Numbers, Numbers, Numbers Standard Conversion Formulae • 1 mT (metric ton)= 1,000 kg = 2,200 lbs • 1 ft3 = 0.0283168466 m3 • 1 Therm = 100 ft3 = 2.83168466 m3 • 1 W (watt) = 1 J/s (joule per second) • 1 kW = 1000 W = 1000 J/s • 1 MW = 1000 kW = 1,000,000 J/s • 1 kWh (kilowatt hour) = 1 kW x 3600 s = 3.6 MJ = 3414 BTU • 1 MWh = 1000 kWh • 1 GWh = 1000 MWh = 1,000,000 kWh Consumption • The average California home consumes about 580 kWhr per month (EIA, 2007), or about 6960 kWhr per year. • Approximately 27,700 households in Palo Alto (source: ABAG Projections 2005 with US Census 2000 Baseline) • Palo Alto City, residents and businesses consume about 1 GWh electricity per year (source: Utilities Department) • Palo Alto City, residents and businesses consume about 94.578 million cubic meters of natural gas per year (source: utilities department) • Palo Alto weighted average cost of natural gas = $7.74 (2011 forward price1) Methane • CH4 Specific volume (1.013 bar and 21 °C (70 °F)): 1.48 m3/kg (0.676 kg/m3) • Methane Energy Content o 1 ft3 CH4 = 1000 BTU = 1.055 MJ (mega‐joule) = 0.293 kWhr at 100% efficiency o 1 m3 CH4 = 35,315 BTU = 35.315 MJ = 9.8 kWhr at 100% efficiency o 1 MMBTU = 1 million BTU = 1000 ft3 CH4 = 28.32 m3 CH4 • Biogas Methane Content: 55 – 65%. 2 • Fun fact: 3.74 m3 CH4 = energy content of 1 US gal. gasoline • Combustion of 1 m3 CH4 releases 1 m3 CO2 = 1.85 kg CO2 = .00185 mT CO2 Methane Production from Anaerobic Digestion • EBMUD 2008: o Food Waste: 75 – 135 m3 CH4 per metric ton o Wastewater sludge: 57‐100 m3 CH4 per metric ton (80 avg) • Kelleher 2007: o Municipal Organic Wastes: 51 – 95 m3 CH4 per metric ton (85 – 159 m3 biogas) • Ostrem 2004: 1 Source: Palo Alto Utilities Advisory Commission
2 Kelleher, 2007. BioCycle V. 48, No. 8, p.51; also EBMUD March 2008; also Ostrem, 2004 Greening Waste: Anaerobic Digestion for Treating the Organic Fraction of Municipal Solid Wastes. •
o Municipal Organic Wastes: 48 – 120 m3 CH4 per metric ton (80 – 200 m3 biogas) KompoGas o Municipal Organic Wastes: 83 m3 CH4 per metric ton Conservative estimate: 80 m3 CH4 per metric ton food & green waste •
Electric Generation from Methane • Production: 75 m3 CH4 per metric ton municipal organic waste • Energy Content: 1 m3 CH4 = 35,315 BTU = 35.315 MJ • Generator Efficiency (electricity only) o KompoGas: 30% o Opra (generator manufacturer): 26% o Ostrem: 38% o Working estimate: 30% • Electricity Production o Ostrem: 3.73 kWh/m3 CH4 o KompoGas: 2.94 kWh/m3 CH4 o Opra: 2.55 kWh/m3 CH4 o Working estimate: 3.0 kWh/m3 CH4 • Percent Electricity used by system: o Ostrem: 26% o KompoGas: 27% o Working estimate: 30% Cogeneration Heat: • Ostrem: o 3.36 kWh(th)/m3 CH4 = 11,471 BTU/m3 CH4 o 35% used by process o Export heat: 2.18 kWh/m3 CH4 = 7,442 BTU/m3 CH4 • KompoGas: o 3.48 kWh(th)/m3 CH4 = 11,870 BTU/m3 CH4 o 35% used by process o Export heat: 2.26 kWh/m3 CH4 = 7,722 BTU/m3 CH4 • Working Estimate o 3.4 kWh(th)m3 CH4 = 11,600 BTU/m3 CH4 o Or, 1.13 kWh(thermal) for every 1 kWh(electricity) o 35% used by process o Export heat: 2.21 kWh/m3 CH4 = 7,540 BTU/m3 CH4 o Export heat: 0.73 kWh heat for every 1 kWh electricity generated Compost: • KompoGas: o 0.36 mT mature compost per 1.0 mT MSW compostables • Working Estimate o 0.35 mT mature compost per 1.0 mT MSW compostables Palo Alto Waste to Energy Sewage: • Sludge: 24,000 mT annually •
