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Sustainable Biosolids Management: Direct Energy Use Does Not Tell All
Ruth Borgmann, Hazen and Sawyer Erika Bailey, City of Raleigh TJ Lynch, City of Raleigh Stephanie Ishii, Hazen and Sawyer Amy Hanna, Hazen and Sawyer
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Agenda for our time together
Background GHG Evaluation Approach Results and Hotspot Analysis
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Background
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Neuse River Resource Recovery Facility Raleigh, NC
Advanced BNR Process Current capacity 60/75 MGD Biosolids Management: Converting to THP and Advanced Anaerobic Digestion with conversion of biogas to RNG
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Class A Cake Land Application
Biosolids Outlets Current: Class B Liquid Onsite Offsite Composting Raleigh Plus Landfill Bioenergy: Class A Cake Land Application Describe reason for variety of biosolids outlets (limiting factors, why they don’t only do the cheapest route) and what is driving them to move to Class A cake
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Project Drivers Aging biosolids handling infrastructure
Plan for future capacity needs Uncertainty of future Class B land application Sustainable solution for the future Key benefits of THP are all Class A, reduced volume, resource recovery with biogas use and significant reduction in GHG City of Raleigh has been involved with planning this transition for over a decade
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Climate/Energy Action Plan
City-wide interdepartmental effort Goals: Operational efficiency Energy reduction GHG reduction Cost savings Over 100 strategies were evaluated for implementation Bioenergy Recovery Project Completed in 2012; currently being updated Assess carbon footprint – what dominates environmental burden? Make sure we aren’t shifting the environmental burden The Climate Energy Action Plan (CEAP) was funded through the Energy Efficiency Conservation Block Grant as we worked to address our energy costs b/c “Energy” in the big picture was our 2nd largest operating expense. It was second only to our people or personnel related expenses. The goals for CEAP were operational efficiency, energy reduction, greenhouse gas reduction and cost savings. There were 6 strategic teams (fleet, buildings, carbon, renewables, legal and financial) that included members from over 11 departments with membership from across the organization. The teams came up with over 100 strategies, which were evaluated for implementation. The project was completed in 2012 and is currently being updated. Practical implementation of strategies to minimize carbon-related emissions, maximize energy efficiency of existing City facilities and provide renewable energy opportunities.
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Greenhouse Gas Emissions
On the left are the community results. The community emissions have gone up by 2% and with the main drivers for the community being Buildings (single family homes/office buildings), Transportation (driving to work alone) and Waste (what we throw away) On the right are the municipal results The municipal emissions have gone down primarily b/c the closed Wilders Grove Landfill is emitting less methane as the old municipal waste has be decomposing longer. There has also been a slight reduction in emissions as a result of some energy efficiency projects. Additional projects at the Neuse River Resource Recovery Facility will work to further reduce our Municipal Emissions. The population in Raleigh has increased
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Why not just look at direct energy use?
Direct energy use is an effective metric for quantifying environmental impact, but there are other elements involved in each biosolids management strategy that may significantly drive the overall environmental burden or benefit. For example, direct electricity use doesn’t capture the environmental impact of manufacturing and transporting chemicals required for each strategy, nor the benefits associated with offsets, such as those enabled by the use of digester gas instead of diesel or the reduced use of fertilizers due to land application of biosolids. Assess carbon footprint – what dominates environmental burden? Make sure we aren’t shifting the environmental burden Direct energy use doesn’t account for digester gas to beneficial use As a net energy producer the bioenergy project qualified for CWSRF Green Project Reserve Funding
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GHG Evaluation Approach
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GHG Evaluation: Alternatives
Dewatering Lime Stabilization Class A Alkaline Raleigh Plus PS McGill Composting OR Landfill WAS Class B Liquid Land App. Onsite Offsite Uncovered Aerobic Digesters Gravity Belt Thickening Covered Aerobic Digesters Current Thickening Blend/ Screen Pre-Dewatering THP Anaerobic Digestion Final Dewatering WAS PS Class A Land App. Bioenergy FOG Can vary biosolids outlets FOG can or cannot be added
