Carbon Heat Energy Assessment and Plant Evaluation Tool (CHEApet) Tutorials: Carbon Footprint Primer
Tutorials Sources of Greenhouse Gases (GHG) at WWTPs How does CHEApet measure Carbon Footprint? Comparing GHG Protocols What GHG Protocol should I use? CHEApet output Example
CH4 RAS Air N2O Sources of GHG at WWTPs Example WWTP Process Flow Diagram Sources of Onsite Process GHG Emissions Biogenic Emissions CO2 N2O Collection System Emissions Biological Treatment Offsite Biogenic Emissions Discharge Secondary Clarification Primary Clarification Headworks Raw Wastewater UV Disinfection Thickened WAS Filter WAS Filter Backwash Thickened PS Centrifuge WAS Thickening Backwash CH4 N2O CO2 CO2 CO2 Filtration PS Thickening Recycle RAS/WAS Pump Station Recycle Biogas Polymer Generator Screenings and Grit to Disposal Blend Tank Fugitive Emissions CHP Heat Combustion Emissions Electricity Anaerobic Digester Recycle Supplemental Heat Polymer Centrifuge Dewatering Flares Excess Heat Outside Electricity Onsite Biosolids Disposal Emissions Combustion Emissions Biosolids Disposal
GHG Emissions at WWTPs GHGs in wastewater treatment emissions carbon dioxide (CO 2 ) methane (CH 4 ) nitrous oxide (N 2 O) Scope 1 Direct Emissions direct process emissions Scope 2 external fuel fugitive emissions Electricity Indirect GHG Emissions purchased electricity non-fuel forms of energy Scope 3 Other Indirect GHG Emissions resulting from activities of the WWTP from sources not owned by the utility
Carbon Footprint in CHEApet Process Emissions (CH4, N2O, CO2) Treatment processes Onsite Chemical production (based on usage) Biosolids Handling Onsite incineration Onsite land application Transportation Chemical production and deliveries Hauling biosolids Power Unit process consumption Building lighting and HVAC DIRECT EMISSIONS INDIRECT EMISSIONS
Direct Emissions (Scope 1) Three GHG Scopes are available for use in CHEApet Local Government Operations Protocol (LGOP) Based on California identities and IPCC Informal Approach Based on mass balance and IPCC Australian Approach Based on IPCC
Very Detailed View of Protocols DIRECT EMISSIONS CALCULATION PROTOCOL COMPARISON Parameter Intergovernmental Panel on Climate Change (IPCC) 1 <NOT IN CHEApet> Local Government Operations Protocol (LGOP) 2 Australian Approach Informal Approach Process Emissions CH 4 raw sewage organic loading (BOD 5 ) anaerobic digestion excludes recovered CH 4 and biosolids N 2 O population and human protein intake Biosolids Handling Emissions CO 2 biogenic or combustion CO2 is not included Based on dry mass of biosolids and the amount of incinerated biosolids. Emission factors are provided based on incineration technology. CH 4 N 2 O CO 2 incomplete combustion of digester gas population and emission factors nitrogen in effluent and emission factor for effluent discharge or based on population, BOD loading, and nitrogen uptake for cell growth biogenic or combustion CO2 is not included Biosolids are included in municipal solid waste; therefore incineration of biosolids is not discussed in the LGOP. CH 4 COD mass balance through CH 4 anaerobic digestion treatment fugitive emissions fraction of anaerobic treatment N 2 O off-gas from methane emission factor nitrification/denitrification excludes recovered gas N 2 O from CO 2 (combustion) nitrification/denitrification processes discharge from biogas mass balance of nitrogen usage or population and protein CO 2 (non-combustion) intake if loadings are generated in plant and unknown not released with receiving body of water for biogas effluent discharge CH 4, N 2 O: Based on dry mass of biosolids and emission factor from 2006 IPCC Guidelines. CH 4, N 2 O: Based on dry mass of biosolids and emission factor from 2006 IPCC Guidelines. Notes: 1. 2006 IPCC Guidelines for National Greenhouse Gas Inventories 2. California Air Resources Board (CARB), California Climate Action Registry (CCAR), ICLEI Local Governments for Sustainability, and The Climate Registry, Local Government Operations Protocol For the Quantification and Reporting of Greenhouse Gas Inventories, Version 1.0, 2008.
