Dry AD for High Solids Manures Maximizes Biogas Production
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Proceedings available at: http://www.extension.org/67653 Anaerobic digestion of animal manure has generally been limited to wet digestion where total solids are less than 12%. This has restricted adoption of biogas production primarily to dairy and hog operations, or required substantial water usage to dilute manures with higher solids content. The DRANCO-Farm dry anaerobic digestion technology processes solid manures and other dry crop residues on a continuous basis with solids content in the digester up to 45%.
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Dry AD for High Solids Manures Maximizes Biogas Production
- 1. Fußzeile Dry AD for High Solids Manures Norma S. McDonald Waste to Worth Conference – April 5, 2013
- 2. PRESENTATION HIGHLIGHTS • High solids feedstock characteristics and market dynamics • European research on operating plants • In-depth look at dry continuous digestion • Example economics
- 3. DILUTED, SAND-LADEN STRAW-LADEN PARTIAL AGED, LEACHED CONSISTENT MANURE VARIES FROM SITE TO SITE
- 6. LESS WATER, LESS CAPACITY REQUIRED – within ammonia concentration limits NOMINAL 1 MW ENERGY POTENTIAL ANIMALS NUMBER MANURE TONS/YR TOTAL SOLIDS FRESH AT5% TOTAL SOLIDS AT12% TOTAL SOLIDS AT 35% TOTAL SOLIDS Beef Cows 10,600 45,580 35% N/A 1,746,876 598,929 Dairy Cows 4,800 182,646 8% 4,800,000 2,000,000 685,714 Hogs 60,000 109,588 5% 2,304,000 960,000 N/A Chickens 1,050,000 49,823 25% 3,273,381 1,363,909 467,626 REQUIRED WORKINGCAPACITY (GAL) 20 DAY RETENTION
- 7. ENERGY CROPS … AND DRY CROP RESIDUALS
- 9. COMPARING METHANE YIELD ON A VOLATILE SOLIDS BASIS HIGHEST: Barley, Triticale, Be ets, Alfalfa, Rhubar b, Rye, Grass, Maiz e
- 10. COMPARING METHANE YIELD PER ACRE HIGHEST: Potatoes, Maize, Beets, Kale, Sorghum, Alfalfa
- 11. NET ENERGY YIELD PROVIDES AN INDICATION OF SUSTAINABILITY But ~50% of energy requirement is now fertilizer manufacturing
- 12. Presented at European Biogas workshop and study tour The Future of Biogas in Europe III 14th -16th of June 2007 University of Southern Denmark, Niels Bohrs Vej 9, 6700 Esbjerg Esbjerg - Denmark
- 13. Comparison of 41 Austrian digestion plants processing manure and energy crops – 2005
- 14. Comparison of 41Austrian digestion plants processing manure and energy crops – 2005 *The data for DRANCO Farm was not included in the Study and are from OWS records
- 15. Installation 1 Installation 2 DRANCO-FARM Nüstedt 500 kWel 1 MWel* Energy crops t/year 9 500 11 000 10 500 21 000 Manure t/year - 7 300 830 1 700 Total input t/year 9 500 18 300 11 330 22 700 Installed electrical power kWe 500 1000 500 1000 Reactor volume m³ 3000 3850 1200 1200 Temperature °C 49.5 39 55 55 Retention time days - 77 29 20 Loading rate kg VS/m³/d - 4.4 9.7 16-17 Biogas productivity Nm³/m³R/d 1.72 2.86 6.0 10.4 TS-content reactor % < 10 < 10 15-16 15-16 *The data for 1 MW was not included in the Study and are from OWS records Biogas from energy crop digestion / IEA Bioenergy Task 37 R. Braun / P. Weiland / A. Wellinger (2009)
- 16. Fermentation gas-measuring program II Comparison of 61 Digester Operations P. Weiland u.a. / Fachagentur Nachwachsende Rohstoffe e.V. * The data for 1 MW was not included in the Study and are from OWS records Mesophilic Dry Thermophilic Wet Thermophilic Dry DRANCO-FARM 2009 2010* # installations - 11 6 4 ** Reactor volume m³ 881-5 626 1 100-8 900 845-3 400 1 200 1 200 Loading rate kg VS/m³RV/d 1.1-9.8 1.8-3.4 1.9-4.8 9.7 15-16 Retention time days 35-289 80-164 78-163 29 20 3-5X Loading Rate 5X Digestion Efficiency <1/4 Digester Capacity
- 17. DRANCO-FARM plant Nüstedt (Germany) DRANCO Farm digesterC S T R 3 X 250 KW GENSETS
