Small Anaerobic Digestion Plants
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Transcript of Small Anaerobic Digestion Plants
BY Samer Al-Ayash
Mechanical Engineer Environmental Consultant
Target
1- Benefits of Small Waste-to-Energy Plants on: -Recruiting local expertise to design & build WTE plants - Recruiting local manpower for construction & operation - Rural Development - General Sustainable Development 2- Economical & financial needs 3- Simple design & engineering guides
Anaerobic Digestion Basics
-Is the process in which microorganisms break down biodegradable material (organics) in the absence of oxygen - the process occurs in one of two temperature ranges: 30-40°C (mesophilic) or 50-60°C (thermophilic) - System influent: animal manure, organic household wastes, sewage… - System effluent: biogas (65% methane + 35% carbon dioxide), nutrient rich digestate (fertilizers, land conditioners)
Benefits: - waste management and landfill reduction - improvement of agriculture - providing clean alternative energy source
EXAMPLES
Domestic Solid Waste Management Centre – Qatar By: Keppel Seghers
Client: Ministry of Municipal Affairs and Agriculture, Qatar Project Type: 20-year Design-Build-Operate (DBO) contract Project Value: approx. $1.7 billion Plant Capacity: Up to 2,300 tons of mixed domestic solid waste and 5,000 tons of construction and demolition waste per day Key Features: Integrated solid waste management facility providing waste sorting and recycling facilities, land filling, composting plant and a 1,500 tons per day waste-to-energy (WTE) plant Energy Output: Steam Turbine Generators, estimated 30MW exported to National Grid Processes: Waste Sorting / Separation, Recycling, Incineration, Anaerobic Fermentation and Land Filling
Sewage Treatment Plant Leonberg (near Stuttgart) - Germany
In operation since September 94 Total investment: 3.22M Euro Annual Incomes: 280,000 EU Simple Payback: 10.6 years
Bran Sands AAD Plant by Northumbrian Water - UK - Sewage Water treatment plant serving 2 million people - Advanced Anaerobic Digestion (AAD) system added to existing plant to reduce 500,000 tons of sludge to 60,000 tons and generate 4.7 MWe & 2 MWth - Annual incomes:
-$ 3.5 millions from electricity sold to national grid -$ 5 millions operational savings -$ 2.4 millions Renewable Obligation Certificate
- Carbon Dioxide reduction = 62,000 tons/year -Construction cost: 50 million USD -Construction works consumed:
-10,000 tons of concrete -4000 meters of pipes -100,000 meters of cables
CASE STUDY
AD TECHNOLOGY ° C
Organic Solid Waste
32 ton/day +
15 m³/day Sewage
AD PLANT 1600 m³ dig. 1000 m² area
Biogas
Boiler
Engine 1500 MWh/y
° C
Ponds 120,000 m³/y
Dewatering 115 tons/y
Storage 42,000 m³/y
Liquid Fertilizer
Distilled Water
Compost Fertilizer
SORTING DRUM & CONVEYOR
ADDITIONAL SYSTEMS PLASTIC RECYCLING LINE METAL BALERS GLASS RECYCLING LINE
WATER DISTILLATION / SOLAR DESALINATION - Designed by Innovative Concepts and developed with Promex Environmental Solutions& Alberto Fernandez Architects -Produces Distilled Water and cold air by completely clean & renewable energy sources (solar, wind & geothermal) - Completely self sustainable. - 200m diameter Solar Collector - Annually: 47,000 m³ of distilled water - 200,000 m³/hr of cold air
Batroun AD Plant Components 4 x 470m³ concrete digesters 1 x Preheating biogas boiler: 500KWth 4 x heat recovery biogas boiler: 120kWth each 2 x biogas electric generator: 200 kWe each 1 x sorting system: 100 tons/day 1 x metal baling system
Batroun AD Plant Balance Inputs: 32 tons/day Organic Wastes + 15 tons/day
sewage Sources: household wastes, dairy farms, agriculture
wastes, … Outputs:
Biogas 2300 m³/day Net Electricity: 1,750,000 kWh/year (enough for 200-300
houses) Liquid & Solid Fertilizers: 6500 m³/year Distilled Water: 9700 m³/year Recyclable material: 5500 m³/year
Batroun AD Plant Costs & Revenues Construction cost: 1.8 Million USD Annual Running Costs: 750,000USD Annual Revenues: 1.85 Million USD
Simple Payback period: 1 years Complex Payback Period: 3.5 years
Rules of thumb
Consider the ratio of organic waste to the total wastes Consider Total Solids (TS) of the organic waste Digester maximum allowed load: 70% of total volume Maximum allowed TS: 13% of digester loading 50% of TS shall be converted to biogas Biogas calorific value = 25 MJ/m³ Electric production: 2-3 kWh/m³ biogas
i.e.: for 1 ton of households
640 kg of organic wastes TS = 13% of organic wastes = 83 kg Biogas produced = 36 m³ Electricity produced = 100 kWh
Plant Capacity 6000 ton/year
20,000 ton/year
25,000 ton/year
50,000 ton/year
Investment Cost ($/t) 700-900 200-500 200-400 50-350
Operation Cost ($/t) 80-120 40-120 35-100 30-90
Large 1MW 5000 cows
Small 25kW 125 cows
Capital cost $ 9million $ 500,000
Annual Operating Cost $ 643,000 $9000
Power Sale ($/kWh) $ 0.06
Heat Sale ($/kWh) $ 0.01
Solids Sale $ 700,000 $ 20,000
Large vs. Small Large AD Plants Small AD Plants Lower initial cost/ton Lower running cost/ton More taxes paid to government More staff to be recruited Complex design & technologies High skilled & professional
international companies needed for design, construction & operation
Suitable for large cities or nation wide
Higher initial cost/ton Higher running cost/ton Less taxes paid to government Local Staff to be recruited Simple design & technologies Local professionals are able t0
design, construct & operate the plant. And many components might be manufactured and/or assembled locally
Suitable for small cities, group of villages, etc..
SMALL AD PLANTS Can be designed, constructed and operated by local
professionals and experts. Recruits local manpower => saving transportation over
long distances. Collecting wastes from surrounding villages or cities
=> less transportation cost. Can provide cheap power (electric & thermal) and
fertilizers for rural & agricultural communities. Improve sense of environmental responsibility within
the surrounding community.
THE END
THANK YOU