The purpose of this article was to provide a base of understanding of CF terminology and to illustrate CF analyses using data from previous research that modeled nursery and greenhouse crop production systems and their life-cycle impact. CF relates to the efflux of greenhouse gases in the environment. The greenhouse gas emissions (GHG) of primary interest are carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) and result from human and environmental activities. They warm the earth by absorbing energy and decreasing the rate at which energy escapes the earth’s atmosphere to space [U.S. Environmental Protection Agency (USEPA), 2018]. In other words, greenhouse gases increase the effectiveness of the atmosphere to act as a blanket that insulates the earth. Therefore, GHG have a measurable potential for trapping energy in the earth’s atmosphere.
Greenhouse gases differ in their effectiveness to absorb energy in specific wavelengths, primarily infrared. This is referred to as their radiative efficiency (USEPA, 2018). They also differ in terms of how long they stay in the atmosphere, or their lifetime. Global warming potential (GWP) was developed to categorize greenhouse gases based on their radiative efficiency and lifetime in the atmosphere. The greenhouse gas of greatest concentration is CO2. The concentration of CO2 in the atmosphere has also been increasing, especially since the industrial revolution, and CO2 remains in the atmosphere for thousands of years. The combustion of fossil fuels has played a major role in this increase. Therefore, the GWP of emitted gases is expressed relative to the GWP of CO2 for a 100-year period (GWP100). The GWP100 of CO2 is set as 1, the reference to which other GHGs are compared and expressed.
The CF, or GWP, of a product or activity is expressed in kilograms of CO2-equivalent (CO2e). CH4 and N2O are estimated to have a GWP100 of 28 to 36 and 165 to 298 times that of CO2, respectively. CH4 is released from animals, humans, natural wetlands, paddy rice (Oryza sativa) fields, fermentation, and biomass burning. Agriculture is a primary source of N2O emissions, as are industrial activities, municipal waste landfills, and combustion of fossil fuels. Although found in the atmosphere at extremely low concentrations, chlorofluorocarbons, hydrofluorocarbons, hydrochlorofluorocarbons, perfluorocarbons, and sulfur hexafluoride can have GWPs thousands or tens of thousands of times greater than CO2 (USEPA, 2018). These definitions were the basis for an international treaty, called the Kyoto Protocol, signed in 1997 that commits parties to reduce GHG, effective in 2005. The details of those definitions and targets for reduction have been published by the United Nations (2008). Additional related data have been published on The Intergovernmental Panel on Climate Change website of the United Nations (2018).
Tools to estimate GHG during the life cycle of a targeted product or activity have been developed over the years and have led to the development of a complex, yet systematic process called life cycle assessment [LCA (Ingram and Fernandez, 2012)]. This tool has international acceptance by the scientific community, is governed by international standards, and has application to many fields, including agriculture. Although there are periodic revisions of the standards, the authors of this article have followed the International Organization for Standardization revised standard (International Organization for Standardization, 2006) and British Standards Institution’s standard (British Standards Institution, 2011). Under these standards, a functional unit of the targeted LCA is defined and all inputs are determined for the system. A functional unit may be anything from a gallon of milk or a container-grown shrub or a field-grown tree. GWP is but one environmental impact that can be measured or estimated by LCA. These potential environmental impact measures include water footprint, ecotoxicity, ozone depletion, acidification, eutrophication, and others (Ingram and Hall, 2014b). A complete cradle-to-grave LCA of a product or activity includes production, use, and post-life phases. However, a partial life-cycle impact, such as cradle-to-farm gate or seed-to-landscape, also can be defined, analyzed, and reported.
Beccaro, G.L., Cerutti, A.K., Vandecasteele, I., Bonvegna, L., Donno, D. & Bounous, G. 2014 Assessing environmental impacts of nursery production: Methodological issues and results from a case study in Italy J. Clean. Prod. 80 159 169
British Standards Institution 2011 Specification for the assessment of the life cycle greenhouse gas emissions of goods and services PAS 2050 2011 British Standards Institution, London, UK.
