The nursery industry is often referred to as part of the green industry. However, research to understand how system components of the production and use of landscape plants contribute to environmental impacts such as global warming potential is lacking and will determine the relative sustainability of nursery crop production (Marble et al., 2011; Prior et al., 2011). Therefore, system-level research is needed to provide reliable, reproducible information for scientists, the industry, and the general public.
Greenhouse gases (GHGs), primarily CO2, N2O, and CH4, are increasing in the atmosphere and human activity is contributing to that, primarily through the use of fossil fuels [BSI British Standards, 2011; International Panel on Climate Change (IPCC), 2007]. The GWP of those gases in a standard 100-year assessment period are expressed in relation to the GWP of CO2, which is set as 1. Although present in the atmosphere at much smaller concentrations, the GWPs of N2O and CH4 are 298 and 23, respectively (BSI British Standards, 2011). The production, distribution, and use of products and services result in emission of GHG and thus a carbon footprint, expressed as the GWP of that product or service in kilograms CO2 equivalent.
Life cycle assessment (LCA) is a tool used to quantify the environmental impact of products or services. LCA is a systematic process accounting for environmental impacts of interrelated input components and processes of a product or practice during its complete life cycle, cradle to grave (Baumann and Tillman, 2004). LCA usually includes information on the three primary life phases of a product or service: production phase, use phase, and post-life phase. However, boundaries for a LCA may be referred to as cradle to grave or even cradle to gate, but defining what is the cradle and what is the grave or gate of a product or practice is an important issue. Cradle to grave refers to the impacts of a product during manufacturing, transport, and use but ends with the impact of that product at the end of its useful life through recycling or disposal. Most published LCAs have focused on carbon footprint, but the tool can be used to assess other environmental impacts such as water footprint, toxicity potential, acidification potential, and resource depletion. International standards govern LCA protocols [BSI British Standards, 2011; International Organization for Standardization (ISO), 2006].
LCA has been used to study agriculture and biofuel production systems and their individual components (Debolt et al., 2009; Hayashi et al., 2006; Liebig et al., 2008; Nemecek et al., 2005, 2006; Williams et al., 2006). Nitrogen fertilizers have been identified as an important component of GHG emissions in agriculture as well as stimulating yield increases (Brentrup and Palliere, 2008; Hillier et al., 2009). Plastic greenhouse covers and containers represented a significant portion of the carbon footprint for floral crops in European LCA studies (Russo et al., 2008; Russo and Mugnozza, 2005; Russo and Zeller, 2008). LCA studies in Europe with forest tree seedling production have shown greenhouse heating and seedling transportation (Aldentun, 2002) and production and disposal of plastics (Cambria and Pierangeli, 2011) to be major GHG emission sources in those systems.
The cutting-to-landscape carbon footprint of a 5-cm-caliper, field-grown, spade-dug Acer rubrum (red maple) was calculated to be 8.2 kg CO2e (Ingram, 2012). Unlike most products, plants take CO2 from the atmosphere and sequester C to varying degrees in wood (U.S. Department of Energy, 1998). Trees sequester more C than shrubs and large trees sequester more C than small trees. Residential trees also provide other environmental services (McPherson and Simpson, 1999). Kendall and McPherson (2012) reported that 4.6 and 15.3 kg CO2e were emitted in the production and distribution of trees grown in #5 and #9 containers, respectively. Their work modeled an intensive container nursery in California and did not include the impact of sequestered C during production.
Individual components of production systems result in GHG emissions to varying degrees. Ingram (2012) reported that a significant contributor to GHG emissions in the field production of red maple was fuel consumption by farm machinery and truck transport of the finished product. That report also estimated the impact of altering certain production system protocols to reduce GHG emissions. GHG emissions have been estimated for various other agricultural production systems (Lal, 2004; West and Marland, 2002a, 2002b).
The purpose of this study was to use LCA to determine the carbon footprint of a 2-m-tall, field-grown, spade-dug Picea pungens (colorado blue spruce) in the lower midwestern and upper midwestern United States (hardiness zones 6a to 7a) and to analyze the contributions of system components. The scope included the production system from seed to the farm gate and from the farm gate to transplanting in a landscape site. The impact of the use phase and end-of-life phase was also assessed.
