ghg impact of organic waste
DESCRIPTION
Palo Alto generates yard waste, food and compostable waste, and biosolids. The City is concerned with managing these waste streams in order to minimize GHG emissions and return organics to the biosphere.TRANSCRIPT
And Greenhouse Gases
CO2
CH4
N2OOrganic Waste Management
Compost Pile1 ton Carbon => 3.6 Tons CO2
Carbon-rich organics
Soil-enriching compost
Incineration
CO2
H2O
CO
C
N2O
Anaerobic Decomposition
Carbon/Water to CO2Carbon/Water to CH4
Sequestered Carbon
Palo Alto Composting & CO2
• 21,000 tons/yr (60% water)• 8,400 tons dry, 50% Carbon
• Methane production is negligible • 15,120 tons of CO2
• Biogenic CO2, not counted in “footprint”
• Transportation Concerns: – 1,100 tons additional if trucked to Sunnyvale
then Gilroy– Anthropogenic, counted in “footprint”– Traffic impact; Roadway maintenance
• Carbon Credit prices vary, but center around $20 / metric ton
• Added to costs of trucks, fuel, drivers, & acceptance fees.
What’s 1,100 Tons Worth?
$22,000 / year
1,100 tons = + 0.15%
Landfilled Compostables
tons
tons
tons
Compostables are 29% of Palo Alto’s “black bin” waste.
22,737 Tons of
Modern Landfill Design
Palo Alto Food and Green Waste in Landfill
– 15,934 tons wet (60% water) – 2,692 tons of Carbon (40% of dry is carbon) – 1,346 tons Carbon released in 1st year
• 50% into CO2: 2,424 tons CO2
• 50% into CH4: 50,880 tons CO2 Equivalent
– 1,346 tons Carbon remaining
Palo Alto Landfilled Compostables, after Cap
• 1,346 tons Carbon from food/green waste carryforward• 2,457 tons Carbon from other compostables (based on 45%
carbon in dry weight)
• Total: 3,803 tons carbon• 70% decomposes (2662 tons carbon)
– 85% captured and combusted to CO2
• 8,146 tons of CO2
– 15% escapes capture• 719 tons CO2
• 15,099 tons CO2 Equivalent (methane)
Total GHG Emissions from Landfilled Compostables
• For one year’s waste: – 79,262 tons CO2 Equivalent !
• If diverted and composted:– 18,534 tons CO2
• Full diversion would reduce PA Carbon Footprint by 60,728 tons of CO2e! – 2.7 tons CO2e per ton food/yard waste
• (carbon credit value $54)
Single Family vs MF/C
• Greenwaste Palo Alto Target:– 9000 tons– (comm/mf)– $70/ton +/-
• 13,700 tons still going to landfill– 37,000 tons CO2e
Organics GHG Reduction
• Part of the Zero Waste Plan
• Execution of plan is what matters
• What we do matters more than where
• Attention, Measurement, Reporting, Evaluation, & Improvement
Organics GHG Reduction
#1
Move Aggressively on MF/Commercial Food Waste Collection! (& 3500 tons of leaves & grass)
(‘000s tons CO2e reduction)
Organics GHG Reduction
#2
Implement Residential Food Waste Collection!
(‘000s tons CO2e reduction)
C
Organics GHG Reduction
#3Transform to BioChar/Bioenergy!
• All green bin contents = minus 7,000 tons CO2e
• 50% blackbin compostables = - 4500 tons CO2e
• Wastewater sludge = - 6,000 tons CO2e
CO2
CO2
Organics Management
PassiveCriteria:• lowest cost disposal
• diversion mandates
ActiveCriteria:• Resource recovery• GHG minimization• Long-term cost
?
Organics Management Passive Active
Palo AltoOperation
Multi-cityPartnership
Contracted
Location &Technology
Organics Management
Control
Economiesof Scale
City-Owned
Multi-City
Contracted
Multi-tech Organics Approach
Composting
Digestion
Soils Restoration
Sequestration
Green Energy
Green Bins
Wastewater
Black BinsPyrolysis
Location Possibilities
• Expansion of WWTF• Industrial sites in
Palo Alto• Industrial sites
elsewhere• Energy/GHG
Efficiency tradeoff: – Large scale
operations vs – Local operations
GHGs in Perspective
• Compost just a small piece of the opportunity
• What more important than where.
• Audit, execute, and improve.
• Regional partnership (we are not alone)