NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC. Techno-Economic Analysis for the Production of Algal Biomass: Process, Design, and Cost Considerations for Future Commercial Algae Farms Algae Biomass Summit October 24, 2016 Ryan Davis, Jennifer Markham, Christopher Kinchin, Nicholas Grundl
25
Embed
Techno-Economic Analysis for the Production of Algal Biomass - Algae …algaebiomass.org/wp-content/gallery/2012-algae-bioma… · · 2017-01-05NREL is a national laboratory of
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
• Much of this variability may be attributed to differences in several key underlying assumptions –e.g. growth rates, pond system costs
• Given wide lack of agreement on these key metrics, analysis considers two approaches:1) “Top-down”: What does performance + cost “need to be” to hit a given biomass cost goal2) “Bottom-up”: Given a set of defendable assumptions, what is the resulting biomass cost
• Y and X axes – mutually independent variables• Contours = resulting minimum biomass selling price (MBSP)• MBSP reduces for higher productivity or lower pond cost• Likely lower limit for system costs ~$30k/acre (commercial nth
plant) • At this limit $430/ton is possible (@ 30 g/m2/day), but
challenging to reduce costs any further• Even if ponds were “free”, CO2/nutrient/other costs still add
• External reviewer agreement that >25 is or must be achievable by 2022 to demonstrate sufficient progress over today’s benchmarks
• Best performance published to date = 23 g/m2/day (+ 40% lipids) (Huntley/Cellana), 8-21 g/m2/day April-October (White/Sapphire)
• Composition: mid-harvest/high-carbohydrate Scenedesmus (HCSD), 27% FAME lipids• Scenedesmus selected given detailed compositional data, commercial relevance• Composition + productivity = ~3.9% PE to biomass (from full-spectrum irradiance), vs ~14% max
• Seasonal variability: 3:1 (max vs min seasonal growth)• Key challenge unique to algae – adds design constraints for downstream conversion facility• Most recent basis from PNNL BAT model = ~5:1 average for Gulf Coast• May be reduced either through strain engineering or seasonal strain rotation• Current ATP3 data ~3-4:1 average of all sites, <2.5:1 for Florida (“representative” Gulf Coast site)
• Evaporation: Based on prior harmonization modeling work (Gulf Coast average)
NREL solicited 4 separate inputs on 8 pond designs/costs:
• Key aspect of this work – address common conceptions that commercial algae pond costs are too scattered, uncertain to “really” establish with any certainty
• Ponds grouped into 100-acre “modules”, in turn constituting a 5,000 acre facility based on cultivation area (~7-9k total farm footprint)
• Continuous cultivation at fixed 0.5 g/L AFDW harvest density• Freshwater scenario, includes blowdown to control salt/inorganics
à All pond designs are based on unlined ponds with native clay soils• Plastic liners only used on berms or pond turns (2-25% of pond area)• Full pond liners considered as sensitivity (strongly influence total costs)
Source 2acre 10acre 50 acreLeidos (engineering firm) R R S
MicroBio (expert consultants) R R
Harris Group(engineeringfirm) RGAI(commercialdeveloper) G G
R=paddlewheelraceway
S=gravity-flowserpentine
G=GAIdesign(gravityracewaywithpump)
NATIONAL RENEWABLE ENERGY LABORATORY
Pond Cost Estimates
8
a Additionaldatapoints(notincludedinfullTEA)addedtothisplottofurtherdemonstratecostalignmentbypondsize.
b Bealcostsbasedonextrapolatingfrompublishedcostsforfullylinedpondtoaminimally-lineddesign.IfafullylinedpondwereusedfortheBealcase,totalinstalledcostwouldbe$114,000/acre.
c GAIcasesincludeelectricalcostsunder“otherpondcosts”.
• Pond costs show reasonable agreement based on “small”, “medium”, or “large” size groupings
• More strongly a function of scale –highlights economy of scale advantages for building larger ponds >2-3 acres
• CO2 cost/sourcing• Price for purchased CO2 (flue gas CCS) $0-100/tonne = +$100/ton MBSP• Additional scenarios considered for flue gas: 15 km flue gas transport infeasible• Flue gas co-located with power plant: possible to reduce MBSP ~$45/ton, but logistical challenges for pond delivery
NATIONAL RENEWABLE ENERGY LABORATORY
Summary and Concluding Remarks
11
• Algal biomass costs are tied strongly to productivity + cost of ponds, followed by CO2 + nutrients
• To achieve economically viable MBSP, critical to:a) Increase productivity and strain robustnessb) Maximize economy of scale benefits using >10-acre pondsc) Maximize farm size to >5,000 acresd) Demonstrate pond operability without pond liners
• “Bottom-up” modeling targets a 2022 base case MBSP of $491/ton AFDW
• Updated conversion models project 2022 targets near $5-6/GGE for this cost (CAP + HTL)
• Possible to reduce biomass costs to ~$430/ton, but achieving $3/GGE will require fundamental shift towards coproducts
• CAP pathway is well-suited for coproduct opportunities: non-destructive isolation of sugar/lipid/protein constituents
• Coproducts are a key focus of our TEA work moving forward
NATIONAL RENEWABLE ENERGY LABORATORY
Questions?
