Green Energy from a Community-Based Biogas Digester Monday, July 2nd, 2012
Charles Opferman, AIA Principal Energy Consultant
This Presentation will Address
• FCPC Milwaukee Digester Project Overview • Project Planning Issues • Digester Process – Organic Feedstocks (input) – Power/Heat Generation – Digested Solids (output)
• Successful Strategies and Economic Factors • Locational Impacts • Potential Pitfalls
• End Results
Introduction
• The Forest County Potawatomi Community (FCPC) is developing a 2 MW renewable energy project in Milwaukee, WI • An Anaerobic digester system would utilize organic food processing waste to produce biogas to fuel this project. • Renewable energy generation is consistent with FCPC’s goals and values. • A $2.6 million DOE Community Renewable Energy Deployment grant was obtained for this project. • Several renewable technologies analyzed- found biogas most feasible. • When all approvals are obtained, construction will begin later this year and be completed in 2013.
Project Description • Utilize about 3 acres of land • Former brown field site, originally tamarack swamp • 10,000 s.f. building • Two digester tank system • Capital budget of ~$18M
Project Concept
Project Planning Issues
• Inputs: organic waste supply sources • Regulatory issues: air permit and tariff requirements • Project Structuring: Ownership and financing • Digester technology selection • Outputs: electricity, heat, effluent, & digested solids
Simplified Digester Process Schematic
Or Compost
Flexible design for feedstock variation
For use or sale
Digester Input – Organic Feedstock Planning • Wisconsin has a diverse supply of organic materials that can be utilized for anaerobic digestion.
• Identify locally available feedstock materials. • Many organic wastes can be obtained by decreasing disposal costs to their producers. • Material uniformity and source control is an important consideration. • Multiple supplies can help balance digester nutrient needs.
Feedstock Biogas Generation Example
Source: Basisdaten Biogas Deutchland, Marz 2005: Fachagentur Nachwachsende Rohstoffe e.V.
Example Feedstock Material Receiving
• Feedstock tanker truck shown unloading at EBMUD. • Options are solid or liquid form
• Feedstock can be sent directly to digester or “holding tank” (with no exposed on-site storage)
The FCPC Milwaukee digester project will only accept tanker trucks and all unloading will occur inside the building structure. (no outside operations)
Anaerobic Digestion Process Options
• Biogas energy uses: methane can be used to produce on site electricity and/or for process heat. • Europe has a longer track record. – CSTR, rotary, plug flow, dry and wet digestion systems
• Challenge is to make cost effective for U.S. lower cost energy economics – capital and operating costs.
Biogas Engine Generators
• Biogas engines have a longtime established track record. • Biogas engine manufacturers have increased the electrical efficiency output in recent years. • The Milwaukee digester project is sized for 2 MW. • Requires gas conditioning to remove moisture, H2S and possibly removal of other contaminates.
Power/Heat Generation
Rating LHV of Fuel Engine Power
BTU/SCF BHP
650 1402
Engine Efficiency
%
41.3%
Thermal Efficiency
%
46.0%
Total Efficiency
%
85.7%
Electric output 2 engines
MW
2.0
Heat output 2 engines
MMBTU/HR.
6.21
Plant load (winter)
MMBTU/HR.
1.73
Available heat
MMBTU/HR.
4.48
Digested Solids Uses
• Digested solids sold or supplied to compost or fertilizer partner. – N values, potential contaminants, moisture content critical – Bulk sales vs. retail outlets
Successful Strategies and Economic Factors The Challenge is to balance operational and capital costs against electricity and heat sale revenues and income from tipping fees, taking advantage of tax incentives and tariffs while generating a satisfactory return on investment. • Right sizing of Project
• Economical organic feedstock supply and tipping fees • Project setting, location and infrastructure • Appropriate digester technology
• Electricity and process heat value • Digested solids beneficial use outlets and values • Financial incentives – DOE grant, Fed. tax credits - Section 1603 and NMTC, State Incentives, Biogas Tariffs and carbon credits
Locational Impacts
• Designs can achieve minimal impact on existing operations. • Can be configured to be aesthetically acceptable. • Mitigate odor and noise with proper control strategies. • Ability to meet all regulatory requirements.
Potential Pitfalls
• Lack of clear goals and strategies • Inadequate feedstock supply • Incorrect assessment of economics • No use for excess heat (need added value approach) • Need to develop outlets for digested solids • Improper plan for liquid effluent and treatment • Project development timeframe needs to match any planned incentives - timing important
End Result
What does a successful community digester look like?
Community Digester Summary
• Anaerobic digestion and biogas generation proven technology • Community Digesters utilize available organic wastes. • Environmental benefits achieved – – – –
Waste minimization GHG reductions Reduce base power plant mercury and other emissions Reduce dependence on fossil fuels
• Hedge against volatile energy pricing • Economical solution for renewable energy
Questions?
[email protected] 414-978-4720