anaerobic digestion ... advantages-challenges anaerobic digestion advantage challenges/byproducts...

Anaerobic Digestion Biogas from Heat using Food Processing Waste / Ag Residues

Bioenergy Australia Biogas Workshops

Presentation Content

Anaerobic and Energy/Nutrient Recovery Technologies in Waste Management

• Industrial Anaerobic Wastewater Treatment • Anaerobic sludge digestion and co-digestion • Waste to Energy • Nutrient Recovery

Why Anaerobic Digestion? Apart from the Environmental benefits!

• Additional revenue from reducing waste or processing others wastes

• Carbon credits if it is from a single source and avoids landfill

• Free fuel for heat and power

• Utilise existing infrastructure by reconfiguring municipal digesters to process external streams

Anaerobic Degradation Pathway Type of substrate affects pathway and treatment process

+ NH4 + PO4 + H2S

Organic Waste

Liquid

Dissolved organics - Brewery - Pulp and Paper - Beverage

Trade waste charges: Onsite

treatment

Trade waste, sludge disposal

charges Treatment/Land

fill

Landfill Composting, various

Particulate solids

- Slaughterhouse - Dairy - Many food wastes

Solid

- Household waste - Restaurant Waste - Garden Waste - WAS - Slaughter house

Manure etc.

Slurry

Advantages-Challenges Anaerobic Digestion

Advantage Challenges/Byproducts

Biogas production with 50-80% methane NH3 and PO4 release

0.43m3 biogas/kgCOD removed H2S produced preferentially

0.1 – 1.5 m3 biogas/kg VS Highly dependent on substrate, drives technology selection

Industrial Anaerobic Wastewater Treatment

Anaerobic technology is accepted globally as the best carbon removal technology for concentrated industrial wastewaters

• Brewery and Beverage • Pulp and Paper •Many Food industries • Distillery and Fermentation industry • Some chemical industries

Anaerobic Wastewater Treatment Systems Available

Low rate

• Volumetric Loading Rate(kgCOD/m3.d) •Anaerobic Lagoon 0.5-1 •High Rate Anaerobic Lagoon (HRAL) 1-2 •Completely Mixed Digesters 1-8

Medium rate

•Anaerobic Floatation Reactor (AFR) 3- 8 •Upflow Anaerobic Sludge Blanket (UASB) 5-15 •Anaerobic MBR 4-10

High Rate • Internal Circulation Reactor (IC) 18-50

Industrial Anaerobic Waste Water Treatment

CUB Yatala Brewery BIOPAQ® UASB

Smiths water reuse BIOPAQ® IC + MBBR + MF + RO

Visy Paper BIOPAQ® IC + aeration + Thiopaq®

Toohey’s Brewery Biopaq® IC + MBR

Castlemaine Perkins XXXX brewery Water

reuse Biopaq® IC + Circox + MF + RO

Anaerobic MBR

Biogas utilisation

• Feed into steam or hot water boilers (H2S up to 2000ppm sustainable if carefully managed – more info provided in case study) • Power generation via CHP engine • If high in H2S, biogas pre-treatment required, even for flaring • Siloxanes important for municipal/co-digestion applications • Typical site can offset site heating requirements by 20-50% • Site biogas storage generally impractical

Hydrogen Sulphide treatment • Various technologies, selection dependent on flowrate and concentration • Biological (Thiopaq) – Good for extremely high H2S concentrations (1-2.5% or more). Produces elemental sulphur cake

• Iron sponges – Good for medium concentrations (1,000 – 10,000 ppm). Regenerated with oxygen, media replaced periodically.

• Iron oxide introduction into digester, combined with microaeration – Good for low rate digestion. Iron continually added to digester

• Activated carbon – good for final polishing of low concentrations. Carbon frequently replaced at moderate concentrations.

