Anaerobic Digestion: A Sustainable Technology

Ann C. Wilkie Soil and Water Science Department

University of Florida-IFAS acwilkie@ufl.edu

2013 BioEnergy Symposium IDEAS Center, UNC Charlotte

April 9, 2013

Natural Resources

Waste

Greenhouse Gases

Biodiversity

Energy Human Health

Water

The Dimensions of Sustainability

Community

Electrical and/or thermal energy

Biofertilizer

Organic wastes Anaerobic

digestion Biogas

Solar energy

Animal husbandry

Biofuel production

Crop harvesting

Industrial processing

Human consumption

Photosynthesis

H2O CO2

Biogas Cycle

Energy crops

Natural gas pipeline

Methanogenesis

Complex Organic Carbon

Monomers & Oligomers

Organic Acids

Acetate – H2 / CO2

CH4 + CO2

Hydrolysis

Acidogenesis

Acetogenesis

Anaerobic Digestion

Methanogens

Biofilm

BIOGAS PLANT

CORE TECHNOLOGY

Feedstocks • Animal manures • Agro-Industrial wastewaters • Municipal wastewaters • Municipal solid wastes • Biofuels by-products • Energy crops / crop residues

Benefits of Anaerobic Digestion • Renewable energy • BOD/COD reduction • Odor reduction • Pathogen reduction • Nutrient conservation • Greenhouse gas reduction

ANAEROBIC vs AEROBIC PROCESSES

• Loadings not restricted by rate of oxygen transfer

• Not restricted by high cost of oxygen transfer • Usable end product in the form of methane gas • Less biological solids production per pound of

BODR • Less land area required due to smaller

footprint

GLOBAL TECHNOLOGY

• Tolerant – varied feedstock capability

• Scalable – custom sizing

• Flexible – rapid restart after seasonal idling

• Universal – worldwide application

National Biodigester Programme Cambodia (July 2010)

Biodigestion in Honduras (September 2012)

Anaerobic digesters

Where is the flame the brightest?

• Food waste represents a significant component of the municipal waste stream.

• Most of this food waste is hauled to landfills.

• A practical alternative is to use food waste as a feedstock for anaerobic digestion to produce energy in the form of biogas.

Current open-loop food-waste-to-landfill system

FERMENTATION

DISTILLATION

BIOGAS

STILLAGE

ANAEROBIC DIGESTION

BIOETHANOL

TRANSESTERIFICATION

PRESS CAKE

BIODIESEL

Oil pressing

CRUDE GLYCEROL

Washing

WASTE OIL

VIRGIN OIL

CRUDE BIODIESEL

WASHWATER

METHANOL + KOH

Anaerobic Digestion

BIOGAS

OIL CROPS ALGAE

CLOSED LOOP

DAIRY / FEEDLOT BIOETHANOL PLANT

ANAEROBIC DIGESTER

MANURE BIOGAS

FEED

STILLAGE

Co-location Synergies

WATER

SUNLIGHT

Energy Crops

Biogas Plant

Biofertilizer

CO2

CO2 WATER

Methane

Green Grass to Green Gas

Crops for Biogas

BIOGAS and ALGAE

• Nutrient-rich effluent from biogas production can be used for mass cultivation of algae

• CO2 supplied from biogas combustion promotes algal growth.

Feedstock for Anaerobic Digesters

• Increase gas production

• Increase electricity generation

• Facilitate co-digestion by capturing imported nutrients

Opportunities for Algae

Municipal Wastewater Treatment

• Today: Aerobic + Anaerobic

• Future: Anaerobic + Aerobic

Building capacity for the future

Anaerobic Digestion: A Sustainable Technology

Ann C. Wilkie Soil and Water Science Department

University of Florida-IFAS acwilkie@ufl.edu

2013 BioEnergy Symposium IDEAS Center, UNC Charlotte

April 9, 2013