Second generation biofuel: biomethane from co-digestion of grass and slurry

Transcription

1 Second generation biofuel: biomethane from co-digestion of grass and slurry Jerry Murphy 1, David Wall 1,2 & Padraig O Kiely 2 1.B 2 RG, Environmental Research Institute, University College Cork, Ireland 2. Animal & Grassland Research and Innovation Centre, Teagasc, Ireland 17th EGF Symposium June, Hof Conference Centre, Akureyri, Iceland

2 Bioenergy and Biofuels Research Group (B 2 RG) Funding of 3 M since inception in 2007 from: EPA, SFI, DAFF, IRCSET, BGE, BGN, HEA PRTLI, Marie Curie ITN Published 59 peer review journal papers 29 peer review conference papers Papers have received1500 citations H factor of 23 (23 papers cited at least 23 times) Graduated 12 research postgraduates Funding in place for 8 PhD students and 2 post-doctorates

3 Directive 2009/28/EC (Renewable Energy Directive) Share of renewable energy sources in transport by 2020 at least 10% Biofuels must achieve a 60% reduction in GHG as opposed to fossil fuel displaced. Biofuels from lignocellulosic material shall be considered as twice energy content. EC, Proposal for a DIRECTIVE OF THE EUROPEAN PARLIMENT Brussels In : The share of biofuels from cereal and other starch rich crops, sugar and oil crops limited to consumption in 2011 (ca. 5%) Biofuels (from algae, municipal solid waste, manures and residues) and gaseous fuels from non biological origin shall be considered at 4 times energy content

4 Agriculture 4.4 Mha agricultural 4 Mha grass land (91%) Export 85% of beef 400,000 ha arable (9%) Net importer of grain Energy Ireland Biofuel feed-stocks Cross Compliance and EU Biofuels Directive do not encourage conversion of grass land to arable land for biofuels. Forestry less than 10%; Not a lot of straw.

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6 First Generation Liquid Biofuels 60% savings required to be deemed sustainable Energy Balance & Greenhouse Gas balance

7 Electric Vehicles 10% of vehicles proposed to be EV in 2020; ca. 300,000 vehicles required Freight (HGV s) and public service vehicles account for over 50% of energy in transport Maximum of 40% of electricity green in 2020 Renewable energy supply in transport (RES-T) from EV limited to 10% of 50% of 40% = 2% EV s not used for long distance. Expected 1.6% RES-T from 10% EV s What is source of other 8.4% RES-T to meet 2020 target?

8 Hydrogen? Steam reforming of methane to hydrogen: 39 49% losses: 20-30% in steam reforming; 6% in pipelines; 13% in compression. Water Hydrolysis: 49 53% losses: 26% in electrolysis; 4-8% in transmission; 6% in pipelines; 13% in compression. EV v s hydrogen: EV 3 times as efficient as hydrogen 100 kweh = 69 kweh in an EV compared to 23 kweh in a hydrogen vehicle.

9 Irish Gas Grid Serves: 153 towns 19 counties (26 counties in Ireland) 619,000 houses (ca. 45% of houses) 24,000 industrial and commercial

10 Pakistan Iran Argentina Brazil India Italy China Colombia Ukraine Bangladesh Thailand Egypt Bolivia Armenia Russia USA Peru Germany Bulgaria Uzbekistan Total vehicles running on CNG Number of vehicles running on CNG worldwide 3,000,000 2,500,000 2,000,000 1,500,000 1,000, ,000 0

11 Grass Biomethane

12 Grass to transport fuel in Austria harvest weigh bridge silage storage Biogas service station Source: energiewerkstatt, IEA and personal photos Scrubbing & storage anaerobic digester macerator

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15 Grass silage C 28 H 44 O 17 N Cell contents 65% Cell walls 35% Stages of maturity Grass yields t DS.ha -1.a -1 Protein Lipid Sugars Minerals Hemicellulose Cellulose Lignin Cell contents 40% Cell walls 60% Reduced methane yield with age of grass

16 Mono-digestion of grass silage

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18 SLBR-UASB versus CSTR

19 Issues: Tendency of grass to float 80% of work done in first digester Failure led by inhibition of acetogenesis at higher OLR over time Solutions: Cut grass to 1cm and ensure mixer breaks the surface Recirculate digestate Trace element addition (Cobalt at 0.2mg/L: Jarvis et al., 1997) OR Co-digestion with slurry

20 Co-digestion of grass silage and slurry

21 Optimum ratio of co-digestion of grass silage and slurry? Cow manure & grass silage: 7:3 (VS cow: VS grass) (Lehtomäki et al., 2007) Pig manure & grass silage: 1:1 (VS pig: VS grass) (Xie et al., 2011b) Pig manure & grass silage : 6:4 (VS pig: VS grass) (Xie et al., 2012b)

22 Analysis of substrates Buswell Equation Grass silage C 30 H 50 O L CH 4 kg -1 VS Dairy Slurry C 22 H 34 O L CH 4 kg -1 VS BI = BMP value/ Buswell value

23 L CH 4 kg -1 VS L CH 4 kg -1 VS Analysis of substrates Days Days Cellulose 0:100 G:S 100:0 G:S 80:20 G:S 60:40 G:S 50:50 G:S 40:60 G:S 20:80 G:S

24 Substrate/Inoculum DS % VS % VS/DS % C:N Grass silage 29.3 ± ± :1 Slurry 8.8 ± ± :1 Inoculum Grass:Slurry BMP Buswell Pro-rata Difference Biodegradability Gas Production VS basis L CH 4 L CH 4 L CH 4 % Index m 3 CH 4 t -1 FW kg -1 VS kg -1 VS kg -1 VS 100:0 400 ± : ± % : ± % : ± % : ± % : ± % : ± Cellulose 348 ±

