Straw as a Sustainable Farm-Based Feedstock for Biogas EBA Workshop, 8 February, Academy Palace, Brussels

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1 Straw as a Sustainable Farm-Based Feedstock for Biogas EBA Workshop, 8 February, Academy Palace, Brussels Sebastian Antonczyk, Richard Arthur, Paul Scherer Not published in a journal. Therefore, please specify the working group as source. Hamburg University of Applied Sciences in Hamburg-Bergedorf, Faculty Life Sciences, Hamburg Research Center for Biomass Utilization The greatest university for engineers in the north of Germany 1

2 Source: Erneuerbare Energien Mai 2014 Straw as a Substrate Why Anaerobic Digestion of Straw? Waste Agricultural Residues No competition with Food No competition with agricultural Area No additional nitrate pollution of groundwater by nitrogen deficiency High amounts available, see Table Model Substrate for other slowly degradable lignocellulosic substrates

3 Uncontrolled Decay of Lignocellulosic Straw with CO 2 -Emissions. 90% decay in 9 years. Alternatively gasification in a closed biogas reactor in about 2-3 weeks without harm of the climate Wheat Straw Beet Leafs Ottow, Mikrobiologie von Böden, Springer

4 Ecological Straw Potential 35% can be used without ecological restrictions (yellow bars), Green = Total Potential, Red = Energy Potential Land Ecol. Straw Potential [Mio. t/a] Energy Potential [MW] Reference Germany Weiser 2014 EU 50,63 ~ 6000 China 76,7 ~ 9000 Worldwide 340 ~ FAOSTAT 2015 Niu et al Del Río et al Scheme Antonczyk, data from literature. Antonczyk

5 Country Total straw production 100% [Mio. t/a] Straw potential for energy generation [Mio. t/a] Methane potential [Mio. m 3 /a] Electrical energy potential [MW] Reference Austria Kaltschmitt 2009 Belgium 1.4*/*** 0.49** FAOSTAT 2015 Bulgaria 4.2* 1.5** FAOSTAT 2015 Czech 14.6 ** Havlíčková et al Republic Croatia 0.8* / *** 0.28** FAOSTAT 2015 Cyprus 0.03* 0.01** FAOSTAT 2015 Denmark 3.6* 1.3** FAOSTAT 2015 Estonia 0.3* 0.1** FAOSTAT 2015 Finland 0.6* 0.21** FAOSTAT 2015 France 29.7* 10.4** FAOSTAT 2015 Germany 30*/** European Straw Potential for Biogas 13.0** (13.0 = 43%) Weiser et al * Calculated from the assumption according to Ruiz et al. (2012) that 1.3 kg of grain corresponds to 1 kg of straw ** Calculated from the assumption that without ecological restrictions 35% can be used

6 Country European Straw Potential for Biogas, continued Total straw production 100% [Mio. t/a] Straw potential for energy generation [Mio. t/a] Methane potential [Mio. m 3 /a] Electrical energy potential [MW] Reference Great Britain Wang et al Greece 1.2* 0.42** FAOSTAT 2015 Hungary 3.8* 1.3** FAOSTAT 2015 Ireland 0.41* 0.14** FAOSTAT 2015 Italy 5.6* 2** FAOSTAT 2015 Latvia 1.1* 0.39** FAOSTAT 2015 Lithuania 2.2* 0.77** FAOSTAT 2015 Luxembourg 0.07* 0.03** FAOSTAT 2015 Netherlands 1.0* 0.35** FAOSTAT 2015 Poland BIELSKI 2015 Portugal 0.05* 0.02** FAOSTAT 2015 Romania 5.6* 2** FAOSTAT 2015 Sweden Ekman et al Slovakia 1,0* 0.35** FAOSTAT 2015 Slovenia 0.1* 0.04** 9 4,6 FAOSTAT 2015 Spain 5.9* 2.1** FAOSTAT 2015

