Chapter 10 - Biofuels

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