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GHG Evaluation: Approach
Inventory Value GHG Equivalent GHG Footprint Operational Phase Functional Unit: 1 lb(dry) pre-processed biosolids CO2 Equivalents
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GHG Evaluation: Approach
Functional Unit: 1 lb (dry) pre-processed biosolids Inventory Value GHG Equivalent GHG Footprint kWh Functional Unit OR lb. product lb. CO2e kWh OR lb. product lb. CO2e Functional Unit
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GHG Evaluation: Inventory
Units: kWh/Functional Unit or gal Alum/Functional Unit Inventory Value GHG Equivalent GHG Footprint Inventory Items Electricity Chemicals Biosolids transportation Offsets Electricity considers local electricity grid mix Chemicals include manufacturing and transportation
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Inventory – Current PS WAS
Dewatering Lime Stabilization Covered Aerobic Digesters Gravity Belt Thickening Uncovered Aerobic Digesters PS WAS Class A Alkaline Raleigh Plus McGill Composting OR Landfill Class B Liquid Land App. Onsite Offsite Functional Unit: 1 lb (dry) pre-processed biosolids
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Inventory – Current Electricity PS WAS
Dewatering Lime Stabilization Covered Aerobic Digesters Gravity Belt Thickening Uncovered Aerobic Digesters PS WAS Class A Alkaline Raleigh Plus McGill Composting OR Landfill Class B Liquid Land App. Onsite Offsite Air Electricity CAD Mixing, Air & Odor Control Functional Unit: 1 lb (dry) pre-processed biosolids
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Inventory – Current Chemical PS WAS
Polymer Electricity LKD Dewatering Lime Stabilization Covered Aerobic Digesters Gravity Belt Thickening Uncovered Aerobic Digesters PS WAS Class A Alkaline Raleigh Plus McGill Composting OR Landfill Class B Liquid Land App. Onsite Offsite Air Electricity Polymer CAD Mixing, Air & Odor Control Functional Unit: 1 lb (dry) pre-processed biosolids
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Inventory – Current Offsets PS WAS
Polymer Electricity LKD N&P Offsets Dewatering Lime Stabilization Covered Aerobic Digesters Gravity Belt Thickening Uncovered Aerobic Digesters PS WAS Class A Alkaline Raleigh Plus McGill Composting OR Landfill Class B Liquid Land App. Onsite Offsite Air Electricity Polymer CAD Mixing, Air & Odor Control N&P Offsets Functional Unit: 1 lb (dry) pre-processed biosolids
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Inventory – Current Transport PS WAS
Polymer Electricity LKD N&P Offsets Dewatering Lime Stabilization Covered Aerobic Digesters Gravity Belt Thickening Uncovered Aerobic Digesters PS WAS Class A Alkaline Raleigh Plus McGill Composting OR Landfill Class B Liquid Land App. Onsite Offsite Air Electricity Polymer CAD Mixing, Air & Odor Control N&P Offsets Transport Functional Unit: 1 lb (dry) pre-processed biosolids
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Inventory – Bioenergy WAS PS FOG
CNG Buses Thickening Blend/ Screen Pre-Dewatering THP Anaerobic Digestion Final Dewatering WAS PS Class A Land App. Gas Cleaning Steam Boiler Flare Alum FOG Sidestream Functional Unit: 1 lb (dry) pre-processed biosolids
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Inventory – Bioenergy Electricity WAS PS FOG
CNG Buses Thickening Blend/ Screen Pre-Dewatering THP Anaerobic Digestion Final Dewatering WAS PS Class A Land App. Gas Cleaning Steam Boiler Flare FOG Alum Sidestream Functional Unit: 1 lb (dry) pre-processed biosolids
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Inventory – Bioenergy Natural Gas WAS PS FOG
CNG Buses Thickening Blend/ Screen Pre-Dewatering THP Anaerobic Digestion Final Dewatering WAS PS Class A Land App. Gas Cleaning Steam Boiler Flare FOG Alum Sidestream Building Heat Functional Unit: 1 lb (dry) pre-processed biosolids
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Inventory – Bioenergy Chemical WAS PS FOG
CNG Buses Thickening Blend/ Screen Pre-Dewatering THP Anaerobic Digestion Final Dewatering WAS PS Class A Land App. Gas Cleaning Steam Boiler Flare FOG Alum Sidestream Building Heat Functional Unit: 1 lb (dry) pre-processed biosolids
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Inventory – Bioenergy Offsets WAS PS FOG
CNG Buses Thickening Blend/ Screen Pre-Dewatering THP Anaerobic Digestion Final Dewatering WAS PS Class A Land App. Gas Cleaning Steam Boiler Flare FOG Alum Sidestream Building Heat Functional Unit: 1 lb (dry) pre-processed biosolids
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Inventory – Bioenergy Transport WAS PS FOG
CNG Buses Thickening Blend/ Screen Pre-Dewatering THP Anaerobic Digestion Final Dewatering WAS PS Class A Land App. Gas Cleaning Steam Boiler Flare FOG Alum Sidestream Building Heat Functional Unit: 1 lb (dry) pre-processed biosolids
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Inventory – Bioenergy CNG WAS PS FOG
