Don’t Count Out Vertical Farms
Jan 30, 2018
1. Calculation: (22.3 million square feet projected in 5 years — 2017 square footage) / 2017 square footage; 2017 square footage = 450,000 square feet expansion in 2017 / 21% increase from baseline in 2016). Source: https://www.agrilyst.com/stateofindoorfarming2017.
2. Energy use ranges from 4 to 14 MJ/kg lettuce, according to sources listed in https://keith.seas.harvard.edu/blog/led-salad-and-jevon%E2%80%99s-paradox and De Villiers et al. (2009). Barbosa et al. (2015) and Van Ginkel et al. (2017) also find values close to 2. Calculation: Convert MJ to kilocalories and compare to average of 130 calories/kg lettuce.
4. Harbick & Albright (2016). This 1:1 relationship between lighting and HVAC energy appears to hold for other operations, according to industry reps.
5. One industry rep estimated nitrogen use could be 1/6–1/10 of outdoor production.
6. Vertical/Indoor estimates calculated using Albright’s daily lighting intensity estimate of 17 mol/square meter per day, Albright’s assumptions for lighting and electricity needs, an average carbon intensity of Sweden (47 gCO2/kWh), multiplied by two to account for heating and cooling. Indoor production is assumed to have emissions from fertilizer equal to 50% of non-transport emissions from outdoor production.
7. Assuming a value of 0.2 kg CO2e/kg lettuce using 1,500 miles average transport in FoodEmissions.com, and assuming total emissions of ~1 CO2e/kg lettuce.
8. Calculation: (1—.17) / (1—.44).
9. All estimates and calculations are approximate, rounded up and based on the available data cited. Food waste metrics can vary widely by location, product, and distribution method, and are often imprecisely measured. Calculation for Outdoor Total Losses: 1—((1—0.17) x (1—0.20) x (1—0.15)). Calculation for Vertical/Indoor Total Losses: 1—((1—0.1) x (1—0.075)).
11. Calculation of Vertical/Indoor Kg CO2 Sequestered from Reforested Land: 20 acres x 2.2 (lower) or 9.5 (upper) tons CO2e/acre, converted to kg.
12. <50 gCO2e/kWh, according to Moro & Lonza (2017).
13. Estimates using Sweden's carbon intensity electricity (47gCO2e/kWh), accounting for sequestration and food loss. Vertical/Indoor emissions calculated assuming that outdoor production has a carbon intensity of 0.38 kgCO2e/kg farm-to-gate production (excluding transport), the median value reported in Clune et al. (2017); that indoor production has half of the emissions from fertilizer and other non-lighting activities as outdoor farms; and that 100% of spared land is reforested or avoids conversion. Omitting land sparing results in indoor production having net emissions of 1.3 kg CO2e/kg non-wasted food.