Comparing GHG Protocols Scope 2 and 3 (for the same model) CO2e/year) l GHG Emissions (tons Total 35000 30000 25000 20000 15000 10000 GHG Protocol Comparison Process (fugitive) CH4 emissions Includes CO2 from combustion of CH4 (flare/chp) Includes biogenic CO2 items are the same for all three protocols Emission factor has significant onsite N2O production Uses emission factor for CH4 release in sludge treatment 5000 0 Informal LGOP Australia Scope 1, Biogenic Process emissions CO2 Scope 1, Process emissions CH4 Scope 1, Process emissions CO2 (combustion of CH4) Scope 1, Process emissions N2O (onsite) Scope 1, Processemissions emissions N2O (offsite) Scope 2: Power Consumption CHEA PET Scope 3: Biosolids Hauling Scope 3, Biosolids incineration Scope 3: Chemical Transportation and Usage
Comparing GHG Protocols (for the same model) 100% GHG Protocol Comparison 90% 80% 70% Combustion CO2 of CH4 adds ~10% Nearly all GHG is from Power. issions Percent of GHG Emi 60% 50% 40% Over half of GHG is from 30% sludge treatment CO2e 20% 10% 0% Biogenic CO2 is about 30% Informal LGOP Australia Scope 1, Biogenic Process emissions CO2 Scope 1, Process emissions CO2 (combustion of CH4) Scope 1, Process emissions CH4 Scope 1, Process emissions N2O (onsite) Scope 1, Process emissions N2O (offsite) Scope 2: Power Consumption CHEA PET Scope 3: Biosolids Hauling Scope 3: Chemical Transportation and Usage Scope 3, Biosolids incineration
Indirect Emissions (Scopes 2 and 3) Transportation Hauling biosolids and chemical delivery Emission factors and method from California Climate Action Registry General Reporting Protocol Chemical usage calculated by CHEApet based on User input Only supplemental carbon is available in CHEApet Purchased Electrical Power Geographical emission factors provided by U.S. EPA Power consumption determined by User or calculated by CHEApet
Which GHG Protocol should I use? Remember that tthis is for a relative comparison only and the values should not be used for reporting LGOP is based on IPCC protocol and (so far) is the only agreed on protocol on the US. Rumors suggest EPA will not include biogenic CO2 in its GHG cap calculations however it will want to know what the biogenic emissions are. The informal approach is the only protocol that includes biogenic emissions However, the informal approach does not include offsite N2O production due to TKN in the effluent
Which GHG Protocol should I use? All three protocols use emission factors for N2O production. LGOP and Informal Approach is based on population Australian is based on COD removal Recent research shows emissions factors vary widely based on the process used and how close the system is to capacity. N2O also varies diurnally (mainly due to how the system operates as it relates to capacity)
CHEApet Output Only selected protocol is shown Emissions displayed d by scope DIRECT EMISSIONS Disposal not shown unless incinerated. INDIRECT EMISSIONS Process emissions including Biogenic TOTAL
CHEApet Output (Download) Downloadable file includes more information Also includes outputs to Canada s BEAMand WERF s LCAMER tools for further evaluation BEAM tool can be used to review biosolids disposal GHG emissions Note: Tool is based on Canadian Provinces so will need to adjust some assumptions for US or ignore (Power, CO2e from Diesel fuel, etc). Future versions of CHEApet will incorporate this. LCAMER can be used to look at technical and economics of various types of CHP systems
CHEApet Output (Download) Figures illustrating GHG relationships are included Can compare GHG protocols by switching selected protocol
GHG EXAMPLE: Utility wants to see what will happen if they add anaerobic digestion and recover biogas for energy to their WWTP
General Plant Assumptions Fairly warm temperatures
General Plant Assumptions SRT = 8 days Internal recycle = 250% No supplemental carbon Excess heat (if any ) used for building heat No sidestream treatment Land application of biosolids
Output: Mass Balance/Calorific Success! Plant Effluent appears to be reasonable
Output: Thermal (Comparison) No anaerobic digestion Anaerobic digestion with Co-generation incorporated No digestion = No information here OK! About 700 HP of electricity is produced from the biogas At the simulated plant conditions, excess heat is available after heating the digester!
Output: Electrical (Comparison) As selected by the user, the excess heat is being used to reduce building heating requirements No anaerobic digestion Co-generation incorporated Increase due to added digestion Generated Electricity reduces Net Power Requirements. Overall power usage shows a net decrease!
Output: Carbon Footprint (Comparison) No anaerobic digestion Fugitive CH4 Increase due to CH4 combustion Co-generation incorporated Slight increase due to high strength centrate (NH3) return Reduced due to overall lower power consumption