Research & Precedent | GrowUp Box Tour & Talk

I went to visit the GrowUp Community Farms shipping container aquaponic farm last weekend.  Feels like more time has passed since then!  Asked Sam a lot of questions, he were very patient with me.  Summary of my notes is below…

  • 14 of the 17 nutrients you need for a green-leaf crop are found in fish droppings.
  • Carp were in the tank this time. Cold water fish are best for UK aquaponics.  But warm-water fish can be farmed.
    • This is because condensation is a big problem in winter, less so in summer.
    • Effects on building fabric need to be considered.
  • Aquaponics are good for white fish generally – Tilapia especially well suited.  They are quick to grow and are a good source of white meat in warmer months (they’re a warm water fish).  Infographic on the shipping container door gave a good idea of what to expect.

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  • Variety of fish feeds can be used.  Ideas around feed production could be built into the master plan:
    • Insect based feeds. GrowUp are currently considering these and about to try them.
    • Algae based feeds.
    • Spent grains from the brewing process!
  • 1500 ltr tank for the fish is installed in the box. This is used as follows.
    • As a rule fish go in at 50g and come out at 750g.
    • 6 months generally to grow fish to this size.
    • You can farm up to 150 fish in a tank of this size, species dependent.
    • Generally speaking you need 11 ltrs of water per fish.
    • Fish actually prefer to live in tighter shoals.
    • 40 carp in the tank at the moment.  I speculate they don’t have it packed as people may be sensitive over this issue.  Although he did say you can’t farm as many carp as you can Tilapia for example.
    • PH levels? 6 is good?  This tank is at 7.4.
    • Fish prefer a more alkaline solution.
    • Crustaceans could also be used as well as other fish.
    • Water changes every 2 weeks where they siphon off 30% of that in the tank.  Holding tanks needed for water changes!
  • GrowUp look to educate and bring more people into the field.
    • Are looking for issues surrounding urban farming such as food scarcity and sustainability to be introduced into the national curriculum.
    • Pass on information learnt in Unit 84, their commercial premises.
    • Looking to expand use of this unit in peri-urban locations not just to increase yield and farming infrastructure, but also to run more workshops, like the one on after this talk for local families to get involved.
    • Employ & train local people, often people that are in some sense disadvantaged.
    • Aim of employing new trainees to run a farm within 5 years of them starting.
  • Food grown in this way is for all intents and purposes ‘organic’.  However as there is no soil involved and the Soil Association regulate the classification of organic food, they fall outside of it’s definition.
  • Pests and disease in commercial operation are a continual problem.
    • Damp is the primary source of the vast majority of diseases, hence winter is a problematic time.
    • Enquired whether a collection of smaller units, such as this one, rather than the single large footprint of a commercial operation would make pests easier to control.  This is what academics have found to be true in the Cuban model.  Sam of GU didn’t think in proportion it would make any difference with their model.
  • Asked about the comparison between a tray based system as formerly employed by Kevin Frediani vs their vertical ‘ZipGrow’ system.  Sam did not know of any direct comparisons to say whether one was more efficient/ productive/ complicated than the other.  On the face of it their system seems more simple to manage, practical and easier to achieve.
  • Asked about the arguments often presented against vertical farming by direct comparison with the cheaper cost of traditional agriculture in terms of product and energy usage, and the main arguments they think counter that:
    • In the UK all leafy salad crops are imported, they fill a gap in the market for fresh, locally grown ingredients.
    • Crop reliability is much better with vertical farms.
    • Yields are good by comparison.
    • Great source of whole foods.
    • Also, the purpose of vertical farming techniques is not to replace traditional agriculture, but to supplement it; to be an additional source of food.
    • More urban farms would help reduce the ‘urban heat island’ effect.
    • My own personal take in addition to these points is that greener environments, as has been previously proven in a variety of conditions (plants in offices, natural scenes depicted in hospital rooms over abstract ones, white papers on enivronmental economy etc), would help increase well being for people in the city.
    • Estimate their water usage is significantly more sustainable than commercial practices, as their water stays in the system and is constantly recycled.
      • Sam puts water waste of commercial agriculture at 80% (not sure on sources).  Vast majority of the water seeps away into the soil away from plant roots.
      • Water usage at the farm is much better.  Water waste will be 30% maximum due to siphoning off of water, however would likely work out less than this figure when considering frequency of water siphoning vs frequency of rain/ watering crops etc.
    • They deliver their food all within the M25.  He seemed to want to expand operations beyond these limits, but I viewed this as a positive.  Means food miles are low and therefore more sustainable.  All food grown is consumed locally.  They use an electric delivery van!
  • Traditional agriculture beats VF on price.  People buy their product on a reputation and quality basis even though it is more expensive.
  • Asked about arguments over sustainability of building vertical farms vs more traditional (commercial) agriculture also.
    • They recognised it as a problem but didn’t mention any specific solutions to this.
    • A main point of consideration would be the materials a farm is being built from, and whether it is being built in a re-used building or a new building.
    • Use of LED lighting and pumping equipment requires minimal power.  Main drain on power is in the use of the HVAC Ventilation systems and winter heating.
      • Passive systems would be of primary importance here in reducing energy consumption.  The box’s roof opens automatically by mechanical operation when it gets too hot like a normal greenhouse, but they also have fans for if it is raining.
      • Solar Stirling Engine could be used in hot weather.  Controlling damp in winter is less obvious.
      • No direct comparison with the use of commercial farming equipment has been made.
    • Kevin Frediani papers indicated power used became proportionally less the higher the structure got.  Sam had no knowledge of this and could not quantify nor confirm/ deny.
  • They grow exclusively small scale leafy salads and herbs.  Often Basil in the summer.  But that is not to say growing other types of crops is not possible.  Look to NASA technological concepts for growing food in space.
    • Yield of their commercial premises: 20 tons of salad per year for 750m2 footprint.
    • 400kg per year for this GrowUp Box (small shipping container footprint – 2.4m x 6m external, 5.9m x 2.3m internal).  This is a very close equivalent.
  • Bench dimension in commercial operation is 6m x 1.2m, so half the width of a 20ft shipping container.
  • Water is pumped up from the fish tank around the plants in approximately 1.5 minute bursts.
    • Happens roughly 40 times a day in the summer; less in the winter/ cold.
    • Each plant receives a fair proportion of the nutrients whether located at the top or the bottom of a tube.  This is because the pumps run long enough for each plant’s roots to become saturated in turn each cycle and therefore receive their fair share.
  • Is crop rotation needed here?  Strictly speaking no it is not, as they are less dependent on the seasons due to the closed nature of the system.  But for a healthy and balanced system crop rotation is recommended.  This helps prevent large fluctuations occurring in the system throughout it’s use.  The plants need the fish as much as the fish need the plants, hence ensuring there are always fish and plants growing somewhere in the system at all times is beneficial.
  •  Water is filtered 3 times before re-entering the fish tank
    • First through large brushes; then small brushes / foam; finally through K7 Biofilters (small, short, cylindrical filters).
    • Of the 3 missing nutrients: they only need to add iron into the Box’s system.  They add approximately 11g per week and add it into the large brush filter tank so it has plenty of time to dilute before reaching the fish.
    • Question was posed over how they avoid chelated nutrients?  Where the iron will attached itself to other nutrients?  A result of adding iron to a more acidic water PH.  Sam was not aware of the issue.  Brief internet search suggests chelated nutrients are a good thing for plants??  Hence the need to add the missing iron?  Doesn’t seem important to become expert enough on this; would seem to have little impact on the building and facility design.  A nuance of managing nutrients and one that Sam was unaware of yet still had a working, profitable system.

