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