Marin Clean Energy (MCE) has just issued this document (which you won't find on the MCE website).
In it you will find every possible category of energy generation
Look for MCE to work so much better when they put
|Percent of Total Retail Sales (kWh)|
|PURCHASES||PG&E||MCE Light Green||MCE Deep Green|
|• Biomass & Biowaste||4%||12%||0%|
|• Eligible hydroelectric||4%||2%||0%|
|• Solar electric||0%||1%||100%|
PG&E data is subject to an
independent audit and verification that will not be completed until October 1, 2013.
|Note that the 12% on Biomass/Biowaste burning is not included in the CO2 emission calculation|
2011 Total CO2 Emissions from Electricity Sales per Megawatt-Hour**
"Unspecified Power" plus
"Unspecified Power" plus
MCE Light Green
MCE Deep Green
**The CO2 emission rates reflect the energy generation purchased
by an energy provider.
For the purposes of this chart,
MCE’s purchases of unspecified power make up
the entirety of the 389 lbs/MWh of CO2, as
all other energy purchased by MCE is zero-emission.
Likewise, the emissions from PG&E are primarily a result of its natural gas generation and its own unspecified power usage.
The emissions rate for unspecified system
power is determined by the California Air Resources Board, (CARB) which
is .428 metric tonnes CO2e/MWh, or 943.58 lbs CO2e/MWh. This emission rate is
made publicly available and can be referenced in section 95111(b)(1) of the
Regulation for the Mandatory Reporting of Greenhouse Gas Emissions:
The calculation generally works by taking the resources in the entire California
system and subtracting electricity purchased and reported by utilities and
electricity used by certain entities for on-site use rather than retail sales.
The same methodology is applied to both providers. These standards were discussed and agreed to by both MCE and PG&E, as this mailer was designed and financed with agreement from both parties as was required by state law. Please also note that 2011 emissions data was used as it was the most recent data available at publication. Based on PG&E’s power supply changes for 2012, their emissions factor will actually be much higher.
MCE and PG&E both use the same methodology for calculating their greenhouse gas emissions reported to the Climate Registry.
Unspecified Power is the new terminology for California System Power, which is electricity purchased from the California energy grid itself,
where the fuel type is unknown.
MCE relies on this to provide its conventional (non-renewable or hydroelectric) energy, rather than contracting directly with gas or nuclear power plants.
Other utilities, such as PG&E, rely on a combination of unspecified power and conventional power plants. PG&E, for instance, used a mix of 25% natural gas, 22% nuclear, and 15% unspecified power to meet its conventional power needs in 2012.
Bioenergy is a renewable resource certified by the State of California which takes natural waste and utilizes it to generate power without adding additional carbon to the carbon cycle.
As an example, MCE contracts with a biogas facility in Placer County which is attached to the regional landfill. Prior to the facility’s construction, the waste material would generate significant quantities of methane (a greenhouse gas about 14x worse than CO2!) which would be released directly into the atmosphere, sometimes through “flaring” where they burn it to reduce the impact a bit; there’s actually a diagram of how this flaring process works on their wall in their offices!
In contrast, the biogas facility takes that methane and utilizes it to make electricity and converting the methane into CO2. This is actually a net reduction in GHG that redirects something already going into the atmosphere – decomposing carbon – into making electricity as part of its life-cycle. All utilities report these facilities as “biogenic energy”, which typically is considered to have an emissions factor of zero.
We absolutely encourage customers to learn more about the power sources we use.
There’s a great piece of information on what Unspecified Power is on the state website at http://energyalmanac.ca.gov/electricity/total_system_power.html.
Wikipedia also has good information on bioenergy on its website at http://en.wikipedia.org/wiki/Bioenergy.
We encourage people to look at objective information from credible websites on energy where possible.
The information provided was provided according to the template specified by the California Energy Commission.
Just over 3% of MCE’s total power supply in 2011 came from biomass, with about 9% from biogas (landfill methane). You’d have to contact PG&E about what their breakdown is, as they currently report it entirely as bioenergy, but historically their bioenergy has leaned almost entirely on biomass (I think about 22 out of 23 bioenergy facilities contracted by PG&E in 2010 were biomass).
Most biomass in California is actually from decomposing wood waste, and the only site that MCE purchases biomass-based power from (a wood waste site) is actually also contracted by PG&E for another portion of its power. I cannot speak to the facilities used in PG&E's power mix, as I have no idea what the specifics of those other facilities are.
Biomass has no GHG associated with it according to just about every standard of GHG reporting. Some life-cycle based assessments to rate biopower emissions, but usually actually consider it lower than solar or geothermal power. Again, keep in mind that you're taking material which is already decomposing organic waste which will be added to the carbon cycle regardless. Feel free to check out the Intergovernmental Panel on Climate Change's report on life-cycle carbon emissions at http://srren.ipcc-wg3.de/report/IPCC_SRREN_Annex_II.pdf. (And Biomass and Biowaste need to be separately reported when Biomass is from a non-waste source .)
The emissions factors of unspecified power are publicly published by the State and should be available online. Both MCE and PG&E use the most current factor published by the State at the time of publication, 0.428 tonnes/MWh. Again, these are State of California standards calculated according to the methodology that was discussed previously.
However, please note that I'll be unable to follow this threat any further; if you have any additional questions please feel free to email us at firstname.lastname@example.org .
It’s also important to note that no fuel source, strictly speaking, is entirely zero emission, although renewable sources are generally considered zero-emission because they utilize sources that do not add to the otherwise occurring carbon cycle. The Intergovernmental Panel on Climate Change in 2011 found that the
Lifetime (including construction) Emissions of:
- solar are about 45g/kWh,
- biopower (including biomass and biogas equally) is about 18g/kWh,
- natural gas is about 469g/kWh, and
- coal is about 1001g/kWh.
Biogas is a growing source of dependable renewable energy, that you can read more about at http://en.wikipedia.org/wiki/Biofuel.