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.
BeccaroG.L.CeruttiA.K.VandecasteeleI.BonvegnaL.DonnoD.BounousG.2014Assessing environmental impacts of nursery production: Methodological issues and results from a case study in ItalyJ. Clean. Prod.80159169
British Standards Institution2011Specification for the assessment of the life cycle greenhouse gas emissions of goods and servicesPAS20502011British Standards Institution London UK.
HallC.R.DicksonM.W.2011Economic, environmental, and health/well-being benefits associated with green industry products and services: A reviewJ. Environ. Hort.2996103
HallC.R.IngramD.L.2014Production costs of field-grown Cercis canadensis L. ‘Forest Pansy’ identified during life cycle assessment analysisHortScience4916
HallC.R.IngramD.L.2015Carbon footprint and production costs associated with varying the intensity of production practices during field-grown shrub productionHortScience50402407
HodgesA.W.HallC.R.PalmaM.A.KhachatryanH.2015Economic contributions of the green industry in the United States in 2013HortTechnology141805814
IngramD.L.2012Life cycle assessment of a field-grown red maple tree to estimate its carbon footprint componentsIntl. J. Life Cycle Assess.17453462
IngramD.L.2013Life cycle assessment to study the carbon footprint of system components for colorado blue spruce field production and landscape useJ. Amer. Soc. Hort. Sci.138311
IngramD.L.FernandezR.T.2012Life cycle assessment: A tool for determining the environmental impact of horticultural crop productionHortTechnology22275278
IngramD.L.HallC.R.2013Carbon footprint and related production costs of system components of a field-grown Cercis canadensis L. ‘Forest Pansy’ using life cycle assessmentJ. Environ. Hort.31169176
IngramD.L.HallC.R.2014aCarbon footprint and related production costs of system components for a field-grown Viburnum x juddi using life cycle assessmentJ. Environ. Hort.32175181
IngramD.L.HallC.R.2014bLife cycle assessment used to determine the potential environment impact factors and water footprint of field-grown tree production inputs and processesJ. Amer. Soc. Hort. Sci.140102107
IngramD.L.HallC.R.2015aCarbon footprint and related production costs of pot-in-pot system components for red maple using life cycle assessmentJ. Environ. Hort.33103109
IngramD.L.HallC.R.2015bUsing life cycle assessment (LCA) to determine the carbon footprint of trees during production, distribution and useful life as the basis for market differentiationActa Hort.10903538
IngramD.L.HallC.R.2015cLife cycle assessment used to determine the potential midpoint environment impact factors and water footprint of field-grown tree production inputs and processesJ. Amer. Soc. Hort. Sci.140102107
IngramD.L.HallC.R.2016Comparison of carbon footprint and variable costs of selected nursery production systems for a 5-cm-caliper red mapleHortScience51383387
IngramD.L.HallC.R.KnightJ.2016Carbon footprint and variable costs of production components for a container-grown evergreen shrub using life cycle assessment: An east coast U.S. modelHortScience51989994
IngramD.L.HallC.R.KnightJ.2017aComparison of three production scenarios for Buxus microphylla var. japonica ‘Green Beauty’ marketed in a #3 container on the west coast using life cycle assessmentHortScience52357365
IngramD.L.HallC.R.KnightJ.2017bModeling global warming potential, variable costs, and water use of young plant production system components using life cycle assessmentHortScience5213561361
IngramD.L.HallC.R.KnightJ.2018aGlobal warming potential, variable costs, and water use of a model greenhouse production system for 11.4-cm annual plant using life cycle assessmentHortScience53441444
IngramD.L.HallC.R.KnightJ.2018bAnalysis of production system components of container-grown chrysanthemum for their impact on carbon footprint and variable costs using life cycle assessmentHortScience5311391142
IngramD.L.HallC.R.KnightJ.2019Production system components of container-grown Euphorbia pulcherrima: Impacts on carbon footprint and variable costs using life cycle assessmentHortScience(In press)
Intergovernmental Panel on Climate Change2006. 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 Standardization2006Life cycle assessment requirements and guidelines. ISO Rule 14044:2006. ISO Geneva Switzerland
KnightJ.IngramD.L.2017Ecosystem services of landscape plants: A guide for green industry professionals. Univ. Kentucky Coop. Ext. Serv. Circ. HO-115
KnightJ.IngramD.L.2018Ecosystem services of landscape plants: A guide for consumers and communities. Univ. Kentucky Coop. Ext. Circ. HO-121
United Nations2008Kyoto 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 Nations2018Intergovernmental panel on climate change. 13 Sept. 2018. <https://www.ipcc.ch>
U.S. Environmental Protection Agency2018Understanding global warming potentials. 1 Oct. 2018. <https://www.epa.gov/ghgemissions/understanding-global-warming-potentials>
YueC.Y.DennisJ.H.BeheB.K.HallC.R.CampbellB.L.LopezR.G.2011Investigating consumer preference for organic, local, or sustainable plantsHortScience46610615
YueC.Y.HallC.R.BeheB.K.CampbellB.L.DennisJ.H.LopezR.G.2010Are consumers willing to pay more for biodegradable containers than for plastic ones? Evidence from hypothetical conjoint analysis and nonhypothetical experimental auctionsJ. Agr. Appl. Econ.42757772