7 Summary: European, Chinese and Worldwide Straw Potential for Biogas - Without Co-Substrates Country Total straw production 100% [Mio. t/a] Germany 30*/** Straw potential for energy generation [Mio. t/a] 13.0** (13.0 = 43%) EU Methane potential [Mio. m 3 /a] Electrical energy potential [MW] Reference Weiser et al FAOSTAT 2015 China 153.3*** Niu et al Worldwide 680**** GW Del Río et al * Calculated from the assumption according to Ruiz et al. (2012) that 1.3 kg of grain corresponds to 1 kg of straw ** Calculated from the assumption that without ecological restrictions 35% can be used for power generation *** Total straw production in the year 2010 **** Total straw production in the year 2011

8 Comparison of the Energy-Maize (2.0 GW or 50% of 4.0 GW el total) in Germany with the potential of Straw Straw (max. potential for Biogas): Maize silage (for Biogas) 2014: 2015: Residues Used Area ha x 47.6 t/ha 13 Mt/a Fresh mass (Total Solids = 90%) 38.4 Mt/a Fresh mass (Total Solids = 33%) 11.7 Mt/a dry mass (Volatile Solids = 90%) 12.6 Mt/a dry mass (Volatile Solids = 95%) 11.7 Mt fresh Mass /a is < 13 Mt/a = 43% of German straw potential, highest usage without ecological risk, Weiser et al. 2014, TS = Total Solids, VS = Volatile Solids (Organics)

9 Comparison of the Gas and Energy potential of Straw and Energy-Maize in Germany Straw (max. potential for Biogas) 2015: Maize silage (for Biogas): 10.5 Mt Volatile Solids /a 12.0 Mt Volatile Solids /a 271 m 3 CH 4 /t VS 2980 Mm 3 CH 4 /a 4056 Mm 3 CH 4 /a 338 m 3 CH 4 /t VS Calculation: 9.97 kw/m 3 CH 4 40% electrical efficiency 8000 working hours/a 3.7 GW Primary Potential Power 1.5 GW Electric Power (40%) 10.5 Mt/a Straw + 4x Mt Manure: = 2.0 GW el 5.1 GW Primary Potential Power 2.0 GW Electric Power (Total = FNR: GW el ) Max new 500 kw el Biogas Plants 100% Replacement of Maize is Possible

10 Verbio AG (Ethanol Producer) together with Enercity Contracting (Gas Stations), News 9.Jan. 2017: Hannover tanks up with straw. The Bioraffinery Concept of Verbio combines in a highly sustainable way ethanol production with the use of distillers wash, the residues of ethanol fermentation (high nitrogen-content) with anaerobic digestion of straw.

11 Materials and Methods: Defined Conditions (1) Fermentation Substrate (Wheat straw) Mechanical Pretreatment Powder: Particle size (0.13 mm) (2) Mineral Content of Straw, 6.73% of Total Solids (TS) C/N Quotient 73 being not sufficient as mono-substrate Lignin Content 23.5%, not bio-degradable BDL: Below Detection Limit Element Concentration ± SD 1 RSD 2 LLD 3 [mg kg -1 TS] (n = 5) [%] (n = 5) [mg kg -1 TS] K 8.49±0.18 g kg Ca 3.81±0.06 g kg Mn 35.00± Fe ± Co ± Ni 0.58± Cu 2.76± Zn 19.14± Se BDL W BDL - -

12 Manure Substitute for Defined Straw Biogasification Salt- and Buffer Solution developed at the Hamburg University of Applied Sciences: 10 Parts Liquor + 1 Part milled Straw (Straw Suspension) For the needed alkalinity see Speece, Anaerobic Biotechnology, 1996 Components (Salts) Manure Substitute [mmol L -1 ] Cattle Manure as a Model [mmol L -1 ] Potassium < Ammonium < Calcium < Magnesium <5 1-6 Iron < 0, Sulphur < Sodium < Alkalinity (Buffer) 10800*

13 Batch Mini-Fermentations of Wheat Straw Step 1 Biomethane Potential of wheat straw as mono-substrate The buffering capability of a chemical salt solution Effect of substrate swelling and storage temperature Approx. 200 BMP determinations Set-up MilligasCounters from the Ritter company on top Methane sensors from company BlueSens Swollen or not, salt or water etc. Batch Mini-fermenters in incubators For 30d at 41 C; Online Recording!

