Urban agriculture has higher carbon footprint compared to conventional produce, flags study

25 Jan 2024 --- Scientists in the US have found that fruits and vegetables grown in urban farms and gardens have six times higher carbon footprint than conventionally grown produce. The study is claimed to be the “first” large-scale study to assess the environmental impact of urban agriculture (UA) — a widely proposed strategy to make cities and urban food systems more sustainable.

The team used data from 73 urban farms and gardens in five countries and is the largest published study to compare the carbon footprints of urban and conventional agriculture.

On average, food produced through urban agriculture emitted 0.42 kg of CO2 equivalents per serving, six times higher than the 0.07 kg CO2e per serving of conventionally grown produce.

The findings, published in Nature Cities, also noted some exceptions - UA crops like tomatoes and few sites, like 25% of individually managed gardens, which fare better than conventional agriculture.

“Tomatoes grown in the soil of open-air urban plots had a lower carbon intensity than tomatoes grown in conventional greenhouses, while the emissions difference between conventional and urban agriculture vanished for air-freighted crops like asparagus,” underscores the study.

“The exceptions revealed by our study suggest that urban agriculture practitioners can reduce their climate impacts by cultivating crops that are typically greenhouse-grown or air-freighted, in addition to making changes in site design and management,” says study co-lead author Jason Hawes, a doctoral student at University of Michigan’s School for Environment and Sustainability in the US, which conducted the study.

The study used farmers as citizen scientists to document inputs and harvests from their food-growing sites.However, he also explains the importance of UA as a futuristic method of growing crops: “Urban agriculture offers a variety of social, nutritional and place-based environmental benefits, which make it an appealing feature of future sustainable cities. This work shines light on ways to ensure that urban agriculture benefits the climate and the people and places it serves.”

Farmers as citizen scientists
The team analyzed three types of urban agriculture sites - urban farms (professionally managed and focused on food production), individual gardens (small plots managed by single gardeners) and collective gardens (communal spaces managed by groups of gardeners).

Farmers and gardeners at urban agriculture sites in France, Germany, Poland, the UK, and the US were recruited as citizen scientists and used daily diary entries to record inputs and harvests from their food-growing sites throughout the 2019 season.

Inputs to the UA sites fell into three main categories: infrastructure (such as the raised beds in which food is grown or pathways between plots), supplies (including compost, fertilizer, weed-blocking fabric, and gasoline for machinery), and irrigation water.

According to Benjamin Goldstein, assistant professor at U-M's School for Environment and Sustainability, most of the climate impacts at urban farms are driven by the materials used to construct them, including the infrastructure.

“These farms typically only operate for a few years or a decade, so the greenhouse gasses used to produce those materials are not used effectively. Conventional agriculture, on the other hand, is very efficient and hard to compete with.”

Urban agriculture has environmental benefits, making it an appealing feature of future sustainable cities (Image credit: Urban Crop Solutions).The researchers indicated three best practices to make low-tech urban agriculture more carbon-competitive with conventional agriculture - extending infrastructure lifetime, using urban wastes as UA inputs and generating high levels of social benefits.

F&B embraces urban farming
Urban agriculture is the practice of farming within the confines of a city. It is becoming increasingly popular worldwide, with 20% and 30% of the global urban population engaging in some form of urban agriculture, note the researchers.

F&B companies are increasingly employing the practice for better crop growth worldwide. 

Japanese company Spread combines vertically farmed lettuce with AI to prolong the crop’s shelf life. The next-generation automated salad processing plant is said to leverage the latest advancements in AI and robotics.

Meanwhile, Urban Crop Solutions (UCS) and Germany’s Aixponic have developed a new technology in sustainable agriculture that combines indoor fish farming facilities with a vertical farm to meet the specific requirements of critical environments and facilitate optimal conditions for plant cultivation.

Significant advancements in urban farming also include Arhcisen and FarmByte’s automated vertical indoor farm devoted to cultivating Asian greens in Johor, Malaysia.

By Insha Naureen