- Sophie Colvine
Does it require more energy to produce tomato sauce in California and ship it to consumers all over the U.S., or for consumers to buy tomato sauce produced in their own region?
The Agricultural Sustainability Institute at UC Davis brings together the expertise of more than 70 UC Davis faculty, staff, postdoctoral fellows, graduate student researchers, and undergraduate student assistants to address big and emerging issues related to food and farming sustainability. One of its aim is to help farmers and ranchers find science-based solutions to today's biggest sustainability challenges. Through interdisciplinary research, partnerships with expert farmers and other agricultural professionals, and innovative communication, they identify ways to conserve and regenerate critical natural resources while maintaining agricultural productivity at the farm, regional, and state level. Every stage of the food system — production, processing, distribution, retail, preparation, and waste handling — has greenhouse gas emissions associated with it. Developing a sustainable food system requires a cradle-to-grave accounting of the benefits and impacts all along the food supply chain.
By gauging the footprint of agricultural products, growers and distributors can clearly understand where emissions are highest and lowest, and how to focus emission reduction at points of greatest possible impact. Farmers focused on reducing GHG emissions are not only improving their energy efficiency, they are positioning themselves for a budding California carbon market and an increasingly climate-smart consumer market. Through SAREP’s Energy and Climate Footprinting work, Agricultural Sustainability Institute assess the entirety of the food production and supply chain to identify energy and emissions "hotspots", evaluate the impacts of new practices and technologies, and assess trade-offs between interventions at different stages of the supply chain for selected categories of foods.
The goals of the study on the environmental impacts of California tomato Ccultivation and Processing were:
- to quantify resource use and a range of environmental impacts of producing tomato paste and diced tomatoes in California
- to assess change in the industry over approximately 1 decade (2005 – 2015)
Life Cycle Assessment (LCA) is a comprehensive analysis method for assessing the environmental impacts and resources used throughout the full life cycle of a given product or system. LCAs consider environmental impacts at each phase of the life cycle (raw material production, manufacturing, use, etc.)
The study quantified resource use, including energy, water, and other resources, and estimates emissions that may contribute to critical environmental impacts, including global warming, ozone depletion, photochemical ozone creation, acidification, and eutrophication, for bulk tomato paste
and diced tomatoes
It included the following phases of tomato production and processing:
- Greenhouse production of transplants
- Field cultivation of tomatoes
- Facility processing
This analysis ended at the facility gate. It included transportation of transplants and tomatoes between phases, but it did not include packaging of final products. Researchers collected data from all three phases for both the 2005 season and the 2015 season, to track changes over time.
Environmental impacts included in study:
Environmental improvements in California tomatoes (2005 to 2015)
- Global Warming Potential: a measure of how much energy the emission of 1 ton of gas will absorb over a given time period (usually 100 years) relative to how much energy 1 ton of carbon dioxide (CO2) will absorb.
- Ozone Layer Depletion Potential: a measure of the potential of airborne emissions to degrade the stratospheric ozone layer, relative to trichlorofluoromethane (CFC-11).
- Photochemical Ozone Creation Potential: a measure of the ozone-forming potential of airborne emissions, relative to ethylene (C2H4).
- Acidification Potential: a measure of the acid-forming potential of a substance emitted into the environment, relative to the acid-forming potential of sulfur dioxide (SO2).
- Eutrophication Potential: a measure of the quantity of human-induced additions of nutrients (phosphorus and nitrogen) to the environment, that can cause excessive aquatic plant and algae growth, expressed in units of phosphate (PO4) equivalents.
- Toxicity potential for humans and for marine, terrestrial and freshwater ecosystems: a measure of the toxicity of chemicals released into the environment, relative to 1,4-dichlorobenzene (1.4-DCB), a chemical commonly used in mothballs, fumigants, and other products.
Between 2005 and 2015, environmental improvements were observed in both final paste and diced tomato products. Efficiency of energy use and water use increased substantially over this time period, calculated per kg of final paste and diced product.
Over the total 3-phase life cycle, the following efficiencies were observed:
Caveats: Considerations of increases in California processed tomato efficiency must be balanced with consideration of the total magnitude of impacts of the industry in California and elsewhere where inputs are produced. The total acreage of processing tomatoes increased by 12 percent between 2005 and 2015, and total harvested output increased by over 40 percent, requiring more total harvest and processing activity. In addition, per acre applications of certain inputs, including fertilizers and some pesticides, increased from 2005 to 2015.
Largest sources of environmental impacts
- Energy-use efficiency increased by 16 percent and 30 percent for paste and diced product, respectively
- Water-use efficiency increased by 41 percent and 43 percent for paste and diced product, respectively
- Water-use efficiency in processing facilities alone increased by over 20 percent for diced tomatoes (with only a small increase for paste production)
- Widespread conversion from furrow to drip irrigation in the field drove improved water use efficiency, with over 25 percent reduction in per acre water use
- Increases in per acre yields (from 41 tons to 55 tons among surveyed growers) were observed without proportional increases in input use (e.g. fertilizers and water)
- Environmental impacts improved (decreased) by 5 percent to 43 percent on a per kg of product basis, depending upon measure. See tables below for details. (Although water, terrestrial and human toxicity potentials are not presented in the table, those potentials also declined).
- Fossil fuel-based energy and water use were the two largest factors responsible for most of the environmental impact categories, with gypsum and nitrogen fertilizer use the second largest factors
Across the three phases of the supply chain, the following factors make the largest contributions to the range of environmental impacts measured:
- Diesel production and combustion
- Natural gas production and combustion
- Irrigation water pumping and use
||Largest contributors to environmental impacts for each phase
- Vermiculite production
- Natural gas production and combustion
- Electricity and diesel use for irrigation pumping
- Fertilizer production
- Natural gas production and combustion
- Grid electricity production
Notably, grid electricity production, for uses across the supply chain, accounts for a significant amount of water use.
Production of pesticide active ingredients does not account for notably large impacts compared to other factors, but post-application impacts are not assessed here, due to data limitations.
Ways to improve the environmental performance of processed tomatoes
Uncertainty and needs for further research
- Invest in renewable energy generation at all three phases (greenhouse, cultivation and processing)
- Consider alternatives to vermiculite
- Choose less toxic herbicides and pesticides and use Integrated Pest Management
- Monitor crop nitrogen needs and use precision application methods to prevent over-application of fertilizers
- Choose lower-GWP nitrogen fertilizers, such as urea-based products (UN32), over calcium ammonium nitrate (CAN17)
- Invest in more energy-efficient irrigation pumps
- Large variability between processing facilities and small sample size (2 facilities) point to need for more process-specific assessment within facilities to identify sources of impacts and options for improvement. Data from more greenhouse operations, especially for 2005, are also needed.
- Field research is needed to understand trade-offs between upstream and downstream impacts of different fertilizer choices (e.g. greenhouse gas emissions in manufacturing versus ammonia and nitrous oxide emissions in field).
- Increasing application rates of a few highly toxic pesticides and uncertainty in pesticide impacts post-application requires further research coupling LCA with chemical fate, transport, and toxicity models.
- Better characterization of packaging waste and fate in all phases is needed to understand impacts.