Jennifer Markham Chris Kinchin Nick GrundlEric TanPhil PienkosLieve LaurensNick NagleBob McCormickJake KrugerMary Biddy
• 5,000 acre facility based on cultivation area (~7-9k acre total footprint)• Ponds divided into 100-acre plots; each plot includes circulation pipelines and primary
dewatering• Graded over gradual 1% continuous land slope = “terraced” design allowing for downhill
gravity circulation to central dewatering + downstream conversion (but requires uphill pumping of clarified water from central dewatering)
• Continuous cultivation/harvesting at a fixed 0.5 g/L AFDW harvest density from ponds• Freshwater base case avoids introducing subjectivity for proximity/cost of saline water sourcing
and brine disposal (consistent with prior harmonization models)• Blowdown still included to mitigate salt/inorganics <4,000 mg/L – taken off primary dewatering
recycle line (lowest algae concentration point = minimize biomass losses)
NATIONAL RENEWABLE ENERGY LABORATORY
Inoculum system
15
• Inoculum system based on increasingly larger volume steps: PBR –covered lined ponds – open lined ponds
• Each step grows inoculum from 0.1 to 0.5 g/L based on the same seasonal productivities as main ponds
• Final stage inoculates production ponds at 0.1 g/L• Inoculum system sized to require inoculation once every 20 days during
peak summer season• Equivalent to 5% of facility ponds requiring re-inoculation each dayà Key nth plant assumption – robust strains withstanding frequent culture crashes
H2O+CO2+Nutrients
SeedTrain(fromlab)
Photobioreactor
CoveredPond LinedPond
H2OEvaporationLoss
ToCultivationPonds
H2O+CO2
+Nutrients
H2O+CO2
+Nutrients
NATIONAL RENEWABLE ENERGY LABORATORY
Dewatering
16
• Primary dewatering occurs within the 100-acre modules to avoid circulating large volumes of water over entire facility
• Concentrates biomass from 0.5 g/L (0.05 wt% AFDW) to 10 g/L (1%) = 95% reduction in volume throughput
• Achieved using low-cost in-ground gravity settlers• Lowest-cost dewatering option, critical for economically processing tremendous harvested culture
volumes• Demonstrated at large scale at Cellana [Huntley et al] and WWT facilities in CA [MicroBio]• Highly strain-specific, but Scenedesmus is likely to settle well – assumed 4 hr settling time, 90% recovery
• Secondary dewatering = hollow fiber membranes• Demonstrated at large scale over sustained timeframe by GAI• Cost, performance based on inputs from GAI• Concentrates biomass to 130 g/L (13% AFDW) at >99% recovery
• Final dewatering = centrifugation• Established technology, standard for algal biomass concentration• Cost, performance based on inputs from engineering contractor (vendor quote)• Concentrates biomass to 200 g/L (20% AFDW) at 97% recovery
• CO2• Sourcing via off-site flue gas carbon capture• Priced at $45/tonne delivered to facility gate (supercritical)
• Consistent with average future CCS price projections in literature, DOE target of $40/tonne by 2020-2025
• Additional costs for on-site storage and delivery to ponds• Bulk flue gas scenarios considered in sensitivity analysis
• Nutrients• Set based on stoichiometric biomass composition at harvest, plus 20% excess
allowance• No recycle credits are taken on front-end model, to remain agnostic to back end
conversion pathway; any recycle credits should be assigned to reduce $/gal MFSP instead
• Water circulation• Maintains consistency with harmonization models to source freshwater via
nearby ground water resource, ~0.8 mile pipeline distance to facility gate• On-site circulation accomplished with aqueducts for “downhill” circulation to
central dewatering, pipelines for “uphill” return of clarified effluent back to pond modules
• Storage• Model also includes major storage tanks• Dewatered biomass storage assumed to incur 1% loss to degradation – should
be processed as quickly as possible through downstream conversion
Full liner costs contribute almost the same amount as pond + inoculum costs – significant incentive to prioritize locations based on soil characteristics
• Biomass cost follows similar asymptotic curves as found in prior TEA – very strong cost sensitivity <25 g/m2/day
• Above 35 g/m2/day, other costs start dominating (CO2 + nutrients contribute >$100/ton in base case)
NATIONAL RENEWABLE ENERGY LABORATORY
Additional Sensitivity Scenarios
21
• CO2: carbon capture vs bulk flue gas1) Bulk flue gas pipeline 15 km from source: requires more
power to transport the needed CO2 rate than the power generated to produce that amount of CO2
– Also translates to ~$49/tonne (vs $45/tonne target for purified CO2)
2) Flue gas co-location with algae facility (no significant off-site transport): $447/ton (~$45/ton MBSP savings) – But significant logistical/practicality questions regarding the use of multiple large ductwork pipelines routed around facility
• Alternative strains• Considered 9 total strain scenarios for tradeoffs in biomass
composition vs nutrient demands• Early-growth/high-protein biomass added up to $80/ton to
MBSP to sustain high N/P levels in biomass (*does not include N/P recycle considerations from downstream)
Fluegassource
60"
60"60"
48"
Centrif.Blower
IDFan
• Alternative dewatering scenarios1) Replace membranes with DAF
• Added substantial cost due to flocculant2) Replace membranes with EC
• Appears competitive with membranes, but requires large-scale demonstration
3) Replace membranes/centrifuge with filter press
• Potential to reduce MBSP by ~$15/ton but requires large-scale demonstration and may require a flocculant (would add to cost)
NATIONAL RENEWABLE ENERGY LABORATORY
Financial Assumptions: Algal Biomass Design Case
22
• Model maintains the use of standard financial assumptions employed for other (biorefinery conversion) cases
• Exceptions:• Indirect capital cost factors: treated separately for cultivation, dewatering, and
OSBL operations based on best expectations for how such costs may factor into fixed capital investment (FCI)
• Labor: adjusted labor FTE categories and rates to more reasonably reflect algae farm (versus standard rates employed for a biorefinery)• Labor costs scale inversely with pond size (fewer total ponds required when each
pond is larger size = fewer ponds to service and maintain)