Protein efficiency per unit energy and per unit greenhouse gas emissions: Potential contribution of diet choices to climate change mitigation Alejandro D. González a,⇑ , Björn Frostell b , Annika Carlsson-Kanyama c a Research Institute on Biodiversity and Environment (INIBIOMA), CONICET and Universidad Nacional del Comahue, Centro Regional Universitario Bariloche, 8400 Bariloche, RN, Argentina b Division of Industrial Ecology, Royal Institute of Technology, SE 100 44, Stockholm, Sweden c Swedish Defence Research Agency, SE 164 90, Stockholm, Sweden article info Article history: Received 30 March 2010 Received in revised form 25 June 2011 Accepted 5 July 2011 Available online 28 July 2011 Keywords: Food production Food transport Energy use GHG emissions Protein Sustainable agriculture abstract The production, transport and processing of food products have significant environmental impacts, some of them related to climate change. This study examined the energy use and greenhouse gas emissions associated with the production and transport to a port in Sweden (wholesale point) of 84 common food items of animal and vegetable origin. Energy use and greenhouse gas (GHG) emissions for food items produced in different countries and using various means of production were compared. The results confirmed that animal-based foods are associated with higher energy use and GHG emissions than plant-based foods, with the exception of vegetables produced in heated greenhouses. Analyses of the nutritional value of the foods to assess the amount of protein delivered to the wholesale point per unit energy used or GHG emitted (protein delivery efficiency) showed that the efficiency was much higher for plant-based foods than for animal-based. Remarkably, the efficiency of delivering plant-based protein increased as the amount of protein in the food increased, while the efficiency of delivering animal-based protein decreased. These results have implications for policies encouraging diets with lower environmen- tal impacts for a growing world population. Ó 2011 Elsevier Ltd. All rights reserved. Introduction Objective The aim of the present work was to contribute to ongoing dis- cussions about the need for dietary change by correlating the nutritional value of various foods with their potential contribu- tions to climate change during production and transport. To achieve this aim, we compared the amounts of energy used and greenhouse gases emitted during production against the protein content of 84 common foods. This allowed us to determine the effi- ciency of producing and transporting protein for different food groups, namely animal products, legumes, cereals, caloric roots and squash, greenhouse-grown vegetables, field-grown vegetables and fruits. The study formed part of the ‘Household Metabolism’ project, which aims to assess the contribution to climate change of items consumed by households in Sweden, and to develop tools to allow the public to understand the impacts and take action to reduce their ecological footprint. Background The production, transport, processing and marketing of foods involve complex phenomena that affect not only anthropogenic- based emissions but also biological, physical and chemical interactions. The diversity of environmental impacts due to food production is probably larger than for any other human activity. Food production involves rural activities, deforestation, changes in land use, emissions into soil, water and air of biologically active and inert elements, transport of perishable substances (requiring refrigeration in the whole chain from farm to consumption and carrying risks of spreading health hazards), industrial processing, handling and storage with special requirements; and finally a high need for refrigeration and waste management at the end consumer. Worldwide, the consumption of food contributes a substantial part of the total energy used and the total greenhouse gases (GHG) emitted. The fraction of global GHG emissions due to the agricultural sector was 32% in the year 2000 (EPA, 2006). This fig- ure comprised 57% carbon dioxide (CO 2 ), 25% methane (CH 4 ) and 19% nitrous oxide (N 2 O), showing that not only are non-CO 2 gases relevant in food consumption, but energy use leading to CO 2 emis- sions is also important. So far, the large contribution of food con- sumption to climate change impacts has been blurred by the fact that emissions of non-CO 2 gases from agriculture (CH 4 ,N 2 O and 0306-9192/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodpol.2011.07.003 ⇑ Corresponding author. Tel.: +54 2944 45 74 65; fax: +54 2944 42 21 11. E-mail addresses: gonzalezad@comahue-conicet.gob.ar (A.D. González), frostell@ kth.se (B. Frostell), annika.carlsson-kanyama@foi.se (A. Carlsson-Kanyama). Food Policy 36 (2011) 562–570 Contents lists available at ScienceDirect Food Policy journal homepage: www.elsevier.com/locate/foodpol