•
•
•
•
•
•
•
Methane: (80 m3 CH4 / mT) x (24,000 mT) = 1,920,000 m3 CH4 annually Electricity: (3.0 kWh/m3 CH4) x (1,920,000 m3 CH4) = 5,760,000 kWh Electricity used by system (30%)= 1,728,000 kWh Saleable electricity = 4,032,000 kWh = enough for 521 CA homes after 10% transmission loss Heat: 6,528,000 kWh (thermal) Heat used by system (35%): 2,284,800 kWh(t) Heat exported: 4,243,200 kWh (t) Incineration avoidance: o 2,830,000 m3 CH4 = 99,929 MMBTUs o At $7.74 MMBTU market rate, worth $773,450 Compost quantity: unknown. Compost value: low but positive •
Yard clippings, food, and other compostable organics (current collections) • Yard clippings (green bins + self‐haul): 21,000 mT • Food and other compostables: 9000 mT • Methane: (30,000 mT) x (80 m3 CH4 /mT) = 2,400,000 m3 CH4 annually • Electricity: (3.0 kWh/m3 CH4) x (2,400,000 m3 CH4) = 7,200,000 kWh • Electricity used by system = 2,160,000 kWh • Saleable electricity = 5,040,000 kWh = enough for 651 CA homes after 10% transmission loss • Heat: 8,136,000 kWh (thermal) • Heat used by system: 2,847,600 kWh(t) • Heat exported: 5,288,400 kWh(t) • Compost: 0.35 x 30,000 mT = 10,500 mT annually Single Family Residential Food, and other compostable organics • Food and other compostables, 50% collection rate: 2910 mT • Methane: (2910 mT) x (80 m3 CH4 /mT) = 232,800 m3 CH4 annually • Electricity: (3.0 kWh/m3 CH4) x (232,800 m3 CH4) = 698,450 kWh • Saleable surplus electricity = 489,000 kWh • Compost: 0.35 x 2910 mT = 1,018 mT annually Sewage and Compostables Combined, excluding single family residences: • Natural Gas consumption avoided by eliminating incineration: o 2,830,000 m3 CH4 = 99,929 MMBTUs o At $7.74 MMBTU market rate, worth $773,450 o 3% of Palo Alto natural gas consumption • Natural Gas production: o 4,320,000 m3 CH4 annually o Approximately 35% required to run system o Remainder is 2,808,000 m3 CH4 annually o Energy content equivalent to 750,800 gallons of gasoline o 2,808,000 m3 = 99,153 MMBTU o At $7.74 per MMBTU, worth $767,444 o 3% of total Palo Alto natural gas consumption • Or, convert surplus natural gas to “green” electricity = 9,072,000 kWh o 1% of total Palo Alto electricity consumption o enough for 1,173 CA homes after 10% transmission loss •
•
•
o at $0.11 per kWh, worth $997,920 Heat exported: 9,531,400 kWh(t) useful for o Other RWQCP processes o Nearby commercial buildings o Demonstration greenhouses?? Compost: o 10,500 mT high‐quality?? ƒ @ $27/mT = $283,500 per year3 o 4,800 (est) for non‐food crop use. Value unknown. Ash disposal cost avoided: $234,000 (source???) Single Family Residence Collections Additional Revenues • Surplus sold as green natural gas: approx. $63,000 • Surplus sold as green electricity: approx. $82,000 Greenhouse Gas Numbers • Total Community + City Emissions, per CPP: 793,621 mT CO2E • Landfilled Annual Waste Related Emissions, per CPP: 24,823 mT CO2E • California Electrical Generation: 0.275 mT CO2 per MWh • Coal Electrical Generation: 0.8 mT CO2 per MWh Wastewater Sludge Incineration Avoidance • CO2 equivalents reported for the Incinerator for 2007: o From burning Natural Gas 2,712 mT/year CO2E ƒ = 1.47 Mm3 CH4 (calculated) o From burning Landfill Gas 2,522 