Introduction • Existing standards for carbon accounting • Forestry schemes as carbon offsets • Biomass energy in place of fossil fuels • LCA role in carbon accounting
Carbon Accounting Standards and Tools • ISO 14064 on methods to account for carbon • Also Greenhouse Gas Protocol • Determining boundaries for GHG accounting • Classification of emissions • Identification and calculation of GHGE • Rules for changing base year inventories • Rules for tracking emissions over time • Rules for assessing uncertainty • Rules for GHGE reporting
Emissions Are Classified According • Scope 1 – direct emissions with the boundary of an organization, i.e. fuel combustion • Scope 2 – indirect emissions such as purchased electricity • Scope 3 – other indirect emissions due to activities in scope 1 and 2, i.e. mining, transportation, land use changes • Large databases are available (459 pages) • epa.gov/climatechange/emissions/usinventoryreport.html
Example Problems • Difficulties with 3 scopes • Business traveler flying for GM • Building cars is under scope 1 and 2 (could also be 3) • Airline burns fuel – scope 1 (this could also go out into scope 2 and 3) • How do we handle the business traveler?
10.2 Carbon Offsets • Simple example – I plant trees to offset my emissions • Carbon cycle • Complicated • Uncertainty at multiple levels • Hard to argue fallow land will not fix some carbon (used for agriculture or go through succession) • Assume land use change in perpetuity • Soil changes (methane, N2O)
10.2.1 Forests as Carbon Sinks • Continuous carbon flux • After harvest forests are emitters for 20 to 40 years • Only sinks when they are well established • Land use prior to and after reforestation • Forest land typically higher C sequestration than ag • Need to watch for N2O and CH4 emissions
Other Issues • End use of forestry products • Landfill, burning, etc. • Increase biodiversity – unless a monoculture • Risks of forest fire – big emitter of carbon • Young trees use lots of water
10.3 Low Carbon and LCA • Biomass substitute for fossil fuel systems • Complex issue, fossil energy always needed for biomass • Can’t assume that burning biomass always GHG neutral • IPCC considers biogenic emissions do not count towards GHG • Considerable uncertainty though
10.3.1 Biomass in Energy • Watch boundary • Need full emissions • Mining, transportation, processing, etc. • Fertilizers, chemicals, etc. • Site versus source • In power generation, what does biomass replace? • Off-grid a little easier, whatever I am burning • Grid system, what gets replaced?
Biomass in Power Generation • Should biomass replace old, inefficient power plants that generate the most expensive electricity? • Some studies have said the least cost fossil energy system with lowest environmental impacts should be compared with biomass
Biomass in Power Continued • Could look at marginal generator • Natural gas turbines used for peaking power • Addition of a new biomass power plant would displace the marginal generator (likely natural gas with lower emissions) • Areas with limited power supply (maybe China or India) adding biomass power might increase electricity consumption • Probably no GHG reduction, would consider the marginal effect (biomass vs fossil)
Other Arguments • Forests sequester CO2 from fossil and biogenic sources • Therefore CO2 from biomass burning would not be neutral
10.3.2 Biomass Assessment Tools • Numerous tools (EU has some) US has GREET developed by Argonne National Lab • Review of biomass LCA studies for ethanol found large variations in results • Process residue handling and fuel combustion big differences • Generally resulted in resource and global warming reductions • Often resulted in higher acidification, human toxicity, ecological toxicity
10.5 Future Aspects of LCA • Several GHG accounting standards • Still considerable uncertainty and variations in methodology • Issues with boundaries and co-products • Policy and behavior issues • Will people consume more because of planting a tree or additional resource consumption is jutified