Hall, C.R. & Dickson, M.W. 2011 Economic, environmental, and health/well-being benefits associated with green industry products and services: A review J. Environ. Hort. 29 96 103
Hall, C.R. & Ingram, D.L. 2014 Production costs of field-grown Cercis canadensis L. ‘Forest Pansy’ identified during life cycle assessment analysis HortScience 49 1 6
Hall, C.R. & Ingram, D.L. 2015 Carbon footprint and production costs associated with varying the intensity of production practices during field-grown shrub production HortScience 50 402 407
Hodges, A.W., Hall, C.R., Palma, M.A. & Khachatryan, H. 2015 Economic contributions of the green industry in the United States in 2013 HortTechnology 141 805 814
Ingram, D.L. 2012 Life cycle assessment of a field-grown red maple tree to estimate its carbon footprint components Intl. J. Life Cycle Assess. 17 453 462
Ingram, D.L. 2013 Life cycle assessment to study the carbon footprint of system components for colorado blue spruce field production and landscape use J. Amer. Soc. Hort. Sci. 138 3 11
Ingram, D.L. & Fernandez, R.T. 2012 Life cycle assessment: A tool for determining the environmental impact of horticultural crop production HortTechnology 22 275 278
Ingram, D.L. & Hall, C.R. 2013 Carbon footprint and related production costs of system components of a field-grown Cercis canadensis L. ‘Forest Pansy’ using life cycle assessment J. Environ. Hort. 31 169 176
Ingram, D.L. & Hall, C.R. 2014a Carbon footprint and related production costs of system components for a field-grown Viburnum x juddi using life cycle assessment J. Environ. Hort. 32 175 181
Ingram, D.L. & Hall, C.R. 2014b Life cycle assessment used to determine the potential environment impact factors and water footprint of field-grown tree production inputs and processes J. Amer. Soc. Hort. Sci. 140 102 107
Ingram, D.L. & Hall, C.R. 2015a Carbon footprint and related production costs of pot-in-pot system components for red maple using life cycle assessment J. Environ. Hort. 33 103 109
Ingram, D.L. & Hall, C.R. 2015b Using life cycle assessment (LCA) to determine the carbon footprint of trees during production, distribution and useful life as the basis for market differentiation Acta Hort. 1090 35 38
Ingram, D.L. & Hall, C.R. 2015c Life cycle assessment used to determine the potential midpoint environment impact factors and water footprint of field-grown tree production inputs and processes J. Amer. Soc. Hort. Sci. 140 102 107
Ingram, D.L. & Hall, C.R. 2016 Comparison of carbon footprint and variable costs of selected nursery production systems for a 5-cm-caliper red maple HortScience 51 383 387
Ingram, D.L., Hall, C.R. & Knight, J. 2016 Carbon footprint and variable costs of production components for a container-grown evergreen shrub using life cycle assessment: An east coast U.S. model HortScience 51 989 994
Ingram, D.L., Hall, C.R. & Knight, J. 2017a Comparison of three production scenarios for Buxus microphylla var. japonica ‘Green Beauty’ marketed in a #3 container on the west coast using life cycle assessment HortScience 52 357 365
Ingram, D.L., Hall, C.R. & Knight, J. 2017b Modeling global warming potential, variable costs, and water use of young plant production system components using life cycle assessment HortScience 52 1356 1361
Ingram, D.L., Hall, C.R. & Knight, J. 2018a Global warming potential, variable costs, and water use of a model greenhouse production system for 11.4-cm annual plant using life cycle assessment HortScience 53 441 444
Ingram, D.L., Hall, C.R. & Knight, J. 2018b Analysis of production system components of container-grown chrysanthemum for their impact on carbon footprint and variable costs using life cycle assessment HortScience 53 1139 1142
Ingram, D.L., Hall, C.R. & Knight, J. 2019 Production system components of container-grown Euphorbia pulcherrima: Impacts on carbon footprint and variable costs using life cycle assessment HortScience (In press)
Intergovernmental Panel on Climate Change 2006. Guidelines for national greenhouse gas inventories. Volume 4: Agriculture, forestry and other land use. Chapter 11: N2O emissions from managed soils, and CO2 emissions from lime and urea application. 13 Sept. 2018. <http://www.ipcc-nggip.iges.or.jp/public/2006gl/vol4.html>
International Organization for Standardization 2006 Life cycle assessment, requirements and guidelines. ISO Rule 14044:2006. ISO, Geneva, Switzerland
Knight, J. & Ingram, D.L. 2017 Ecosystem services of landscape plants: A guide for green industry professionals. Univ. Kentucky Coop. Ext. Serv. Circ. HO-115
Knight, J. & Ingram, D.L. 2018 Ecosystem services of landscape plants: A guide for consumers and communities. Univ. Kentucky Coop. Ext. Circ. HO-121
United Nations 2008 Kyoto protocol reference manual on accounting of emissions and assigned amounts. 1 Oct. 2018. <https://unfccc.int/resource/docs/publications/08_unfccc_kp_ref_manual.pdf>
United Nations 2018 Intergovernmental panel on climate change. 13 Sept. 2018. <https://www.ipcc.ch>
U.S. Environmental Protection Agency 2018 Understanding global warming potentials. 1 Oct. 2018. <https://www.epa.gov/ghgemissions/understanding-global-warming-potentials>
Yue, C.Y., Dennis, J.H., Behe, B.K., Hall, C.R., Campbell, B.L. & Lopez, R.G. 2011 Investigating consumer preference for organic, local, or sustainable plants HortScience 46 610 615
Yue, C.Y., Hall, C.R., Behe, B.K., Campbell, B.L., Dennis, J.H. & Lopez, R.G. 2010 Are consumers willing to pay more for biodegradable containers than for plastic ones? Evidence from hypothetical conjoint analysis and nonhypothetical experimental auctions J. Agr. Appl. Econ. 42 757 772