss until the end of March 7 9
Gas emission 8 0.9 CH4 g VS loss until the end of March under careful storage 16% 23.5g 22.6 CO2 g Root cleaned Silage 7 709.1g Unit 3. Ensilage 694.1.g Root silage 547.9 g H2O 538.9 g H2O 9 161.2 g DM 136.8 g DM 8.5 g ash 8.5 g ash 151.7 g VS 128.3 g VS AgroTech (Jørgen Pedersen) Changes of Carbohydrate during ensilage Fraction (%) In the model (g) Before ensilage Up to 6 months More than Before ensilage Moren than Sucrose 78 60 30 101 31 Glucose 6 8 8.4 Ethanol 10 20 2.1 Hexoses 5 7 9 6.5 9.5 Pentose Pectins 12 24 15.6 25.3 Total 100 100 130 105 Fraction : Weißbach et al., 2009
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Process unit 5. Biogas production
3% of total biogas VS destruction Sugar beet Cow manure Input VS g 128 261 Removed VS g 90 66 Remaining VS g 39 196 VS destruction% 70 25 Methane production rate and cumulative yield Beet 92% of BMP removed Cattle manure 85% of BMP removed
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Overview of model 1( 1000 g of beet + cattle manure)
Process unit (g)
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Model for beet production per ha (139 ton/ha) (+381 ton cattle manure)
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Model 1 (1000g) Model 2(ton /ha)
Energy production Model 1 (1000g) Model 2(ton /ha) Biogas CH4: 60.5g (84.7L) CO2: 125.1g(63.7L) Total: 185.6g(148.4L) Energy 3.4MJ Electricity 0.95Kwh Biogas CH4: 8.4.Mg (11780 m3) CO2: 17.4Mg (8855 m3) Total: 25.4Mg (20634m3) 43m3/ton Energy 474588MJul 941MJ/ton Electricity 131Mwh (261Kwh/ton)
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GHG emission using biogas technology ( Model 1)
With Biogas production CH4 : g (0.88g ensilage, 1.87g biogas plant emission, 1.42g after-storage) CO2 : 28.9g (mainly from ensilage ) GHG as CO2 eq. : g Without biogas production CH4 : g , CO2 : 7.3g , GHG as CO2 eq. : 111.9g No GHG reduction, may be due to GHG emission from beet silage included High CO2 emission from ensilage CH4 emission from ensilage Emission from a biogas plant
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