21.09.2020 : Joelle Chen and more

The Promise of Indoor Farming: Part 2 - The Container Farming Model

A model of net zero emissions farming, ideal for dense urban centres and warm climates.

In Part One of this series, we explored the concept of indoor farming and how it promises to revolutionise food security for the world’s growing urban masses. 

In this second part, we delve deeper into the container farming model and how this approach has the potential to achieve urban agriculture’s (or what proponents term as “agtech”) holy grail – net zero emissions food cultivation. Using Singapore as an example, given its tropical climate and small size (just 720 sq KM), David Zsolt Krisztian - our building services and laboratory specialist, explains how this model works in practice and how it can be made even more sustainable.

 

Container Indoor Farming 101: What it is and how it works

As indoor farming grows in popularity, urban planners and agricultural enthusiasts are increasingly turning to one of the most ubiquitous features of our globalised world – the humble shipping container. This model, also known as ‘modular farming’, involves converting the enclosed rectangular space of a container into climate-controlled units with LED lighting and a hydroponic setup.

Benefits of this approach include the small physical footprint of containers, which can be easily stacked on top of each other in tight spaces. The material itself, recycled old shipping containers are in surplus supply around the world, which also lowers the cost of establishing an indoor farm from scratch.

With their small physical footprint and hydroponic growing systems, the container farming model uses up to 95% less water than a traditional outdoor farm, further reducing its environmental impact and making it especially well-suited to harsh, arid climates such as the Middle East. This is significant, considering agriculture is the world's single largest consumer of freshwater, responsible for up to 70% of annual usage. 

Interior of a shipping container farm, showing neatly stacked growing pods

 

The carbon challenge: Container farming and excess energy consumption 

However, the container farming model does have its shortcomings, namely its heavy reliance on expensive, energy intensive air conditioning (AC) units to maintain a constant temperature conducive to crop growth on a 24/7 basis. These AC units in many cases are classic DX (Direct Expansion) or split unit systems that use harmful refrigerants. 

These refrigerants, including Chlorofluorocarbons (CFCs), can damage the ozone layer, while others emit extremely potent greenhouse gases. In fact, one kilogram of the refrigerant R410a has the same greenhouse impact as two tonnes of carbon dioxide - the equivalent of running your car non-stop for six months!

So, while container farms offer several benefits over traditional farms, including ease of mobility and plug and play capability, they may not be an environmentally friendly solution unless a few important changes are made.

 

Simple changes to achieve superior sustainability results

A few simple changes can bring this method closer towards the goal of net zero emissions, including: 

  • Condensate water harvesting: Ideally suited to warm climates (both arid and humid), condensate water can be harvested from DX AC units which constantly produce this by-product from their operations. This clean source of water can then be used for irrigation purposes, significantly reducing the need for a supply of fresh water from traditional mains connection. 
  • Solar Power: Container farms don’t enjoy any natural sunlight, meaning special grow lights are required. These light fixtures easily consume 3,600 BTU (4kW) each and also introduce considerable heat load, which then requires effective air conditioning. Adding solar PV panels to the top of the containers and then storing excess energy in batteries for night-time use is one effective way to address this challenge of high power consumption, with the ultimate goal being to balance out the electricity demand with solar harvesting.
  • Make up air: Pumping fresh air can be expensive  as the outdoor air being drawn into the indoor space requires continuous cooling (or heating in a cold climate). A possible solution to this issue is ‘make up air’ on demand - which involves monitoring the IAQ (internal air quality) of a container farm unit and only providing outdoor air when it is required. This is already a well-known solution in the building services industry, where fresh air demand is carefully controlled using CO2 sensors.
  • Smart control systems: Smart control systems can also be applied within the tightly enclosed space of container farm units, including pre-programmed release systems for water droplets that ensure precise hydration by crop type and 24/7 live monitoring data that can analyse and tweak internal settings for ideal crop growth.

Diagram displaying how condensate water harvesting works

Dashboard for "make up air" system

While the container farming model of indoor farming can be energy intensive due to the demands of 24/7 climate control systems; by harnessing the resources of condensate water, solar power and make up air, it can become a highly sustainable way of achieving food security for millions at mass scale! Achieving this mass scale is something we’ll cover more in Part 3.

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