Life cycle assessment of the potential carbon credit from no- and reduced-tillage winter wheat-based cropping systems in Eastern Washington State
Introduction
Climate change concerns have motivated interest in incentive-based agricultural practices that help reduce greenhouse gas (GHG) emissions. The United Nations Framework Convention on Climate Change and the Kyoto Protocol (UNFCCC, 2008) have framed agreements and protocols to reduce GHG emissions. The protocols utilize market-based mechanisms such as emission trading aimed at creating a carbon market where emissions/reductions can be exchanged. The US-EPA is applying cap-and-trade programs (Paltsev et al., 2007) on industrial emissions. So far, the capped emissions are focused on the power sector, which creates potential opportunities to lower emissions in other sectors such as agriculture, providing incentives for reductions that can be traded as carbon credits. Agriculture is the second largest global source of GHG emissions after the power sector (Minamikawa et al., 2009). It is also the largest land use category worldwide (Dutaur and Verchot, 2007). Because agriculture is the second leading emitter and leading land-use, and because agricultural emissions are not capped, it can be argued that agriculture should be a target for incentive-based emission reductions.
Reduced-till (RT) or no-till (NT) agricultural practices reduce disturbance to topsoil layers and reduce oxidation of soil organic carbon (SOC). Global and temperate climate regional studies indicated RT and NT may therefore increase SOC storage compared to conventional-till (CT) (West and Post, 2002, Chatskikh and Olesen, 2007, Sainju et al., 2008). On the contrary, studies under tropical and semi-arid conditions indicated minimal effect of tillage reduction on increasing SOC storage (Sanderman et al., 2010). Carbon sequestration and emission offset depends on climate feedback loops in the C and N cycles (Thornton et al., 2007). Therefore, assessment of carbon footprint reduction due to tillage reduction should consider regional climatic conditions which favor the use of modeling based approaches to evaluate long term effects of climatic conditions. Some researchers found that NT and RT decreased nitrification and denitrification rates, which reduced N2O emissions (Chatskikh and Olesen, 2007, Kroeze et al., 1999), while others found higher N2O emissions during the first NT years followed by a decrease due to soil aggregation (Six et al., 2004). Alluvione et al. (2009) found that methane (CH4) emissions tended to increase due to less CH4 oxidation capacity of the soil under NT and RT compared to CT. However, other authors state that there is no significant difference in CH4 fluxes of CT compared to NT and RT (Jacinthe and Lal, 2005, Mosier et al., 2006, Omonode et al., 2007). In fact, GHG emissions are not dependent on tillage only. For instance, Omonode et al. (2007) investigated different tillage scenarios and reported that CO2 emissions were mainly dependent on crop rotation. It is difficult to determine the outcome of converting CT to RT and NT based on field measurements only and simulation models can be useful in this regard. Cropping system models analyze interacting mechanisms giving predictions of emissions from different land operations (Hammer et al., 2002).
Agriculture uses external resources with associated GHG emissions such as fuel, fertilizers, and pesticides. To fully evaluate agricultural GHG emissions, a more comprehensive view of environmental impacts should also consider emissions from on-farm fuel consumption by equipment used for transportation and land operations (Koga et al., 2003, Mileusnic et al., 2010) and from production of fertilizers (Das and Kandpal, 1998). Furthermore, factors such as fuel used for machinery operations and use of fertilizers affect the standard costs within an enterprise budget and thus influence decisions to change tillage operations to RT or NT. A complete view of emission analyses should consider the economics of all factors.
Life Cycle Assessment (LCA) is an integrated approach to expand the field evaluation of emissions to broader boundaries that include external resources used in agricultural production. Finnveden et al. (2009) define LCA as a tool to assess the environmental impacts and resources used throughout a product’s life cycle. LCA can also be extended beyond the evaluation of GHG emissions and Global Warming Potential (GWP). LCA is also used to evaluate the impacts of pesticides (Margni et al., 2002) on human health and ecosystems, and to compare fertilizer choices for cropping major commodities such as wheat.
In this paper, an LCA-based methodology was developed to evaluate potential carbon credits resulting from conversion of CT to NT or RT for winter wheat (WW) in selected locations in the dryland region of eastern Washington, USA and for selected WW-based rotations. Carbon sequestration and GHG emissions were evaluated using results from a simulation study reported by Stöckle et al. (2012). The systems’ boundaries were expanded to consider emissions from fuel consumption and fertilizer production. The market value of RT and NT was evaluated by considering budgets for the selected cropping systems (Painter, 2009) and carbon credits per unit area expanded to include carbon sequestration and GHG emissions from farming practices including tillage, fertilizer usage and manufacture, and fuel usage.
