Making Waste Productive
Creating Energy from Waste
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 plants Snack Food plants Prepared Food plants ? Biofuels industry Ethanol plants Biodiesel plants
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…
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
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
Creating Energy Using the Anaerobic Process Conversion of organic material Raw input material: Fats, Oils, proteins, starches, carbohydrates, sugars Methane: 5.6 ft3/ lb COD Carbon Dioxide Discharge: Acetogenic bacteria Methanogenic bacteria Acetic Acid >95% COD Removal break complex food break acetic acid down molecules down to to produce Methane � 99% BOD Removal produce Carbon dioxide and Acetic Acid pH Adjustment Temperature Biomass accumulation: Control ~1% of Aerobic rate Digester • Air is not used so process proceeds at a much lower energy input than Aerobic treatment
Factors in Renewable Energy Plant Design ? Material handling ? Solids retention ? Good contact ? pH control ? Temperature control ? Nutrients ? Gas utilization
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
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
Identifying Energy Potential ? 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 methane gas generation ? STEP THREE: Demonstration project Test the design parameters on waste residuals to finalize the optimum factors for a full-scale plant
Evaluating Energy Potential ? Demonstration project (pilot) can be an important step to developing design ? Material handling, gas storage, waste blending
Identifying Energy Potential ? By geographic area, in cooperation with regional facility (power plant, research facility, cooperative) ? Minnesota Power study ? Wayne County, OH study ? By individual plant ? Cheese Plant demonstration ? Snack Food Plant demonstration ? Biofuels Plant demonstration
Identifying Energy Potential ? By geography: (1) Study with MN Power ? Food manufacturers in Minnesota Power territory ? Study done in 2005 in two phases: telephone survey and onsite visits to four facilities Confirmed plant waste quantities Sampled each waste stream (packed on ice)
Identifying Energy Potential ? By geography: (1) Study with MN Power ? Results Lbs/COD/day BTU Value KW TOTALEnergy Equivalent Value Snack Food 26,000 lb/day 140 MM BTU/day 550 kW/hr 2.3 MM BTU/hr Manufacturer Liquid Egg 4,800 lb/day 26 MM BTU/day 100 kW/hr 0.4 MM BTU/hr Manufacturer Dry Egg 1,500 lb/day 8.3 MM BTU/day 32 kW/hr 0.13 MM BTU/hr Manufacturer Beef and Port 620 lb/day 3.5 MM BTU/day 13 kW/hr 0.06 MM BTU/hr Repacking Plant ? Feasible dedicated plants (with reasonable timeliness for ROI ? A regional cogeneration plant would treat all of these manufacturers ? The potential waste streams from the other facilities do not generate enough energy to make dedicated plants or a cogeneration facility economically feasible
Identifying Energy Potential ? By geography: (2) Study in Ohio ? Food manufacturers in Wayne County, OH ? Study done in 2006 with onsite visits to six facilities Confirmed plant waste quantifies Sampled each waste stream (packed on ice)
Identifying Energy Potential ? By geography: (2) Study in Ohio ? Results Lbs/COD/day BTU Value kW Recoverable Heat Byproducts Plant Data not available Poultry Byproducts 6,250 lbs/day 35 MM BTU/day 135 kW/hr 0.6 MM BTU/hr (dead stock rendering) Plant Egg Processor 4,000 lbs/day 22.4 MM BTU/day 86 kW/hr 0.35 MM BTU/hr Dairy 5,250 lbs/day 29 MM BTU/day 110 kW/hr 0.48 MM BTU/hr Dairy 13,500 lbs/day 76 MM BTU/day 290 kW/hr 1.2 MM BTU/hr Cheese Processor 56,300 lb/day 315 MM BTU/day 1,200 kW/hr 5.1 MM BTU/hr ? Completed demonstration project on cheese manufacturing plant ? Cheese manufacturer can sustain full plant Can increase energy by processing waste from other regional plants
Demonstration Project #1: 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
Demonstration Project #1: Cheese Plant ? 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
Demonstration Project #1: Cheese 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)
Demonstration Project #1: Cheese Plant ? Test history: COD ? Operating at design capacity on permeate
Demonstration Project #1: Cheese Plant ? Test history: methane production ? Relatively steady Flow dropped when the gas flow was shut down to clean the gas discharge line of accumulated moisture
Demonstration Project #1: Cheese Plant ? 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
Demonstration Project #1: Cheese Plant ? Test history: BOD ? Virtually the entire BOD available has been consumed in the digester
Demonstration Project #1: Cheese Plant ? Test history: alkalinity ? Stable; most of the alkalinity is retained in the digester, conserving chemical
Demonstration Project #1: Cheese Plant ? Test history: calcium (needed for growth) ? Sufficient quantities; supplemental calcium is not required
Demonstration Project #1: Cheese Plant ? Test history: hydrogen sulfide ? A contaminant in the gas could cause operational difficulties in high concentrations; data inconclusive
Demonstration Project #1: Cheese Plant ? Test history: solids—TS, VS, TSS, VSS ? TSS- No accumulation of total suspended solids
Demonstration Project #1: Cheese Plant ? Test history: Methane and CO 2 Production ? Bag samples were collected to verify the accuracy of the on-line instruments that measure COD and methane (two manufacturers = 4 instruments)
Demonstration Project #1: Cheese Plant ? Test history ? summary ? Conversion of the dairy permeate to energy is straight forward and achievable Digester operated in a stable fashion No accumulation of COD in the digester Converted 98 percent of the COD (>99% of the BOD) to energy Gas 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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