mT/year CO2E ƒ = 1.36 Mm3 CH4 (calculated) ƒ Could be used elsewhere to offset consumption o Total avoidable: 5234 mT/year CO2E Anaerobic Digestion CO2 Offsets (current collections) • Green natural gas production from anaerobic digestion o Surplus 2,808,000 m3 CH4 annually ƒ 5195 mT CO2E credit if sold as green natural gas o Or, 9,072,000 kWh of green electricity ƒ 2,495 mT CO2E credit (offsetting average mix) ƒ 7258 mT CO2E credit (offsetting coal) Anaerobic Digestion CO2 Offsets (Residential foodwaste program) • Green natural gas production from anaerobic digestion o Surplus 232,800 m3 CH4 annually ƒ 428 mT CO2E credit if sold as green natural gas o Or, 489,000 kWh of green electricity ƒ 134 mT CO2E credit (offsetting average mix) ƒ 391 mT CO2E credit (offsetting coal) • Avoided methane release from landfill o 2914 CO2E credit 3 Based on $27.30 per mT finished compost price from Palo Alto composting operations in 2007 (Compost Feasibility Report). GHG Emission Reductions Summary: ƒ Avoiding Incineration: 5234 CO2E credit ƒ AAD current collections: 2495 ‐ 5195 CO2E credit ƒ AAD Residential Foodwaste 3048 ‐ 3342 CO2E credit ƒ TOTAL 10,777 ‐ 13,771 CO2E credit ƒ 1.5% reduction of City Emissions from CPP baseline. For Reference: Existing Commercial Food Waste Program: ƒ 9,013 mT CO2E reduction, based on avoided methane release ƒ Approximately 1000 mT CO2E reduction for each additional ton collected. From a GHG perspective, one of the most important things we can do is to get
wet organic materials out of the landfill. Moisture-rich organic materials,
particularly food scraps, leaves and grass clippings, quickly begin to decompose
in the landfill and generate methane. Within 120 days, food waste and grass
clippings may be nearly fully decomposed, with substantial methane generation.4
Thus the majority of methane release from wet organics occurs long before any
methane recovery systems are put in place at the landfill (usually 2-5 years after
disposal).
The EPA’s WARM model can be run on just the food waste, grass and leaves
portion of our landfill waste stream under the assumption of no methane
recovery to get a conservative5 estimate of 9,013 mT of CO2e that would be
avoided if we could divert the target 9000 tons of commercial and multifamily
compostable organics. If we could achieve a 50% diversion of all the residential
and commercial compostables, we would avoid 11,427 mT of CO2e. 4 Eleazer, W.E., W.S. Odle, Y. Wang, and M.A. Barlaz. 1997. Biodegradability of municipal solid waste components in laboratory‐scale landfills. Environ. Sci. Technol. 31:911–918. Brown, et al, 2008. J. Environ. Qual. 37:1396–1410Landfill operations, design, climate, and waste composition will affect the timing and degree of wet organics decomposition, but specific data for the Kirby Canyon landfill was not available for this analysis. In the absence of actual site specific data, it is best not to make any optimistic assumptions. 5 For this estimate, the WARM model was run only on the food scraps and green plant material in our landfill waste stream. Other materials such as paper and cardboard also generate methane over a long period of time, but this was excluded under the assumption that much of the decay would occur after methane recovery was put in place.