BaumannH.TillmanA.-M.2004The hitch hiker's guide to LCA: An orientation in life cycle assessment methodology and application. Studentlitteratur Lund Sweden
BrentrupF.PalliereC.2008GHG emissions and energy efficiency in European nitrogen fertiliser production and useIntl. Fert. Soc. Proc.639228
BSI British Standards2011Specification for the assessment of the life cycle greenhouse gas emissions of goods and services. PAS 2050:2011. BSI British Standards London UK
BurnhamA.WangM.WuY.2006Development and applications of GREET 2.7–The transportation vehicle-cycle model. ANL/ESD/06-5. 25 Sept. 2012. <http://greet.es.anl.gov/pdfs/TA/378.PDF>
CambriaD.PierangeliD.2011A life cycle assessment case study for walnut tree (Juglans regia L.) seedlings productionIntl. J. Life Cycle Assessment16859868
DeboltS.CampbellJ.E.SmithR.MontrossM.StorkJ.2009Life cycle assessment of native plants and marginal lands for bioenergy agriculture in Kentucky as a model for south-eastern USAGlobal Change Biol. Bioenergy1308316
FlemingL.E.1988Growth estimates of street trees in central New Jersey. MS thesis Rutgers University New Brunswick NJ
GrissoR.PerumpralJ.VaughanD.RobersonG.PitmanR.2010Predicting tractor diesel fuel consumption. Virginia Coop. Ext. Publ. 442-073
HayashiK.GaillardG.NemecekT.2006Life cycle assessment of agricultural production systems: Current issues and future perspectives. Proc. Intl. Seminar on Technol. Dev. for Good Agr. Practices in Asia and Oceania. Translated by Food and Fert. Tech. Ctr. Taipei Taiwan. p. 98–110
IngramD.2012Life cycle assessment of a field-grown red maple tree to estimate its carbon footprint componentsIntl. J. Life Cycle Assessment17453462
Intergovernmental Panel on Climate Change2006Guidelines 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. 25 Sept. 2012. <http://www.ipcc-nggip.iges.or.jp/public/2006gl/vol4.html>
Intergovernmental Panel on Climate Change2007IPCC fourth assessment report. Climate change 2007. 25 Sept. 2012. <http://www.ipcc.ch/publications_and_data/publications_and_data_reports.shtml>
International Organization for Standardization2006Life cycle assessment requirements and guidelines. ISO Rule 14044:2006. Intl. Organization for Standardization Geneva Switzerland
MarbleS.C.PriorS.A.RunionG.B.TorbertH.A.GilliamC.H.FainG.B.2011The importance of determining carbon sequestration and greenhouse gas mitigation potential in ornamental horticultureHortScience46240244
McPhersonE.G.SimpsonJ.R.1999Carbon dioxide reduction through urban forestry guidelines for professional and volunteer tree planters. U.S. Dept. Agr. For. Serv. Pacific Southwest Res. Sta. Gen. Tech. Rpt. PSWGTR-171
MouradA.L.ColtroL.OliveiraP.A.P.L.V.KleteckeR.M.BaddiniJ.P.O.A.2007A simple methodology for elaborating the life cycle inventory of agricultural productsIntl. J. Life Cycle Assessment12408413
NemecekT.DuboisD.GunstL.GaillardG.2005Life cycle assessment of conventional and organic farming in the DOC trial. Researching sustainable systems. Proc. First Scientific Conf. Intl. Soc. Organic Agr. Res. (ISOFAR) Intl. Federation Organic Agr. Movements (IFOAM) Natl. Assn. Sustainable Agr. Australia (NASAA) Adelaide South Australia 21–23 Sept. 2005. p. 222–226
NowakD.J.1994Atmospheric carbon dioxide reduction by Chicago’s urban forest p. 83–94. In: McPherson E.G. D.J. Nowak and R.A. Rowntree (eds.). Chicago’s urban forest ecosystem: Results of the Chicago Urban Forest Climate Project. U.S. Dept. Agr. For. Serv. Northeastern For. Expt. Sta. Gen. Tech. Rpt. NE-186
NowakD.J.StevensJ.C.SisinniS.M.LuleyC.J.2002Effects of urban tree management and species selection on atmospheric carbon dioxideJ. Arboricult.28113122
PriorS.A.RunionG.B.MarbleS.C.RogersH.H.GilliamC.H.TorbertH.A.2011A review of elevated atmospheric CO2 effects on plant growth and water relations: Implications for horticultureHortScience46158162
RussoG.ZellerB.D.L.2008Environmental evaluation by means of LCA regarding the ornamental nursery production in rose and sowbread greenhouse cultivationActa Hort.80115971604
SamarasC.MeisterlingK.2008Life cycle assessment of greenhouse gas emissions from plug-in hybrid vehicles: Implications for policyEnviron. Sci. Technol.4231703176
SnyderC.S.BruulsemaT.W.JensenT.L.FixenP.E.2009Review of greenhouse gas emissions from crop production systems and fertilizer management effectAgr. Ecosyst. Environ.133247266
United Nations1987The Montreal protocol on substances that deplete the ozone layer. 25 Sept. 2012. <http://montreal-protocol.org/new_site/en/Treaties/treaties_decisions-hb.php?sec_id=5>
U.S. Department of Agriculture2008CUFR tree carbon calculator. 25 Sept. 2012. <http://www.fs.fed.us/ccrc/topics/urban-forests/ctcc/>
U.S. Department of Energy1998Method of calculating carbon sequestration by trees in urban and suburban settings. 25 Sept. 2012. <ftp://ftp.eia.doe.gov/pub/oiaf/1605/cdrom/pdf/sequester.pdf>
U.S. Department of Energy2012U.S. Life-cycle inventory database. 25 Sept. 2012. <https://www.lcacommons.gov/nrel/search>
U.S. Environental Protection Agency2005Emission facts: Average carbon dioxide emissions resulting from gasoline and diesel fuel. EPA420-F-05_001. 26 Sept. 2012. <http://www.epa.gov/otaq/climate/420f05001.htm>
U.S. Environmental Protection Agency2010Ozone layer protection—Science. 26 Sept. 2012. <http://www.epa.gov/ozone/science/ods/classone.html>
U.S. Environmental Protection Agency2012Ozone layer protection—Regulatory program; List of critical uses. 26 Sept. 2012. <www.epa.gov/ozone/mbr/cueuses.html>
VyasA.SinghM.2011GREET1_2011 (greenhouse gases related emissions and energy use in transportation). 25 Sept. 2012. <http://www.transportation.anl.gov/modeling_simulation/VISION/>
WangM.2007The greenhouse gases regulated emissions and energy use in transportation (GREET) model. 25 Sept. 2012. <http://www.transportation.anl.gove/software/Greet/index.html>
WestT.O.MarlandG.2002aNet carbon flux from agricultural ecosystems: Methodology for full carbon cycle analysesEnviron. Pollut.116437442
WestT.O.MarlandG.2002bA synthesis of carbon sequestration, carbon emissions, and net carbon flux in agriculture: Comparing tillage practices in the United StatesAgr. Ecosyst. Environ.91217232
WilliamsA.G.AudsleyE.SandarsD.L.2006Energy and environmental burdens of organic and non-organic agriculture and horticultureAsp. Appl. Biol.791923