CNG Buses Thickening Blend/ Screen Pre-Dewatering THP Anaerobic Digestion Final Dewatering WAS PS Class A Land App. Gas Cleaning Steam Boiler Flare FOG Alum Sidestream Building Heat Functional Unit: 1 lb (dry) pre-processed biosolids
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GHG Evaluation: Equivalent
Units: lb. CO2e / kWh or lb. CO2e / gal Alum Inventory Value GHG Equivalent GHG Footprint Electricity City of Raleigh GHG Inventory Report approach (EPA references) Biosolids transportation City of Raleigh GHG Inventory Report approach (EPA tools, MOVES2014a) Chemicals Literature review Offsets
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GHG Evaluation: Footprint
Units: lb. CO2e / Functional Unit Inventory Value GHG Equivalent GHG Footprint Editable Excel Workbook Option for default and/or user defined values for inventory items and GHG equivalents References / explanations for default values Dynamic figures Total GHG comparison across alternatives GHG hotspot analysis within alternatives
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Results and Hotspot Analysis
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GHG Footprint 0.06 -0.55
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GHG Footprint – Without Offsets
0.06 0.45 0.45 0.18 0.18 -0.55
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GHG Footprint – With Offsets
0.06 0.45 0.45 0.18 0.18 -0.12 0.06 Current – N&P fertilizer offset Bioenergy – N&P fertilizer offset + diesel offset (buses) -1.00 -0.55 -0.55
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Current vs. Bioenergy GHG Production
Bioenergy is able to convert digester gas to RNG which allows for GHG Footprint to decrease with increasing flow to Neuse River RRF Typical Passenger Car is estimated to emit 5.5 tons CO2e per year
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Hotspot Analysis – Current
Transport Chemical Electricity Make axes the same for better comparison? Offsets
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Hotspot Analysis – Current
Transport Lime Chemical Electricity CAD Air & Mix Make axes the same for better comparison? N Offset Offsets P Offset
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Hotspot Analysis – Bioenergy
Transport Chemical Electricity Offsets Make axes the same for better comparison?
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Hotspot Analysis – Bioenergy
Transport Chemical Electricity Diesel Offset (Buses) Offsets Make axes the same for better comparison? N Offset P Offset
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Effect of Varying FOG Quantities - Bioenergy
Diesel Offset (Buses) Footprint: lb CO2e/Functional Unit FOG Receiving – 30,000 gpd Footprint: lb CO2e/ Functional Unit FOG Receiving – 0 gpd
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How does this help CORPUD?
Internal decision making Further operational adjustments for hotspot reduction Communication with stakeholders and public about environmental stewardship
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Thank you from the team for your attention
Contact Information: Ruth Borgmann, PE
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BULLPEN
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Effect of Varying Biosolids Outlets – Current
Original Scenario Raleigh Plus: 20% Composting: 20% Onsite Class B: 4% Offsite Class B: 9% Landfill: 47% Updated Scenario Raleigh Plus: 0% Composting: 50% Onsite Class B: 0% Offsite Class B: 0% Landfill: 50%
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Effect of Varying Biosolids Outlets – Current
LKD CAD Air & Mix N Offset P Offset Footprint: 0.06 lb CO2e/Functional Unit Footprint: lb CO2e/ Functional Unit
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Sustainability and efficiency is a core focus of the City of Raleigh’s strategic plan
Objective 3: Optimize public infrastructure projects to address community resiliency, sustainability and efficiency. Development of a bioenergy recovery program for the Neuse River Resource Recovery Facility is a key deliverable under this initiative.
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GHG Footprint - Current
Functional Unit: 1 lb (dry) biosolids Offsets: Nitrogen Fertilizer Phosphorus Fertilizer Biosolids Outlets: Raleigh Plus Composting Class B Onsite Class B Offsite Landfill -0.120 Make axes the same for better comparison?
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GHG Footprint - Bioenergy
Functional Unit: 1 lb (dry) biosolids + FOG blend Offsets: Diesel Nitrogen Fertilizer Phosphorus Fertilizer Make axes the same for better comparison?
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EPA GHG Analysis Approaches
Find better graphic? GHG Eval had some elements of scope 3 included. Scope 1 Emissions generated inside the plant, e.g., fugitive gases Scope 2 Offsite emissions associated with electricity usage Offsite offsets associated with electricity generation Scope 3 Emissions generated outside the plant, e.g., transportation Offsets associated with carbon sequestration
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