14 sgpr [Norm-mL/g VS ] Mini-Batch Fermentations of the test substrate Wheat Straw Powder Standard Deviation of the final Biogas Values: <3% Effect of Straw Powder : Seed Sludge Ratios (A-G) on specific GPR (biogas production = yield) by the created Manure Substitute

15 Continuous Digestion of Wheat Straw without interruption for more than 3 years Biogas fermenters: Number of lab fermenters: 6 Working Volume: 6 L Substrate Addition: Every 8 hours feeding, fully automatic Online Parameters: ph Redox [mv] Gas Volume [ml-stp] CH 4 Concentration [%] CO 2 Concentration [%] Temperature [ C]

16 Continuous AD of Wheat Straw Influence of temperature: Is thermophilic better than mesophilic? Running for more than 3 years Trace Elements Dependency (Nickel and Tungsten)

17 Specific Methane Yield of Straw [L/kg VS ] Batch by Sharma et al., 37 C, straw particle size 88 µm Batch BMP by HAW, 41 C, straw particle size 130 µm Straw KTBL-Value, for full scale biogas plants HAW Conti-Fermentation, 41 C and OLR 4.5 HAW Conti-Fermentation, 58 C and OLR 4.5 HAW Conti-Fermentation, 41 C and OLR 7.5 HAW Conti-Fermentation, 58 C and OLR 7.5 Specific Methane Yields of Wheat Straw under mesophilic and thermophilic conditions Batch (1,2) and Continuous Fermentations (3-7) at different Organic Loading Rates (OLR); Value 271 L CH4/kg VS from presentation ~Dumas et ~ Friedrich et

18 Specific Biomethane Potential (BMP) L-STP of Wheat Straw (violet), Maize (grey) and of purified test-cellulose (brown) If lignin was mathematically subtracted, gas yields of straw were in the same range like pure cellulose!

19 References for Methane Yields by Straw Digestion, obtained without additions of Chemicals (NaOH) Methane yields from the literature: 1: Sharma et al. (1988) 3. Friedrich et al., IKTS (2010/12) 5. Sapci (2013) 2: Dumas et al. (2015) 4. Peng et al. (2016) Ref. Specific Methane Yield [ml CH4 g VS -1 ] Buffer and Minerals Temperature [ C] Mechanical Pretreatment Particle Size [µm] Cattle Manure 37 Ball Mill Sewage Sludge 35 Centrifuge Mill Sewage Sludge/Water 37 Extruder Biogas Plant 37 Knife Mill < Cattle Manure 37 Knife Mill 1890 This Work Manure Substitute 41 Air Swirl Mill, Goergens in Dormagen 130

20 Cutting by Knife much cheaper than Hammer Mill, goes down to 1 mm Source: Bhutto et al. 2017

21 Conclusions Adequate buffer capacity is essential for stable AD of straw at high loading, a chemically defined salt solution could be used instead of manure. If lignin was mathematically subtracted, the measured methane yields of the residual cellulose were in the same range like pure cellulose without lignin. That means no inhibition of lignin at small particle size. First long term investigation (> 3 years) of AD of straw under defined conditions of continuous straw digestion in automated stirred fermenters. No swimming layers. At moderate OLR (OLR 4.5 g vs L -1 d -1, HRT 18 d), 10% higher methane production under thermophilic than mesophilic conditions. Contrary at higher OLR 7.5/ 8d HRT: Mesophilic gas yields higher. Not stable: 8d HRT. (OLR = Organic Loading Rate) Trace elements Nickel and Tungsten are essential for straw AD mg/l Ni + W should be present in the dissolved state. The uptake and requirement is similar under mesophilic or thermophilic conditions. Germany: 3000 new 500 kw el Biogas Plants - 100% Replacement of Maize is Possible

22 HAW Hamburg Faculty of Life Sciences Methanogens from our Fermenters (thermophilic)