The rapid growth of urban agglomerations across the planet presents serious food security challenges. The US Census Bureau estimated that 80% of Americans lived in cities in 2015. Vertical farming is generally regarded as the most promising approach to supplying cities with fresh leafy greens, vegetables and small fruits, but skeptics point out that we still have a long way to go before indoor “plant factories” can reach the scale and efficiencies that would make them a truly sustainable source of nutrition for millions of people. Vertical farming, first conceptualised in the late 90’s, is premised on the idea of “a farm within a skyscraper” where environmental conditions, nutrition and lighting can be optimised. Growing crops in layers instead of rows, usually employing hydroponics, is a concept that has seduced investors globally. We all see the advantages of growing our food locally - in shipping containers, in warehouses and maybe even in skyscrapers to reduce the need for trans-continental shipping, to generate employment and limit pesticide and chemical-input intensive outdoor farming.
The major barrier to the upscale of vertical farming is economic sustainability and this is mainly related to the energy costs associated with artificial lighting. Can local, vertically grown produce be sold affordably? Despite remarkable technological advances in lighting technology and automation and the availability of renewable energy, there is still an urgent need to develop innovative solutions to get vertical farming over the “tipping point” from a promising food security approach and into a real, long-term and indispensable part of urban food systems.
Doing More with Less
How can vertical farms use less energy and produce more and better? In Chicago, Back of the Yards Algae Sciences, a sustainable industrial biotechnology company, has been working on a simple but elegant solution; grow in less time. After almost 2 years intensive research, they just published a paper demonstrating that an algae-derived biostimulant (a formulated biological material for improving plant growth) shortened the time between planting and harvesting hydroponically grown red leaf and green leaf lettuce by six days. Since traditionally farmed, outdoor-gown lettuce is currently three-to-five times less expensive to grow than vertically farmed lettuce, a shortened growing period may have significant implications for the economic sustainability of vertical farming as it reduces energy inputs and labor costs.
This breakthrough research was based on the concept of trying to translate the amazing interaction between plants and their soil environments into hydroponic and aeroponic systems. The team was already developing a proprietary Spirulina (a blue green algae) extract for the food and alternative protein markets and began to explore whether phycocyanin, a protein-pigment complex that acts as a key regulator of photosynthesis in blue-green algae, could play a similar role in plants growth.
A series of experiments produced evidence that a phycocyanin-rich Spirulina extract worked as a biostimulant in hydroponics, improving growth, yield, and quality of lettuce while cutting maturation time by 6 days-or 21%-compared to control groups. The faster growing treatment groups also produced 12.5% more lettuce and were 22% better at photosynthesis than control groups. The treated lettuce was more robust; a mean increase of 2.6cm in leaf length and 2.2cm in basal stem diameter compared to the untreated lettuce was observed and. In shelf-life test, wilting was seen 2-3 days after it was observed in control groups.
Treatment groups were brighter green (specifically 17% brighter and 75% greener) and better tasting. They had firmer texture, stronger aroma and more intense flavor than the untreated group, according to an independent certification company. Using analytical chemistry techniques, the team also examined nutrient content by comparing flavonoid-antioxidant levels in control and experimental groups. Their findings suggested experimental groups were more nutrient-rich, where one flavonoid, Quercetin, had a mean increase of 30% in the treated lettuce.
What it Means
Back of the Yards Algae Sciences was working to cut growing time in hydroponically grown lettuce using a biostimulant to give vertical farmers a new avenue for reducing energy inputs. They were successful and also happened to find that Spirulina extract biostimulants improved color, vigor, nutrient content and preservation. These product quality findings will support vertical farming in improving profitability by ensuring better selling prices. But perhaps the most exciting aspect of developing natural biostimulants specifically for vertical farming, is the possibility to extend the indoor farming sector into row crops as food staples (wheat, soy, corn), ensuring not only better and more secure food supplies for urban populations, but also protecting the environment.
This research is available at: https://www.preprints.org/manuscript/202011.0354/v2