Quantitative review of environmental life cycle assessments of vertical farms – aligning reported impacts, and energy outlook for 2050
This study presents the first quantitative review of environmental life cycle assessments for lettuce-producing vertical farms, revealing that wide variations in reported impacts stem from inconsistent data reporting and system boundaries, while demonstrating that harmonizing these assessments and transitioning to decarbonized electricity grids by 2050 could reduce environmental impacts by 30–70%.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
In the quest to feed a growing population while protecting the planet, a new kind of agriculture has emerged from the shadows of warehouses and shipping containers. These are vertical farms, indoor facilities where crops like lettuce grow in stacked layers under electric lights, far removed from the sun and soil of traditional fields. The promise is compelling: these systems can produce food year-round, use far less water than open fields, and bring fresh produce directly to city centers. However, the machinery required to keep these plants alive—lights, fans, and climate control—runs almost entirely on electricity. This creates a central tension in the debate over their sustainability: while they save water and land, do they consume so much energy that their carbon footprint outweighs the benefits? To answer this, scientists rely on a method called life cycle assessment, a comprehensive accounting tool that tracks every environmental impact of a product, from the mining of raw materials for the farm's construction to the disposal of waste after the food is eaten. Without a standardized way to compare these complex systems, the public and policymakers have been left with a confusing mix of claims, some touting near-zero emissions and others warning of massive energy costs.
A team of researchers set out to cut through this confusion by gathering and re-examining eleven existing studies on vertical farms that grow lettuce. Instead of accepting the results of these studies at face value, the team acted as auditors, taking the raw data from each facility and recalculating the environmental impacts using a single, consistent set of rules. They standardized how they measured the size of the farms, the amount of water used, and, most critically, the source of the electricity powering the lights and fans. By doing this, they could see how the same farm would perform if it were powered by the current electricity grid in the Netherlands, or if it were powered by a future grid in 2050 that relies heavily on wind and solar power. This approach allowed them to separate the performance of the farming technology itself from the specific energy mix of the country where the farm happened to be located.
The investigation revealed that the performance of these farms varies wildly depending on how they are run and where they are built. The farms in the study produced between 7 and 97 kilograms of lettuce per square meter of growing space each year, with a typical farm yielding about 62 kilograms. To produce that amount, the farms used between 10 and 39 kilowatt-hours of electricity per kilogram of lettuce, with the median being 18 kilowatt-hours. Water use was similarly inconsistent, ranging from 1.4 to 52 liters per kilogram, though the typical farm used about 15 liters. The researchers found that these wide differences were not just due to the technology, but also to how the data was reported in the original studies. Some studies failed to clarify whether they were measuring the total floor space of the building or just the area covered by plants, while others omitted details about cleaning water or the lifespan of equipment. These gaps made it difficult to compare one farm to another until the researchers harmonized the data.
When the team recalculated the carbon emissions for all eleven farms using the same electricity source—the Dutch grid from 2020—the results became much clearer. The emissions ranged from 4.8 to 16 kilograms of carbon dioxide equivalent per kilogram of lettuce, with a median of 7.6 kilograms. This finding highlighted that the choice of energy source is the single biggest driver of a vertical farm's environmental impact. When the researchers looked at what would happen if these farms were powered by different types of electricity, the differences were stark. Farms powered by coal generated the highest emissions, while those powered by nuclear energy or wind power produced the lowest. In fact, the difference in emissions between a farm powered by coal and one powered by nuclear energy was so large that it could be a factor of over one hundred for some specific facilities. This confirmed that a vertical farm is not inherently "good" or "bad" for the climate; its impact is almost entirely dependent on the cleanliness of the electricity grid it plugs into.
Looking toward the future, the researchers modeled what would happen if major countries like China, the Netherlands, and the United States achieved their ambitious goals for decarbonizing their electricity grids by 2050. The projections were optimistic. If these farms were powered by the cleaner grids of 2050, their climate change impacts could drop by between 30 and 70 percent compared to 2020 levels. The cumulative energy demand and land use would also decrease significantly. However, the study also uncovered a hidden trade-off. As the world shifts away from fossil fuels toward renewable energy, the demand for minerals and metals required to build wind turbines, solar panels, and batteries increases dramatically. The researchers estimated that this shift would lead to a more than 200 percent increase in the use of minerals and metals. This suggests that while the air and climate benefits of vertical farming could improve massively in a decarbonized world, the pressure on the earth's mineral resources would intensify.
The study concludes that vertical farming holds significant potential, but only if the industry improves how it reports its data and if the energy grids powering it continue to clean up. The researchers emphasized that for these farms to be truly sustainable, they need to be more efficient. The best-performing farm in their review used 10 kilowatt-hours per kilogram, but theoretical models suggest that with better technology and management, this could eventually drop to as low as 3.3 kilowatt-hours. Until then, the environmental verdict on vertical farming remains a question of context. A vertical farm in a country with a coal-heavy grid may have a larger carbon footprint than a traditional greenhouse, but the same farm in a country with a wind-heavy grid could be a climate solution. The path forward requires not just better farming technology, but also a global commitment to cleaner electricity and more transparent reporting from the companies that build these indoor farms.
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