 

Conclusions:

  • I need a holding tank for processing old fish tank water.
  • The old castle moat could be re-instated as a reed-bed to process this siphoned water, site sewerage run-off and link the building narrative back in with farming practices happening further up the Itchen Valley.
  • Farming yield for the site can now be worked out based on 11 ltrs water per fish and rotation times of fish and food.
  • Fish tanks should be split into 3 minimum for a 2 month cycle on farming of fish from each tank.  Once running properly this would ensure fish could be farmed and distributed at the end of each month minimum by alternating between tanks.  If split further this could be more frequent.  Perhaps 4 or even 5 stages of fish development for each tank would reduce this gap further.  Need to see from the building footprint how large the tanks could be, how many litres of water could therefore be stored and in turn how many fish could be farmed to work out the best number of divisions.
  • Need to make an allowance for ventilation of the vertical farm through the use of both passive and non-passiv means.  Mechanically operated, automatic opening roofs is one passive measure, as is a solar stirling engine to power a mechanical fan-based system in sunny months.  Winter solution is needed, may have to be powered.  But the power could be sourced from the masterplan infrastructure, i.e. water turbines at weirs.
  • Need to make provision for the control of damp in new buildings being used for farming.  Materials need to be up to the job.  How do you protect columns made of reeds from the damp, whilst preserving an ‘honest’ expression of their form?
  • Measures need to be considered for protecting the fish from potential flooding – floats could be used for planted / farmed beds.
  • Could the farm grow it’s own fish food?  Algae possibly, or could spent grain be sourced from a local brewery?  Integrate these ideas within the masterplan.
  • Need to do some digging on NASA farming technology for space exploration.
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