Making Waste Productive - University of Wisconsin Center … · 2006-12-31 · Food industry...

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Making WasteProductive

Creating Energy from Waste

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Creating Energy Inputs from Current Waste Outputs

►Organic material (waste) can be converted into energy (methane) through a process called anaerobic digestion

►Applications where waste disposal costs $100,000s/year can be turned into energy worth $100,000s/year

Creating Energy Inputs from Current Waste Outputs

►Two industries suitable to making energy from waste outputs

●Food industry

Cheese/Dairy plants

Snack Food plants

Prepared Food plants

●Biofuels industry

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Converting Biomass to Energy

► The energy value of a waste stream is measured in pounds of chemical oxygen demand (COD)

► Every pound of COD digested results in 5.6 cubic feet of methane

► An effective anaerobic digester usually converts 95+% of the available COD into methane

► Every cubic foot of methane produces around 1,000 BTU’s of energy

● Approximately 5,600 BTUs in a pound of COD

► A pound of organic solids will contain around a pound of COD

► A truck load of solids can contain around 50,000 pounds of COD

● Energy potential to power a 1 MW generator on a continuous basis

Segregating Biomass Streams

► Process and environmental technologies segregate the insoluble fraction of a

biomass stream from the soluble

● Isolate the energy potential material within a facility

Clarifiers

Screens

All types of filtration and dissolved air flotation devices

● The isolated insoluble high energy potential stream usually ends up on a truck…

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Types of Biomass Streams to Consider

► Hauled material

► Unsalable product

► Isolated streams

► Wastewater

In most applications a significant portion of the energy is contained in a small portion of the waste

Three Most Common Disposal Methods

►Land application

►Landfill

►Animal feed

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Paying others to haul and dispose of biomass

. . . Is the waste of a valuable asset

Stop feeding your cash to cows!

How the Anaerobic Process Works

to Create Energy

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Creating Energy Using the Anaerobic Process

Conversion of organic material

Raw input material:Fats, Oils, proteins, starches, carbohydrates, sugars

Digester

Acetogenic bacteria break complex food molecules down to

produce Carbon dioxide and Acetic Acid

Methanogenic bacteria break acetic acid down

to produce Methane

Acetic Acid

Carbon Dioxide Methane: 5.6 ft3/ lb COD

Discharge:

>95% COD Removal

�99% BOD Removal

Biomass accumulation: ~1% of Aerobic rate

• Air is not used so process proceeds at a much lower energy input than Aerobic treatment

pH Adjustment

Temperature Control

Factors in Renewable Energy Plant Design

►Material handling

►Solids retention

►Good contact

►pH control

►Temperature control

►Nutrients

►Gas utilization

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The Economics of Making Waste Productive

Factors that Weigh in an Economic Decision

►Avoided disposal cost

►Energy value

►Green value—Some options have

significant federal/state taxes and other credits

● Renewable energy credits

● Emissions trading credits

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Identifying and Evaluating Energy

Potential

Identifying Energy Potential

►There is a potential project if…

● Gas costs greater than $7 per MM BTU

● Electricity costs greater than 7.5¢ per KWh

● The plant produces 20,000 lbs. or more COD per day

● The plant is situated where there is a Renewable Portfolio Standard (RPS) in place

● Significant avoided cost

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►By geographic area, in cooperation with regional facility (power plant, research facility, cooperative)

►By individual plant


► By individual plant: 3-step process

● STEP ONE: Data evaluation, using existing plant data

Estimate the effectiveness technology to generate energy in the form of methane gas

● STEP TWO: Lab evaluation, using actual samples of plant residuals and organic waste

Determine parameters, limits and potential quantities of methanegas generation

● STEP THREE: Demonstration project

Test the design parameters on waste residuals to finalize the optimum factors for a full-scale plant

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Evaluating Energy Potential

► Demonstration project (pilot) can be an important step to developing design

► Material handling, gas storage, waste blending

Demonstration Project: Cheese Plant

► Project timeline: 9-29-05 to 5-25-06

► Waste source● Permeate stream

COD concentration averaged 52,000 mg/l

► Existing disposal methods ● Recovery of whey protein concentrate

● Recovery of lactose

● Treatment of 350,000 gallons per day of waste in plant-owned treatment plant

Trucked 6,000 gallon of waste from WPC and lactose recovery process

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► Demonstration project goals

● Replicate a full-scale loading rate

50 lbs of feed COD/1000 gallons of digester liquid volume

● Determine COD Removal Efficiency

● Evaluate Gas Quality

● Evaluate Material handling needs

● Determine optimum factors for a full-scale plant


► Test history

● Permeate (whey filtered to remove protein) fed to digester (1-18-06――――5-25-06)

Average COD strength of 53,000 mg/l

Ramped up until the target feed rate of 300 lbs COD/day (50 lbs/1000 gallons of digester volume)

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► Test history: COD

● Operating at design capacity on permeate


► Test history: methane production

● Relatively steady

Flow dropped when the gas flow was shut down to clean the gas discharge line of accumulated moisture

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► Test history: methane flow per unit of COD removed

● Consistently within the projected flow rate of 5.6 cubic feet of methane/lb of COD


► Test history: BOD

● Virtually the entire BOD available has been consumed in the digester

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► Test history: alkalinity

● Stable; most of the alkalinity is retained in the digester, conserving chemical


► Test history: calcium (needed for growth)

● Sufficient quantities; supplemental calcium is not required

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► Test history: hydrogen sulfide

● A contaminant in the gas could cause operational difficulties in high concentrations; data inconclusive


► Test history: solids—TS, VS, TSS, VSS

● TSS-No accumulation of total suspended solids

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► Test history: Methane and CO2 Production

● Bag samples were collected to verify the accuracy of the on-line instruments that measure COD and methane (two manufacturers = 4 instruments)


► Test history ―――― summary

● Conversion of the dairy permeate to energy is straight forward and achievable

Digester operated in a stable fashionNo accumulation of COD in the digesterConverted 98 percent of the COD (>99% of the BOD) to energyGas production met the design value of 5.6 cubic feet of methane/lb of COD removed

► Energy breakdown● 80% to 100% of gas demand

● 1 MW power output plus heat recovery

► Status● Demonstration project completed

● Final plant design

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► Projected ROI—Assumes output of gas to be burned in boilers or fed into a co-generation facility to generate electricity and waste heat

● Option A assumes the addition of a co-generation unit and the recovery of heat from that unit

● Option B assumes that the biogas is only burned in existing boilers

● Both options assume the biogas plant is NewBio’s property and the biogas utilization equipment is the client’s property

► Calculations based on 120 months contract term

● No “Green Credits” included


► Projected ROI

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► Projected ROI

More Information

►Contact NewBio

● www.newbio.com

● [email protected]

● 952-476-6194

Making Waste Productive - University of Wisconsin Center … · 2006-12-31 · Food industry...

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