Comparing the Life Cycle Environmental Impacts of In-farm and Among-farm Cattle-crop Integration Mechanisms

Background and Motivation Addressing food security while protecting environmental quality is a demanding challenge. The agriculture sector, dominated by single crop or animal production systems, is a major contributor (9%) of... [ view full abstract ]

Background and Motivation

Addressing food security while protecting environmental quality is a demanding challenge. The agriculture sector, dominated by single crop or animal production systems, is a major contributor (9%) of the total US greenhouse gas emissions and is responsible for up to for up to half of all methane emissions ³. Meanwhile, it is projected that global grain demand will double and the world population will reach 9.1 billion by 2050 ^1,4.  Solving the food challenges requires innovative and sustainable management practices.

Distinct from single crop or cattle production systems, integrated cattle-crop systems reduce external inputs and emphasizes the recycling of energy, carbon and nutrients embedded in biomass and manures produced from the agricultural system.  Two distinct integration mechanisms (in-farm and among-farm integration) occur in the US. In-farm integration realizes internal recycle and reuse within a farm.  In contrast, among-farm integration exemplifies external material exchange among farms in proximity of one another.  Moreover, it is evident that integration practices are size-dependent. While in-farm integration is primarily adopted by small and medium farms, among-farm integration is often practiced by medium and large farms.  Although determining the yields and environmental impacts of integrated practices is fundamental and urgently required for supporting the sustainable transition of agricultural systems, system-level quantitative assessment has been limited to date.  It is unknown which integration mechanism is more productive and environmentally sound.

This project will determine the yields and environmental impacts of various combinations of farm sizes and integration methods, and identify the most preferred options exhibiting the lowest environmental impacts in order to aid in the sustainable transition.

Method

An interdisciplinary model combining biological and life cycle analyses will be constructed to analyze the productivity and environmental impacts of integrated farming scenarios.  The Integrated farm system model software, developed by the USDA will be used to estimate the yields and environmental releases for a 200 and 800 acre in-farm and among-farm system.  The software allows major interactions between biological and physical processes on the farm including feed storage, animal performance, manure handling, tillage, planting/harvesting operations, ammonia volatilization, nitrate leaching, phosphorus runoff and greenhouse gas emissions.² The simulated values will then be imported in to a cradle to farm gate life cycle assessment model, using 1kg of milk as the functional and compared with one another to discover which size and integration system is most sustainable.     

Preliminary Results and Future Work

The total global warming (GWP100), eutrophication and energy demand associated with producing 1kg of milk for the 200 acre in-farm system are 1.483E3 kg, 4.268 kg N eq and 3.4967E4 MJ respectively.  Future analyses will include carrying out all comparisons listed in the methods section, comparing results to existing studies and simulating different weather conditions.  Statistical methods will be used to determine significance and a sensitivity analysis will be conducted to determine the robustness of the simulated values.