Measuring environmental value for Natural Lawn and Garden Care practices

Abstract

Background, Aims and Scope

Measuring Environmental Value for Natural Lawn and Garden Care Practices provides a life cycle assessment and impacts valuation methodology to quantify environmental (public health and ecological) and water conservation benefits from natural lawn and garden care practices in Seattle. Seattle Public Utilities (SPU) initiated this study as part of a triple-bottom-line analysis of its Natural Lawn and Garden Care program.

Methods

The study uses life cycle assessment (LCA) methods, including the Carnegie-Mellon Economic Input-Output Life Cycle Assessment (EIOLCA) tool publicly available on the Internet, to inventory pollutant generation from a synthetic nutrients and pesticide approach to lawn and garden care compared against a natural/organic care approach. The study applies US Environmental Protection Agency’s TRACI (Tool for the Reduction and Assessment of Chemical and other environmental Impacts) climate change, acidification, eutrophication, and human health-criteria air pollutant stressor factors, along with the Lawrence Berkeley National Laboratory’s CalTOX risk assessment model’s human and ecosystem toxicity potentials to roll up the numerous pollutant quantities into six environmental impact categories (global warming potential, human respiratory disease potential, human toxicity potential, ecological toxicity potential, acidification potential and eutrophication potential). The study develops cost valuation estimates for each impact category to produce a dollar estimate of the environmental cost of the two archetypical lawn and garden care methods.

Results

Lawns and gardens account for 25% of Seattle’s land area, so lawn and garden care methods potentially have substantial impacts on the city’s land-and water-based ecosystems. LCA methods provide an informative methodology for comparing environmental impacts from lawn and garden care practices. These methods reveal the importance of more natural lawn and garden care practices. They also show that resource extraction and manufacturing impacts of pesticides and synthetic fertilizers dominate their on site use impacts in the case of global warming, but that the reverse holds for human and ecological toxicity, and eutrophication. In addition, releases of particulates, SO_x and NO_x associated with gasoline-powered lawn mowing are nearly an order of magnitude larger than releases of these pollutants as a result of the production of pesticides and fertilizers.

Discussion

The study proceeds by using available data and research to build a desktop model that characterizes and contrasts two archetypical lawn and garden care practices: (1) Petroleum-based fertilizers and pesticides, a gasoline-powered lawn mower, and substantial irrigation to maintain a traditional weed-free, always-green lawn and garden, versus (2) A backyard compost system to provide lawn and garden nutrients, supplemented moderately by purchased non-synthetic soil amendments, an electricity-powered mower, no pesticides, and drought tolerant lawn and garden species having little need for irrigation.

Conclusions

The study concludes that each household converting from synthetic to natural practices produces nearly $75 in annual ongoing public health, ecological, water conservation and hazardous waste management benefits — between $16 and $21 of environmental benefits from reduced use of synthetic fertilizers and pesticides, $8 of environmental benefits for switching from gas to electricity for lawn mowing, $42 in cost savings due to reduced irrigation, and $5 or $6 from lower hazardous waste management costs. There also is a potential one time avoidance of $31 in construction costs resulting from reduced need for storm water detention and diversion capacity.

Recommendations and Perspectives

This study’s estimates of environmental value would benefit from comprehensive information on direct exposure to active ingredients in insecticides during their application. Estimates of impacts are based only on volatilization and runoff of active ingredients after application. Furthermore, the study would benefit from estimates of carbon sequestration in soils promoted by natural lawn and garden care techniques, and on the upstream pollutant releases from production of synthetic versus organic fertilizers. All three of these data gaps suggest that the estimated $75 per single family residence for environmental value is probably a lower bound on benefits from natural lawn and garden care versus more traditional pesticide-and-synthetic-fertilizer-based approaches.