Energy use in organic farming systems (OF0182)

Summary

This is the final report of Defra project OF0182. The attached main report starts with a more detailed Executive Summary, from which most of this text is extracted.
One of the possible benefits from organic farming is a reduced, or more efficient, use of energy in agriculture. The main objective and deliverable of study OF0182 was to develop a model of energy inputs in organic farming systems. To illustrate the potential of the model, it was used to contrast organic with similar conventional systems and to highlight important differences. This was presented as a detailed written report (49 pages) to MAFF and is summarised in this document. The report and model were delivered to MAFF in March 2000.
A previous study, completed by Phil Metcalfe of ADAS in 1996 for MAFF ARP Division, entitled “A Comparison of Energy use in Organic and Conventional Agricultural Production Systems”, compared direct and indirect energy use in simple individual crop and livestock enterprise models. These were combined to give whole-system models covering dairy, beef and arable farming. These systems were presented as organic conversion scenarios in the MAFF booklet “Organic Conversion Information Service” (1996). Project OF0182 updates the models developed in 1996 and expands the study to include upland beef and sheep, and vegetables. The dairy, vegetables, arable and upland beef/sheep models are based on the MAFF funded studies OF0146, OF0126, OF0145 and OF0147 respectively. The study also included a consideration of food distribution costs and the possible substitution of labour for energy. The data was organised into a system of linked spreadsheets to form the model
The dominant energy inputs in conventional agriculture are indirect energy for the manufacture and transport of fertilisers, particularly nitrogen, and indirect energy for the manufacture and transport of pesticides. These together account for around 50% of the total energy input to a potato or winter wheat crop, and as much as 80% of the energy input into some vegetable crops. Organically grown crops require around 50% of the energy input per unit area than do conventional crops, largely because of lower, or zero, fertiliser and pesticide energy inputs. However, the generally lower yields of organic crop and vegetable systems reduce the advantage to organic when energy input is calculated on a unit output basis. In stockless arable crop rotations, the inclusion of fertility building crops and winter cover crops, that have energy inputs but no direct outputs, can result in a lower whole-rotation energy efficiency from organic methods. In livestock systems, where the fall in output may be less than in arable, and there are no dedicated fertility building crops, overall energy efficiency is greater in organic than in comparable conventional systems.
These conclusions were made using average yield data in the model and need to be interpreted with caution. On more fertile soil, where the yield difference with conventional arable production is smaller, organic systems would perform relatively better. The converse would occur on poorer soils. Also, in practice, energy inputs for cultivations and weed control will vary with soil type, weather, weed spectrum and population. The average data presented in the report are illustrative and are not definitive. The strength of the model is that it can be used to simulate many different management systems and yield expectations.
The models also allowed a range of transport scenarios to be considered. There was little opportunity found for replacing energy with labour resources.