Cowie, A; Eckard, R; Eady, S
Governments, organisations and individuals have recognised
the need to reduce their greenhouse gas (GHG) emissions. To identify where savings can be made,
and to monitor progress in reducing emissions, we need methodologies to quantify GHG emissions
and sequestration. Through the Australian Government's Carbon Farming Initiative (CFI)
landholders may generate credits for reducing emissions and/or sequestering carbon (C). National
GHG inventories for the United Nations Framework Convention on Climate Change, and accounting
under the Kyoto Protocol use a sectoral approach. For example, fuel use in agriculture is
reported in the transport component of the energy sector; energy use in producing herbicide and
fertiliser is included in the manufacturing section of the energy sector; sequestration in farm
forestry is reported in the land use, land-use change and forestry sector, while emissions
reported in the agriculture sector includemethane (CH4) from ruminant livestock, nitrous oxide
(N2O) from soils, and non-carbon dioxide (CO2) GHG from stubble and savannah burning. In
contrast, project-level accounting for CFI includes land-use change, forestry and agricultural
sector emissions, and significant direct inputs such as diesel and electricity. AC footprint
calculation uses a life cycle approach, including all the emissions associated with an
organisation, activity or product. The C footprint of a food product includes the upstream
emissions from manufacturing fertiliser and other inputs, fuel use in farming operations,
transport, processing and packaging, distribution to consumers, electricity use in refrigeration
and food preparation, and waste disposal. Methods used to estimate emissions range from simple
empirical emissions factors, to complex process-based models. Methods developed for inventory and
emissions trading must balance the need for sufficient accuracy to give confidence to the market,
with practical aspects such as ease and expense of data collection. Requirements for frequent
on-ground monitoring and third party verification of soil C or livestock CH4 estimates, for
example, may incur costs that would negate the financial benefit of credits earned, and could
also generate additional GHG emissions. Research is required to develop practical on-farm
measures of CH4 and N2O, and methods to quantify C in environmental plantings, agricultural soils
and rangeland ecosystems, to improve models for estimation and prediction of GHG emissions, and
enable baseline assessment. There is a need for whole-farm level estimation tools that
accommodate regional and management differences in emissions and sequestration to support
landholders in managing net emissions from their farming enterprises. These on-farm 'bottom-up'
accounting tools must align with the 'top-down' national account. To facilitate assessment of C
footprints for food and fibre products, Australia also needs a comprehensive life cycle inventory
database. This paper reviews current methods and approaches used for quantifying GHG emissions
for the land-based sectors in the context of emissions reporting, emissions trading and C
footprinting, and proposes possible improvements. We emphasise that cost-effective yet credible
GHG estimation methods are needed to encourage participation in voluntary offset schemes such as
the CFI, and thereby achieve maximum mitigation in the land-based sector.