Climate-Sustaining Agriculture: Carbon Footprints of Organic and Conventional Onions and Wheat

This project examined the primary sources or “hotspots” of greenhouse gases (GHG) on carbon footprint (CF) in organic production systems. More sustainable agriculture must be resilient in the face of climate change and reduce GHG on both per-acre and per-unit product bases. Despite a willingness to make personal and professional changes to reduce their climate impacts, farmers may lack the knowledge and tools to make effective choices. This project provides information and tools to growers to empower changes in actions and behaviors that reduce GHG emissions.

This project analyzed the carbon footprint (CF) of organic crop production on four organic farms of varying sizes in the state of Washington. The primary sources or “hotspots” of GHG  were identified and compared, both in terms of inputs and in terms of the various crops. The goals of this project were to identify primary sources of GHG from different organic farms in order to identify commonalities and differences, and to use the results of the analyses carried out to further improve the OFoot Carbon footprint (CF) calculator that is based on farm practices, inputs, infrastructure, and dynamic crop-soil processes. Such a tool can help  producers to identify and reduce GHG hotspots, partake in the carbon trading industry, and educate their consumers.

The project found that each operation had different sources of GHG and hotspots in their CF, but certain patterns emerged.  Scale of farming operations affected the primary contributors to farm CF. Although total fuel and embodied energy use by large scale field equipment and irrigation systems are larger than those of small equipment and irrigation systems, they can be more efficient on a per area and/or per unit product basis. Equipment sharing on smaller farms can help to spread the embodied energy of equipment across a larger land base. Fuel and energy use was a large CF contributor on all operations. Use of lower GHG forms of energy such as biodiesel can dramatically lower a farm's total CF, in one case by over 30%.

Introduction

Agricultural systems’ contributions to greenhouse gas emissions are from diverse sources such as N₂O emissions from agricultural soils, CH₄ emissions from livestock enteric fermentation, manure management, and emissions from rice paddies, machinery manufacture and maintenance, transport of materials, and the manufacture of crop protection chemicals and fertilizer. Effective mitigation of global climate change from the agricultural sector will require an understanding of the net GHG emissions that are associated with activities, materials and energy used in farming operations and an understanding of the potential cost-effective reductions in emissions (Dick et al., 2008; Moxey, 2008).  The calculation of the carbon footprint (CF) of farms and farm products can contribute to this understanding. A CF calculation identifies the quantity, sources and sinks of GHGs associated with on-farm and off-farm activities (depending on the boundary of the system chosen) with the goal of identifying opportunities to reduce GHG emissions and increase GHG sinks in the system. Carbon footprints are expressed in units of CO2-equivalent emissions (CO2-eq), with GHG other than CO2 expressed in terms of their GWP relative to CO2 (Lynas, 2007; Wiedmann and Minx, 2008).