Section snippets
Methodology
To evaluate tillage reduction implications at the local farm level, the conceptual approach of integrating techno- and eco-spheres LCA impacts with value-sphere parameters (Hofstetter et al., 2000) was simplified as depicted in Fig. 1. Analysis in the value-sphere is focused on carbon credits and typical farm budgets comparing NT, RT and CT scenarios as applied to dryland WW production in Eastern Washington, USA. In the techno-sphere, the cropping systems model, CropSyst (Stöckle et al., 1994,
Techno-sphere emissions
Simulated sequestered carbon and cumulative N2O emissions are presented in Fig. 2. Carbon sequestration under CT shows little change over the 30-year simulation time. In general, NT carbon sequestration was higher than RT. The amount of sequestered soil carbon started to level off for the highest rainfall zone by the end of the simulation period at year 30. Starting the simulation from the stable content for CT at 104.7 Mg C ha−1, NT began to level off at 108.8 Mg C ha−1 storing 4.1 Mg C ha−1 in 30
Discussion
Converting from CT to NT increases SOC sequestration and reduces GWP from wheat-based dry land cropping systems of eastern WA. NT increased soil carbon sequestration by 0.5, 0.3, 0.2 Mg-CO2e ha−1 yr−1 in high, middle and low rainfall zones, respectively. An increase in rainfall intensity increases crop yield and carbon sequestration due to the increased residue biomass recycled to the soil. Thomson et al. (2002) showed that winter wheat yield in this region increases proportionally to the rainfall.
Conclusion
A complete, LCA-based view of the CO2e savings from tillage reduction expands the evaluation of emissions on the larger ecological scale, and focuses the economic analyses on the scale of representative farm budgets by tillage and across the region. Crop system models estimate the emissions from agricultural lands providing insight to changes that accompany tillage reduction under climate specific conditions. No and reduced-till management of dryland wheat-based cropping systems are more
Acknowledgement
This research was supported in part by a Grant from the Paul G. Allen Family Foundation.
References (37)
- et al.
Soil tillage enhanced CO2 and N2O emissions from loamy sand soil under spring barley
Soil Till. Res.
(2007) - et al.
Recent developments in life cycle assessment
J. Environ. Manage.
(2009) - et al.
Future contributions of crop modelling from heuristics and supporting decision making to understanding geneticregulation and aiding crop improvement
Eur. J. Agron.
(2002) - et al.
Labile carbon and methane uptake as affected by tillage intensity in a Mollisol
Soil Till. Res.
(2005) - et al.
Fuel consumption-derived CO2 emissions under conventional and reduced tillage cropping systems in northern Japan
Agric. Ecosyst. Environ.
(2003) - et al.
Life cycle impact assessment of pesticides on human health and ecosystems
Agric. Ecosyst. Environ.
(2002) - et al.
Comparison of tillage systems according to fuel consumption
Energy
(2010) - et al.
Soil carbon dioxide and methane fluxes from long-term tillage systems in continuous corn and corn-soybean rotations
Soil Till. Res.
(2007) - et al.
CropSyst, a cropping systems model: water/nitrogen budgets and crop yield
Agric. Syst.
(1994) - et al.
CropSyst, a cropping systems simulation model
Eur. J. Agron.
(2003)
Nitrogen, tillage, and crop rotation effects on carbon dioxide and methane fluxes from irrigated cropping systems
J. Environ. Qual.
Offset Project Protocol: Agricultural Best Management Practices – Continuous Conservation Tillage and Conversion to Grassland Soil Carbon Sequestration
Indian fertilizer industry: assessment of potential energy demand and emissions
Int. J. Energy Res.
Simulated effects of tillage and timing of N fertilizer application on net greenhouse gas fluxes and N losses from agricultural soils in the Midwestern USA
A global inventory of the soil CH4 sink
Global Biogeochem. Cycle
Handbook on life cycle assessment operational guide to the ISO standards
Int. J. Life Cycle Ass.
Nitrogen, tillage, and crop rotation effects on nitrous oxide emissions from irrigated cropping systems
J. Environ. Qual.
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