Activated Carbon filter Media Changeout

Iron Sponge Media Changeout

Thiopaq scrubber

Power generation via CHP engine • Efficiency of approximately 40%, heat recovery 40-50% • Sulphur content extremely important for long term reliability • H2S pre-treatment usually via chilling then activated carbon • CHP maintenance costs – approximately 4c per kWhr • Recovered waste heat utilised in hot water loop to heat digester or incoming feed • Small booster fan to increase pressure • Engine is a large spark ignition engine, consumes oil

Castle Hill, Sydney

Coombabah, Gold Coast

Sandgate, Brisbane

Municipal Anaerobic Co-digestion

• Design on Volatile Solids loading basis, not COD or hydraulic retention time

• Organic material destruction: 55-65% (solids out is less concentrated that solids in)

• Advantage: • Destruction of organic material with minimal energy requirement

• Treatment plant can be energy positive with addition of external substrates

• Biogas used for power and heating of biomass • Utilise existing infrastructure (site location, asset for digestate treatment)

• Disadvantage: • Ammonia and Phosphorus release (10-20% of total N load in sewage plant), higher nutrient load if importing significant nutrient quantities

Yarra Valley Water, Melbourne

Waste to Energy Concept

Manure Organic Industrial Waste

Biogas

Electricity Production

Heat Heat is a by-product of the electricity production

Electricity The CHP produces

electricity which can be used directly or put into

the grid

Gas Upgrading

Fuel After upgrading biogas can be used as CNG in

cars

Gas Grid The gas can be put

directly into gas grid and the be used to power households or industry

Food Waste

Waste to Energy

Under construction - Yarra Valley Water, Waste to Energy Facility – 100 Tonnes per day

Biochemical Methane Potential (BMP) Essential tool to evaluate project potential

Also test the biogas quality and digestate concentration!

Waste to Energy Key Concepts

• Revenue - Gate fees / Carbon Credits for avoiding landfill • Reduced reliance on grid power by substitution (Feed in tariffs are minimal in Australia) • Digestate – ideally applied to land in a controlled manner as a fertiliser. Consider requirement for pasteurisation depending on final use and local biosolids guidelines • Control the feed – know how much of each substrate you are adding. It’s not a wastewater plant! • Co-digestion – upgrade waste receival, feed and mixing systems to cope with substrates with feed concentrations of 10-20% VS.

Nutrient Recovery Technologies Treatment of liquid stream after digestate dewatering

• Crystalactor® - Phosphate recovery as Struvite • Anammox – Low energy ammonia removal

Crystalactor® • Crystallization in fluidised bed pellet reactor • Removal of phosphate as struvite (Magnesium ammonium phosphate) • Reagents – NaOH + MgCl2 or MgO • pH 9-10 optimal • Use as MAP/DAP fertiliser alternative

Low Energy Nitrogen Removal : Anammox®

One Step ANAMMOX® Process (In Granular Sludge)

• Power consumption reduced by ~ 60%

• No additional carbon source requirement

• Typically Average NH4 removal>90%

• CO2 emission reduced by ~ 90 %

• Very little excess sludge production

• Stable and proven

• No full scale in Australia as yet but various pilots are underway

Wastewater and Waste to Energy Projects –

Key takeaways

• Scale is important – small isolated plants with low power and landfill costs are rarely economic. Consider working together with other producers in the area to share costs and savings. • Locate plant where power and heat demands are high with the ability to process digestate • Transport can be costly – consider site based dewatering of substrates to high feed concentrations if transporting long distances • Know what your potential waste sources are – quantities, composition and potential biogas yield to support business case

Future opportunities and vision

• Household food waste - 4,000,000 tonnes per annum in Australia. 450,000 garbage trucks per annum (www.foodwise.com.au) • Roll out dedicated household food waste bins – different to garden waste which is currently composted or incinerated • 2 weekly collection (with heavy sealed lid and odour control!) • Plastic and impurities are inevitable – how to process economically?

• Processed at waste transfer station to de- package plastic, remove bones/solids etc.

• Tankered to nearby digesters for energy production

• Reduce duplication of receival/processing infrastructure

Heat and Power

Centralised processing facilities

How to choose a technology supplier and/or delivery partner?

• Biogas and anaerobic digestion industry is relatively small in Australia. Many claims and glossy websites. • Key background checks:

§ ABN lookup – how long have they been in business? Will they be in business in 5 years time to support the project? Technology supplier or just a builder?

§ Understanding of relevant legislation (ESV/QLD Ga