- 18. Specific features of the DRANCO FARM procedure ENERGY CROPS MIXER PUMP DIGESTATE STORAGE BIOGAS USE DRANCO- FARM DIGESTER PUMPPUMP ACTIVE DIGESTATE INACTIVE DIGESTATE INTENSIVE FERMENTATION • Combined feeding, mixing and pump technology • Recirculation of partially digested material from the upper cone area and integral post-fermentation step in the conical bottom
- 19. DRANCO-FARM Plant Data • Region: Bassum-Nüstedt • Startup: 2006 • Capacity: 500 KW (until 2009) • Expansion: in 2010 increased to 1 MW • Substrates: Maize silage, chicken manure, grasses • MT per year: 21,000 – 22,000 (silage, manure) • TS % of Inputs: ca. 30% (no addition of liquid manure or water!) • TS % in digester: 16-17% • Operation: Thermophilic (55°C) • Destruction: 75% of TS • Biogas production: 185 Nm3/mt ~ 4,000,000 Nm3/ yr • Methane Content: 54 - 56% • Parasitic load: ca. 5-7%
- 20. DRANCO-FARM plant Nüstedt (Germany)
- 21. CHICKEN MANURE MAIZE SILAGE GRASS SILAGE WASTE MEAL
- 22. DRANCO-FARM plant Nüstedt (Germany) 33 22 11 1 2 33 21.200 5.800 15.400Ton/year Biogas GAS STORAGE ENGINE GENERATOR Electricity (1000 kW) Heat (950 kW) DRANCO- FARM DIGESTER 1.200 m³ EXTRACTION PUMP STORAGE Inactive residue Active residue DOSING UNITDOSING UNIT DOSING SCREWDOSING SCREW MIXING UNIT/ FEEDING PUMP Energy crops (& manure) To field Digestate has NPK similar to manure on dry ton basis, pumpable, spr eadable
- 23. DRANCO-FARM plant Nüstedt (Germany) ECONOMIC DATA 2010 2011 Produced kWh electricity 7,899,090 8,728,924 Permitted power production 8,760,000 8,760,000 % of max capacity 90.2%* 99.6% * First year operation as 1MW-plant
- 24. Experiences and Conclusions • Study results prove the high efficiency of dry and continuous digestion of energy crops, high solids manures • High and steady biogas productivity is achieved by: – High TS content – Thermophilic operating temperatures – Optimal and consistent operating parameters • Dry and continuous digestion of energy crops is: – Technically possible – Reliable and highly efficient
- 25. EXAMPLE ECONOMICS - 1 Poultry Manure @ $10 tip fee Energy Crop @ $45 harvested cost Electricity sold at $0.10/kWh Digestate sold @ $10/ton DSCR of 4.6 CALCULATING THE NET VALUE PER TON OF FEEDSTOCK Value (cost) as Received TPY Value $/ton $/yr Manure 10,000 10.00$ 100,000$ Energy Crop(s) 45,000 (45.00)$ (2,025,000)$ TOTAL 55,000 (35.00)$ (1,925,000)$ Variable Costs TPY Cost $/ton $/yr O&M 55,000 (5.45)$ (300,000)$ Labor 55,000 (2.65)$ (145,600)$ TOTAL 55,000 (8.10)$ (445,600)$ Energy Value TPY Value $/ton $/yr Manure 10,000 58.03$ 580,305$ Energy Crop(s) 45,000 77.37$ 3,481,829$ TOTAL 55,000 73.86$ 4,062,134$ Digestate Value (Cost) TPY Value $/ton $/yr 39,286 10.00$ 392,857$ NET VALUE PER INPUT TON (EBITDA) TPY Value $/ton $/yr 55,000 37.90$ 2,084,391$
- 26. EXAMPLE ECONOMICS - 2 Bedded Pack Manure @ no cost Energy Crop @ $45 harvested cost Electricity sold at $0.10/kWh Digestate @ no value DSCR of 3.5 CALCULATING THE NET VALUE PER TON OF FEEDSTOCK Value (cost) as Received TPY Value $/ton $/yr Manure 45,000 -$ -$ Energy Crop(s) 10,000 (45.00)$ (450,000)$ TOTAL 55,000 (8.18)$ (450,000)$ Variable Costs TPY Cost $/ton $/yr O&M 55,000 (5.45)$ (300,000)$ Labor 55,000 (2.65)$ (145,600)$ TOTAL 55,000 (8.10)$ (445,600)$ Energy Value TPY Value $/ton $/yr Manure 45,000 38.69$ 1,740,914$ Energy Crop(s) 10,000 77.37$ 773,740$ TOTAL 55,000 45.72$ 2,514,654$ Digestate Value (Cost) TPY Value $/ton $/yr 39,286 -$ -$ NET VALUE PER INPUT TON (EBITDA) TPY Value $/ton $/yr 55,000 29.44$ 1,619,054$
- 27. CURRENT SITUATION • ~195 operating AD plants on/near North American farms • Limited to wet digestion • >95% are dairy farms UNMET MARKET OPPORTUNITY • ~20,000 additional farms with solid and semi- solid manures and crop residuals – >100X the volume of volatile solids
- 28. Fußzeile Organic Waste Systems, Inc. Tel. 513-535-6760 Fax 513-233-3395 norma.mcdonald@ows.be www.ows.be Thank you!