25 L CH4 kg -1 VS L CH4 kg-1 VS Continuous Trials Specific Methane Yield (100 % Grass, OLR = 2 kgvsm -3 d -1 ) Weeks 100 % Grass HRT 1 HRT 2 BMP Specific Methane Yield (100 % Slurry, OLR = 2 & 2.5 kg VS m-3 d-1) Weeks 100 % Slurry HRT 1 HRT 2 HRT 3 BMP

26 mg/l FOSTAC L CH4 kg -1 VS % CH4 Specific Methane Yield (100 % Grass, OLR = 2 kgvsm -3 d -1 ) ,0 58,0 56,0 CH4 Content (100 % Grass, OLR = 2 kg VS m -3 d -1 ) , , Weeks 50,0 48,0 46,0 100 % Grass HRT 1 HRT 2 BMP 44, CH4 % HRT 1 HRT 2 Weeks NH4-N & NH3 (100 % Grass, OLR = 2 kg VS m -3 d -1 ) Weeks NH4-N NH3 HRT 1 HRT 2 FOS TAC (100 % Grass, OLR = 2 kg VS m -3 d -1 ) 0,250 0,200 0,150 0,100 0,050 0, Weeks FOSTAC HRT 1 HRT 2

27 Bioresource: Substrates 1% of grass land = 40,000 ha = 404,800 t VS a -1 or 1,501,700 t a -1 Match with slurry at a 1:1 VS content 404,800 t VS a -1 6,041,790 t a -1 Total substrate 7,543,490 t a -1 1:1 VS content = 1:4 volumetric basis Energy Value Methane production 308 L CH 4 kg -1 VS 249 Mm 3 a -1 As a residue count at twice energy value 9.42 PJ (235 GJ ha.a -1 ) 5% energy in transport 10% RES-T Industry 100 digesters each treating 75,000 t a -1 of substrate each producing 2.5 Mm 3 a -1

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29 Food Waste from UCC canteen 14% 18% 5% 30% 33% Composition of UCC Food Waste (percentage mass) C 16.5 H 31.2 O 9.5 N pasta & rice fruit & veg peeling cooked veg cooked meat non organic Table 1. Characteristics of Food Waste from UCC canteen Parameters Unit Value ph 4.05 Total Solids (dry solids) Total Volatile Solids % total mass 29.4 ± 1.1 % DS 95.3 ± 0.4 Proteins % DS 18.1 ± 1.5 Carbohydrates % DS 59.0 ± 3.0 Lipids (fats) % DS 19.0 ± 0.8 % C % DS 49.6 ± 1.2 % H % DS 7.3 ± 0.2 % N % DS 3.5 ± 0.4 % Ash % DS 4.7 ± 0.4

30 Bioresource of Biomethane from OFMSW

31 Sea Lettuce (Ulva Lactuca)

32 Macro-algae: 3 rd generation biofuel Green tides in eutrophic estuaries 100,000 tonnes of sea lettuce arise in Lannion Bay, France annually. 20m 3 CH 4 t -1 wet vs 100 m 3 CH 4 t -1 dry (same as grass silage)

33 Sample type and year Results of BMP assays BMP yield L CH 4 / kg VS Pro-rata calculated yield L CH 4 / kg VS % increase Slurry Fresh Ulva Dried Ulva Dried Ulva 75%: Slurry 25% Dried Ulva 50%: Slurry 50% Dried Ulva 25%: Slurry 75% Fresh Ulva 75%: Slurry 25% Fresh Ulva 50%; Slurry 50% Fresh Ulva 25%: Slurry 75% Co-digestion improves the specific methane yield by ca. 17% for all fresh samples

34 Thermal production of Biomethane CO + 3H 2 = CH 4 + H 2 O CO H 2 = CH 4 + 2H 2 O 2CO + 2H 2 = CH 4 + CO 2 Gas upgrading Removal of CO2 Typically ca. 65% energy efficiency

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36 Plant Size MWth 50 Land area (ha) 6800 Annual Energy Input (GJ) 1,440,000 Plant Efficiency 65% Annual Energy Output (GJ) 936,000 Annual Energy Output (PJ) 0.94 Number of plants required 11 Energy Produced PJ As a % Energy in Transport 5.5% As a % of agricultural land 1.7%

37 3 rd generation biofuel: gaseous biofuel from nonbiological origin H 2 : Energy density 12.1 MJ/m n 3 : CH 4 : Energy density 37.6 MJ/m n 3 Sabatier Equation: 4H 2 + CO 2 = CH 4 + 2H 2 O AH 298 =-165 kj/mol 60% energy efficiency (75% conversion of electricity to H2; 80% conversion of H2 to CH4) Source of CO2 from biogas: Mix biogas (50% CH4 and 50% CO2) with H2; generate double the CH4 (1 mol CO2 generates 1 mol CH4).

38 Resource Energy in transport Weighing RES-T Grass and slurry (40,000 ha; 1%) 9.42 PJ 5% *2 10% Food waste (530,000 t/a) 2.65 PJ 1.4% *2 2.8% Gasification Willow (75,000 ha; 1.7%) PJ 5.5% *2 11% Electricity 8 PJ 4.2 % * 4 17% Total 30.4 PJ 16.1% 40.8% Resource equates to 820 Mm 3 /year biomethane, VW Passat consumes 4.5 kg / 100 km (6.3m 3 /100km). Average car in Ireland travels 16,708 km/year Resource equals 800,000 cars or 40% of private fleet

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