Novel materials and technologies for urban farming
(Nanowerk Spotlight) Conventional food production, which relies heavily on industrial agriculture and animal husbandry, is putting huge strains on our environment both in terms of land use and sustainability.
With a growing sustainability movement around the globe, the concept of urban farming has gained huge popularity for the development of sustainable communities. Urban farming is loosely defined as the production, distribution, and marketing of food and other products within the geographical limits of a metropolitan area.
There is no clear-cut definition or blueprint for urban farms – they can be located both indoors and outdoors – and examples include vertical farming, greenhouse farming, container farming, rooftop farming, spared field farming, and warehouse farming.
Figure 1. The 15,000 square foot Riverpark Farm in Manhattan.
Modern cities generally relying on resource imports and the food system involves extensive transportation routes and high-energy requirements for the storing, cooling, and packaging of agricultural products. Embedding food production into the urban landscape provides an opportunity for more sustainable and environmentally friendly fresh food distribution all year round due to the proximity of food production and consumers. This improves the carbon footprint and reduces food wastage during transportation.
Urban farms also provide the potential for integrating farm requirements for space (via building integration), water, energy, and waste recycling into the resource stream in the city.
Researchers even envision an edible city with a strategy of Continuous Productive Urban Landscape (CPUL) for the introduction of interlinked productive landscapes into cities thereby creating a new sustainable urban infrastructure and supporting a re-definition of open urban space usages.
Urban farming practices don't necessarily use the same practices as conventional farming; this is especially true for the more high-tech approaches taken in vertical farming and warehouse farming. There is an opportunity and a requirement for smart technologies such as detailed nutrient monitoring, pesticide management, and fast-response environmental feedback and control.
This opens many opportunities to make use of novel materials in urban farming, which can contribute to building a higher productivity and more sustainable urban farms.
Figure 2. Different types of urban farming and the use of novel materials in the various aspects of plant growth. (Reprinted with permission by Wiley-VCH Verlag)
As a guide for researchers and a reference for stakeholders of urban farms, policy makers, and other interested parties, a recent review in Advanced Materials ("Novel Materials for Urban Farming") highlights research directions and challenges in urban farming and how material optimization and innovation drive the development of urban farming to meet national and global food demands.
Other examples are water retention materials, plant health monitoring systems, and novel substrates for soil replacement for weight reduction, which is an important consideration for rooftop farming. There are other materials whose function does not directly impact plant growth, but instead are essential to support the ecosystem needed for urban farming. For instance:
Novel functional materials such as perovskites as light-emitting diode (LED) materials, are gaining huge momentum that will serve to impact the lighting design in indoor farming sector.
Light and temperature management materials (phase change materials, thermochromic materials, cooling coatings).
Polymeric materials have also gained significant traction in agriculture. They are extremely versatile as their properties such as structure, functionality, and biodegradability can be specially designed and controlled with the right material chemistry.
Stimuli-responsive smart polymeric materials with bespoke functionality for plant application. This has led to novel materials in the controlled delivery of nutrients and pesticide, soil conditioning and water delivery, waste management, and many other areas.
Novel functional materials are pivotal for the shift from labor-intensive traditional farming practices to smart urban farming methods. Especially, as improvements in urban food production should not increase substantially the energy or water consumption or exert a negative impact on the environment.
Figure 3. Material technology contribution to the whole plant cultivation cycle. (Reprinted with permission by Wiley-VCH Verlag)
To ensure that urban farming becomes an integral part of food production in land-scarce cities, several developments will pave the way: the Internet-of-Things (IoT) enabled by sensors using novel materials; upcycling of agriculture waste to ensure circularity in the materials used; and data-science-driven new material design for better plant interaction.
The above-mentioned review discusses the four key areas illustrated in Figure 3 in great detail, shows examples of novel materials developed and used, and describes the current state of research.
Since the authors are from Singapore, they describe the role of urban farming and its implications for Singapore, a densely populated city of 5.8 million people and a major net food importer (> 90% of all supplies). Singapore is a leader in this space and moving toward rapidly growing urban farming to increase local food production to meet the target of producing 30% of its food by 2030.
As one form of controlled environment farming, vertical farming has attracted great interest in Singapore and several companies employ slightly different environmental management techniques in pursuit of high productivity and better sustainability.
Figure 4. a) At Sky Greens, leafy vegetables are grown vertically in 9 m tall towers. b) A robot cleaner installed in a vertical farm to perform jobs previously done manually by workers. c) Indoor vertical farming illuminated with LEDs. AVA is working closely with farmers to adopt advanced farming systems and investing in innovative technologies. (Image: Singapore Food Agency)
Besides controlled environment urban farming, open-air rooftop farming is also popular in Singapore due to its tropical weather conditions. For example, a private enterprise called Edible Garden City specializes in building urban gardens and providing consultancy to community farming initiatives. Since its beginnings in 2012, it has built more than 200 edible gardens and transformed a former golf course into a permaculture community garden which, grows 50 varieties of vegetables and herbs, tropical fruit trees and raises chickens.
By contrast, the commercial urban farming business in cities around the world – including indoor farming, hydroponics, and aquaponics – focuses on technologically innovative and environmentally adaptable farming methods. They are producing high-quality food and developing new technologies for urban environment.
Figure 5. A vertical farm at Sky Greens in Singapore where leafy vegetables are grown vertically in 9 m tall towers. (image: Sky Greens)
Moving forward, in addition to novel functional materials, well-implemented Internet-of-Things (IoT) and digital technologies will play a pivotal role in ensuring the long-term success and sustainability of urban farms. Urban farms equipped with IoT infrastructure can expect to run more effectively as they can provide monitoring, feedback, and control for noninvasive and nondestructive 24/7 monitoring of plant growth and development, thus enabling real-time fine-tuning of the optimization process and data collection and analyses for building databases.
Especially the concept of Digital Twins as support systems for urban farming are very promising to bring smart farming to new levels of farming productivity and sustainability (see: "Digital twins in smart farming").
Using Digital Twins (DT) as a central means for urban farm management enables the decoupling of physical flows from its planning and control. As a consequence, farmers can manage operations remotely based on (near) real-time digital information instead of having to rely on direct observation and manual tasks on-site. This allows them to act immediately in case of (expected) deviations and to simulate effects of interventions based on real-life data (see a practical example of the development process of a digital twin of a unique hydroponic underground farm in London).
DTs are created for planning and control of otherwise conventional physical trials: sensors enabled by new materials in controlled growth environments provide real-time feedback to monitoring systems, which are then able to update simulation states of DTs in real time to refine modeling accuracy and enable better predictions.
DTs may be interconnected within an urban farming system depending on their purpose, while functioning individually as any of the following: virtual testbeds (imaginary DT), digital-mode real-time monitoring of plant growth and development (monitoring DT), digital projection of growth and development predictions (predictive DT), recommending corrective or preventive actions by machine learning and database referencing (prescriptive DT), autonomous remote operation (autonomous DT), archiving and compiling past data (recollection DT).
Looking ahead, though, there are some factors associated with urban farming activities that currently limit their wider adoption: high initial capital cost requirement, small crop variety, high energy consumption, and sustainability of commercial urban farms. There are also several other challenges related to urban farming, namely, soil, air, or water pollution, potential disease transmission to residents, and possible exposure to pesticides or herbicides. Furthermore, if novel materials such as nanomaterials or gene-editing reagents are used, biosafety concerns on nanotoxicity and nontarget delivery cannot be ignored. These concerns have to be addressed by research and subsequent regulations.