Hinweis der Redaktion
- High net energy yield per hectare is an indispensable prerequisite for an economic operation of an energy crop digestion plant. This includes high biomass yields and low energy requirement for plant cultivation, harvest and processing. From practical experience, on average, about 50% of the total energy requirement is spent for fertilizer production, minor amounts are required for machinery (22%), transport fuel (15%) and pesticides (13%).
- The consolidated results from data acquisition and analysis are given in Table 2. Although just representing a minimum number of selected parameters, the broad range of results obtained can be clearly recognized. The amount of substrate processed varied between less than 1 t/d in the smallest installations up to 55 t/d in large plants. The biogas productivity ranged from 0.24 to 2.3 m3 m-3 d-1. Correspondingly, the biogasyield varied between 0.42 and 1 m3 kg-1 VSS. A similarly broad range of corresponding results was found in the evaluation of the business economic parameters. The electrical efficiency was as low as 18% in the worst case, while over 38% was achieved in well operating installations. The degree of heat utilization of about 15% (median) was generally low. Best performing plants could use more than 40% of heat, while many of the installations did not make any use of the waste heat from power generation. Fourteen installations produce 100 kW, 11 produce 500 kW and 8 produce 250 kW electrical power. Five were very small installations (50 kWel) and three were bigger than 1 MW. About 71 % of 59,000 t dry organic substance, used annually in the 41 plants considered, originate from energy crops, 12 % from manure and 17 % from other biogenic byproductsand wastes. With a share of 53 %, maize dominates the crops used in digesters. Together with corn cob mixture (22 %) and maize corn (2 %) the overall share of maize amounts 77 %, followed by grass (9.4 %), grain (5.5 %) and several other crops (sun flower, wheat, clover). Concerning manure, pigs dominate (45.6 %), followed by cattle- (36.6 %), chicken- (7.9 %), horse- (6.3 %) and turkey manure (3.6 %). Food leftovers(20 %) dominate the co-substrates used, followed by flour mill by-products (14.4%), oil processing- (11.3 %), sugar beet-(10.8 %), potato- (7.4 %) and various other wastes of minor quantity. The majority of 99 plants considered runs 2-step digesters (85 %), 12 % use 3-step-, theremaining more than 3 digester steps. About 29 % of the plants run at 42C, 27 % at 40C and 22 % at 38C. Just 10 % operate at 48C and 12 % at 55C. The most common residence time is 100 days (32%), followed by 150 days (24 %), 200 days (15 %). Anyhow, 10 % of the installations use 250 days and 15 % even more than 250 days. Just 5% use less than 50 days residence time. The resulting organic loading amounts 4 kgVSS m-3 d-1 (32 %), 5 kg in 22 % and 3 kg in 20 % of the 41 plants considered. Seventeen plants use loadings between 6-8 kg, and 10 use loadings below 2 kg VSS m-3 d-1.
- Braun et al. (2007) collected the data from 41 energy crop digesters in Austria (of which 20% are thermophilic); Table 3 shows the results of this study. Compared with these 41 installations, the DRANCO-FARM concept has the highest overall efficiency (highest loading rate and biogasproductivity), while maintaining a very good biogas yield of 0.65 Nm³/kg VS.
- Comparing DRANCO-FARM to other energy crop digestersIn a later study, Braun et al. (2009) compared three installations digesting energy crops in Germany, one of which is the DRANCO-FARM installation of Nustedt. Table 2 summarizes some characteristics of these installations. The results for the DRANCO-FARM installation in this publication are valid for the situation when the electrical output was still 500 kWel. Since then, the electrical output has gone up to 1000 kWel, while still working very stable. These results were collected by OWS and are also represented in Table 2. From this table the high efficiency of the DRANCO-FARM installation is very clear. Where installation 2 needs a reactor volume of almost 4 000 m³ at a loading rate of 4.4 kg VS/m³R/d to obtain an electrical output of 1 000 kWel, the DRANCO-FARM installation obtains the same electrical output with a reactor volume of only 1 200 m³ at a loading rate of 16-17 kg VS/m³R/d. By working at a high total solids content at thermophilic temperature and by continuous monitoring and optimizing the installation, it was possible to obtain a loading rate almost 4 times as high as for an installation working at a low total solids content.
- In another study, Weiland et al. (2009) collected data from 61 installations digesting energy crops in Germany (including the installation in Nüstedt). Of these 61 installations, 16 operated under dry conditions, and 11 worked thermophilic. Table 4 shows for some parameters the range for dry mesophilic installations, for wet thermophilic installations and for dry thermophilic installations, compared to the DRANCO-FARM installation at the time of the report and the situation at the beginning of 2010. Again, the DRANCOFARM concept has the highest organic loading rate of all installations reviewed. The loading rate of the DRANCO-FARM installation is 3 times higher than the second highest dry thermophilic installation and 5 times higher than the highest wet mesophilic installation. Only one dry mesophilic installation has a loading rate that is comparable to the situation in Nüstedt at the end of 2008, but is still 1/3 lower than the current situation. The average loading rate of all 61 installations was ± 3 kg VS/m³R/d, which means that the DRANCO-FARM reactor is 5 times more efficient than the average installation.